Amid a salvo of orbital missions preparing to launch from the American east coast, a SpaceX Falcon 9 is set to launch the fourth GPS III satellite for the United States Space Force. Liftoff is scheduled for 9:43 PM EDT on Friday, October 2 (01:43 UTC on October 3), the opening of a 15 minute window.
(Lead photo via Stephen Marr for NSF)
The 45th Weather Squadron of the United States Air Force’s 45th Space Wing at Patrick Air Force Base in Florida predicts a 70% chance of acceptable weather for launch. The forecast deteriorates to a 20% chance of favorable weather for the backup launch opportunity on Saturday evening.
The mission will launch from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Air Force Station in Florida. Following the initial ascent, the Falcon 9 first stage will attempt a propulsive landing on Just Read the Instructions, one of SpaceX’s Autonomous Spaceport Drone Ships stationed in the Atlantic Ocean. SpaceX’s pair of fairing recovery ships, GO Ms. Chief and GO Ms. Tree, are also positioned downrange.
The SpaceX recovery fleet has been responding to several shuffles of the SpaceX launch schedule over the last several days. The other drone ship, Of Course I Still Love You, is also stationed nearby awaiting the next Starlink mission, currently slated for no earlier than Saturday morning.
After the pre-launch static fire test, the launch of GPS-III-SV04 was targeted for September 29. The mission was first delayed until September 30 for improved launch and recovery weather, and then to October 2 due to a range conflict.
The conflict may have been one or both of a United Launch Alliance Delta IV Heavy rocket on the NROL-44 mission and a Northrop Grumman Antares rocket launching the Cygnus NG-14 mission to the International Space Station. Northrop Grumman have delayed their launch to no earlier than Friday evening due to a ground support equipment issue, and ULA is currently working to address an abort in the final seconds of their most recent launch attempt. This has cleared the eastern range for a pair of Falcon 9 missions, including GPS-III-SV04 and a Starlink mission.
The first stage supporting this mission is B1062, a brand new Falcon 9 core. The stage completed a successful static fire test at SLC-40 on September 25 ahead of this launch.
Previous missions for the US Department of Defense, including the GPS-III-SV04 mission, have been required to launch on new Falcon 9 boosters. Now, the United States Air Force has approved the use of reused boosters on the GPS-III-SV05 and SV06 launches, the first SpaceX national security launches which will be permitted to use flight proven stages. The Department of Defense was the last major SpaceX customer requiring new boosters prior to this approval, after NASA cleared Crew Dragon missions to launch on reused Falcon 9s. This change by the US military could open the door for similar plans for other SpaceX national security missions.
When SpaceX launched their first GPS III mission, the launch customer requested that Falcon 9 fly in an expendable configuration, without landing legs or grid fins. After the successful launch, without any recovery attempt of the first stage, SpaceX was approved to attempt stage one recoveries on future GPS launches. Falcon 9 B1060 was successfully recovered aboard Just Read the Instructions after launching GPS-III-SV03.
The same drone ship departed Port Canaveral on September 26 in support of the launch of SV04. At launch, Just Read the Instructions will be stationed 635 kilometers downrange, to the northeast of Cape Canaveral.
On the GPS-III-SV03 launch, Falcon 9’s second stage featured a gray band of paint. The dark band, different from the usual completely white stage, improves the thermal conditions within the propellant tanks during long duration missions, such as GPS launches to Medium Earth Orbit. This gray stripe was also seen being tested on the CRS-18 Cargo Dragon mission. The second stage launching GPS-III-SV04, however, does not have the paint band, suggesting that SpaceX was testing its effects on prior missions, rather than implementing it on all GPS launches.
Falcon 9 will deploy the spacecraft into an approximately 1,200 by 20,000 kilometer transfer orbit at an inclination of 55 degrees. The satellite will then use its own propulsion to maneuver into a circular orbit at 20,200 kilometers in altitude. This is the operational orbit where the GPS III satellites will carry out their missions.
The GPS-III-SV04 spacecraft arrived or pre-launch processing at Cape Canaveral aboard a US Air Force C-17 cargo aircraft on July 14. The satellite was built by Lockheed Martin, based on the A2100M satellite bus. Ten of the GPS III satellites have been ordered to date.
Each GPS III satellite carries a navigation payload provided by L3Harris Technologies. The Block III series of GPS navigation satellites are replacing the Block II series, enabling more accurate signals, increased jamming resistance, and extended spacecraft lifespan. SV04 is the fourth GPS III satellite to launch, and the third to launch on a Falcon 9, excluding one spacecraft which launched on the final flight of the Delta IV Medium rocket.
The Falcon 9 flight profile to Medium Earth Orbit will include two upper stage burns. After stage separation, as the first stage returns to Earth for landing, the second stage will perform the first burn in order to achieve orbit. During this burn, the payload fairing is separated, and the two halves will descend towards the SpaceX recovery vessels for a potential recovery attempt about 45 minutes after launch.
After SECO-1, the end of the first upper stage burn, the stage and GPS satellite will coast for approximately 55 minutes. Then, the second upper stage burn will begin, lasting just 45 seconds. After a 25 minute coast phase, the GPS-III-SV04 satellite is deployed.