The first radar images of Saturn's rings.

Details The first radar images of Saturn's rings. The first radar images of Saturn's rings.

May 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000dda....31.0803n&link_type=abstract

American Astronomical Society, DDA Meeting #31, #08.03; Bulletin of the American Astronomical Society, Vol. 32, p.864

Astronomy and Astrophysics

Astronomy

Scientific paper

In October 1999 we obtained the first radar images of Saturn's rings, using the recently-upgraded Arecibo telescope operating at a wavelength of 12.6 cm. The opening angle of the rings was 19.9o, and dual-circular polarization data were collected over a period of 5 days. The resulting delay-Doppler maps have a range resolution of 100 msec and a frequency resolution of 2 kHz, corresponding to a spatial resolution cell of 15000 x 2000 km. Previous radar observations (e.g., Ostro et al. [1982] Icarus 49, 367) demonstrated the rings' high cross section and depolarization ratio, but did not yield 2-dimensional images. The most striking feature of the new maps is a very pronounced azimuthal asymmetry in the brightness of the A Ring, reminiscent of that seen in some ground-based and Voyager images, and more recently documented in HST images (see French et al., this meeting). In both circular polarizations, the rings are brighter on the far quadrant on the receding (western) ansa and on the near quadrant of the approaching (eastern) ansa. The asymmetry averages 25%, but appears to be greater on the eastern ansa. The azimuthal asymmetry is generally ascribed to small-scale trailing wakes generated by local gravitational instabilities in the rings, and as such may be expected to be more pronounced among the meter-sized particles which dominate the radar cross-section than for the cm-sized and smaller particles which contribute significantly to the rings' visible reflectivity. We have attempted to isolate the source of asymmetry by generating synthetic delay-Doppler images of the individual ring components and subtracting these piecewise from the Arecibo images. These models show that the azimuthal asymmetry is indeed concentrated in the A Ring, where it is at least twice as strong as that seen in nearly simultaneous HST images at 439 nm. The models also suggest a smaller asymmetry in the B Ring, with the same phase as that in the A Ring. Also noteworthy is the apparent absence of any detectable echo from the C Ring. At the 3σ level, we can set an upper limit of 0.06 on the ratio of its cross-section to that of the B Ring, which may be compared to a reflectivity ratio of 0.2 at optical wavelengths and low phase angles.

Affiliated with

Also associated with

No associations

Rating

The first radar images of Saturn's rings. 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 The first radar images of Saturn's rings., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The first radar images of Saturn's rings. will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1128724