Conditions for high-resolution bistatic radar observations of Apophis in 2029

On 2029 April 13, asteroid Apophis will pass within six times of the Earth's radius (similar to 31000km above the surface) in the closest approach of this asteroid in recorded history. This event provides unique scientific opportunities to study the asteroid, its orbit, and surface characteristics at an exceptionally close distance. In this paper, we perform a novel synthetic geometrical, geographical, and temporal analysis of the conditions under which the asteroid can be observed from the Earth with a particular emphasis on the conditions and scientific opportunities for bistatic radar observations, the most feasible radar technique applicable during such a close approach. For this purpose, we compile a list of present and future radio observatories or radio facilities around the globe, which could participate in bistatic radar observation campaigns during the close approach of Apophis. We estimate signal-to-noise ratios, apparent sky rotation, surface coverage, and other observing conditions. We find that a global collaboration of observatories across Australia, Africa, Europe, and America will produce high-resolution delay-Doppler radar images with signal-to-noise ratios above 10(8), while covering similar to 85 percent of the asteroid surface. Moreover, if properly coordinated, the extreme approach of the asteroid might allow for radio amateur detection of the signals sent by large radio observatories, and citizen science projects could then be organized. We also find that for visual observations, the Canary Islands will offer the best observing conditions during the closest approach, both for professionals as well as for amateurs. The apparent size of Apophis will be 2-3 times larger than typically seeing, allowing for resolved images of the surface.

Automated summary

On April 13, 2029, asteroid Apophis will pass by the Earth at a distance of about 31,000 kilometers, providing unique scientific opportunities for studying its characteristics. This paper analyzes the conditions for observing the asteroid from Earth, focusing on bistatic radar observations. By compiling a list of radio observatories around the world, the study estimates the observing conditions and concludes that a global collaboration can produce high-resolution radar images. It also suggests the potential for amateur radio enthusiasts to detect signals and citizen science projects. For visual observations, the Canary Islands are recommended for professionals and amateurs due to the apparent size of the asteroid.