Planetary Imaging with

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Planetary Imaging with PILOT Jeremy
Bailey Anglo-Australian Observatory March 26th
2004
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Summary

• Advantages of Antarctic Site
• Excellent seeing (diffraction limited using
  selective imaging - dont 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.

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Selective Imaging(Lucky Imaging)
ANU 0.6m Steve Massey
Mercury Mount Wilson 60-inch 7.7 arc sec dia. 27
degrees elevation 18 degrees from Sun In
daylight Ron Dantowitz
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UKIRT Mars Images (2003)
Further image processing (unsharp masking and
smoothing)
Long exposure image (Mauna Kea natural seeing)
Selected best short exposure image
UKIRT/UIST 0.06 arc sec pixels. 1.64mm 1Kx1K InSb
detector windowed to 512x512, 90ms exposure.
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HST / Ground-Based Comparison
UKIRT Sep 4 2003, 1.64mm
HST Aug 24 2003, ACS
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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
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D/r0 at 0.5mm
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D/r0 at 2.0 mm
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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.
• Dont need AO
• Just as well since AO doesnt work on bright
  planets.

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24 Hour Monitoring
When planets are in the South they can be
observed continuously. When they are in the
North they are always below the horizon. The
next few oppositions of Mars are all in the
north. However 2018 will be really good.
Venus - Nov 7 2005 Elevation from Dome C
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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.

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Science

• Venus cloud dynamics
• 2.2-2.4mm imaging of night side.
• 2.0mm imaging of day side (?)
• 0.35mm imaging of day side.
• Compare with Venus GCMs

CASPIR - Sep 2002
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Venus Upper Atmosphere Photochemistry and Dynamics

• Use 1.27mm airglow line.
• Study variability over 24 hours.

CASPIR Sep 2002
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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 cant provide global imaging, local
  time coverage, high time resolution, 24 hour
  monitoring.

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Aug 17 2003
Sep 4th 2003
UKIRT 2.2mm albedo UKIRT CO2
band depth MGS MOLA topography
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Other Planets

• Jupiter, Saturn
• Much easier than Mars or Venus as diameter
  doesnt change much.
• Continuous monitoring to study atmospheric
  dynamics.
• Small objects (Jovian satellites, Titan, Uranus,
  Neptune)
• Visible imaging.

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Instrumentation

• In Visible
• 2K x 2K pixels, 0.03 arc sec, 60 arc sec field
• Short exposures (
• 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.