  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 X 2.2 km X 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 hours. 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 degrees, 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.
