Space Rock Round-up

When we think of observing asteroids, the first things that come to mind, for me at least, are telescopic observations of small moving dots in the sky and space missions taking the iconic images, like those we have seen of objects like Bennu, Eros, and Ida with little Dactyl. It’s easy to forget that powerful radar facilities are able to obtain cool 3D shape models of passing space rocks.

A collection of high resolution asteroid images acquired by NASA, ESA, and JAXA spacecraft. Asteroids are all shown to the same scale.

Since 1968, NASA Deep Space Network has used the Goldstone facility to both communicate with distant spacecraft and to radar-image nearby asteroids. We are lucky that small asteroids don’t get super close to Earth all that frequently, and large asteroids very rarely get anywhere near us. This means that it can be days between targets, and it has taken 53 years for Goldstone to rack up its 1000th rock.

This animation shows asteroid 2016 AJ193 rotate as it was observed by Goldstone’s 70-meter (230 foot) antenna on Aug. 22, 2021. Three-quarters of a mile (1.3-kilometers) wide, the object was the 1,001st near-Earth asteroid to be measured by planetary radar since 1968. Credit: NASA/JPL-Caltech

That 1000th rock, currently designated 2021PJ1, was observed Aug 14. It was just 65–100 feet wide, and passed at a distance of over 1 million miles or more than 4 lunar distances away. Such a small rock at such a large distance didn’t allow for particularly interesting radar returns to be acquired, so I am actually showing you Aug 22 radar returns of asteroid 2016 AJ193, which was twice far away, but also a whooping 40 times larger…