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Millimetron

VIEWS: 21 PAGES: 35

  • pg 1
									Table of content

1. EXECUTIVE SUMMARY ................................................................................................................ 2

2. INTRODUCTION............................................................................................................................. 3

3. SCIENTIFIC OBJECTIVES .............................................................................................................. 3

  3.1 Cosmic Vision themes addressed by Millimetron ................................................................... 3
  3.2 Science with a 12m single-dish................................................................................................ 4
  3.3 Space-ground VLBI science .................................................................................................. 12

4. MILLIMETRON MISSION PROFILE ............................................................................................. 15

  4.1 Launcher ................................................................................................................................ 15
  4.2 Millimetron orbit.................................................................................................................... 16
  4.3 Millimetron observing modes ................................................................................................ 16
  4.4 Ground segment requirements ............................................................................................... 17
  4.5 Special requirements .............................................................................................................. 17
  4.6 Critical issues ......................................................................................................................... 17

5. MILLIMETRON PAYLOAD........................................................................................................... 18

  5.1 Overview................................................................................................................................ 18
  5.2 The 12m space telescope........................................................................................................ 19
  5.3 Scientific instrumentation ...................................................................................................... 21
  5.3.1 Single-dish instrumentation ................................................................................................ 21
  5.3.2 Space segment VLBI instrumentation ................................................................................ 24
  5.3.3 Special requirements ........................................................................................................... 26

6. BASIC SPACECRAFT KEY FACTORS ........................................................................................... 26

7. SCIENCE OPERATIONS AND ARCHIVING .................................................................................. 28

8. KEY TECHNOLOGY AREAS ......................................................................................................... 29

9. PRELIMINARY PROGRAMMATICS/COSTS ................................................................................. 30

  9.1 International collaboration ..................................................................................................... 30
  9.2 Proposed management structure ............................................................................................ 30
  9.2 Schedule................................................................................................................................. 31
  9.3 Preliminary costing ................................................................................................................ 32

10. COMMUNICATIONS AND OUTREACH ...................................................................................... 33

11. INSTITUTIONS CONTRIBUTING TO THE MILLIMETRON PROPOSAL ...................................... 34

12. REFERENCES............................................................................................................................. 35




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1 Executive Summary

The InfraRed (IR) and submillimeter wavelength regime was recognized by ESA’s astronomy
working group (AWG) as one of the few areas were great progress could be expected in
astrophysics as soon as high angular resolution and good sensitivity could be achieved. A
passively cooled 12m dish optimized for the far-IR/submillimeter range, with an instrument suite
building on Herschel heritage, provides just this capability.

We propose European participation in the Russian mission Millimetron whose goal is the
exploration of the cool universe seen in submillimeter and far-infrared wavelengths as well as the
study of very energetic phenomena associated with compact radio sources in the millimeter and
submillimeter regime with extremely high spatial resolution.

The spectral range with wavelengths between 60μm and 600μm is of crucial importance for
understanding how stars, planets and galaxies form and evolve. Furthermore, Very Long Baseline
Interferometry (VLBI) in (sub-)millimeter waves will give micro-arcsecond access to compact
sources such as black holes, neutron stars, and gamma-ray afterglows.

Millimetron will be the only mission able to make unique contributions to all four themes of the
Cosmic Vision program by combining high spatial and high spectral resolution as well as
photometric and spectroscopic capabilities in the submillimeter/FIR regions. Millimetron will
• explore of the life cycle of gas and dust that leads to stars and planets (theme 1),
• measure the deuterium content in the giant planets of solar system (theme 2)
• investigate the physical parameters and processes near the event horizons of black holes and
    near the surfaces of neutron stars with sub-micro-arcsecond resolution (theme 3)
• trace the formation and evolution of black holes, trace the life cycles of matter in the Universe
    along its history, and resolve the far-infrared background (theme 4).
Millimetron will have two distinct scientific operational modes: (1) as a single-dish 12m diameter
submillimeter space observatory, and (2) as space antenna of a sub-/millimeter space-ground VLBI
interferometer. This will provide unreached angular resolutions in the millimeter to far-infrared
regime of a few arcseconds in single-dish mode and micro-arcsconds in VLBI mode.

A suite of heterodyne instruments covering the astrophysically important bands around 557, 1100,
1900, 2700 and 4700 GHz as well as a FIR photometer/spectrometer will be part of the instrument
complement. In addition, receivers at four ALMA bands and K-band will provide VLBI capability.
The instruments will be based on technology and designs as developed for Herschel and ALMA
thus decreasing risk and cost.

The Russian Space Agency has included Millimetron in its Federal Space Plan with the
commitment to provide the 12m space telescope, the spacecraft, launch, operations and ground
segment. In this Cosmic Vision proposal, we ask ESA to contribute the following payload
elements: telescope heat shields, instrument cryo-cooler, participation in the ground segment,
communication link, and on-board mass storage memory for VLBI. The total cost for the ESA
contributions is estimated as 66 M€. The scientific instrument would be built by a European
instrument consortium comprising leading science and technology institutes with relevant
experience in Herschel and ALMA instruments.

The Millimetron mission will give European astrophysicists the possibility to join a unique space
observatory and reap the exciting, scientific results emerging from it. With a small ESA
investment the wish of the AWG – to have a FIR observatory – can become true, early in the
Cosmic Vision plan.




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2 Introduction

This proposal is for ESA participation in the Russian-led space mission Spectrum-M
(Millimetron). This mission will enable astronomers to observe the universe with unprecedented
sensitivity and angular resolution in the far-infrared and submillimeter spectral bands. These bands
are crucial regimes for the study of the formation and evolution of stars, planets, and galaxies. In
addition, extremely high-angular resolution imaging by VLBI allows exploration of ultra-compact
radio sources including black holes.

Millimetron is a large (12m diameter) space observatory for millimeter, submillimeter and far-
infrared observations. It has two scientific observing modes each of which is unique and represents
a major step forward in the investigation of the universe we are living in. Firstly, Millimetron will
be used as a 12m diameter single-dish space observatory for high-sensitivity and high angular
resolution observations of the submillimeter universe. Secondly, Millimetron will be used as a
VLBI (Very Long Baseline Interferometry) antenna in millimeter and submillimeter wavelength
bands providing extreme angular resolution of better than one micro-arcsecond. Observations in
both observing modes will substantially contribute to solving questions as outlined in the Cosmic
Vision themes.

Spectrum-M (Millimetron) is part of the Space Plan of the Russian Federation. The Russian Space
Agency (RSA) has approved the mission and has allocated funds for the development and
implementation of Spectrum-M (Millimetron). At present, the Astro Space Center (ASC) in
Moscow is carrying out studies for Millimetron which are funded by the RSA. Concerning
Millimetron, ASC has established contacts with ESA, ESO, and lately with SRON Netherlands
Institute for Space Research with the aim to explore possibilities for European participation in the
mission.

A number of technologies required for Millimetron, including the 12m diameter space antenna, are
based on the Russian RadioAstron mission which is currently undergoing flight hardware
integration and will fly a 10m deployable antenna in 2008/09 for ground-space VLBI. The higher
frequency range of Millimetron as compared to RadioAstron means more demanding
specifications in such areas as antenna surface precision, time reference system, phase stability etc.
The instrumentation for Millimetron is based on the substantial investment into Herschel
instruments and ALMA receivers and will build on developed (and largely space qualified)
detector and instrument techniques.


3 Scientific objectives

3.1 Cosmic Vision themes addressed by Millimetron

Millimetron will be operated as a single-dish and as space VLBI system. The Cosmic Vision
themes 1 and 2 will be addressed in single-dish mode, and the themes 3 and 4 in both single-dish
and VLBI mode.

Theme 1 - What are the conditions for planet formation and the emergence of life?
Millimetron will investigate the processes that lead “from gas and dust to stars and planets” with
high angular and high spectral resolution. With its high sensitivity as a 12m diameter single-dish
space observatory it will be able to “map the birth of stars and planets by peering into the highly
obscured cocoons where they form”. The ability to probe far-infrared lines of water, C+, O and
HD with high spatial and spectral resolution is a big step beyond Herschel and crucial to our
understanding of the processes leading to stars and planets.




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Theme 2 – How does the Solar System work?
Millimetron will make a unique contribution to Solar System science by measuring the deuterium
content of the giant planets through the HD emission line at 2.7 THz. This measurement provides a
crucial piece of information for our understanding of the origin of the Solar System.

Theme 3 – What are the fundamental physical laws of the Universe?
Millimetron in space-ground VLBI mode will have the ability to explore “matter under extreme
conditions” by investigating the physical parameters and processes near the event horizons of
black holes and near the surfaces of neutron stars with sub-micro-arcsecond resolution.

Theme 4 - How did the Universe originate and what is it made of?
The combination of sensitivity, sub-micro-arcsecond angular resolution (in VLBI mode) and high-
resolution spectroscopy on Millimetron allows to “trace the formation and evolution of the super-
massive black holes at galaxy centers – in relation to galaxy and star formation – and trace the
life cycles of matter in the Universe along its history.” It can “resolve the far-infrared background
into discrete sources, and the star-formation activity hidden by dust absorption”.


3.2 Science with a 12m single-dish

Introduction: Zooming in on the formation of stars and galaxies
Two prime foci of 21st century astrophysics are the studies of the obscured universe and the
molecular universe, at far-infrared and submillimeter wavelengths. The reason is that only through
such studies, which target cool dust and gas, we can obtain crucial information about the formation
processes of stars and galaxies, the central issues in astrophysics. Millimetron will permit to make
the important next steps in spatial resolution as well as sensitivity.

Following up on the IRAS mission, ISO and Spitzer have subsequently truly opened the dusty and
molecular universe. These missions observed in great detail the processes involved in small- and
large-scale star-formation, at mid- and far-infrared wavelengths. ISO revealed the presence of cold
(15 K) dust in galaxies and established the unexpected fast decay of starburst episodes. Mid- and
far-infrared luminosities, colors, and spectra of the [CII] and [OI] cooling provided insight in the
physics of star formation. Imaging of the warm dust in nearby galaxies proved to be a fine tool:
ISO revealed fascinating cases of obscured star-formation such as in the Antennae galaxies
NGC4038/39 (Fig.1). The spectroscopic capabilities of ISO and Spitzer permitted great advance in
our understanding of the gas properties of nearby dusty and gas-rich objects, including the
important class of ULIRGs. The magnificent spectra obtained with the Spitzer IRS provide
conclusive evidence for the starburst-AGN symbiosis (as suggested from ISO observations) in a
variety of extragalactic objects.




                                                  Fig. 1 – Antennae galaxies NCG4038/39
                                                  (Spitzer Space Telescope)




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The Herschel Space Observatory, ESA’s fourth cornerstone mission, will continue where its
predecessors ISO and Spitzer stopped. Herschel will extend the wavelength range into the
submillimeter, at much greater sensitivity, considerably higher spatial resolution, and much higher
spectral resolution. These qualifications will permit studying the mid- and far-IR out to high
redshift for the first time. Simultaneously, from the ground, ALMA will bring sub-arcsecond
resolution to the submillimeter window.

