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We report Doppler-only (cw) and delay-Doppler radar observations of Bacchus obtained at Goldstone at a transmitter frequency of 8510 MHz (3.5 cm) on 1996 March 22, 24, and 29. Weighted, optimally filtered sums of cw and delay-Doppler echoes achieve signal-to-noise ratios of ∼80 and ∼25, respectively, and cover about 180° of rotation phase (period=14.90 h; Pravec et al. 1998). Our cw observations place...
We report initial results of daily delay/Doppler observations of Toutatis with the Goldstone 8510-MHz (3.5-cm) radar during Nov. 25–Dec. 3, 1996. Using the physical model of Toutatis derived from 1992 radar observations (Hudson and Ostro 1995,Science270, 84–86) to analyze the new data, we obtain refined estimates of the asteroid's orbit, spin state, and surface properties. The asteroid's centimeter-to-decameter...
Optical lightcurves reported by J. R. Spenceret al.(1995,Icarus117, 71–89) and a radar-derived shape and spin-state model (R. S. Hudson and S. J. Ostro, 1995,Science270, 84–86) are used to estimate the Hapke parameters of the Earth-crossing Asteroid 4179 Toutatis. We find a particle single-scattering albedow= 0.261 ± 0.019, opposition surge widthh= 0.036 ± 0.023 and amplitudeB 0 = 1.20 ± 0...
We use new analysis techniques to constrain the shape of 433 Eros with Goldstone radar data obtained during the asteroid's close approach in 1975. A previous analysis of these data (Ostro, Rosema, and Jurgens, 1990,Icarus84,334–351) used estimates of the echo's spectral edge frequencies as a function of asteroid rotation phase to constrain the convex envelope of Eros' pole-on silhouette. Our approach...
A 167-parameter, 3-D shape model of the Earth-crossing asteroid Castalia, obtained from inversion of delay-Doppler images (Hudson and Ostro, 1994,Science263,940–943) constrained the object's pole to lie on a cone of half angle 55 ± 10° centered on the radar line of sight (right ascension 0.3 hr, declination 25.4°) at the time of observations (Aug. 22, 1989) but could not constrain the pole's azimuthal...
Asteroids 1 Ceres, 2 Pallas, and 4 Vesta were observed with the 13-cm Arecibo radar and the 3.5-cm Goldstone radar during several apparitions between 1981 and 1995. These observations help to characterize the objects' surface properties. Echoes from Ceres and Pallas are ∼95% polarized (μ C = σ SC /σ OC ≈ 0.05) in the sense expected for specular (mirror) reflection yet broadly...
Goldstone radar observations of Geographos from August 28 through September 2, 1994 yield over 400 delay-Doppler images whose linear spatial resolutions range from ∼75 to ∼151 m, and 138 pairs of dual-polarization (OC, SC) spectra with one-dimensional resolution of 103 m. Each data type provides thorough rotational coverage. The images contain an intrinsic north/south ambiguity, but the equatorial...
We report 13-cm wavelength radar observations of the mainbelt asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda obtained at Arecibo between 1980 and 1989. The echoes are highly polarized yet broadly distributed in Doppler frequency, indicating that our targets are smooth on decimeter scales but very rough on some scale(s) larger than about 1 m. The echo spectra are generally consistent...