NTRS - NASA Technical Reports Server

Back to Results
Radar observations of Comet HalleyFive nights of Arecibo radar observations of Comet Halley are reported which reveal a feature in the overall average spectrum which, though weak, seems consistent with being an echo from the comet. The large radar cross section and large bandwidth of the feature suggest that the echo is predominantly from large grains which have been ejected from the nucleus. Extrapolation of the dust particle size distribution to large grain sizes gives a sufficient number of grains to account for the echo. The lack of a detectable echo from the nucleus, combined with estimates of its size and rotation rate from spacecraft encounters and other data, indicate that the nucleus has a surface of relatively high porosity.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Campbell, D. B. (National Astronomy and Ionosphere Center Ithaca, NY, United States)
Harmon, J. K. (National Astronomy and Ionosphere Center Arecibo, PR, United States)
Shapiro, I. I. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
March 15, 1989
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 338
ISSN: 0004-637X
Subject Category
Distribution Limits