In space, a far-infrared interferometer is still far beyond the horizon, and larger antennas must
make the necessary next step. If such a telescope delivers improved detector sensitivity at the same
time, its advantages are even greater. The Millimetron mission will be able to deliver all this. Its
sensitive receivers and its large collecting area will allow at least one order of magnitude
improvement with respect to Herschel. Whereas Herschel will study the formation of stars and
galaxies in a global fashion, Millimetron will zoom in on the processes, and observe fainter, more
distant objects. The development of Millimetron would therefore be a wonderful far-infrared
parallel to the submillimeter developments on the Chajnantor plateau!

Diagnostic features in the far-infrared regime
The infrared (IR) and submillimeter (submm) regions are crucial regimes because they reveal the
radiative response of gas and dust in galaxies to the input of energy from stars (photon absorption)
or by the dissipation of mechanical energy (shocks). The resulting spectrum contains the
fingerprints of the astrophysical processes governing the formation of stellar populations and of
supermassive black holes. Unfortunately, the Earth's atmosphere is opaque in essential regions of
the far-IR/submm regime, such as the region from 50 to 200 micron which contains the
fundamental interstellar gas cooling lines: [CII] 158 micron (1900 GHz) and [OI] 63 micron (4700
GHz). By providing observing capability in this region at unprecedented resolution (3-4") and
sensitivity, Millimetron will revolutionize this field.

Table 1: Main spectral features targeted by Millimetron
Line                  Frequency         Goal                              Competitive Edge
                      (GHz)
H2O 1(10)-1(01) & 556.9 &               Tracers of star formation         Superior sensitivity and
1(11)-0(00)           1113.3                                              resolution wrt Herschel
Dust continuum        500 - 5000        Mass and temperature              Superior sensitivity and
                                        diagnostic                        resolution wrt Herschel
p-H2D+ 1(01)-         1370.1            Unique tracer of protostellar     Superior sensitivity and
0(00)                                   condensations                     resolution wrt Sofia
[CII] 2P(3/2)-        1900.5            Main coolant of interstellar      Superior sensitivity and
2P(1/2)                                 gas                               resolution wrt Herschel
HD J=1-0              2675.0            Origin of molecular clouds        Velocity information
                                        and giant planets                 unique to Millimetron
[OI] 3P(1)-3P(2)      4744.8            Tracer of heating by shocks       Velocity information
                                        and UV                            unique to Millimetron

Emission lines in the far-IR are excellent diagnostics of the physical conditions in interstellar gas,
which are not affected by dust extinction. In relatively cold regions, the dominating line is the fine-
structure transition in the ground state of ionized carbon. In warmer conditions, the corresponding
transition of neutral atomic oxygen makes a significant contribution or even outshines the carbon
line. In addition, the dust emits thermal emission which is a sensitive probe of mass and
temperature, especially since the emission peak falls in the far-IR for the relevant temperature
range. In denser regions of the ISM, molecular lines take over the role of tracers from the atomic
fine-structure lines. In particular, the far-IR hosts key molecular lines which trace all stages of the
star formation process: the HD 1-0 line traces the transition from atomic to molecular clouds, the
H2D+ line at 1370 GHz traces the formation of dense cores in these clouds, and the ground state




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transitions of H2O are excellent tracers of gas warmed up by young stars. Table 1 lists the major
spectral targets for Millimetron.

Spatially resolving the Cosmic IR Background
The Cosmic Infrared Background (CIRB) is a fundamental component of the present radiation
content of the Universe and is made essentially of the long wavelength output from all sources
throughout the history of the Universe from the present time till the epoch of recombination, only
400 thousands years after the Big Bang. In contrast, the Cosmic Microwave Background,
dominating the radiation spectrum for frequencies lower than 800 GHz, has been produced in the
hot and dense phases of the universe before the recombination. Note that the very different spectra
of the CIRB with respect to the CMB allow them to be relatively easily separated for wavelengths
shorter than 1 mm, and in this wavelength regime the CIRB dominates the galactic emission by a
factor 4 in the lowest cirrus regions.

Our current understanding of the CIRB considers it to be the integral of the reprocessed light by
dust during phases on enhanced activity in galaxies and active nuclei. Dust, which is observed to
be ubiquitous in galactic star-forming regions and star-forming galaxies in general, is likely to
have been present also during the major past events of the formation of stellar populations.
According to this interpretation, the long-sought primeval galaxies would be undetectable in the
optical, and would have left an important trace in the CIRB. This is supported by recent
observations with SCUBA/JCMT, ISO and Spitzer, able to resolve a few percent of the CIRB into
sources, some of which appear indeed as very luminous IR sources. This indicates that the most
important phases of the formation of galaxies and their nuclear supermassive black holes
(responsible for the nuclear activity) might only be investigated in the far-infrared and in the sub-
mm, where the CIRB peaks.

A crucial theme of observational cosmology for the next several years will then be this exploration
of the far-IR & sub-mm sky in the attempt to identify and characterize the enigmatic sources of the
CIRB. Figure 2 is a model representation illustrating the capabilities of future long-wavelength
space missions (nothing can be done unfortunately from ground in this spectral domain) to resolve
this background, in a similar fashion as it was done for example for other extragalactic relics like
the X-ray or radio backgrounds.

Limited sensitivity and resolution make it impossible to resolve the CIRB with the forthcoming
Herschel mission or future space observatories like SPICA: all these will produce confusion-
limited images able to resolve the CIRB only at its short wavelength boundary (see Figure 3).
Similar considerations apply to its long wavelength (λ>500 μm) boundary accessible by ground
based millimetric observatories. A solution to the problem of the formation of galaxies and cosmic
structures will only be achieved after the enigmatic sources of the CIRB will be properly resolved
into sources, which is only possible by a large far-IR/sub-mm telescope in space with adequate
suite of imagers and spectrographs.

The spectral capabilities of Millimetron will allow a spectral characterization of these sources
through redshifted fine-structure emission lines characteristic of either stellar photoionization
([NeII], [SIII] lines) or photoionization by the hard continuum of an active galactic nucleus
([OIV], [NeV]). It will thus be able to trace directly the coeval buildup of stellar population and
black hole with redshift in galaxies of a range of luminosities. Millimetron will thus provide the
currently missing window on the region of photoionized gas, and provide direct complementarity
to ALMA, which will probe principally the neutral molecular gas in the same objects.




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   Fig. 2 - The CIRB spectrum and fractions of it that will potentially be resolved by future missions (HSO,
   SPICA). Only a large (10-12m) diffraction-limited space observatory, like Millimetron, would completely
   resolve the CIRB into sources.

Star-forming galaxies at low redshift
Low-redshift galaxies form crucial laboratories for studying the physical processes occurring at
higher redshifts in detail. By probing the neutral star-forming medium, we probe both the
conditions in the prestellar gas phase and the feedback of the star formation (or black hole
accretion) process on the ambient medium. Here Millimetron provides unique insight: the H2O
ground-state transition forms a probe of warm, dense, cooling molecular gas that is not available
from the ground. Simultaneously, the [CII] and [OI] lines probe the more extended lower density
medium. The change in cooling balance from quiescent to actively star-forming galaxies such as
ULIRGs is shown by the decreasing importance of [CII] cooling with increasing luminosity. For
instance, in ultraluminous infrared galaxies (ULIRGs) the cooling by the CO rotational lines
approximately equals that in [CII], indicating a totally different thermal balance than in lower
luminosity objects (Papadopoulos et al. 2007). While Herschel will be able to skim the surface of
this subject, what is really required is a study of fainter galaxies, both locally and at higher
redshift, in order to establish the cooling properties as a function of physical parameters such as
galaxy luminosity, type, environment, metallicity, presence (or not) of an active nucleus, etc, etc.
Such as systematic study will form an indispensable benchmark for the study of higher redshift
galaxies, both with Millimetron and other facilities such as ALMA. As a case in point, we note
that in crucial aspects, the interstellar medium of low-metallicity galaxies resembles that of
primeval galaxies. In metal-poor environments, heating and cooling of the gas operates in
different ways from those in the Milky Way. Low dust-to-gas ratios allow UV radiation to
penetrate deep into molecular clouds. The primary molecular cloud coolant CO is much reduced in
abundance, but H2 itself is largely unaffected. CO is no longer a useful tracer of molecular gas
column densities. Dissociation of CO increases the C and C+ abundances and thus the cooling
luminosity of the [CII] line.

Far-infrared spectroscopy of star-forming galaxies
With a resolution of 3 – 4 arcsec at the wavelengths of the important [OI] and [CII] cooling lines,
the medium-resolution (imaging) spectrograph on Millimetron will be able to trace accurately the
location of the main cooling radiation and therefore characterize the thermal balance of the ISM of
galaxies at a resolution comparable to seeing-limited observations in the visual regime. At the
distance of the nearest ULIRG (Arp220, D=74 Mpc) the Millimetron resolution at 60 microns
corresponds to ~1000 pc, sufficient to resolve the central concentration and gas and dust where



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most of the luminosity originates. Given the linewidths of galactic nuclei, a spectral resolution
R=3000 is sufficient for revealing the kinematic structure of the emitting gas.

Finally, an attractive application of Millimetron is the search for primeval (metal-free) galaxies. In
the absence of metals a cloud of molecular gas must cool through H2 line emission and the
rotational H2 lines will be redshifted into the Millimetron regime. This process has been modeled
in detail by Mizusawa et al. (2005) who demonstrate that for a cloud contracting at a rate
(expressed as a star formation rate) of 100 Msun/yr a flux of 10-23 W/m2 is expected in the brightest
H2 line for a source at z=6 (presumable the end of reionization). If such sensitivities can be
reached, Millimetron could for the first time detect population III (metal-free) galaxies, in the era
just before or during cosmic reionization. While a blind search for such galaxies could be
prohibitively time-consuming, targets may be preselected from Ly-alpha narrow-band imaging
(since such galaxies are expected to be significant Ly-alpha emitters) or from high-z Gamma-Ray-
Burst surveys.

Physical conditions in Galactic regions of star formation
The heating of interstellar gas reflects the action of powerful shocks driven by jets and outflows
from young stellar objects. Alternatively, UV photons from nearby young massive stars
photodissociate and heat the surrounding gas, forming a photon dominated region (PDR). Both of
these types of environments are cooled by infrared atomic fine structure line emission.
Calculations for shocks in the dense ISM have been presented by Hollenbach & McKee (1989)
and for PDRs by, e.g., Tielens & Hollenbach (1985a+b), Liseau et al. (1999) and Kaufman et al.
(1999). The latter paper, in particular, contains the results of an extensive parameter study, viz. for
n(H) = 10 – 107 cm-3 and Go = 10-0.5 -106.5 in units of the average UV field of the solar
neighbourhood 1 .




