Observing planets with PILOT School of Physics at UNSW Sydney by mikesanye

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									Planetary Imaging with
        PILOT
      Jeremy Bailey
    Anglo-Australian Observatory


     March 26th 2004
                     Summary
• Advantages of Antarctic Site
   – Excellent seeing (diffraction limited using selective
     imaging - don’t need AO).
   – 24 hour continuous observations possible.
   – Low daylight sky brightness.
• Disadvantage
   – Can only observe planets when they are in the south.
• Science
   – Studies of atmospheric circulation - provides input to
     General Circulation Models (GCMs) of planetary
     atmospheres.
       Selective Imaging
       (Lucky Imaging)




                       ANU 0.6m
Mercury                Steve Massey
Mount Wilson 60-inch
7.7 arc sec dia.
27 degrees elevation
18 degrees from Sun
In daylight
Ron Dantowitz
         UKIRT Mars Images (2003)




Long exposure image     Selected best short   Further image processing
(Mauna Kea natural      exposure image        (unsharp masking and
seeing)                                       smoothing)



UKIRT/UIST 0.06 arc sec pixels. 1.64mm 1Kx1K
InSb detector windowed to 512x512, 90ms exposure.
 HST / Ground-
Based Comparison


                       UKIRT Sep 4
                       2003, 1.64mm




                   HST Aug 24
                   2003, ACS
      Selective Imaging - Theory
Probability of a short exposure having phase variations
less than 1 radian (and hence diffraction limited with Strehl >
0.37).

P = 5.6 exp (-0.1557 (D/ro)2)        Fried, 1978 JOSA 68, 1651

Where D is telescope aperture and r0 is the Fried parameter

D/r0 = 8         1 in 3800
D/r0 = 7         1 in 367
D/r0 = 6         1 in 50
D/r0 = 5         1 in 9
D/r0 = 4         1 in 2
                                  D/r0 at 0.5mm
                0.5 mm

                                                          Aperture (metres)
Seeing at 0.5mm          r0 (m)    0.25     0.5       1          2        4        8       16       32
       3                  0.03     7.42   14.84   29.68      59.36   118.73   237.46   474.92   949.84
      2.5                 0.04     6.18   12.37   24.74      49.47    98.94   197.88   395.77   791.53
       2                  0.05     4.95    9.89   19.79      39.58    79.15   158.31   316.61   633.23
      1.5                 0.07     3.71    7.42   14.84      29.68    59.36   118.73   237.46   474.92
      1.2                 0.08     2.97    5.94   11.87      23.75    47.49    94.98   189.97   379.94
       1                  0.10     2.47    4.95    9.89      19.79    39.58    79.15   158.31   316.61
      0.8                 0.13     1.98    3.96    7.92      15.83    31.66    63.32   126.65   253.29
     0.65                 0.16     1.61    3.22    6.43      12.86    25.72    51.45   102.90   205.80
      0.5                 0.20     1.24    2.47    4.95       9.89    19.79    39.58    79.15   158.31
      0.4                 0.25     0.99    1.98    3.96       7.92    15.83    31.66    63.32   126.65
      0.3                 0.34     0.74    1.48    2.97       5.94    11.87    23.75    47.49    94.98
     0.25                 0.40     0.62    1.24    2.47       4.95     9.89    19.79    39.58    79.15
      0.2                 0.51     0.49    0.99    1.98       3.96     7.92    15.83    31.66    63.32
     0.15                 0.67     0.37    0.74    1.48       2.97     5.94    11.87    23.75    47.49
      0.1                 1.01     0.25    0.49    0.99       1.98     3.96     7.92    15.83    31.66

Resolution (arc sec)               0.50    0.25    0.13       0.06    0.03
                                D/r0 at 2.0 mm
               2 mm

