NASA's CYGNSS mission, an initiative to send eight small satellites into space on a Pegasus XL rocket, is slated for another takeoff this morning. The launch was originally set for Monday but was scrubbed because of a faulty hydraulic pump, with a second attempt on Wednesday cancelled due to software issues. This morning, NASA will try again, with a scheduled launch time window of 08:35AM ET (originally 08:26AM ET). You should (hopefully) be able to watch the launch in the live stream above.
The satellites being launched are meant to study various aspects of tropical storms and hurricanes from orbit, helping scientists better understand how these cyclones form. But unlike regular satellite launches, these won't be shot into space on top of a rocket taking off vertically from a launch pad on the ground. Instead, the launch will take place in the air.
That's because the Pegasus XL rocket, made by Orbital ATK, launches after being dropped from the underside of an airplane. First, Orbital’s Stargazer L-1011 aircraft will take off from Cape Canaveral, Florida and carry the rocket to a target drop zone over the Atlantic Ocean, an area that sits at an altitude of 39,000 feet. There, the Pegasus is released and ignites its main rocket motor about five seconds later. The vehicle will then ignite two additional motors over the course of the flight to get to the right altitude and orientation for the eight spacecraft to deploy properly into lower Earth orbit.
Once that happens, the spacecraft depart in twos. Opposing pairs of CYGNSS probes will separate every 30 seconds from the deployment module — a tube-like structure that the satellites are connected to throughout launch. The module is also responsible for helping to "kick" the spacecraft out into orbit. About 10 minutes after one satellite deploys, it will automatically open up its solar arrays to get energy from the Sun. Overall, the entire trip — from the launch of the rocket to the last spacecraft deployment — will take about 14 and a half minutes.
NASA will then make contact with the satellites about three hours after they’ve deployed, and that’s when the real work begins. From orbit, the CYGNSS satellites will be studying the ocean surface winds within the inner cores of hurricanes — important indicators of how intense a storm can get. To do this, the probes will receive reflected signals from GPS satellites, which will allow the CYGNSS team to "see" through the parts of hurricanes where it’s raining and measure the surface winds in those areas. It’s something that most Earth science missions aren’t able to do, according to NASA. These measurements will help scientists better predict how strong a hurricane or storm is going to be when it makes landfall.
CYGNSS was originally slated to launch on Monday, but that attempt had to be aborted due to a hydraulic pump that failed to work properly. A second launch on Wednesday was also scrubbed because of "an issue with flight parameter data." NASA said uploading the new flight data was "a very routine procedure" and expected it to correct the issue. Fingers crossed CYGNSS will finally get off the ground today.
Update, December 12th, 14th: Updated each day for revised launch times and cancelled launches.
Update, December 15th, 06:00AM ET: Updated to include Thursday's launch times. 06:30AM ET: Updated again for revised launch times.