This afternoon, NASA will attempt to land its latest spacecraft — a vehicle called InSight that will sit on the planet’s surface and listen for quakes over the next two years — on Mars. But first, it must survive a harrowing descent to the ground. NASA plans to use multiple spacecraft around Mars to confirm that InSight lands intact.

Once the lander hits the top of Mars’ atmosphere, it will perform a complicated multistep landing routine that will last between six and seven minutes. During the first phase, InSight will free-fall through the atmosphere using a heat shield for protection as the surrounding air slams into the spacecraft, heating it up to temperatures of 2,700 degrees Fahrenheit. The atmosphere will slow the lander significantly, but InSight will need to deploy a supersonic parachute to slow even further. Eventually, the lander will ignite onboard thrusters, which will lower the vehicle to the ground.

it will be a matter of hours until we know if the spacecraft is healthy and ready to start its mission

All of these steps need to happen at just the right time to enable InSight to touch down gently on the surface. If it works, the lander will slow from a speed of more than 12,000 miles per hour to just about 5 miles per hour before it hits the surface. If all goes well, we should have early confirmation of the landing right away, but it will be a matter of hours until we know if the spacecraft is fully healthy and ready to start its mission.

During the descent, InSight will send out data about each major step of its landing process using one of its less powerful onboard antennas. Scientists will try to pick up these signals from Earth, but two nearby spacecraft will also be listening in. Those two probes are the MarCO spacecraft, which launched with InSight in May and have been traveling to Mars ever since. The MarCO probes are made from a type of standardized satellite known as a Cube Sat, which consists of 10-centimeter cubes that can be stacked together. Cube Sats have become crucial tools for gathering data in orbit around Earth, but the MarCO satellites are the first to ever be sent into deep space.

The MarCO satellites have been traveling on their own to Mars, separate from InSight, but they should reach the planet right as the landing occurs. They’ll come within 2,175 miles of the planet, and when they do, they’ll attempt to collect the ultra high frequency (UHF) signals that InSight sends out about its landing. The MarCO pair will then decipher all that data and send the information back to Earth. That could provide NASA with a real-time rundown of how the InSight landing is going. And they might even be able to transmit an image of InSight once it’s on the ground.

Technically, the MarCO probes are considered experimental, so they may not work exactly as NASA hopes. If they aren’t able to decipher the data that InSight sends out during landing, NASA’s knowledge of the event will be a little less reliable at first. Antennas on Earth can still pick up the signals that InSight sends out, but without interpretation by the MarCO probes, they won’t tell scientists very much.

“We have the UHF signals that are coming straight to Earth, but they carry no information because it’s too long of a distance to actually be able to decipher any information out of that,” Tom Hoffman, the project manager for InSight at NASA’s Jet Propulsion Laboratory, tells The Verge. At most, NASA will be able to use those signals to determine if InSight experiences a big change in speed, such as when the parachute is deployed. But that’s about it.

The MarCO probes won’t be the only spacecraft observing the landing, though. NASA’s Mars Reconnaissance Orbiter, which has been in orbit around Mars since 2006, will also gather all the data from the landing from overhead. But unlike the MarCO probes, MRO won’t send back that information in real time. It will store the data it receives as the spacecraft falls beyond the horizon, cutting off its view from Earth. Once MRO comes back around Mars — about three hours later — it will then send all of the data it collected back to our planet.

“We’re going to be really happy when we hear that.”

Once InSight is on the ground, it will send a quick signal saying it’s okay, and then it will switch on a much more powerful antenna. About seven minutes after landing, that antenna will send out a big signal to Earth, confirming that InSight made it down in one piece. “We’re going to be really happy when we hear that,” says Hoffman.

But the InSight team won’t be fully celebrating at that moment. After landing, there will still be one last big step for InSight to perform: unfurling its solar panels. These circular arrays are crucial for powering the lander while it’s on Mars, and if they don’t deploy properly, InSight cannot fulfill its mission. Unfortunately, NASA scientists will have to wait a few hours before getting confirmation that the solar panels have been deployed. Shortly after InSight lands, the spacecraft will move out of view from Earth, and it won’t be able to send signals directly to our planet for a while. Luckily, Mars Odyssey, another spacecraft that’s been orbiting Mars since 2001, will pass overhead to see if the panels have been deployed. It will relay that crucial information to Earth about five and a half hours after landing.

“Frankly, I’m not going to be completely relaxed until we know for sure that we have the solar arrays deployed,” says Hoffman.

InSight’s landing is scheduled to take place just before 3PM ET. However, NASA won’t receive word of the landing until eight minutes after it actually happens. Thanks to the current distance between Earth and Mars, one signal of light takes eight minutes and seven seconds to travel between the two planets. But if all goes according to plan, NASA should receive that extra strong signal from InSight post-landing around 3:01PM ET.

NASA plans to provide live coverage of the landing starting at 2PM ET. Check back to see if the space agency pulls off another successful Martian touchdown.