Radar imaging and physical characterization of near-Earth Asteroid (162421) 2000 ET70

Shantanu P. Naidu, Jean Luc Margot, Michael W. Busch, Patrick A. Taylor, Michael C. Nolan, Marina Brozovic, Lance A.M. Benner, Jon D. Giorgini, Christopher Magri

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


We observed near-Earth Asteroid (162421) 2000 ET70 using the Arecibo and Goldstone radar systems over a period of 12. days during its close approach to the Earth in February 2012. We obtained continuous wave spectra and range-Doppler images with range resolutions as fine as 15. m. Inversion of the radar images yields a detailed shape model with an effective spatial resolution of 100. m. The asteroid has overall dimensions of 2.6. km. ×. 2.2. km. ×. 2.1. km (5% uncertainties) and a surface rich with kilometer-scale ridges and concavities. This size, combined with absolute magnitude measurements, implies an extremely low albedo (~2%). It is a principal axis rotator and spins in a retrograde manner with a sidereal spin period of 8.96. ±. 0.01. h. In terms of gravitational slopes evaluated at scales of 100. m, the surface seems mostly relaxed with over 99% of the surface having slopes less than 30°, but there are some outcrops at the north pole that may have steeper slopes. Our precise measurements of the range and velocity of the asteroid, combined with optical astrometry, enables reliable trajectory predictions for this potentially hazardous asteroid in the interval 460-2813.

Original languageEnglish (US)
Pages (from-to)323-335
Number of pages13
Issue number1
StatePublished - Sep 2013
Externally publishedYes


  • Asteroids
  • Near-Earth objects
  • Orbit determination
  • Radar observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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