SpaceX will make another attempt to launch its Falcon 9 rocket this evening at 6:05PM ET. If it's able to get off the ground, Elon Musk's bold vision to make the Falcon 9 "reusable" by landing them safely will be put to the test for the second time.

After the Falcon 9 makes it into space, it will release the Deep Space Climate Observatory (DSCOVR) satellite and return to Earth to land on a 300-by-100-foot barge off the coast of Florida. DSCOVR, meanwhile, will head for what's known as "Lagrange point 1," or "L1." L1 is a stable point between the gravities of Earth and the Sun about a million miles away, or four times further than the Moon. It will observe the Earth from that distance for 110 days and pay close attention to solar winds, which are capable of disrupting power grids, aviation, and GPS.

This particular launch has already been delayed twice. The original launch attempt was pushed from Sunday to Monday because of transmitter problems and a failure in the Air Force's tracking radar, and Monday's launch was postponed due to weather.

The Falcon 9 is not the only SpaceX spacecraft that the company is hoping to safely land today. A Dragon cargo capsule is scheduled return to Earth this evening after being successfully released from the International Space Station this afternoon. It will splash down off the coast of Baja, California, and SpaceX will retrieve it by boat.

SpaceX's first attempt to land on the barge failed last month when the rocket's wings ran out of hydraulic fluid. This time around it will encounter twice the amount of force and four times the heat on reentry, according to Musk. If the launch is aborted, SpaceX has another launch window scheduled for tomorrow at 6:03PM ET. You can watch the launch above, on NASA TV.

Update 05:55PM ET: SpaceX has postponed the launch and rescheduled it for tomorrow evening.