Can Green Bank Telescope Defend Against Asteroid Apophis?

This image is taken from an animation showing the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach. The blue dots are the many man-made satellites that orbit our planet, and the pink represents the International Space Station. Credit: NASA/JPL-Caltech

The National Science Foundation’s Green Bank Telescope (GBT) is teaming up with NASA’s Goldstone Deep Space Communications Complex (GDSCC) to observe this potentially hazardous asteroid. These new observations of Apophis will allow scientists to improve their understanding of the asteroid’s orbit, and better estimate the odds that Apophis could strike the Earth in the future. Predicting if there is a real chance of impact, decades ahead of time, gives scientists the opportunity to take action to manipulate the orbit of Apophis to avoid a collision in the future.

The asteroid Apophis, named after the Egyptian god of chaos, first came to scientists attention in 2004. As it orbits the sun, its trajectory comes very near to earth. Observations March 3rd-14th are using the GBT and GDSCC to carefully study the asteroid on its current pass. 

Apophis, at 340-meters wide, is just under 3 ½ times the size of the GBT’s 100-meter dish.

According to NASA, after reviewing previous data scientists predict that in 2029 Apophis will pass about 19,800 miles from Earth. “While that’s a safe distance, it’s close enough that the asteroid will come between Earth and our Moon,” NASA states, “It’s also within the distance that some spacecraft orbit Earth.”

“An approach this close by an object this large is estimated to be once-in-a millennium event,” stated Marina Brozovic of NASA’s Jet Propulsion Laboratory (JPL) in her application to use the GBT for this project, to gather as much data as possible in advance of the 2029 pass.

Apophis is being observed on this latest fly by using bistatic radar. A telescope at the GDSCC transmits signals to bounce off of the asteroid as it passed by earth. The GBT receives these signals, gathering valuable data to send back to NASA.

Data analyst Amber Bonsall, who was just in the GBT control room two weeks ago for NASA’s Mars Perseverance rover landing, will conduct these observations for 10 evenings. Amber will point the GBT at Apophis and manage the software that collects and processes the radar signal in real time. These observations last from 3-8 hours, from approximately 7 p.m. to 3 a.m. EDT. 

It does not need to be dark for radio telescopes to work – radar signals can be observed anytime day or night. This timing coincides with the availability of the GBT and GDSCC. The GBT is one of the largest fully steerable radio telescopes in the world, with a packed schedule operating 24-hours a day. You can see what the GBT is observing in real time, observations are shared on the Green Bank Observatory Twitter as they begin. You can also see a schedule here. 

The next closest pass of Apophis will come April 13, 2029.

Learn more about Apophis from NASA here.

Learn more about NASA’s GDSCC here. GDSCC is a part of NASA’s Deep Space Network, which is managed by JPL.

To learn more about Green Bank Observatory Observatory science and to see research opportunities visit our website. 

The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.


Contacts: Jill Malusky, Green Bank Observatory Public Relations,