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Lidars in ESA Earth Observation Missions Paolo Bensi Jean Loup

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Lidars in ESA Earth Observation Missions Paolo Bensi Jean Loup Powered By Docstoc
					Lidars in ESA’s Earth Observation Missions
                   Roland Meynart
 European Space Agency, Directorate of Earth Observation
1. Background – The beginnings of lidars at ESA
2. The mission selection mechanism
3. The missions under development
   1. Aeolus
   2. EarthCARE
4. The candidates
   1.   H2O DIAL (WALES)
   2.   CO2 DIAL (A-SCOPE)




CLRL Conference, SNOWMASS, CO, 9-12 July 2007
                              Background (1)

 Lidar R&D started at ESA in the 2nd half of                             (1989)
  the 80s
 First instrument studies for backscatter
  lidar (ATLID)
     “ simple” single-wavelength (1.06 m, 100 mJ,
      100 Hz), single-pol lidar, but scanning

     Not retained on ENVISAT




                   CLRC Conference, Snowmass, CO, 09-12 July 2007   p.3
                                          Background (2)


 Initial laser developments (flash-lamp pumped)
 Technology pre-development in mid-90s
    Diode-pumped laser (1.06 m)
    Detection (Fabry-Pérot filters, APDs)
 Science and instrument studies
    Removal of scanning, lower power
    Need of synergy with other instruments (à la
       Calipso/Cloudsat)




                 CLRC Conference, Snowmass, CO, 09-12 July 2007   p.4
                                        Background (3)

 Early interest in Doppler Wind lidars early 90s
 Initially coherent DWL at 10.6 m
    Numerous designs of scanning DWL as (large) spacecraft or on
      space station
    Breadboarding on high-energy low-PRF CO2 gas lasers (10 J)
        • Turned out to be impractical and beyond capability of industry




               CLRC Conference, Snowmass, CO, 09-12 July 2007   p.5
                                    The reality check



“Don't undertake a project unless it is manifestly important and
nearly impossible”

                        Edwin Land



“Large increases in cost with questionable increases in
performance can be tolerated only in race horses and fancy
women.“

                         Lord Kelvin




             CLRC Conference, Snowmass, CO, 09-12 July 2007   p.6
                                           Background (4)

 1995-1999: First ideas and studies on incoherent DWL in UV (355 nm)
 Numerous performance studies of coherent and incoherent systems
 Impact studies, OSSEs showed that scanning is not indispensable
 Single and affordable technology base for backscatter and wind lidars
  (Nd:YAG lasers, Receivers)
 Initial lab demonstration of Fizeau interferometer (fringe imaging, Mie) and
  dual-filter Fabry-Pérot (Rayleigh)




                                                  Accumulation CCD
                  CLRC Conference, Snowmass, CO, 09-12 July 2007     p.7
                   The ESA Living Planet Programme (1)


Earth Explorer missions


Objective: Research in Earth Sciences and demonstration of
new EO techniques
       Core, ESA-led: cost cap< 300-400 M€
       Opportunity, fast track missions, < 150 M€

Implementation in the EO Envelope Programme (EOEP)
       1st slice 2000 – 2002,
       2nd slice 2003 – 2007,
       3rd slice 2008-2012, (1250 M€/5 year)




            CLRC Conference, Snowmass, CO, 09-12 July 2007   p.8
                              The ESA Living Planet Programme (2)



                                                        : Evaluation and selection
Call for ideas
                       6x
                                                      : Evaluation,
                 Assessment                         consultation and
                   studies         3x                   selection
                                 Phase A
                                                 1-2x


  Technology demonstration                 Pre-development        Implementation:
                                                                   Phase B/C/D/E


       • Mission selection based on scientific merit
       • Multi-step competitive process
       • Technical feasibility and affordability are also selection
       criteria
       • Large number of candidates under study limits extent of
       technological preparation and ambition
                     CLRC Conference, Snowmass, CO, 09-12 July 2007        p.9
                                         The ESA Earth Explorer Missions


                 2005        2006    2007   2008    2009      2010     2011   2012   2013      2014   2015

              CryoSat                                     CryoSat-2
EXPLORER 1

                                             GOCE
EXPLORER 2

                                                   SMOS
EXPLORER 3

                                                       ADM-Aeolus
EXPLORER 4

                                                           SWARM
EXPLORER 5

                                                                                        EarthCARE
EXPLORER 6


                Call
                             Selection
Call for next release
Explorer
                 Proposals                  Selection for implementation
                                                                                                 EXPLORER 7



                               CLRC Conference, Snowmass, CO, 09-12 July 2007           p.10
                                                                    The 1999 competition




    Atmospheric Dynamics
    Mission (ADM)/Aeolus
                             PBL         Tropo-         Strato-
Requirements                             sphere         sphere

