On Monday, SpaceX is slated to do its very first national security mission for the US military — sending a spy satellite into orbit for the National Reconnaissance Office. Dubbed NROL-76, the secretive payload is scheduled to go up on the company’s Falcon 9 rocket early Monday morning from Kennedy Space Center in Cape Canaveral, Florida. After launch, SpaceX will attempt to land the Falcon 9’s first stage — the 14-story high core of the rocket that contains the main engines and most of the fuel — on solid ground back at the Cape.

Just like with other NRO launches, we don’t really know much about this satellite’s final destination or what the probe will do when it gets there. And typically, broadcasts of NRO missions are cut a bit short to hide the true purpose of the satellite and where it’s going. That means we probably won’t get as many shots of the rocket and satellite in space as we normally do when SpaceX does commercial launches. However, we should still get plenty of images of the first stage as it makes its descent to Earth. This will be the fourth time that SpaceX tries to land a Falcon 9 on the company’s Florida landing site.

We don’t really know much about this satellite’s final destination or what the probe will do

This launch comes off the heels of SpaceX’s historic launch a few weeks ago, in which the company flew one of its landed Falcon 9 boosters for the first time. That launch successfully put a satellite into orbit for the Luxembourg-based company SES. SpaceX was also able to retrieve the first stage by landing it on a drone ship in the Atlantic Ocean. The Falcon 9 launching the NROL-76 mission will be using a brand new first stage, however, and it’s not clear when SpaceX will by flying a used booster again.

But this launch is still unique since it marks one of the few NRO missions in the last decade that hasn’t been done by the United Launch Alliance. ULA, a partnership between Boeing and Lockheed Martin, has basically had a monopoly on military launches for the last decade. However, SpaceX received certification in 2015 to launch military satellites after going through two years of reviews with the US Air Force. The idea was to create competition between military launch providers — a move that could potentially lower the costs of government missions. And since receiving its certification, SpaceX has won two contracts from the Air Force that have been publicly put up for bid.

However, the NRO seems to have set up this launch with SpaceX at some unknown time in the past couple years. The NRO announced in May 2016 that it had tapped SpaceX to launch NROL-76 and that it’s possible that more NRO missions could be launched by SpaceX in the future, according to Space News.

While we don’t know a lot about the purpose of Monday’s launch, we do have the signature NRO patch that goes along with the mission. NRO launches have always been accompanied by a wild mission patch, typically depicting some massive animal conquering the Earth or a mystical being like a sorceress or dark knight. The NROL-76 patch deviates from that theme a bit, showcasing Lewis and Clark, both looking very stern, as they prepare to embark on their expedition westward. Specifically, the NRO says the two explorers on the patch are about “to discover and explore the newly purchased Louisiana Territory and report back to the National Command Authority (President Jefferson).” Perhaps that’s some kind of hint about the mission.

Monday’s launch is scheduled to get off the ground at 7:15AM ET, though the rocket can takeoff up until 9AM ET. The launch was originally scheduled for Sunday at the same time, but the mission was scrubbed due to an issue with one of the sensors on the Falcon 9 first stage. But weather is looking mostly good for a launch tomorrow; there’s a 70 percent chance that conditions will be favorable, according to Patrick Military Air Force. SpaceX’s coverage of the launch begins 20 minutes before liftoff, so check back then to watch the mission live.

Update 7:20AM ET, April 30th: Sunday morning, SpaceX stopped the launch of its Falcon 9 less than a minute before take off, citing an issue with one of the sensors on the first stage. The company will try to launch vehicle again tomorrow around 7AM ET.