 Fig. 3 - (left) Line ratio plot for the fine structure lines of OI and CII, where error bars have been omitted
to avoid crowding. The horizontal dashed line indicates the optically thin regime for the
[OI]63μm/[OI]145μm line ratio above about ten. The two open symbols with vertical error bars refer to the
average values of data lying above and below the dividing line, respectively.
Fig. 3 - (right) Numerical results for oxygen line ratios at characteristic interstellar cloud temperatures.
Displayed are the column densities of atomic oxygen N(O), for Δv =1 km s-1, needed to produce the line
ratios for an H2 density of 3·104 cm-3. For these parameters and at 20 K, line center optical depths in this
plot range from min τ0 = 0.05 to max τ0 = 5·105 in the 145μm and in the 63μm lines, respectively. At 100 K,
these values are 26 and in excess of 4·105 (adapted from Liseau et al. 2006).




1
 Go = 1 equals 1.6 ·10-3 erg cm-2 s-1 for photon energies E = 6 – 13.6 eV.


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Comparing theoretical predictions of the line intensity ratios of the [OI]63μm (4.7THz) and
[OI]145μm (2.1THz) lines (unaffected by abundance uncertainties) to the observation of more
than 100 galactic star forming regions (relatively nearby), Liseau et al. (2006) found that more
than two thirds of the observed values were not consistent with the theoretical models. In addition,
Abel et al. (2007) found evidence for optical depth effects in the [OI] and [CII] lines. These
unexpected results implied considerable lack of understanding of the physics of the line emitting
regions, the line excitation mechanisms and/or the line radiation transport.

Optical depth effects in the [OI] lines cannot explain this mismatch between theory and
observation for most cases of interest. Maser action in the [OI] 145μm line is a viable option for
dense and warm regions, such as the Orion-Bar, whereas self-absorption in the 63μm line may
play a role in dense cold clouds (e.g., the ρ Oph cloud). High spectral resolution observations are
needed to settle this issue, which Millimetron will provide.

For protostellar jets & outflows, Hollenbach & McKee (1989) proposed that the luminosity of the
[O I] 63μm line can be used to derive the rate at which the central object looses mass. In the
momentum conserving case, this rate can also be estimated from the observed molecular outflows,
generally mapped in rotational lines of CO. The large scatter in the observed relation clearly calls
for a re-examination of the shock models. Heterodyne observations of the [OI] lines with
Millimetron are clearly needed.

In summary, our understanding of the physics of interstellar clouds is clearly incomplete as shown
by our inability to model the excitation conditions in the cold [C II] and warm [O I] media. Local
emission regions and intrinsic line widths, whether galactic or extragalactic, are expected to be
small. Progress on the observational side therefore clearly requires significantly increased spectral
and spatial resolution compared to what will be offered in the foreseeable future by, e.g., Herschel
and/or SOFIA. A large telescope as that proposed for Millimetron and equipped with heterodyne
receivers would be able to fulfill these requirements. For external ultra-luminous galaxies, the
sensitivity provided by a large collecting area in combination with an intermediate-resolution
spectrometer for far infrared wavelengths would be well adapted to study the [O I] 63μm emission
for large redshifts, z > 3, and hence match the upcoming (lower spatial resolution) observations of
the [C II] 157μm line with Herschel.

Formation of molecular clouds and stars
A large single dish far-infrared telescope equipped with array receivers such as Millimetron is also
the ideal tool for studying the formation of molecular clouds and stars. Stars are born in dense cold
cores inside molecular clouds, but the life time of these cores and their formation within molecular
clouds, as well as the formation of molecular clouds themselves, are far from understood.
Numerical simulations by Hennebelle et al. (2007) and Glover et al. (2007) have shown that
molecular clouds can be formed out of diffuse atomic interstellar gas, and that the structure of the
clouds is both a consequence of the early structure of the atomic gas as well as the condensation
process. Furthermore, while the formation of molecular hydrogen itself can be accelerated by the
shocks driven by turbulence, the formation of CO and other stable molecules requires longer
times, as these molecules are easily photodissociated. Therefore, significant abundances are only
achieved in regions shielded from UV radiation. Hily-Blant and Falgarone (2007) propose that
dense molecular cores are indeed related to more diffuse atomic and molecular gas, from which
the cores accrete material and gain mass.

As the main coolants of diffuse matter, the [CII] and [OI] lines are the best probes to study the
process of core formation in the interstellar medium and test the above theories. Disentangling the
respective roles of turbulence, gravity and magnetic fields requires large scale maps at high
spectral and spatial resolution, as small scale structures are known to exist down to arcsec scale in
the diffuse interstellar medium. The role of the magnetic field will be revealed by the shape of the



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structures, but it is also expected that the line profiles will bear an imprint of the magnetic field ,
because the velocity field of the molecular gas will be affected.

Prior to star formation, the molecular gas becomes very cold in the interior of dense molecular
cores, and most of the heavy molecular species get frozen on grains. Since the substitution of an
hydrogen atom by a deuterium atom is favored at low temperatures, deuterated molecules become
very abundant, and are the best tools to study the physical conditions, gas dynamics and chemistry
in these environments. The recently detected molecular ions H2D+ and D2H+ are key actors in the
deuterium fractionation process. While a single transition of either ion is accessible from the
ground with great difficulty, Millimetron will routinely map both ions, offering unique diagnostic
capabilities of the initial conditions and first steps of star formation. Measurements of the HD
rotational lines at 112 and 56 micron would provide an ideal complement, as HD is the main
deuterium reservoir. While the first detection of the rotational lines have been obtained by ISO, the
diagnostic capabilities of HD have been demonstrated by Spitzer. Neufeld et al. (2006) have
mapped the HD emission from supernova shocks, and show that the R(3)/R(4) ratio is a probe of
gas pressure. HD lines probe the deuterium reservoir, and trace the presence of molecular gas
accurately.

The onset of actual star formation in the molecular condensations is best traced by the water
molecule. Emission in its ground state lines at 557 and 1113 GHz is a clear sign of dense gas that
has been heated up by nearby young stars. While Herschel will excel in the study of water in
advanced stages of star formation, the weakness of the emission and small size of the emitting
region in the very first phases of stellar activity call for the sensitivity and resolution of
Millimetron.

Protoplanetary disks
The past decade has witnessed the discovery of a multitude of planetary systems, exhibiting a wide
variety of properties. This shows that our Solar System is neither unique nor typical.
Understanding how this richness arises from the formation process of planets will occupy
astronomers for the next decades. It will require observations of sufficient spatial resolution that
can penetrate the dense layers of dust present in circumstellar disks, the birth sites of planets.
Millimetron offers two avenues to provide unique insight into the planet formation process:
through ultra-high resolution VLBI observations in the ALMA bands, and through medium
resolution single-dish observations of water lines in particular.

VLBI: ALMA will image the cold gas and dust in proto-planetary disks at resolutions of a few
AU and up at the typical distance of these systems. While these observations will probe the global
planet formation environment, the actual planet formation takes place on much smaller scales
corresponding to a few stellar radii for gas giants, and perhaps the Earth-Moon system for
terrestrial planets. VLBI at ALMA wavelengths with Millimetron provides resolutions of a few
hundred-thousand km at the typical distance of many young stars (140 pc), and should therefore be
capable of directly detecting proto-planets, as well as the gaps they open in disks. We should also
be capable of detecting substructure in the disk induced by the planets, such as spiral waves and
accretion signatures onto the planet. A key question, which with current models cannot yet be fully
addressed, is if the brightness temperatures of these features are sufficiently high to be detectable.
Especially shocks and accretion flows may provide the required heating to generate emission with
brightness temperatures of a hundred K or more.

Single-dish: The water molecule is a key player in protoplanetary disks. Expected to be frozen out
onto dust grains in cold regions (<100 K), it should be present in the gas phase in the disk
atmosphere and the inner few AU of the disk. In these latter regions it is a key player in the
cooling balance of the gas, and its presence in the terrestrial planet formation zone is crucial for
the formation of life. While Herschel will bring the first opportunity to detect the ground-state
water lines from protoplanetary disks, the limited sensitivity and resolution will at best permit
detections in a few exceptional cases. The much larger Millimetron dish will enable systematic


                                                                                                10/35
studies of the water content of protoplanetary disks in nearby star-forming regions, and thus put
the study of habitable planet formation on a solid footing.

Debris disks: After planet formation, the remnant dust particles settle in so-called debris disks.
The classical example is the tenuous disk around Vega, discovered by IRAS. The properties of
such disks are important constraints on theories of planet formation, but are not well known from
observations. The superior sensitivity and resolution of Millimetron relative to Herschel allow us
to detect the dust and [CII] emission from debris disks out to large distances, and permit to study
their physical properties in a statistically significant sample.

Solar system science
A large submillimeter antenna in space like Millimetron would be an important tool to study the
water meteorology in planetary atmospheres and the water activity in comets. The small antenna
beam at submillimeter wavelengths allows mapping the water lines on planets and comets, and by
repeating these observations regularly, we may establish the meteorological system and probably
even start with climate measurement. The atmospheres of planets and moons in our Solar System,
as well as comets are the prime targets for spectroscopic observations. Kuiper Belt Objects are
more easily studied in the continuum. This section addresses all these objects and highlights the
main characteristics. While Millimetron will not be used for in-situ measurements, the power of
remote sensing with a large single dish is such that Millimetron will be able to make a large
contribution to Cosmic Vision Theme 2.

Mars: The current martian climate is governed by 3 cycles: CO2, H2O, and dust. While the dust
and CO2 cycles can be studied by other methods, H2O is best studied through its far-IR rotational
lines. Since these lines are inaccessible from the ground, there are still many unknown sources and
sinks of water, which are crucial to understand the present climate of Mars. The temporal and
spatial column-integrated amount of water has been characterized in the Viking mission. However,
extremely limited information is available on the vertical profile of water, which cannot be derived
from near-IR or UV measurements. Only weak 22 GHz H2O lines and millimeter HDO lines
have provided some results on the water vertical distribution. Herschel will provide the disk-
average abundance and vertical profile of water and its isotopes for different seasons, but only
high angular resolution heterodyne submillimeter and far-IR observations could provide both
spatial and vertical water distributions on Mars. Having this in hand, dedicated O2 observations
could be used to relate its spatial variation with that of water, which is essential to understand their
photochemical interaction. Other expected minor species (OH, NH3, HCl) would constrain the
coupling between photochemical and general circulation models.

Giant Planets: ISO observations of stratospheric water in the giant planets have demonstrated the
external origin of water. Various external sources has been proposed: interplanetary dust particles
(IDPs), local sources (rings, surfaces), and cometary collisions (e.g., SL9). While Herschel will
improve the current measurement of the vertical profile of water and will provide better
constraints on its origin, high angular resolution observations will be essential to disentangle the
different external origins of water. In particular, cometary impacts will have a different spatial
distribution signature than homogeneous sources (e.g., IDPs), while magnetospheric effects
influence the water distribution at polar latitudes.