Vertical range [km]          0-2           2-16             16-20
                                                                                          Earth Radiation Mission
Vertical resolution [km]     0.5             1               2
                                                                                          Backscatter lidar (ATLID)
Along     track    profile         200, 50 km integration
                                                                                          Cloud radar
separation [km]                                                                           Multi-spectral imager
Random error [m/s]            1              2                                            Broadband radiometer
Bias error [m/s]                            0.4
                                                                         Transmitter (Nd:YAG laser)    1.06 m
                                                                          - pulse energy                70 mJ
                                                                          - pulse duration              20 ns
                                                                          - repetition rate             35 Hz
                                                                         Receiver
                                                                          - Telescope diameter          70 cm
                             CLRC Conference, Snowmass,                 CO, 09-12 July 2007
                                                                          - iFOV                      p.11 µrad
                                                                                                        365
                                                                          - Rx optical transmission      0.41
               Explorer 4           Aeolus

• Doppler wind lidar @ 355 nm
• Incoherent detection, molecular +
aerosols
• Single LOS, 35 deg roll
• Orbit 400 km, SSO dawn-dusk
• Mass: 1100 kg, 2200 W




                 CLRC Conference, Snowmass, CO, 09-12 July 2007   p.12
                                       The 2004 Competition




 Earth Cloud-Aeorosol-Radiation             WAter Vapour Lidar Experiment in
  Explorer (EarthCARE)                        Space (WALES)

 Re-submission of ERM                       H2O DIAL @ 935 nm




                   CLRC Conference, Snowmass, CO, 09-12 July 2007   p.13
                                      Explorer 5 EarthCARE (1)

 The Earth Radiation Mission (ERM) reincarnated in the
  Earth Cloud-Aerosol-Radiation Explorer (EarthCARE)

              Needs                         Techniques                EarthCARE
                                                                      Instruments
        Vertical profiles of                High spectral
           extinction and                                                ATLID
                                           Resolution Lidar
     characteristics of aerosols

     Vertical profiles of liquid,
     supercooled and ice water,                 Radar
     cloud overlap, particle size
            and extinction                                                CPR
          Convective updraft
                                            Doppler Radar
          and ice fall speed


      Horizontal structure of               Multispectral
       Clouds and aerosols
                                                                          MSI
                                              Imager

      Shortwave and longwave                 Broadband
          fluxes at TOA                                                   BBR
                                             Radiometer

       Temperature and humidity from operational analysis


                     CLRC Conference, Snowmass, CO, 09-12 July 2007        p.14
                          EarthCARE (2)

                             MISSION PARAMETERS
                             Orbit:
                             • Sun-synchronous
                             • Altitude ~ 450 km
                             • Local time ~13:30 ascending
                             node

                             Mass: 1250 kg, Power: 1200 W
                             Launch date: 2013
                             Mission life: 2 years (+1 yr)


                     SPACE SEGMENT
                     Payload:
                     • Backscatter Lidar (ATLID)
                     • Cloud Profiling Radar (CPR)
                     • Multi-Spectral Imager (MSI)
                     • Broad-Band Radiometer (BBR)




CLRC Conference, Snowmass, CO, 09-12 July 2007        p.15
                                                EarthCARE: ATLID (1)

UV Backscatter Lidar with                                                               Mie scattering peak
                                                           Rayleigh scattering       (cloud/aerosols particles)
High Spectral Resolution Receiver                      contribution (molecular)
                                                                                        High Resolution Filter
      Mie scattering co-polar channel
      Mie scattering cross-polar channel
                                                                                                      Wavelength
      Rayleigh scattering channel

         Detect the return from the thinnest radiatively significant cirrus cloud (extinction
        coeff: < 0.04 km-1) in daytime above dense cloud deck
                                                    Mie co-polar          Rayleigh       Mie cross-
                                                      channel             channel           polar
                                                                                          channel
           Cirrus       Cirrus optical depth                                  0.04

                        Backscatter sr-1 m     -1              8 x 10   -7              2.6 x 10     -5


           Vertical resolution                         100 m                 300 m          100 m

           Required accuracy @ 10 km                   48 %                  15 %           45 %
           integration

         Altitude range: -0.5 to 40 km
         Horizontal sampling interval: < 100 m
         Vertical sampling interval: 100 m below 20 km altitude, 500 m above


                        CLRC Conference, Snowmass, CO, 09-12 July 2007                       p.16
                                                                                                              EarthCARE: ATLID (2)
                 1                                                                                                                  HSR Concept
                0.9                                                    HSR etalon transmission

                0.8                                                    Signal at HSR etalon input
                                                                                                                Transmitter (Nd:Yag)
                0.7                                                                                                Pulse Energy @ 355 nm            20 … 25 mJ
                                                                                                                  Pulse Repetition Frequency        70 … 100 Hz
transmittance




                0.6

                0.5                                                                                               Duty Cycle                           100 %
                0.4                                                                                               Spectral line width                 50 MHz
                0.3                                                                                             Receiver
                0.2                                                                                                Telescope diameter                 ~ 0.6 m
                0.1                                                                                               HSR etalon filter (FWHM)         0.22 … 0.5 pm
                 0                                                                                                Detector                             PMT,
                      -8        -6    -4    -2           0         2           4              6           8                                        L3CCD,ACCD
                                            relative frequency (GHz)

