LOS ANGELES AIR FORCE BASE -- The Advanced Extremely High Frequency 4 satellite, transferred control from the Space and Missile Systems Center out of Los Angeles Air Force Base, California to the 4th Space Operations Squadron at Schriever Air Force Base, Colorado on May 3, one month ahead of schedule. Due to higher than predicted performance of the thrusters, as well as meticulously planned and smooth on-orbit testing, the $1.9 billion asset has been made available for operations and enabled full operational capability of the constellation weeks earlier than anticipated.
Launched aboard an Atlas V from Cape Canaveral Air Force Station, Florida. on Oct 17, 2018, AEHF-4 was the latest satellite to join a growing operational constellation that provides military satellite communications to U.S. and allied forces globally.
SMC’s role began with the acquisition of the AEHF satellite and launch services, and continued into the launch campaign and early orbit operations. After the satellite successfully separated from the launch vehicle approximately 4 ½ hours after liftoff, it underwent 117 days of orbit-raising operations followed by on-orbit testing. A joint Air Force and contractor team based out of Schriever AFB and supported by personnel in Sunnyvale, California performed the work until it was handed over to the operators on May 3.
“The planned duration for placing the satellite into its orbit was 150 days, but with improved procedures and engine efficiencies, the time to orbit was cut by 22 percent and the actual time to orbit was 117 days. During the orbit-raising period, the satellite was propelled by the liquid apogee engine to raise perigee and by hall current thrusters to circularize the orbit. Also, the solar arrays and payload wings deployed during this time,” said Capt. Arthur James, AEHF Operations lead.
Critical to the faster pace in which the AEHF-4 team operated under were the strong partnerships forged. Comprised of orbital analysists, engineers, operators, and managers from the government and industry, the team’s mission was to resolve issues and to ensure the safety and mission success of the satellite during orbit-raising and on-orbit testing.
“This is a great partnership and a very high-performing team. The Lockheed Martin team members operate the satellite, perform engine burns, monitor telemetry and states of health, and conduct on-orbit tests. Northrop Grumman handles all payload operations to include connecting the satellite into the operational constellation, powering on the payload and supporting payload antenna calibrations. Massachusetts Institute of Technology Lincoln Laboratories provides the command and control assets to command AEHF-4 throughout testing, calibration and during day-to-day operations. Each site has SMC, Lockheed Martin, Northrup Grumman, and MIT/Lincoln Laboratories representation throughout launch, orbit raising, on-orbit testing and transition to operations. By maintaining consistent face-to-face interactions, open lines of communication and continuous collaboration, we were able to deliver AEHF-4 to the warfighter one month ahead of schedule,the captain said.
The team’s work began with pre-launch members on console where they monitored many critical criteria such as the health of the satellite and the status of the ground support systems that allow the team to communicate with it following launch. The team at Schriever provided “go/no-go” decisions for launch along with team members located at Cape Canaveral. Once the satellite separated from the launch vehicle, the joint team began 24/7 operations.
The first 12 days are considered critical due to a number of key events taking place such as the major orbit-raising engine burns and system deployments. Throughout the early-orbit operations period, the team sent a series of scheduled and real-time commands to the satellite, which allow the spacecraft to move up to its proper geosynchronous orbit as well as to “open” the payload wings and solar arrays, two key maneuvers that help the satellite function properly. In addition to sending commands to the satellite, the team sent software updates during the ascent, which provided adjustments to the satellite subsystems based on data received from the vehicle.
Once the satellite arrived at its orbit, the communications payload was “turned on” and the joint team conducted a series of on-orbit tests. The purpose of these tests is to ensure the satellite performs its mission properly and communicates accordingly with ground terminals and other satellites in the MILSTAR/AEHF constellation. AEHF-4 is the ninth satellite in the combined satellite communication constellation.
“The purpose of testing is to verify that the satellite functions properly after being launched. The team performed 14 tests consisting of 57 objectives to ensure the satellite met functional requirements, to calibrate the payload antennas and ensure the ground system can command the satellite. The test utilizes six operational terminals from the joint services (USAF, Navy and Army) and five command-and-control assets located in the western hemisphere.
“The test begins by ensuring that the satellite functions as a lone satellite. The team ensures that the satellite can receive, transmit, and operate communications with the ground system. The space vehicle also receives initial calibrations of the payload antennas. Next, the satellite is connected into the constellation, via the crosslinks, to prove that the satellite can send communications through the MILSTAR/AEHF operational constellation. The addition of AEHF-4 in the constellation enables the warfighter to conduct robust and fully operational [extended data rate] communications,” the captain said.
Control of AEHF-4 was officially handed over at a ceremony held at Schriever Air Force Base. Col David Ashley, SMC’s AEHF program manager, handed a ceremonial key to Lt . Col. Armon Lansing signifying 4 SOPS acceptance of satellite control.
“The agency accepting control is responsible for maintaining the health and safety of the satellite as well as making sure it accomplishes the mission it was designed for,” said Lt. Scott Podlogar, 4th SOPS satellite engineer.
The AEHF program is the follow-on to the MILSTAR system, augmenting and improving its capabilities and expanding the MILSATCOM architecture. The final AEHF constellation will consist of four operational satellites with two in reserve in geosynchronous earth orbit providing 10 times the throughput of the 1990s-era MILSTAR satellites with a substantial increase in coverage for users. AEHF-5 is scheduled to launch June 27 aboard an Atlas V from Cape Canaveral.
“For AEHF-5 we will introduce a five-hour coast before spacecraft separation, which will reduce the orbit raising period. Incorporating lessons learned from the AEHF-4 launch, we expect to have an efficient and rapid time to orbit. The team will continue to launch with the Atlas V 551 engine, but have shortened LAE burns from four burns to three to reduce time to orbit. As a result, the new baseline is [approximately] 120 days to orbit, but if the system continues to perform nominally during the orbit-raising phase, the team may find ways to reduce the number of days [even more] in order to deliver AEHF-5 to the warfighter sooner,” James said.