GBT02A-016

Bistatic Radar Imaging of Slowly Rotating Asteroid 1999 GU3

Abstract

This proposal requests time for bistatic radar imaging of near-Earth asteroid 1999 GU3 during its approach within 0.082 AU of Earth in April, 2002. 1999 GU3 is among the smallest known very slow rotators. Very slow rotation is a hallmark of non-principal axis (NPA) rotation, the origin of which is not well understood. Time to observe 1999 GU3 has already been requested from April 20 - 28 at Goldstone and from April 6/7 - 16/17 at Arecibo. Arecibo->GBT bistatic time (4 days) will permit much finer frequency resolution than is possible from Arecibo monostatic observations because we will have the option of integrating for much longer than the round-trip time and applying longer Fast-Fourier Transforms. The signal-to-noise ratios (SNRs) in this bistatic configuration will be strong and should permit 7.5-m delay-Doppler imaging and three-dimensional shape reconstruction. Goldstone->GBT bistatic time (4 days) will double the SNRs and permit commensurably finer resolution of X-band images over those that will be obtainable monostatically at Goldstone and increase the SNRs by nearly an order of magnitude relative to those obtainable with the Goldstone DSS-14 (70 m)->DSS-13 (34 m) bistatic system. We are requesting time for these observations on dates when the asteroid is too far north to observe at Arecibo. The Goldstone->GBT observations will increase sky motion coverage significantly, which experience has shown is the critical factor for shape reconstruction and spin vector estimation with NPA rotators.

Front Ends

Gregorian S(1.73 to 2.6 GHz)
Gregorian X(8.2 to 10.0 GHz)

Back Ends

User supplied or new backend

Type of Observing

Point Source
Continuum
Circular Polarization

Switching Type

Created: Fri May 31 15:39:28 Eastern Daylight Time 2002