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 Steve Massey Mercury 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 (Mauna Kea natural seeing) Selected best short exposure image Further image processing (unsharp masking and smoothing) UKIRT/UIST 0.06 arc sec pixels  m 1Kx1K InSb detector windowed to 512x512, 90ms exposure.

HST / Ground- Based Comparison HST Aug , ACS UKIRT Sep , 1.64  m

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 ( (D/r o ) 2 ) Fried, 1978 JOSA 68, 1651 Where D is telescope aperture and r 0 is the Fried parameter D/r 0 D/r 0 = 8 1 in 3800 D/r 0 D/r 0 = 7 1 in 367 D/r 0 D/r 0 = 6 1 in 50 D/r 0 D/r 0 = 5 1 in 9 D/r 0 D/r 0 = 4 1 in 2

D/r 0 at 0.5  m

D/r 0 at 2.0  m

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

24 Hour Monitoring Venus - Nov Elevation from Dome C 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.

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 –  m imaging of night side. –2.0  m imaging of day side (?) –0.35  m imaging of day side. Compare with Venus GCMs CASPIR - Sep 2002

Venus Upper Atmosphere Photochemistry and Dynamics Use 1.27  m airglow line. Study variability over 24 hours. CASPIR Sep 2002

Mars Imaging in 2  m CO 2 band. –Measures surface atmospheric pressure - key input required for Mars GCMs. –Study thermal tides, midlatitude instabilites. Imaging in CO 2 ice absorption bands. –Polar cap structure and seasonal changes. Imaging in H 2 O ice band (3  m) –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.

UKIRT 2.2  m albedo UKIRT CO 2 band depth MGS MOLA topography Aug Sep 4th 2003

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.