A key contribution of Millimetron will be the measurement of the HD ground state line in the
atmospheres of the giant planets. This line probes the deuterium abundance, a very important
measurement for understanding the formation of planets and the origin of the solar system. The
HD abundance in the atmospheres of Saturn and Jupiter constrains the place in the Galaxy where
our Sun has formed. While SOFIA and Herschel will assess this topic for the first time,
Millimetron will map the HD abundance over the planetary disks, and directly test the origin
assumption. One expects that on Uranus and Neptune, the D/H ratio is enhanced by mixing of their
hydrogen envelopes with D-enriched grains and this process could also be at play on Saturn and



                                                                                                 11/35
Jupiter. Maps of the four giant planets in HD will thus permit the determination of the composition
and origin of the grains in the primitive Solar nebula.

Comets: High-resolution microwave observations of comets allow to study the distribution of the
outgassing at the surface of the nucleus, and the jets spiraling with the rotation of the nucleus.
ALMA will allow to obtain dynamic, 3-D like, maps of several species, but the major species H2O,
which drives both the nuclear activity and the hydrodynamics of the coma, will not be covered.
High angular resolution observations of water with a large antenna in space are urgently needed.


3.3 Space-ground VLBI science

Millimetron will also operate as a space-ground Very Large Baseline Interferometer providing
unprecedented angular resolution. Here we address the important and unique science that can be
done and give its relation to themes 3 and 4 of the Cosmic Vision plan.

The main scientific goal of the Millimetron mission in Space VLBI (SVLBI) mode operation will
be the exploration, with extreme high angular resolution (better than 1 micro arcsecond) of
extremely compact radio sources. The list of the expected results includes:
(1) first direct imaging of the event horizon of super-massive black holes in galaxies at different
    redshifts, particularly for the black hole at the center of our Galaxy; for these super-massive
    black holes and for stellar-mass black holes (microquasars) in our Galaxy and other galaxies
    in the local group, Millimetron will further study the physical parameters and processes near
    the black-hole horizon in direct accordance with theme 3;
(2) determine the cosmological evolution (by measuring black holes at different redshift) of black
    holes parameters at the center of galaxies (themes 4 and 3);
(3) first direct study of particle acceleration regions very close to a black hole (theme 3);
(4) first measurements of proper motion and cosmological proper motion and parallaxes of such
    objects (theme 3);
(5) first measurements of the dynamics of close binary quasars (theme 3);
(6) first direct imaging of structures, physical parameters and process near the surface of neutron
    stars by observation of pulsars and magnetars with inverted radio spectrum (theme 3);
(7) the first detection of structure, and study of the evolution of this structure, of gamma-ray
    bursts radio afterglows (themes 3 and 4).

                                                            All these topics have in common that
                                                            they require sources that are strong
                                                            synchrotron emitters. As it was found
                                                            using ground VLBI observations, the
                                                            most compact radio sources have a
                                                            flat or inverted spectrum (the spectral
                                                            flux increase with frequency), which
                                                            is the result of self-absorption by
                                                            relativistic electrons, or absorption by
                                                            plasma surrounding the compact
                                                            source.      This,     together      with
                                                            interstellar scattering, blurs the image
                                                            of an object and sets the minimum
                                                            resolution that can be obtained at a
                                                            given wavelength. This effect is very
                                                            strong towards the black hole at the
                                                            center of our Galaxy, the source Sgr
 Fig. 4 - Spectrum of the cosmic background radiation for   A*. However, the importance of these
 high galactic latitudes (Henry, 1999). The submillimeter   effects decreases significantly with
 regime shows a minimum.


                                                                                              12/35
frequency, and these effects are negligible in the sub-millimeter band. An additional advantage of
the sub-millimeter band is that in that band there is an absolute minimum of the brightness
temperature of the background radiation (e.g., Henry, 1999), Figure 4, and therefore there one can
obtain the best signal-to-noise ratio. At a wavelength of 250-500 μm (frequency 600-1200 GHz)
there is a deep minimum of the spectral intensity Iν .

Due to the gravitational lensing, black holes would cast a shadow larger than their horizon size
over the background; the shape and size of that shadow can be calculated (item 1, from the list
above). A simple estimate of the angular diameter of a Schwarzschild black hole for Sgr A* (4 106
solar masse at 8 kpc) is 60 microarcsecs, which is under the resolution attainable with current
astronomical instruments. Considering the image blurring by the interstellar medium, such a
shadow image of Sgr A* would only be observable at wavelengths of 1 mm or less (Huang et al.,
2007). Sub-milliarcsecond, and even sub-microarcsecond, astrometry and imaging of Sgr A* and
many extragalactic sources only become possible at submillimeter wavelengths. For the black hole
at the center of M87 (3 109 solar masses at 14 Mpc), the shadow subtends 25 microarcsec. For a
black hole with the mass of that in M87 at a redshift z~1, the size of the shadow would be 30
nanoarcsecs; at larger redshifts the angular size increases as (1+z) (items 1 and 2). A very exciting
prospect is the possibility of observing “hot spots” in the accretion flow. Measurements of those
spots could be used to determine the validity of the Kerr metric and measure all the black-hole
parameters (Broderick & Loeb, 2006).




Figure 1 Sgr A* - A strong and variable source in the center of our Galaxy with a 4 106 solar
masses black hole, with an expected Schwarzschild angular diameter of 50 micro arcsec, and a
flux of ~3 Jy in the 1 mm and 0.3 mm bands. (Figure taken from: Marrone et al. 2006).

Sensitivity estimates and maximum angular resolution are strongly connected. The flux of a
circular Gaussian source with half with diameter φ=λ/B is Fν=πkTBδn-α/(2ln2(1+z)B2). Here λ is
                                                                        B




wavelength, B is the base line projection on the plane of view (10 – 300 103 km), TB is the   B




brightness temperature of the source (1012 K at saturation), δn-α is the Doppler amplification factor,
with n=3 for ballistic motion and n=2 for continuous jet, where α is the spectral index. Without
taking into account the amplification factor, and for previously mentioned baselines, the expected
fluxes are in the range of 30 mJy to 30 Jy, and angular resolutions are in the range of 6
microarcsec to 200 nanoarcsec for λ=0.3 mm. At the Lagrangian point L2 (1.5 billion km
baseline), the resolution would be 40 nanoarcsec.




                                                                                                  13/35
Polarization and Faraday rotation in the millimeter and submillimeter bands contain unique
information on the central engine of such objects, e.g. on the strength of the magnetic field in the
particle acceleration regions. Determination of brightness temperature and Doppler factors would
allow discriminating between electron-synchrotron and proton-synchrotron sources (item 3).

The science item 4 is limited by the astrometric measurements. For a redshift range of z = 0.01 to
1, the main estimates of cosmological proper motion in reference to the systematic motion of 380
km/s with respect to the CMB are (Kardashev, 1986) 1.4 microarcsec/year to 36 nanoarcsec/year
and 34 to 0.9 nanoarcsec/year, respectively.

Item 5 in the list relates to many narrow double nuclei extragalactic sources. The orbits of most
narrow pairs can be measured by accurate astrometric observations.

There is a class of neutron stars for which the inferred magnetic field is in excess to 1014 Gauss, the
so-called Magnetars. Among these objects, XTE J1810-19, with a spin period of 5.54 s, is the only
one so far that has also been detected in the radio regime (Camilo et al., 2006). The radio spectrum
of this object is inverted, strongly polarized, and has high flux in the cm and mm bands. This
means that it is possible to observe this object at shorter wavelengths reaching the limiting angular
resolution (item 6).

Item 7: Recent observations of gamma-ray bursts afterglows reveal extremely fine structure, an
inverted spectrum and, as a result, there appears to be a very weak dependence of observed flux
with redshift (Kuno et al., 2004; Frail et al., 2006). Observations open up the unique possibility to
observe these objects and verify the existing coalescence models. Observations of the radio
afterglow of GRB 030329 at z=0.1685 (Kuno et al. 2005), shows that the expected flux 3 days
after the explosion is ~70 mJy in the 1 mm and 0.3 mm bands.

The RMS sensitivity limit of the Millimetron-ALMA interferometer, for each polarization, for a
bandwidth of 8 GHz and an integration time of 10 s is 0.9 mJy in the 1 mm band and 5 mJy in
the 0.3 mm band.

Amongst the targets for SVLBI observations are: Sgr A*, M87, BL Lac, 3C 273, 0716+714,
OJ287, 0420-014, CTA102, 0528+134, 0642+449, and use of already published data like for the
gamma ray bursts GRB030329.


U-V coverage and multi-frequency synthesis
In order to improve the u-v coverage the technique of multi-frequency synthesis (MFS) can be
used for continuum sources. Rapid frequency changes in the receiver and create more points in the
u-v plane for the same geometrical baseline. As an example, Figure 5 shows the u-v coverage for
simultaneous observations between Millimetron and ALMA using frequency switching (MFS)
within band 6 of ALMA (source 1334-127, 210-290 GHz, 4 channels, two days of observations).
The Millimetron orbit is perturbed by interactions with the Moon which allows to further improve
the u-v coverage if the same astronomical source is revisited after several months.




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Fig. 5 – u-v coverage of the Millimetron-ALMA interferometer for the source 1334-127 using ALMA band 6
and multi-frequency synthesis (MFS).



4 Millimetron mission profile

Millimetron is designed to provide high sensitivity, high to extremely high angular resolution and
high spectral resolution as well as far-infrared imaging and spectroscopic capabilities. All these
characteristics are essential in achieving the science goals outlined in the previous sections. High
sensitivity and (extremely) high angular resolutions are achieved by using a 12m diameter space
antenna, either in single-dish mode or as element of a space-ground VLBI system. High spectral
resolution is obtained by using heterodyne receivers, and the far-infrared imaging/spectroscopy
will be done by an imaging photometer/spectrometer. In order to achieve good u-v coverage in
VLBI mode, an elliptical orbit is chosen.


4.1 Launcher

Launch services will be provided by Russia as the Millimetron mission is included in the Russian
Federal Space Program. The main requirements are: mission payload mass (including space
platform) 5000 kg into an elliptical orbit; fairing envelope diameter 4100 mm, length 15.83 m. The
Russian “Proton” type launcher in combination with a booster fully satisfies the Millimetron
launcher requirements and is going to be used. The upgraded “Proton” heavy class launch vehicle
is characterized by high power capacity. This type of launcher has been used for more than 30
years with very high reliability. The “Proton” payload fairing has been recently enlarged in order
to double the space available for payloads. The Russian “Navigator” space platform is planned to
be used as basis of the spacecraft (see section 6).
For the “Proton” launcher see http://www.roscosmos.ru/Roket1Show.asp?RoketID=24 .




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4.2 Millimetron orbit

Driven by the requirement of good u-v coverage in VLBI mode, an elliptical orbit with high
apogee and an orbital period around the Earth of about 9.5 days is chosen. This orbit evolves as a
result of weak gravitational perturbations from the Moon and the Sun. The perigee radius varies
from 30.000 to 70.000 km, and the apogee radius from 300.000 to 370.000 km. Table 2 lists the
main orbital parameters. Because of the orbit evolution, about 80% of the VLBI radio sources will
be located on the sky close to the orbit plane projection at some time intervals, i.e. for such radio
                                                                sources both very large and small
            Table 2 - Millimetron orbit parameters.             baseline projections will provide
  Period               T = 9.5 days (7 - 10 days)               the possibility to make good
  Semi-major axis      a = 189 000 km                           images with high and moderate
  Inclination          -51.6o or +51.6o (depends on             angular resolution. The remaining
                       scientific program)                      20% of the sources can be observed
  Orbit evolution      perigee 30,000 to 75,000 km;             only with high angular resolution.
                       apogee 300,000 to 370,000 km;            The possibility of transit to a L2
                       Possible transit to L2 (under study)     orbit is being investigated.



