Radar observations of E-class Asteroids 44 Nysa and 434 Hungaria

Michael K. Shepard, Karelyn M. Kressler, Beth Ellen Clark, Maureen E. Ockert-Bell, Michael C. Nolan, Ellen S. Howell, Christopher Magri, Jon D. Giorgini, Lance A.M. Benner, Steven J. Ostro

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15 Scopus citations


We observed the E-class main-belt Asteroids (MBAs) 44 Nysa and 434 Hungaria with Arecibo Observatory's S-band (12.6 cm) radar. Both asteroids exhibit polarization ratios higher than those measured for any other MBA: Nysa, μc = 0.50 ± 0.02 and Hungaria, μc = 0.8 ± 0.1. This is consistent with the high polarization ratios measured for every E-class near-Earth asteroid (NEA) observed by Benner et al. [Benner, L.A.M., and 10 collegues, 2008. Icarus, submitted for publication] and suggests a common cause. Our estimates of radar albedo are 0.19 ± 0.06 for Nysa and 0.22 ± 0.06 for Hungaria. These values are higher than those of most MBAs and, when combined with their high polarization ratios, suggest that the surface bulk density of both asteroids is high. We model Nysa as an ellipsoid of dimension 113 × 67 × 65 km (± 15 %) giving an effective diameter Deff = 79 ± 10 km, consistent with previous estimates. The echo waveforms are not consistent with a contact binary as suggested by Kaasalainen et al. [Kaasalainen, M., Torppa, J., Piironen, J., 2002. Astron. Astrophys. 383, L19-L22]. We place a constraint on Hungaria's maximum diameter, Dmax ≥ 11 km consistent with previous size estimates.

Original languageEnglish (US)
Pages (from-to)220-225
Number of pages6
Issue number1
StatePublished - May 2008
Externally publishedYes


  • Asteroids
  • Radar observations
  • composition
  • surfaces

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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