Update May 5th, 8:35AM ET: United Launch Alliance successfully launched its InSight lander this morning from Vandenberg Air Force Base in California, which will now head off to Mars to conduct its mission when it arrives in November 2018.

NASA’s next robotic explorer is beginning its deep-space voyage to Mars. The lander InSight is set to take off from Vandenberg Air Force Base in California in the wee hours of Saturday morning, the beginning of a six and a half month journey to the Red Planet. Once there, the little spacecraft will listen for quakes to figure out what Mars is made of.

NASA has a long history of launching to Mars, but this trip to the Red Planet is a bit different: It’s the first interplanetary mission to take off from the West Coast. All of NASA’s previous deep-space explorers have launched from Florida, where rockets fly eastward over the Atlantic and get an extra boost of speed from the rotation of the Earth. However, InSight is pretty small; the Atlas V it’s riding on is powerful enough to fly south over the Pacific and still get the spacecraft where it needs to go.

this trip to the Red Planet is a bit different

While getting InSight into space is the main point of the mission, there are also two smaller spacecraft along for this ride. Two satellites, each about the size of a cereal box, are attached to the top of the Atlas V rocket. They’re CubeSats — standardized small satellites that many researchers and companies modify to collect data in space. Most CubeSats only make it out to low Earth orbit, but InSight’s CubeSats are the first ones to go into deep space.

Once the rocket deploys InSight, the satellites — MarCO-A and MarCO-B — will break away, too, and follow the lander all the way to Mars. The twin spacecraft will then serve as a small communications-relay network for InSight when it lands on Mars in November. The MarCO satellites will attempt to send information about the landing to NASA’s Mars Reconnaissance Orbiter, which is circling the Red Planet right now. And then the orbiter will send that information back to Earth.

The satellites aren’t crucial to the InSight mission. NASA just wants to see if these tiny probes can collect and send data so far from Earth. “It’s a demonstration for these CubeSat technologies that have never seen deep space before,” Joel Steinkraus, MarCO lead mechanical engineer at NASA’s Jet Propulsion Laboratory, tells The Verge. “We don’t have a good understanding of how they would perform.”

The Atlas V is slated to take off at 7:05AM ET

InSight’s launch is an early one for anyone in the US. The Atlas V is slated to take off at 7:05AM ET, or 4:05AM for those watching the launch from the West Coast. And there’s worry the weather won’t cooperate: So far, there’s a 20 percent chance that the weather will be good for take off, with fog near Vandenberg being the main concern. Fog might also be a problem on Sunday, the next backup date. The 30th Space Wing, which oversees missions from Vandenberg, says it’s possible that ULA can launch through the fog, but the rocket itself will be hard to see.

If the launch is scrapped, there is still plenty of time to get InSight off the ground. NASA has the option to launch 35 times from May 5th through June 8th. So the odds are good that ULA will find a good time to get InSight into space. NASA’s live coverage of the mission will begin at 6:30AM ET on Saturday, so check back then for updates.