4.3 Millimetron observing modes

Millimetron has two scientific observing modes:
(1) Single-dish submillimeter/far-infrared observations, and
(2) Space-ground VLBI observations (SVLBI) at (sub-) millimeter wavelengths.


Single-dish observing mode

Millimetron observations in single-dish mode do not differ fundamentally from observations with
other space observatories like e.g. ISO or Herschel. The main difference is that space VLBI
observations will take some of the available observing time, however, this amount is limited by the
on-board data storage capacity and the required time for the down-link of the VLBI data (see
Section 7). A demanding requirement is the pointing accuracy which for a 12m antenna operating
at submillimeter and far-infrared wavelengths needs to be better than 1 arcsecond.


Space VLBI observing mode

The space-ground interferometer Millimetron allows having baselines more than twenty times the
Earth diameter. SVLBI observing must be done simultaneously by the space radio telescope and
ground-based radio telescopes. At both locations the received intermediate frequency signal is
digitized and then recorded to a large memory (10TB). The transfer of (scientific and service) data
to the ground tracking station is done by means of synchronization and communication radio links
(1MBps). The scientific data is further processed at the correlation center.
Due to the observing bandwidth (2x8 GHz), limitations in the on-board memory size (10Tbit
foreseen) and the data transfer speed (1 Mbps), a VLBI observing session can last about 5 minutes
before the data have to be down-linked for about 2.8 hours. Thus a total of 40 min VLBI
observations per day are possible. During the data transfer single dish mode observations can be
performed. It is envisaged that Millimetron will be working together with the following ground-
based telescopes:




                                                                                              16/35
•   Atacama Large Millimeter Array (ALMA). Millimetron will carry receivers for four bands
    fully compatible with ALMA. In first contacts between the Astro Space Center and ESO (the
    ALMA Executive in Europe), ESO has expressed interest in this possibility.
•   Suffa radio telescope, a millimeter wave telescope of 70 m diameter which is being built on
    the Suffa plateau in Uzbekistan. It is planned that a dedicated part of telescope time will be
    used for SVLBI with Millimetron.
•   Other telescopes include e.g. Pico Veleta (Spain), Plateau de Bure interferometer (France),
    HHT telescope in the US (Arizona), radio telescopes on Hawaii (USA) as well as the Green
    Bank and Effelsberg 100m diameter telescopes.


4.4 Ground segment requirements

Here we distinguish between the Mission Ground Segment needed for mission operations and
single-dish data transfer, and the VLBI Ground Segment for the VLBI data transfer. The Mission
ground segment needs to provide daily contact with the satellite to exchange telemetry
information, single dish observation data and the observing program. Due to the long orbital
period global coverage will be required. The SVLBI ground segment will be responsible for
SVLBI operations support. The main tasks are:
    • Provide time synchronization signals during SVLBI observations.
    • Receive and record the SVLBI digital data from the satellite. Global coverage is required.
    • Data transfer to the correlation center at the Astro Space Center.
    • Data recording and synchronization at ground telescope locations. The necessary
        equipment will be provided by the Astro Space Center / Russian Space Agency.
With three SVLBI tracking stations in the North (Pushchino near Moscow, provided by ASC),
South (Tidbinbilla in Australia) and West (Green Bank, NRAO,USA) large part of the sky can be
covered. It is proposed that ESA contribute with time on its global tracking stations network to
support SVLBI as well as single dish operations, contributing to the global coverage.


4.5 Special requirements

Special requirements for the Millimetron space mission arise mostly from the VLBI observing
mode. In this mode Millimetron will record data in a large on-board memory and then down-link
the data. Due to the amount of VLBI data a high-speed radio link is required. Preliminary
specifications for this link are: two channels at a data rate of 512 Mbit/s per channel, operation
24h/day. Several ground tracking stations need to be available to cover the spacecraft at any one
time.

Another requirement is the need for cryogenic cooling of the scientific instruments onboard
Millimetron to obtain the best sensitivity (analogous to Herschel). The cooling power of the
cryogenic system is most likely among the most important limiting factors (maybe the most
limiting factor) with respect to the number of scientific instruments on Millimetron.


4.6 Critical issues

A critical issue for a scientifically successful mission is achieving the 10 μm rms accuracy of the
primary dish surface after the deployment of the 12m antenna in space. The deployment itself will
be demonstrated with the 10 m diameter RadioAstron antenna (launch planned for 2008/09) and is
not seen as a high-risk item. However, in order to achieve the required surface accuracy for
Millimetron, an active control system to adjust the (high-precision) petals is needed. Such a system
requires development. We note that JWST will to use deployable, actively controlled mirror


                                                                                             17/35
segments employing wavefront sensing techniques. For the Millimetron mirror operating in
submillimeter wavelength bands, direct position measurement and control of the petals may be
more attractive.

Another important item is the pointing accuracy which needs to be much better than 1 arcsec
because of the small beams of Millimetron. This could be based on the Spitzer Space Telescope
(better than 0.45 arcsec with a stability of ~0.03 arcsec over 600 sec), or an improved Herschel
system.

For the space-ground VLBI mode, phase distortions of the signal traveling through the Earth
atmosphere need to be corrected for. This can be done through monitoring the atmospheric
emission around 183 GHz (an atmospheric water line). The method is used very successfully at
ground-based (sub-) millimeter interferometers and will be used at ALMA as well.

The behavior of the 12m antenna under real operating conditions, i.e. at a physical temperature of
50 K, will have to be investigated. Any approach should include at least three activities: (1)
Accurate thermal and mechanical modeling of the whole telescope assembly, (2) testing of
individual telescope petals (length ~4.5m), and (3) testing of a scaled telescope model in an
environmental chamber. The location of such testing could be part of the ESA-RSA negotiations.


5 Millimetron payload

5.1 Overview

Table 3 gives an overview of all payload elements (with the responsible or proposed partner).

                             Table 3 - Payload elements for Millimetron.
  Payload element       Main characteristics             TRL (as of Jun 07)     Provided by
  Telescope             12m diameter, deployable,        TRL = 6 for            Russian Space
                        passively cooled to ~50K,        deployment             Agency
                        10µm overall accuracy, 2µm       mechanism based on
                        central 3.5m                     RadioAstron mission
  Heat shields          Multi-layer membrane,            TRL = 4 for JWST       ESA (this
                        deployable                       sunshield              proposal)
  VLBI instr.:          Heterodyne front-end             RadioAstron receiver   European
  18-26 GHz                                              has TRL = 6            Instrument
  receiver                                                                      consortium
  VLBI instr.:          Receivers at ALMA bands 1,       Based on ALMA          European
  ALMA bands            3, 6, and 9; with ALMA           development with       Instrument
                        compatible characteristics       TRL = 6                consortium
  Single-dish instr.:   Dual polarization receivers in   557 and 1900 GHz       European
  Submm                 bands around 557 GHz, 1900       based on Herschel-     Instrument
  heterodyne            GHz, and 4700 GHz                HIFI with TRL=6        consortium
  receivers
  Single-dish instr.:   Imaging photometer/              Based on Herschel-     European
  Far-IR                spectrometer covering λ 60-      PACS with TRL = 6      Instrument
  spectrometer          210 µm                                                  consortium
  Closed-cycle          Capable to cool instrument       TRL = 6 for 20 mW      ESA (this
  coolers to 4K         suite, 5yr lifetime              cooling (Planck)       proposal)
  VLBI Mass             ≥ 10 Tbit                        TRL = 8 for 3 Tbit     ESA (this
  memory                                                                        proposal)




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Based on the experience with instruments for Herschel, RadioAstron and ALMA, a first estimate
of the instrument suite requirements (single-dish and SVLBI) on spacecraft resources in given in
Table 4. These first estimates will have to be refined as part of an assessment study. In particular,
the available power for active cooling to 4 K will most likely be the primary limitation for the
number of receiving channels of the instrument suite (with mass, volume and electrical power
being secondary limitations).

               Table 4 - Millimetron instrument interface and resource summary.
  Parameter                      Baseline requirement /          Comments
                                 specification
  Instrument suite mass          < 500 kg total,                 Overall mass of single-dish
                                 distributed over focal plane    and VLBI instrumentation
                                 and service module              including warm electronics
  Instrument suite power         < 1400 W                        Total available power for
                                                                 instrument suite on Navigator
                                                                 spacecraft incl. cooler
  Instrument suite volume        2.7 m3
  Instrument suite cooling       50 mW at 4 K,                   Closed-cycle cryo-cooler to
                                 200 mW at 20 K                  provide instrument cooling,
                                 2 W at 70…100 K                 first rough estimate
                                                                 (requirements to be refined
                                                                 during assessment phase)
  Telemetry                      80 Tbit daily TM                Requires 1 Mbps link
  Pointing                       < 1” required                   Navigator spacecraft to be
                                                                 modified



5.2 The 12m space telescope

Optical and mechanical/thermal parameters, design
The optical design of the telescope is a classical two-mirror Cassegrain type. The main parameters
and a design outline are given in Figure 6 and Table 5. The need for a low physical temperature
telescope requires minimization of the exterior thermal radiation loading driving the telescope
design to a two-mirror system with the secondary mirror “shielded” by the deep main mirror. The
reflective surface of the main mirror is formed by a central solid mirror (3.5m diameter with high
surface accuracy) and outer petals unfolded after launch. It will be made out of C-C or Si-C
(possibly in combination) with metallic (Gold) reflective coating.
Special measures have to be taken to achieve the required telescope surface accuracy. An active
surface control system will be employed including either actuators in the petals’ support structure
or active surface elements in the main optical path and main surface shape measurement system.
The active control system will mainly compensate for inaccuracies in the deployed petals positions
and variations of the overall surface due to temperature changes. This system will ensure that the
requirement for the overall surface accuracy of 10 micron (RMS) will be met for the whole dish
surface. Actuators in the secondary mirror support structure will allow refocusing of the telescope
by mirror displacement. Passive radiation cooling will be used to achieve a telescope physical
temperature of ~50 K.




                                                                                              19/35
                a)                                                     b)

                     Fig. 6 - Millimetron 12m telescope. a) Main distances b) Layout.

