The InSight Mars lander might not be as flashy as a rover that gets to drive all around the planet, but it’s an important instrument in our quest to understand the red planet. After launching earlier this year, InSight is nearing its destination. It should touch down on Mars within less than one week, and NASA has detailed how it’ll monitor the landing from 91 million miles away on Earth.
Mars is several light-minutes away, so it’s impossible to directly control the descent of InSight. As the probe begins its automated landing procedure, it will send a signal back to Earth. These “tones” will act as a tracking signal that NASA can monitor on Earth using radio telescopes. The agency will use two facilities to listen for the tones: the National Science Foundation’s Green Bank Observatory and the Max Planck Institute for Radio Astronomy’s telescope. All that data will end up back at NASA JPL mission control in Denver.
The tones don’t carry any diagnostic information or data transmissions. However, engineers can extrapolate from the frequency of the signal when important events occur during landing. For example, the frequency’s Doppler shift will indicate when InSight begins its descent and when the parachute opens.
You might recall that InSight is not alone on this journey. Two small CubeSats launched along with it, and they’re currently drifting in space behind the lander. These are technology demonstration probes, but they’ll also be able to relay data to Earth from InSight.
When InSight lands, the ton beacon will modulate to indicate a successful arrival. Several minutes later, the probe will send a powerful X-band signal from its main antenna to make sure NASA knows it’s safely down. This ping will include basic status information, but NASA will need to wait several hours to find out if the solar panels deployed correctly.
MASA’s Mars Reconnaissance Orbiter (MRO) will also be watching as InSight makes its way down. It will hold onto that data at first as it passes behind the planet. On its next orbit a few hours later, it will beam back its recording of events. MRO will also be one of the main relays for sending mission data back. Even NASA’s aging Odyssey orbiter will get in on the fun, joining MRO in transmitting InSight’s data back to Earth.
NASA expects InSight to reach the surface on November 26th. It should start running tests to learn about the internal structure of Mars shortly thereafter.