Final GPS IIF satellite moves to next processing phase toward launch
By Chrissy Cuttita, 45th Space Wing Public Affairs
/ Published February 03, 2016
PATRICK AIR FORCE BASE, Fla. -- When a space vehicle is loaded with 320 pounds of hydrazine, the 45th Space Wing's Airmen-led GPS processing team knows they are in their final stages toward launching a premier capability to the warfighter.
All of the intricate processing steps from delivery of the satellite to launching into orbit are part of their standard operations at Cape Canaveral Air Force Station, Florida. But, it's a bitter sweet moment when the team reflects on the extensive years of history they have processing GPS systems for the Air Force.
"GPS II processing at the Cape started while the Shuttle program was here, when the Air Force was still launching Delta IIs and the Cold War was still going on," said Capt. Trung Nguyen, the field program manager for GPS IIF at the 45th Launch Support Squadron. "The GPS processing program has been a staple at the Cape. There are engineers and technicians here who worked on the first GPS II block satellite. Some have launched over 20 satellites. Some have been with the program since 1989."
The 45th LCSS processing team received its 12th and final Air Force GPS IIF model on Oct. 8 and unpackaged it in the NAVSTAR Processing Facility, where successful functional tests of the system made sure the satellite operates as expected when it is in orbit next month. The team is currently in the next phase of preparation for launch at the DSCS Processing Facility where major milestones occur, such as fueling.
"The NPF portion of the campaign lets the customer know that the satellite they paid for works," Nguyen said. "For this final mission, we executed the functional testing like we've always done."
Before they began tests, the team unpackaged the satellite and watched Air Force contracted partners give it a good shake down to ensure the satellite didn't suffer any inadvertent deviations during its transportation from the factory, delivery and transition into the NPF. A team carrying flashlights inspect every nut and bolt to make sure things are in order.
"Just because it looks like the final one, it is not exactly the same; each spacecraft is built by hand and thus is a little different from every previous unit," said Scott Chappie, the lead Air Force responsible engineer for GPS IIF-12, who has processed the previous four satellites that launched.
The Air Force team mounts the satellite to a test stand where an extensive suite of electronic tests are performed to verify the functionality and performance of each unique space vehicle. This process in the spacecraft control room can take up to 10 days with an Air Force mission responsible on station 24/7 to monitor the data received from a variety of cables plugged into the satellite. They don't install batteries until they know everything is operating as expected.
During this functional testing, proper operation of the subsystems is demonstrated, and the test procedure is designed to detect any malfunctions or failures that may have an impact on the satellite while in orbit.
"We also take a photo of every inch of the space craft in case we need to refer to it to trouble shoot something while it is in orbit," said Chappie, who has worked in military space for 20 years before coming to the Cape Canaveral AFS last year. "This forces us to look at every piece again. It is an extremely detailed procedure designed by the contractor - what to do, in what order and what tools are needed."
The closer the team gets to launch day, the higher the value of the satellite. This means there is less room for risk as they move forward. The Air Force team provides independent mission assurance to constantly monitor all launch site processing and assess the risk of those operations on spacecraft mission success.
In the final processing phase at the NPF, the space vehicle propulsion system is pressurized to the maximum expected operating pressure using gaseous nitrogen, which verifies that the reaction control system is working properly without any leaks in a simulated fueling test before it is transported and unpackaged at the DSCS Processing Facility.
Although the GPS moved to another location to continue processing, the control room remained at the NPF and is in contact with the satellite through every other phase of processing until the moment the rocket lifts off from Cape Canaveral AFS.
The DSCS Processing Facility is configured to handle fueling operations safely with minimum personnel in the trench-lined hangar bays. Once fueled up and ready, the satellite can be mated to United Launch Alliance's Ground Transport Vehicle and encapsulated in the payload fairing. During this time, multiple electrical tests occur to ensure that all electrical paths are still operating nominally. Then the satellite will be transported to the Vertical Integration Facility, where it is mated to the top of an Atlas V rocket.
"We are here to protect the interests of the warfighter in this critical national asset," Chappie said. "We verify the satellites functionality and performance before we commit to launch."
T-minus two days from launch the integrated team is on console ready for power configuration to launch. Using fiber optic cables they can test their ability to communicate with the satellite. On the day of launch, they are ready to assist with any situation that may come up with close eyes on the telemetry data.
Following the completion of the processing and launch of the last of the GPS IIF Block spacecraft, the Air Force team looks forward to launching the GPS III spacecraft, which are already being built at a contractor factory.
Compared to other spacecraft, GPS IIF-12 is a modest size platform weighing in at 3,600 pounds, Chappie said. Although the design is impressive, the engineer said the impact it has is astonishing.
"That space craft is going to touch the lives of hundreds of millions if not billions of people on a daily basis," he said. "It not only vastly increases our military's position, navigation and timing capabilities all over the world, but so many people and business activities have also come to depend on GPS. This is a stunningly, successful program -- the way the Air Force conceived it and the way they continue to manage and implement the program."
Members of the mission assurance team, ranging from young military officers to career enlisted troops to seasoned civilians, look forward to the Atlas V's scheduled launch with GPS IIF-12 on board Feb. 5.
Once the satellite is on orbit, it communicates with the GPS Master Control Station, operated by the 50th Space Wing's 2nd Space Operations Squadron at Schriever Air Force Base, Colorado. This squadron is responsible for monitoring and controlling the GPS as a 24-satellite system, consisting of six orbital planes, with a minimum of four satellites per plane. There are currently 40 vehicles in the GPS constellation.
GPS satellites serve and protect U.S. warfighters by providing navigational assistance and timing standards for military operations on land, at sea, and in the air. Civilian users around the world also use and depend on GPS for highly accurate time, location, and velocity information.