                                Table 5 - Main telescope parameters.
Parameter                                                         Value
Main dish diameter                                                12000 mm
Main dish focal length                                            2800 mm
Main dish total surface accuracy (with active control system)     10 micron (RMS)
Main dish central solid part diameter                             3500 mm
Main dish central solid part surface accuracy                     3 micron (RMS)
Petals individual surface accuracy                                5 micron (RMS) (TBC)
Hole diameter in main dish                                        600 mm
Secondary mirror diameter                                         600 mm
Secondary mirror accuracy                                         3 micron (RMS)
Nominal distance from primary focus to secondary focus            4000 mm
Total focal length                                                81550.7 mm
Primary and secondary mirror physical temperature                 ≤ 50 K


Deployment strategy
The main mirror design and deployment strategy is based on the “RadioAstron” project
experience. “RadioAstron” has a 10 meter diameter deployable mirror (Figure 7) which is now
under vibration flight qualification tests and is being readied for launch in 2008. Deployment of
the telescope is made by one drive and is based on a rocker-lever mechanism. Different stages of
the telescope deployment are shown in Figure 8. The launch packaging is shown at the left and the
fully open telescope is shown at the right. The petals will be mechanically joined at the outer edge
of the telescope providing higher accuracy of deployment. The length of the Millimetron petals is
4.3 m and determines the height of the telescope package in the fairing. An active surface control
system will be responsible for the correction of residual errors of the panel positions.




                  Fig. 7 - Different stages of the “RadioAstron” 10m antenna deployment.



                                                                                              20/35
   Fig. 8 - Stages of the Millimetron telescope deployment. Left: launch packaging, right: operational
   telescope.


Heat shielding concept
The telescope surface will be passively cooled to a temperature of ~50K.The basic thermal concept
of the Millimetron telescope is shown in Figure 9. In order to protect the surfaces of the primary
and secondary mirrors from the thermal loading by the Sun, Earth, Moon and spacecraft itself,
deployable multi layer heat screens in the form of cones can be used. The first screen diameter is
30-35m, the second 20-25 m, the third (auxiliary) – 13-15m. The screens could be made of
metallized film similar to Kapton. The first screen has two layers. All film layers have double-
sided metallization. Preliminary thermal modeling indicates the following average temperatures of
the screens: First screen 1 layer – less then 350 K, 2 layer – less than 250 K; Second screen – less
then 150 K; Third screen – less than 50 K. As part of this Cosmic Vision proposal, we propose that
ESA contribute the thermal shields to the Millimetron mission.




             Fig. 9 - Preliminary scheme of thermal screens of the Millimetron observatory.



5.3 Scientific instrumentation

Here we describe a baseline instrumentation plan for the two basic scientific modes of operation
(single-dish and SVLBI). The final instrument suite will depend to a large degree on the available
spacecraft resources with 4K cooling power probably being the most uncertain parameter. An
assessment study needs to refine the instrument technical requirements and evaluate various trade-
off options.

The instrumentation would be built by a European consortium of scientific and technical institutes
similar to the Herschel and ALMA schemes. All the required expertise and experience is readily
available, and many institutions of the present Herschel and ALMA consortia have already
expressed interest to participate.


5.3.1   Single-dish instrumentation

The baseline instrumentation for the single-dish observing mode consists of the two heterodyne
instruments HET-1 and HET-2 and the far-infrared imaging photometer and spectrometer M-
PACS. HET-1, a dual-frequency SIS array, will operate around the astrophysically important
frequencies 557 and 1100 GHz, and HET-2, a three-channel HEB receiver, will cover 1.9, 2.7 and


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4.7 THz (the latter using the central 3.5 m high-precision part of the antenna). M-PACS will be an
adapted copy of Herschel-PACS with improved detectors covering the wavelength regime 60 to
210 µm. The instrument and detector technologies as well as operational modes and calibration
schemes can build heavily on the developments done for Herschel. The technical risk is
accordingly low.

Table 6 lists the key characteristics of the Millimetron science instrumentation for single-dish
observations.

                    Table 6 - Single-dish instrumentation key characteristics.
                          Millimetron Single-dish instrumentation
Instrument Frequency           Ang.     Spectral Detector              Sensitivity         TRL
              (GHz) or         res.     res.        technology
              wavelength       (″)
Heterodyne receivers
HET-1         480 – 700        8…12 ≥ 106           SIS 2x2 mixer      Tsys < 100 K        6
              1100 – 1400      5…6      ≥ 10 6      array with         Tsys < 200 K        6
                                                    multiplier LO
HET-2         1650 – 2000      ~3       ≥ 106       HEB mixers         Tsys < 500 K        6
              2600 – 2700      ~2.5     ≥ 106       with multiplier    Tsys < 700 K        4
              4700 – 4800      4 (1)
                                        ≥ 10 6      or QCL LO          Tsys < 1000 K       4
Far-Infrared imaging photometer/spectrometer
M-PACS        60 – 210 μm      ≥4       few 103     Photoconductor 2 x 10-18 Wm-2          6
                                        spectrom. arrays
Note: (1) Using the central 3.5m dish

HET-1 and HET-2 are heterodyne receivers providing very high spectral resolution (≥ 106) in
combination with a Fast-Fourier-Transform spectrometer (FFTS). The channels up to 2000 GHz
can directly build on the successful developments for Herschel-HIFI, whereas the higher frequency
channels of HET-2 around 2.7 and 4.7 THz, unique to Millimetron, have been demonstrated in the
lab. For HET-1 it is planned to use 2x2 SIS waveguide mixer arrays (Fig. 10) with multiplier chain
local oscillators (LO). This type of technology has been developed for many ground-based
telescopes and Herschel-HIFI. It is interesting to note that multiplier LOs up to 2000 GHz are now
becoming available commercially and at much lower cost than for HIFI. HET-1 will make use of
demonstrated SIS technology using Nb-AlN-Nb tunnel junctions in combination with Nb-SiO2-Nb
on-chip tuning elements as used at all major submillimeter observatories and in Herschel-HIFI.

HET-2 will in principle employ hot electron bolometer mixers (HEBM) as used in HIFI.
However, due to sensitivity and IF bandwidth limitations of HEBM, it is attractive to develop SIS
junction technology up to 2000 GHz by utilizing high energy gap superconducting materials. If
successful, this SIS technology will allow to achieve better sensitivity and IF frequency coverage.
The best technology for the 1650 – 2000 GHz channel of HET-2 can be selected depending on
development result. The 2.7 and 4.7 THz channels will in any case use HEB mixers. Local
oscillators for HET-2 will be multiplier chains and quantum-cascade-lasers (QCL). QCLs have
been used in the lab as THz LO source. Some development is required for the QCL to stabilize its
frequency and reduce the dissipated power at the 30…70 K level.




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                              Fig. 10 - Typical 2x2 array heterodyne scheme

                                 Several developments of HEB mixers and mixer arrays are
                                 underway for frequencies beyond 2 THz. A heterodyne receiver at
                                 2.8 THz using a quasi-optical HEB mixer and QCL local oscillator
                                 has been demonstrated with a noise temperature of 1400 K (DSB)
                                 (Gao et al. 2005). Another interesting development is work carried
                                 out under ESA contract nr. 16940 at Chalmers University
                                 (Sweden), LERMA (Observatoire de Paris) and LAAS (Toulouse)
                                 to build a 4x4 pixel array at 2.5 THz (called SHAHIRA) using
                                 membrane-based HEB mixers. Figure 11 shows a first prototype
 Fig 11 – 4x4 pixel 2.5 THz
                                 of this 16-pixel array ready for device integration.
 HEB mixer array protoype


Heterodyne back-end
The heterodyne receivers will share a Fast Fourier Transform Spectrometer (FFTS) backend
which is a digital spectrometer providing wide instantaneous bandwidth with high spectral
resolution. In the case of a 2x2 pixel receiver (dual polarization) with an IF bandwidth of 4 GHz
each, a total spectrometer bandwidth of 32 GHz is required. Current FFT technology (TRL=6),
field-proven in now almost 2 years of continuous operation at, e.g., the APEX submillimeter
telescope, provides an instantaneous bandwidth of 1 GHz with 8-16 k channels. Under
development at MPIfR (Germany) are single-board FFTs with 1.5 GHz bandwidth /16 k (readiness
mid 2007) and, using the most recent ADC available, 2.5 GHz/8 k channels (spring 2008). With
the latter implementation of a hybrid backend with 3 x 2.5 GHz to combine to a total of ∼7 GHz
(allowing for some overlap) bandwidth is within reach. The enormous increase of ADC bandwidth
during the last years makes it very likely that FFTS can be pushed to instantaneous bandwidths
wider than 3 GHz in the near future, thereby further reducing the complexity of the backend. The
spectral resolution (the number of channels) that can be achieved is basically constrained by the
on-board resources (power dissipation) and the level of complexity that appears acceptable for a
space mission. FPGAs have quite a long space heritage. In any case, digital FFT spectrometers can
provide the back-end capacities required by the Millimetron mission concept. Some development
work will be needed to increase bandwidth, to optimize operation to minimum power dissipation,
to adapt to particular constraints of a space observatory, and to comply with space qualification
requirements.

The Far-infrared photometer and spectrometer M-PACS will be based on the successful
development of the PACS instrument, as built for Herschel which offers photometric and
spectroscopic capabilities in the wavelength band from 60μm − 210μm:
A) Imaging dual-band photometry (60 − 85μm or 85 − 130μm and 130 − 210μm) over a field of
view of 1.75′ × 3.5′, with full sampling of the telescope point spread function.
B) Integral-field line spectroscopy between 57 and 210 μm with a resolution of 175 km/s and an
instantaneous coverage of 1500 km/s, over a field of view of 47′′ × 47′′.
Both modes will allow spatially chopped observations by means of an instrument-internal chopper
mirror with variable throw.


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Fig. 12. Left: Focal plane footprint of PACS. A fixed mirror is used to split the focal plane into the
photometry and spectroscopy channels of the instrument. In the photometry section, the two wavelength
bands are simultaneously imaged with different magnification to reach full beam sampling in both bands. In
the spectroscopy section (right), an optical image slicer re-arranges the 2-dimensional field along the
entrance slit of the grating spectrograph such that, for all spatial elements in the field, spectra are observed
simultaneously. Chopping is along the y axis (left-right in this view) and also allows observation of the
internal calibrators on both sides of the used area in the telescope focal plane.

The focal plane sharing of the PACS instrument modes is shown in Figure 12. The focal plane unit
provides these capabilities through five functional units:
1. Common input optics with the chopper, calibration sources and a focal plane splitter.
2. The photometer optical train with a di-chroic beam splitter and separate re-imaging optics for
    the two short wavelength bands (60 − 85μm / 85 − 130μm) and the long-wavelength band (130
    − 210μm), respectively; band-defining filters on a wheel select one of the two short-
    wavelength bands at a time.
3. The spectrometer optical train with an image slicer unit for integral field spectroscopy, an
    anamorphic collimator, a diffraction grating in Littrow mount with associated actuator and
    position readout, anamorphic re-imaging optics, and a di-chroic beam splitter for separation of
    diffraction orders.
4. Two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, with cryogenic
    buffers/multiplexers and a common 0.3 K sorption cooler, for simultaneously imaging in two
    bands, 60−85μm or 85−130μm and 130−210μm over a field of view of 1.75′ × 3.5′
5. Two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels each, that
    allow to perform imaging line spectroscopy over a field of 50”×50”, resolved into 5×5 pixels,
    with an instantaneous spectral coverage of 1500 km/s and a spectral resolution of 175 km/s,
    with sensitivities (5σ in 1h) of 4 mJy or 3 − 20 × 10-18 W/m2.

