Radar observations of comet 103P/Hartley 2

John K. Harmon, Michael C. Nolan, Ellen S. Howell, Jon D. Giorgini, Patrick A. Taylor

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


Comets rarely come close enough to be studied intensively with Earth-based radar. The most recent such occurrence was when Comet 103P/Hartley 2 passed within 0.12 AU in late 2010 October, less than two weeks before the EPOXI flyby. This offered a unique opportunity to improve pre-encounter trajectory knowledge and obtain complementary physical data for a spacecraft-targeted comet. 103P/Hartley 2 is only the fourth comet nucleus to be imaged with radar and already the second to be identified as an elongated, bilobate object based on its delay-Doppler signature. The images show the dominant spin mode to be a rotation about the short axis with a period of 18.2hr. The nucleus has a low radar albedo consistent with a surface density of 0.5-1.0gcm-3. A separate echo component was detected from large (>cm) grains ejected anisotropically with velocities of several to tens of meters per second. Radar shows that, in terms of large-grain production, 103P/Hartley 2 is an unusually active comet for its size.

Original languageEnglish (US)
Article numberL2
JournalAstrophysical Journal Letters
Issue number1 PART 2
StatePublished - Jun 10 2011
Externally publishedYes


  • comets: general
  • comets: individual (103P/Hartley 2)
  • techniques: radar astronomy

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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