36th DPS Meeting, 8-12 November 2004
Session 4 Phoebe and Iapetus
Oral, Monday, November 8, 2004, 1:30-3:00pm, Lewis

[Previous] | [Session 4] | [Next]

[4.06] Cassini CIRS Observations of Phoebe's Long Wavelength Thermal Emission

J. C. Pearl (NASA Goddard), J. Spencer (Southwest Research Institute), M. Segura (NASA Goddard), CIRS Team

The Cassini Composite Infrared Spectrometer (CIRS) has three focal planes that together cover the thermal spectrum from 10 to 1500 cm-1 (1 mm to 7 micrometers). Focal plane 1 (FP1) covers 10 to 600 cm-1 with a circular field of view of 3.9 milliradians diameter; focal plane 3 (FP3) covers 600 to 1100 cm-1 with a linear array of 10 pixels, each 0.3 milliradians square. Spectral resolution is selectable from 0.5 to 15.5 cm-1 (apodized). During the Cassini flyby of Phoebe, numerous observations were obtained. Preliminary results from the 600-1100 cm-1 data are reported by J. Spencer, et al. (this meeting). Here we report initial results from the 10-600 cm-1 data.

Observations were concentrated at low to midlatitudes, with spatial resolution as high as 9 km near closest approach. At 50 cm-1 (200 micrometers) brightness temperatures varied from 68K in predawn locations, to 101K near the subsolar point. However, strong spectral gradients were apparent in all spectra, with brightness temperatures at 400 cm-1 (25 micrometers) in the above instances varying from 76K to 111K. No strong emissivity variations are present. Consequently, these spectral characteristics are due to a combination of unresolved thermal inertia and slope (shadowing) variations. These effects will be discussed.

[Previous] | [Session 4] | [Next]

Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.