Both the heterodyne instruments HET-1/HET-2 and M-PACS need cooling to ~ 4 K from the
spacecraft instrument cooling system (analogue to Herschel). M-PACS will have its own internal
cooler to 0.3 K. For more detailed requirements on cooling see Section “Special requirements”.


5.3.2    Space segment VLBI instrumentation

Overview
Figure 13 describes in general terms what is needed for performing Space VLBI (SVLBI). The
signal from the telescope is received by one of the SVLBI front ends and down converted to an
intermediate frequency (IF) which is filtered and conditioned in the IF processor unit and then
digitized. Currently quantization of two bits over a 4-8 GHz band with dual polarization is
considered which would result in a data rate of 16 Gbit/s. The digital signals are recorded in a data



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storage unit which should have sufficient capacity to hold approx 40 min of SVLBI data (10 TB
capacity). A high-speed down-link transfers the data to the ground.

SVLBI front-ends
The front end instrumentation for the VLBI observing mode will consist of a low frequency (18-26
GHz) front-end very similar to the one which will be flown on the Russian RadioAstron mission in
2008/09. This receiver on Millimetron will greatly improve the u-v plane coverage achieved by
RadioAstron and is required to ensure proper cross calibration. Unique to Millimetron will be the
VLBI receivers at the ALMA frequency bands 1 (31.3-45 GHz), 3 (84-116 GHz), 6 (211-275
GHz) and 9 (600-720 GHz). Table 7 summarizes the key characteristics of the Millimetron VLBI
instrumentation.




                          Fig. 13 Layout of SVLBI instrumentation package

                        Table 7 - VLBI instrumentation key characteristics.
Instrument            VLBI                            Heterodyne receivers
type                 receiver                        covering ALMA bands
Receiver             VLBI-1        ALMA-1           ALMA-3         ALMA-6           ALMA-9
Frequency          18 – 26       31.3 - 45 GHz 84-116 GHz        211-275 GHz      600-720 GHz
range              GHz
Detector           HEMT          SIS mixers,     SIS mixers,     SIS mixers,      SIS mixers,
technology         amplifier     multiplier      multiplier      multiplier       multiplier
                                 chain LO,       chain LO,       chain LO,        chain LO,
                                 dual pol.       dual pol.       dual pol.        dual pol.
Sensitivity Tsys   < 40 K        < 17 K SSB      < 37 SSB        < 90 K SSB       < 150 K DSB
TRL                6             6               6               6                6

The VLBI-1 receiver will be based on previous developments as carried out for many radio
telescopes and the RadioAstron or VSOP missions. The ALMA bands will follow technology
developed within the ALMA project both for sideband separating SIS mixers, IF amplifiers and
LOs. Adaptation of the ALMA technology for space use should not pose much difficulty as it is
conceptually similar to the one used for Herschel (in fact ALMA uses some components that were
developed for HIFI). Special attention will be paid to the polarization response of these
instruments as observing polarization is one of the scientific goals. All ALMA band mixers require
cooling to 4K like the HET-1 and HET-2 instruments.

On board time, frequency standard
There are two possibilities for onboard time synchronization. The first one is a hydrogen frequency
standard developed in Russia which will be flown on the RadioAstron mission. The second one is
an optical frequency standard with a stability of 3 ⋅10−16 in 5 minutes. This optical standard is
under construction at the Lebedev Physical Institute. The package will be delivered by the Russian
Space Agency.



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A/D converter and data storage
The A/D converter technology will be the same as used for the FFTS backends. Adequate IF
bandwidth can be covered by current technology already (ALMA). More weight/energy efficient
solutions are expected to appear in the near future. On board data storage modules of up to several
TBit are available commercially and space qualified from e.g. EADS-Astrium. It is anticipated that
the maximum available capacity will only grow over the years. 10 TBytes would be sufficient for
the mission but expanding on the capacity up to 30…40 TB will benefit the mission. The mass
storage memory is part of the requested contribution from ESA.

Down link
The high speed down link is a crucial part of the SVLBI system. Its speed will define the ground
tracking station load for data transfer. The currently demonstrated radiolink data rate is two
channels of 512 Mbit/s. It will take 22 hours to transmit 10 TBytes to Earth. A development
towards improving data rates by using optical and other means would be of a great benefit for the
Millimetron mission. The high speed data link is part of the requested contribution from ESA.

Telemetry and time synchronization data links can be common for the single dish and the SVLBI
mode as they do not have high requirements concerning the data rate. Current state-of-the-art
satellite communication equipment cold be used (similar to Herschel).


5.3.3   Special requirements
Special requirements for the scientific instruments are:

Instrument cooling to 4 K
The planned minimum mission life time of 5 years calls for a closed-cycle cryo-cooler to 4 K, also
providing cooling to 20 K and 70…100 K levels. The temperatures below 1 K required for the M-
PACS detectors will be generated within the M-PACS instrument (similar to the Herschel PACS
scheme). A preliminary estimate of the required cooling powers for the scientific instrumentation
gives: 40-50 mW at 4 K, 200 mW at 20 K, and 2 W at 70…100 K, with a temperature stability of
5 mK at 4 K, 10 mK at 20 K, and 0.2 K at 70…10 K. These values are first estimates based on the
specifications and experience with Herschel and ALMA instruments and will have to be refined
during the assessment phase. We propose that ESA develop and contribute the cryo-cooler to the
Millimetron mission.

Mass storage memory
The SVLBI observing mode generates large amounts of data which will have to be stored on-board
before down-link. The duration of SVLBI observations depends on the available mass storage
memory and the IF bandwidth of the recorded data. For an IF bandwidth of 2 x 8 GHz (dual
polarization) of an ALMA band and 300 seconds of observations, about 10 Tbit of memory are
needed. ESA’s Sentinel-2 mission will fly 2 Tbit of memory (provided by EADS-Astrium), and
presently modules of 3 Tbit are commercially available. It is anticipated that the rapid
development of memory technology and density will continue, and that within the coming years
(mostly driven by commercial applications) larger amounts of memory for space applications will
become available. We propose that ESA provide the mass storage memory to the Millimetron
mission.


6. Basic spacecraft key factors

The spacecraft platform for the Millimetron mission will be supplied by the Russian Space
Agency. It will largely be based on the general purpose space platform “Navigator” which is built
by the “Lavochkin Association”. The basic layout of the “Navigator” spacecraft is shown in Figure
14. It will provide attitude control, power and control/telemetry communications to the ground


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segment. The scientific payload instruments, telescope and high speed communication link will be
mounted on a mechanical interface provided by the platform. The “Navigator” platform (current
TRL ≥ 4) will be used for the upcoming space missions “Electro” (launch in 2008), “RadioAstron”
(launch in 2008) and other scientific missions. Some of the underlying systems of this platform
have already been flown successfully.

                                      Radiator          Octahedron-
                On-board                                SC structure
              Service system




                                                                        Solar
                                                                       batteries


        Solar panels
        drive




         Correction and
         stabilization
         drives                Tank     Flywheel



   Fig. 14 - Layout of the space platform “Navigator” (left) and the instrument complex of “RadioAstron”
   mounted on the “Navigator” platform in the Proton launcher fairing (right).

The key requirements of the Millimetron mission to the space platform are shown in Table 8 with
an indication where the current “Navigator” platform will be adapted to the Millimetron needs.
There are several parameters which require modification: the available power, payload mass and
pointing/stabilization accuracy need to be increased. The Russian partner is working on these
elements and takes full responsibility for achieving the mentioned improvements.

                      Table 8 - Spacecraft key requirements for Millimetron.
                                   Provided by        Mission              Status
 Parameter
                                   “Navigator”        Requirement
 Domain of possible                                   Sun, Moon, Earth
                                   Any point                               OK
 orientations                                         avoidance pointing
 Speed of re-orientation           0.2-0.3 deg/s                           OK
 Stabilization amplitude           2.5 arc second     Better than 1″       Modification needed
 Stabilization speed               0.0001 deg/s       ---                  OK
 Solar batteries area              17.51 m2           ---                  Modification needed
 Correction pulse accuracy         0.5 deg            ---                  OK
 Platform mass (dry)               650...850 kg       ---                  Modification needed
                                                                           Modification needed
 Maximal fuel mass (hydrazine) 700 kg                 ---
                                                                           (TBC)
 Maximal payload mass              2600 kg            3000 kg              Modification needed
 Maximal payload consumption 1500 W                   2000 W               Modification needed
 Diameter                          3717 mm            Min 3700 mm          OK
 Height                            700 mm             ---                  OK




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7. Science Operations and Archiving

Science Operations
The science operations group, responsible for the scientific output of the mission, determines a
schedule of scientific observations –in general this is a mix of SVLBI and single dish operations–
to be carried out in the next orbit. The scientific priority combined with the sky visibility
constraints give the main guidelines for observations to be carried out. Clearly for SVLBI
observations the availability of the VLBI ground segment is a main driver as well.
After the observations have been carried out and the first level processing is done the observer is
updated on the status of his program.

When needed dedicated calibration and engineering observations are interspersed between science
observations. These extra observations are used to support instrument health monitoring and
calibration studies by instrument specialists.

Satellite Operations
The observatory will have two distinctly different operations modes for SVLBI and single dish
operations. Before observations are carried out all relevant satellite and instrument commands will
be uplinked for execution on board. During the observations data from the instruments as well as
house keeping data will be stored in the on board solid state memory. After the observations the
data in the SSM will be transmitted to ground.

Satellite health and safety
The onboard control computers continuously monitor satellite parameters and autonomously take
pre-determined corrective action for non-nominal conditions.
A second level safety is provided through house keeping telemetry containing measured voltages,
temperatures etc. of the onboard systems that is continuously generated. This telemetry is received
at the ground station and analyzed by the real time monitoring system. Satellite controllers in the
satellite operations centre can adjust the future operations based on this analysis.

VLBI operations
In VLBI mode the satellite and the earth based VLBI stations will be configured and take data at
high speed (up to 16Gbit/sec) for about 5 minutes generating a total of 10Tb of data. After a 5
minute VLBI observation, the satellite data are down linked which will take about 2.8 hours at full
dual channel downlink rate (2 x 512Mbps). During this time the satellite is available for single dish
observations. The downlinked raw telemetry data are stored in a temporary archive until they have
been correlated with the ground stations.

Single dish operation
When not in SVLBI mode, the observatory will take data as single dish observatory. In single dish
mode data taking is carried out following a predefined schedule containing several days’ worth of
observations (interspersed with VLBI observations). Each observation will be self-contained in
that appropriate calibration measurements (internal as well as external) are taken in the context of
the observation. With the available high downlink bandwith the required downlink time is a very
small fraction of the observing time. Thus after a few days of single dish observations a few hours
ground contact is needed to downlink the acquired data and uplink a schedule for the next few
days.

