Asteroid Radar Opportunities with the Upgraded Arecibo Telescope

The following table outlines what can be done with the Arecibo radar as a function of signal-to-noise ratio (SNR), before and after the upgrade that is now approaching completion, and also after a dedicated optical search for near-Earth asteroids, as in the proposed Spaceguard Survey.

SNR, which increases as the square root of the number of dates, is comparable to the number of pixels that images can place on a target.

Click here for plots of predictions of single-date SNR as a function of asteroid size, distance, and declination, for Arecibo and Goldstone.

These calculations assume a radar cross section equal to 10% of the target cross section, a four-hour rotation period, a diffuse scattering law, and an equatorial view. SNR equals the received power of an optimally filtered echo in units of the r.m.s. receiver noise fluctuation.

Average Number of Objects per Year with Single-Date SNR Greater than
20 100 1000 5000
Main-Belt Asteroids
Before upgrade 0.5 0.0 0.0 0.0
After upgrade 35 5 0 0
Near-Earth Asteroids
Before upgrade, using actual statistics since 1980 3 0.9 0.3 0.1
After upgrade, with current NEA pool 10 6 2 0.6
After Spaceguard Survey (lower bounds):
1 km or larger 80 20 10 4
300 m or larger 160 80 20 7
Science Expectation
disc-integrated properties: |--->
~30-parameter shape model: |-->
identify binary system: |--->
~100-parameter shape model: |--->
see craters clearly: |--->

Author: Steven J. Ostro

Asteroid Radar Research