Cassini RADAR Observations of Phoebe

Astronomy and Astrophysics – Astronomy

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

Scientific paper

The Cassini RADAR instrument, operating in its scatterometry mode, obtained continuous-wave (cw) echo power spectra from Phoebe during the inbound and outbound legs of the flyby, 4 h before and 2.5 h after closest approach. Phoebe's distance and subradar coordinates were approximately (93,000 km, 247 deg W, 26 deg S) inbound and (56,000 km, 323 deg W, 26 deg N) outbound. The durations of the cw sequences were 6 and 5 minutes. Larger intervals in the RADAR windows were devoted to observations with a chirp waveform able to provide range as well as Doppler resolution, and to passive radiometry; those data are not yet reduced.
For Phoebe (and Dione, Mimas, Iapetus, Enceladus, Rhea, Hyperion, and Tethys), scatterometry aims to use estimates of radar albedo and angular scattering law to constrain the near-surface bulk density and/or the relative cleanliness of the icy regolith. The RADAR instrument's wavelength is 2.2 cm, vs. 3.5 cm or 13 cm for most groundbased radar astronomy, but Arecibo and Goldstone observations of the icy Galilean satellites and of asteroids give us no reason to expect significant wavelength dependence in this regime. Comparison of RADAR measurements of Titan and Iapetus with groundbased results will let us evaluate this expectation and will be key to calibrating both our measurements and their interpretation.
Our inbound and outbound Phoebe echoes indicate Lambertian scattering, which requires structural complexity at scales no smaller than a centimeter. However, despite Phoebe's prominent large-scale topography, our spectra are nearly featureless, suggesting that the radar roughness is sub-topographic. We probably are seeing a combination of single scattering and multiple scattering from surface and subsurface structure. At this writing, our calibration indicates that Phoebe's average radar albedo is much closer to that of Iapetus than to those of the icy Galilean satellites.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

Cassini RADAR Observations of Phoebe does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Cassini RADAR Observations of Phoebe, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cassini RADAR Observations of Phoebe will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-1012416

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.