Archiving and data processing
After down linking all data are stored in the central long term Millimetron Science archive. This
archive will be maintained such that data products can be retrieved during the mission and for a
period of at least 10 years after mission end.


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All single dish mode observations are processed using a standard pipeline applying the default
observatory calibration to generate a set of calibrated spectra, ready for further data analysis by the
observers. In this process also quality analysis procedures are used to assess the data and
observation quality. Based on this quality analysis observations may be rejected and scheduled for
re-observation. The pipeline will also generate trend data (e.g. Tsys values) to allow investigation of
the long term behavior of the instruments. These trend data are further analyzed by instrument
specialists to asses the instrument health. The calibrated spectra, quality data and trend data are
also stored in the science archive for later reference.

In VLBI mode the satellite data are correlated with the ground telescope data stream to generate
visibilities. These visibilities are subsequently stored in the long term science archive for retrieval
by astronomers. Based on the calibrated visibilities a set of standard image products will be
generated as well as quality and trend products.

Data access and data rights
Astronomers will have access to the science archive through standard internet web techniques,
allowing them to select observations and download raw data as well as the observatory generated
products for these observations.

For all observation data that are part of an observing program there is a proprietary period of 1
year after the last data in the program have been taken. During this period only the owner of the
proposal is allowed access to the data. After this period the data are accessible to all registered
users of the Millimetron Science Archive.


8. Key technology areas

Table 9 lists the key technology areas. The most critical item appears to be the control of the 12m
dish surface after launch and deployment to achieve the 10 micron surface accuracy. All other key
items are demonstrated at different levels (lab, ground, space, or flight proven).


                          Table 9 – Key technology areas for Millimetron.
Payload element      Technology area                  TRL Comment
Telescope            Telescope petals                 3-4     Russian Space Agency
                     Deployment strategy              6       Based on Russian RadioAstron
                                                              telescope
                     Active surface control           2-4     Development by Astro Space
                                                              Center
                     Heat shields                     4-6     Developed for JWST
Spacecraft           all                              5-6     By “Lavochkin Association”
Scientific           Heterodyne and bolometer         4-6     Spin-off from Herschel
instrumentation      instrument for single-dish
                     operation
                     Heterodyne receivers for VLBI 6          Spin-off from ALMA
                     Cryo-cooler                      4-6     Proposed ESA development
                                                              (TRL 6 for Planck compatible
                                                              cooling power)
                     VLBI mass storage memory         6-7     Available from EADS-Astrium




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9. Preliminary programmatics/Costs

9.1 International collaboration
Millimetron (called “Spectrum-M” when the spacecraft and ground segment are included) is
proposed as a joint mission between the Russian Space Agency and ESA. The scientific
instruments would be provided by a European consortium of institutes with leading expertise and
experience in Herschel instruments as well as ALMA receivers. The instruments would be funded
through national contributions as for Herschel.

The proposed management structure and cost estimate reflects the current situation which is
rapidly evolving. In a recent meeting (27 June 2007) in Moscow, an intergovernmental
commission with representatives of the Russian Space Agency, Astro Space Center, and the China
National Space Administration CNSA have agreed to start negotiations in July 2007 about the
collaboration on scientific space missions including Millimetron. Depending on the outcome of
these negotiations, the proposed mission management structure and cost distribution may change.

9.2 Proposed management structure
The proposed distribution of responsibilities between the Russian Space Agency (RSA), the
Russian Astro Space Center (ASC), the European instrument consortium (coordinated by SRON),
and the proposed contributions from ESA are shown in Figure 15. RSA has the overall
responsibility of the mission including provision of the spacecraft “Navigator” and launch vehicle
and services. ASC is responsible for the 12m space antenna, the scientific payload elements
(which together are called “Millimetron”) and the ground segment. A European instrument
consortium with participation from institutes in ESA countries and Russia is responsible for the
instrumentation payload as described in Section 5. Proposed contributions from ESA are the
provision of the antenna heat shields, the instrument cryo-cooler, the VLBI memory, the scientific
radio link, and participation in the mission ground segment. Table 10 lists the roles of the Russian
Space Agency, the Astro Space Center, ESA (proposed), and SRON.




   Fig. 15 – Spectrum-M (Millimetron) mission product tree with an indication of responsibilities and
   proposed ESA contributions.


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                  Table 10 – Roles of parties in the Millimetron collaboration.
    Party                   Role
    Russian Space Agency - Lead space agency
                            - Financial State representative
                            - Overall budget control in Russia
                            - Satellite platform “Navigator”
                            - Launch vehicle and services
                            - Funding of Astro Space Center Millimetron payload activities
    Astro Space Center      - Russian mission PI
                            - Responsibility and project management for Russian payload
                            contributions
                            - System integration and system project management
                            - Mission ground segment responsibility
                            - VLBI ground segment responsibility
    ESA (proposed)          - Partner Agency and European mission coordinator
                            - Contribution to ground segment and communication link
                            - Contributions to payload
                            - Coordinator of European scientific community
    SRON                    - Coordinate the European scientific instrumentation consortium
                            - Provide European scientific instruments

The proposed management structure foresees three bodies covering the daily management, project
oversight and science. The structure is designed to ensure maximum efficiency by keeping the
Executive Committee (responsible for the daily management) small, provide a forum for all
involved parties to track and steer the project with the Oversight Committee and provide a link to
the science community via the Scientific Committee. In addition to these three committees, there
will be consortium structures in Russia and Europe for their specific contributions.

•   Millimetron Executive Committee (MEC): consists of the Russian project PI, Russian
    Project Manager, European Co-PI, and European Project Manager. Responsible for the
    management of the Millimetron project.

•   Millimetron Oversight Committee (MOC): to provide oversight to the project, both
    technically and management-wise. Consists of the MEC (Millimetron PIs and Project
    Managers) plus representatives from the Russian Space Agency, ESA, Lavochkin Association,
    and SRON.

•   Millimetron Scientific Committee (MSC): to discuss science questions with distinguished
    members from Russia and participating institutes in Europe. Chair and Co-chair are
    determined by committee election and rotating between Russia and Europe.


9.2 Schedule

Figure 16 shows the overall mission schedule for ESA (corresponding to the Cosmic Vision
schedule for a M class mission), the Russian Millimetron project, and the European Instrument
consortium. The mission schedule is mainly driven by the planning of the Russian Space Agency
with a planned launch in 2016 and the ESA Cosmic Vision timetable. Critical technology
development items include the active optics system to achieve the surface accuracy for the 12m
deployable antenna (the deployment mechanism itself is already developed and used in the 10m
RadioAstron antenna), and the cryo-cooler for instrument cooling.




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                              Fig. 16 – Overall Millimetron mission schedule

9.3 Preliminary costing
A rough order of magnitude cost estimate is given in Table 11. The cost of the Russian
contributions cannot be given at this stage due different employed costing systematics and
standards in Russia. Instead, the mission elements provided by the Russian Space Agency and
Astro Space Center are commitments. Cost to ESA is 66 M€, and for the scientific instruments 171
M€ of European national funding are required.

As pointed out in Section 9.1, the outcome of talks between the Russian and Chinese Space
Agencies about collaborations on scientific space mission including Millimetron may impact the
financial and organizational plan.

   Table 11 – Rough order of magnitude estimate of costs. Russian contributions are given as
   commitments and not cost (due to different costing systematics and Russian internal rules).




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10 Communications and Outreach

A space antenna of 12m diameter studying the origins of stars, planets, galaxies and black holes,
will certainly appeal to the general public. In our experience, the statement that “today stars are
still forming” can cause quite some surprise with non-scientists. It is remarkable that outside the
expert circles of professional astronomers and interested laymen, little is known about the general
mechanisms of star and planet formation, its time scales, and the rich chemistry associated with it.
For example, (too) few people know that stars form in clouds of gas and dust, and that in these
clouds more than 100 different types of molecules have been discovered, some of them of organic
nature. Also, the fact that “there is water out there in gas clouds” is often received with
amazement. All this indicates the need for better publicizing some basic facts discovered by
millimeter and (far-) infrared astronomy. In addition, among the astronomical topics receiving
most interest by the general public are black holes – possibly because of their exotic nature.

Millimetron is an excellent opportunity to transmit knowledge on all these themes to a wider
public. Just as it is general knowledge today that the Earth is not at the center of the Universe, and
that the Universe is much larger than our Solar System (two statements which a few centuries ago
were seen as fairly absurd or even heretical), it should become general knowledge that huge gas
clouds, often containing molecules, exist in the Universe, and that new star form in these gas
clouds. The Millimetron mission can be helpful in this.

Apart from the science appeal, an international partnership between Europe and Russia for
building and operating a large space antenna is an opportunity to promote collaboration and
strengthen the relation between two “countries”. With Russia and China now starting talks about
collaboration on scientific space missions including Millimetron, there is the potential to further
enlarge the Russian-European partnership with its associated PR opportunities and possibilities.

As concerns the methods for promoting and disseminating the Millimetron science and
collaboration, we envisage the following activities:
• Press releases related to key events in the project, such as important agreements, hardware
    milestones, launch, and new discoveries
• A publicly accessible web site about the mission itself, the science goals, technology and
    instrumentation etc. in both Russian and English (and possibly other European languages),
• Public events at different occasions (e.g. antenna ready, launch, antenna deployment,
    significant discoveries, etc.) and at various levels (nationally, Europe-wide, bi-lateral Russia-
    Europe),
• Preparation of outreach material for the media and schools.




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11 Institutions contributing to the Millimetron proposal

Institutions in Europe
Centro Astronomico de Yebes, Observatorio Nacional, Spain
Chalmers University of Technology, Sweden
Delft Technical University, the Netherlands
Departamento De Astrofísica Molecular E Infrarroja, CSIC, Madrid, Spain
Eidgenössische Technische Hochschule Zürich, Institut für Astronomie, Switzerland
Istituto di Fisica dello Spazio Interplanetario, INAF, Italy
Leiden Observatory, University of Leiden, the Netherlands
LERMA, Observatoire de Paris, Paris, France
LESIA, Observatoire de Paris, Meudon, France
Max-Planck-Institut für Extraterrestrische Physik, Germany
Max-Planck-Institut für Radioastronomie, Germany
National University of Ireland Maynooth, Ireland
Onsala Space Observatory, Sweden
SRON Netherlands Institute for Space Research, the Netherlands
TKK Helsinki University of Technology, Radio Laboratory, Finland
University of Cologne, KOSMA, Germany
University of Groningen, Kapteyn Astronomical Institute, the Netherlands

Institutions in Russia and Ukraine
Astro Space Center of Lebedev Physical Institute, Russian Academy of Sciences, Russia
Institute of Astronomy, Russian Academy of Sciences, Russia
Institute of Radio Engineering and Electronics, Russia
Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Russia
Lavochkin Association, Russia
Moscow State Pedagogical University, Russia
Space Device Engineering Corporation, Russia
Special Astrophysical Observatory, Russian Academy of Sciences, Russia
State Research Center "Iceberg", Ukraine
Sternberg Astronomical Institute, Moscow University, Russia




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