                                                         Aperture (metres)
Seeing at 0.5mm        r0 (m)    0.25      0.5       1          2        4       8      16       32
       3                0.18     1.41     2.81    5.62      11.25    22.50   44.99   89.98   179.96
      2.5               0.21     1.17     2.34    4.69       9.37    18.75   37.49   74.98   149.97
       2                0.27     0.94     1.87    3.75       7.50    15.00   29.99   59.99   119.97
      1.5               0.36     0.70     1.41    2.81       5.62    11.25   22.50   44.99    89.98
      1.2               0.44     0.56     1.12    2.25       4.50     9.00   18.00   35.99    71.98
       1                0.53     0.47     0.94    1.87       3.75     7.50   15.00   29.99    59.99
      0.8               0.67     0.37     0.75    1.50       3.00     6.00   12.00   23.99    47.99
     0.65               0.82     0.30     0.61    1.22       2.44     4.87    9.75   19.50    38.99
      0.5               1.07     0.23     0.47    0.94       1.87     3.75    7.50   15.00    29.99
      0.4               1.33     0.19     0.37    0.75       1.50     3.00    6.00   12.00    23.99
      0.3               1.78     0.14     0.28    0.56       1.12     2.25    4.50    9.00    18.00
     0.25               2.13     0.12     0.23    0.47       0.94     1.87    3.75    7.50    15.00
      0.2               2.67     0.09     0.19    0.37       0.75     1.50    3.00    6.00    12.00
     0.15               3.56     0.07     0.14    0.28       0.56     1.12    2.25    4.50     9.00
      0.1               5.33     0.05     0.09    0.19       0.37     0.75    1.50    3.00     6.00

Resolution (arc sec)             2.013   1.007   0.503      0.252   0.126    0.063   0.031    0.016
     Diffraction limited imaging

• Diffraction limited planetary imaging with PILOT
  should be possible most of the time in the IR.
   – 0.25 arc sec at 2mm, 0.13 arc sec at 1mm.
• And in the best seeing in the visible as well.
   – 0.06 arc sec at 0.5mm.
   – Comparable with HST.
• Don’t need AO
   – Just as well since AO doesn’t work on bright planets.
               24 Hour Monitoring

When planets are in the
South they can be
observed continuously.                           45

                                                 40

                                                 35




                           Elevation (degrees)
When they are in the                             30

                                                 25
North they are always                            20

below the horizon.                               15

                                                 10

                                                 5
The next few oppositions                         0
                                                      0   5   10       15       20   25   30
of Mars are all in the                                             UT (Hours)

north. However 2018 will
                            Venus - Nov 7 2005 Elevation from Dome C
be really good.
  Daylight (Summer) Observing
• Venus can only be observed in daylight.
• It is bright enough in IR for this to be quite
  feasible.
  – IR Daylight sky background is probably low
    due to low aerosol levels.
                    Science
• Venus cloud dynamics
  – 2.2-2.4mm imaging of
    night side.               CASPIR - Sep 2002

  – 2.0mm imaging of day
    side (?)
  – 0.35mm imaging of day
    side.
• Compare with Venus
  GCMs
       Venus Upper Atmosphere
     Photochemistry and Dynamics
• Use 1.27mm
  airglow line.
                            CASPIR Sep 2002
• Study variability
  over 24 hours.
                          Mars
• Imaging in 2mm CO2 band.
   – Measures surface atmospheric pressure - key input
     required for Mars GCMs.
   – Study thermal tides, midlatitude instabilites.
• Imaging in CO2 ice absorption bands.
   – Polar cap structure and seasonal changes.
• Imaging in H2O ice band (3mm)
   – Water ice clouds, water ice in the polar cap.
• Imaging water vapour distribution?

• Spacecraft can’t provide global imaging, local
  time coverage, high time resolution, 24 hour
  monitoring.
Aug 17 2003




Sep 4th 2003




    UKIRT 2.2mm albedo   UKIRT CO2 band depth   MGS MOLA topography
              Other Planets

• Jupiter, Saturn
  – Much easier than Mars or Venus as diameter
    doesn’t change much.
  – Continuous monitoring to study atmospheric
    dynamics.
• Small objects (Jovian satellites, Titan,
  Uranus, Neptune)
  – Visible imaging.
               Instrumentation
• In Visible
  – 2K x 2K pixels, 0.03 arc sec, 60 arc sec field
  – Short exposures (<10ms)
  – Fast frame rates
• In IR
  – 512 x 512 pixels, 0.1 arc sec, 50 arc sec field
  – Short exposures, fast frame rate.
• Commercially available cameras may be
  suitable.

								
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