GBT21A-392

Radar Observations of NEA 99942 Apophis During the 2021 Apparition

Abstract

Apophis has an absolute magnitude of 19.7 and is one of the most important NEAs due to its extremely close approach within 6 Earth radii in 2029. An approach this close by an object this large is estimated to be once-in-a-millennium event. With Arecibo no longer available, Goldstone and Green Bank bistatic radar observations are the only opportunity for radar imaging of Apophis prior to 2029. Due to the loss of Arecibo, we missed the GBT 2021A regular proposal deadline that would cover observations in March. As such, our only option to obtain radar images of Apophis is to apply for Director's Discretionary Time. We request 12 tracks totaling 49 hours between 2021 March 3 - 14. Goldstone-GBT observations will increase the SNRs by about a factor of two relative to those obtained at Goldstone in 2013, when we obtained coarse-resolution images. We expect to obtain delay-Doppler images with a resolution as fine as 37.5 m/pixel. No other observational technique, optical or thermal, can reveal the level of detail that radar can. Our plan is to refine Apophis' shape, size, spin, and the Yarkovsky acceleration. This is important for assessments of the future impact probabilities that are predicted for 2060-2105.

Investigators

Name	Institution
Michael Busch	SETI Institute
Marina Brozovic *	Jet Propulsion Laboratory
Lance Benner	Jet Propulsion Laboratory
Shantanu Naidu	Jet Propulsion Laboratory
Jon Giorgini	Jet Propulsion Laboratory

* indicates the PI