                                                                                   Rayleigh channel
                                                                                   Mie channel




                 -8        -6        -4    -2          0           2       4              6           8
                                            relative frequency (GHz)




                                                           CLRC Conference, Snowmass, CO, 09-12 July 2007                                         p.17
                                                        WALES (1)

                                        PBL         Low      Tropo-   High Tropo-   Low Strato-
                                                    sphere            sphere        sphere
      Vertical domain                   0-2 km      0-5 km            5-10 km       10-16 km
      Vertical resolution                                1 km                       2 km
      Horizontal resolution             25 km       100 km            150 km        200 km
      Random error                                              < 20 %
      Bias                                                       <5%


 H2O DIAL @935nm
 Direct self-calibrated water vapour profile measurement
    Understanding and modelling of water vapour physical and
     chemical processes from simulations based on observations,
     notably near the tropopause.
    Methodologies to deduce climate trends, through intercalibration
     of passive remote sensing techniques.
    First reliable climatology at high latitudes using high
     temporal/spatial coverage .


                            CLRC Conference, Snowmass, CO, 09-12 July 2007                 p.18
                                          WALES (2)

Observation technique
4 wavelengths to cover dynamic/
altitude ranges




               CLRC Conference, Snowmass, CO, 09-12 July 2007   p.19
                                                WALES (3)


 450 km altitude, dawn-dusk
 1.5 ton, 3kW+solar arrays (instrument: 1.5
  kW)
 1.75-2 m single- or multiple-aperture
  telescope
 4 wavelengths (3 on, one off) near 935 nm
  to optimise vertical coverage from 2 lasers
  (75 mJ at 25 Hz each wavelength)
 Each laser made of one double-frequency
  Nd:YAG laser, pumping alternatively 2
  Ti:Sapphire seeded by stabilised injection
  lasers. Redundancy: 2 out of 3
 Receivers: Fabry-Pérot filters
 Technology chosen for performance and
  availability

 Larger and more complex than Aeolus



                    CLRC Conference, Snowmass, CO, 09-12 July 2007   p.20
              The new competition round (1)




CLRC Conference, Snowmass, CO, 09-12 July 2007   p.21
                                            The new competition round (2)

                                                                   TRAQ
                                                Objective: to monitor air quality and long-
                                                range transport of air pollutants.
                                                Spectrometers/sounders from UV to TIR



                    BIOMASS
Objective: global measurements of forest biomass,
P-band (432-438 MHz) SAR


              Core H20
Objective: snow, ice and water cycle
X- and Ku-band SAR




                                                                                     PREMIER
                          FLEX                                 Objective: understand processes linking trace gases,
Objective: global photosynthesis through the measurement       radiation, chemistry and climate
of fluorescence.                                               Sub-mm wave + IR limb sounders
Fraunhofer and Atmospheric Lines Imaging Spectrometer
                          CLRC Conference, Snowmass, CO, 09-12 July 2007                      p.22
                                      The 6th candidate: ASCOPE


Advanced Space Carbon and Climate Observation of Planet Earth

Objective: improve understanding of the global carbon cycle and regional
  carbon dioxide fluxes.

   Measurement of spatio-temporal variations and gradients in total-
   column CO2 to 1 ppm accuracy over 50 horizontal integration


          Instrument Type        Nadir viewing pulsed CO2 DIAL,

          Random error           1.5-0.5 ppm [CO2 column-averaged dry air
                                 mixing ratio]
          Systematic error     10% of random error

          Coverage             Global with 50 km sampling scale
          Ranging capability     < 1 – 8 m for the lowest 250 m
                                 < 0.1 – 1 m for the lowest 100 m ( for
                                 canopy height vertical distribution)


                     CLRC Conference, Snowmass, CO, 09-12 July 2007         p.23
                 ASCOPE (2)




 Pulsed CO2 DIAL at 1. 6 or 2 m (2 wavelengths);
 Detection of hard-target returns (integrated path
  differential absorption)
    Same principle as OCO or GOSAT, but with an artificial source !
    Use of fiber lasers or OPO/OPA laser pumped by Nd/Yb-YAG
      laser
    Average instrument power in the 300 W range
    Range to surface provided by instrument
    but atmospheric pressure to be provided by models at 1hPa
      accuracy
    High laser spectral purity required
 Cloud imager to provide contextual information (see EarthCARE)



                CLRC Conference, Snowmass, CO, 09-12 July 2007   p.24
                                      Operational lidars ?

 Successor of EPS/METOP planned for 2019
 Backscatter Lidar, DWL and H2O DIAL are
  part of the post-EPS “missions”
 But lidars are not compatible with platforms
  flying at 800 km, need of free flyer (back to
  the nineties!)
 To avoid data gap, post-EPS could be
  anticipated with a constellation of Aeolus
  satellites (phasing, backward looking)




                                                       Is it affordable?

                 CLRC Conference, Snowmass, CO, 09-12 July 2007   p.25
Thank you for your attention

      Please visit us @
        www.esa.int

				
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