United Launch Alliance’s Atlas V rocket has deployed an advanced communications satellite for the US Air Force Thursday morning. Atlas lifted off from Cape Canaveral with the AEHF-5 satellite aboard, during a two-hour window that opens at 05:44 Eastern Time (09:44 UTC). After resolving a couple of minor issues, the launch occurred at 06:13 Eastern (10:13 UTC).
AEHF-5 is the fifth satellite to be launched in the US Air Force’s Advanced Extremely High Frequency (AEHF) program. This is a system of satellites dedicated to providing global survivable, secure, protected and jam-resistant communications to the armed forces of the United States and her allies.
AEHF serves to augment the legacy Milstar communications system, a network of satellites deployed from 1994 to 2003 with which it is designed to be backward-compatible, as they approach the end of their service lives. AEHF will eventually replace the Milstar system, ensuring uninterrupted service to its users.
AEHF was conceived as a constellation of six satellites, however, this was scaled back to three with the advent of the planned Transformational Satellite (TSAT) system.
When TSAT was canceled in 2010, additional AEHF satellites were reinstated, bringing the constellation up to five, and then back to six spacecraft. The first three satellites were launched in August 2010, May 2012 and September 2012, all aboard Atlas V rockets.
The AEHF constellation adds new enhancements over its Milstar predecessors, including an extreme data rate (XDR) capability in addition to the legacy low data rate (LDR) and medium data rate (MDR). XDR became fully operational with the entry into service of the AEHF-4 satellite, now named USA-288.
Launched last October, this satellite completed a ring of AEHF spacecraft in geostationary orbit, allowing signals to be routed around the globe. XDR offers data transfer at speeds of up to 8.192 megabits per second – up from maximums of 2.4 kilobits and 1.544 megabits per second achievable with LDR and MDR respectively. A single AEHF satellite provides greater total capacity than the entire legacy Milstar constellation.
Several different types of communications antennae are carried aboard AEHF-5 to support different applications. A low-gain antenna is used to transmit and receive across the visible disc of the Earth, while six medium-resolution coverage antennae (MRCA) produce 24 spot-beams covering specific areas.
A pair of high-resolution coverage antennae (HRCA) can be used to cut through jamming to ensure tactical communications with units in the field. Phased array antennae are used to provide worldwide spot beams where needed. An AEHF satellite provides enhanced global coverage compared to Milstar, operating up to 68 simultaneous worldwide beams.
Two cross-link antennae allow AEHF satellites to conduct bi-directional communications with other spacecraft in the AEHF and Milstar constellations. This allows signals to be routed across the constellation, passing directly between satellites without using a ground station as a relay.
AEHF crosslinks have a bandwidth of 60 megabits per second, compared to the 10 megabits per second possible between Milstar satellites. The enhanced capabilities of AEHF over Milstar give warfighters in the field access to faster and more resilient communications than were previously available to them.
As well as benefiting the United States, AEHF will be used by allied nations, including the United Kingdom, Canada and the Netherlands. With its focus on secure tactical communications, AEHF is part of a US Military Satcom fleet that also includes the Wideband Global Satcom system geared towards more strategic communications, the US Navy’s Multi-User Objective System (MUOS) and the National Reconnaissance Office’s Satellite Data System (SDS), which relays data from surveillance satellites back for analysis.
Lockheed Martin is the prime contractor for the AEHF satellites, which are based on the company’s A2100M platform. With a mass at liftoff of 6,168 kilograms (13,600 lb), these large satellites have an expected on-orbit lifespan of at least fourteen years.
Each AEHF carries an IHI Aerospace BT-4 liquid apogee motor for initial orbit-raising, along with four Aerojet Rocketdyne XR-5 Hall thrusters which will complete insertion into geostationary orbit and aid in stationkeeping operations. Monopropellant thrusters are also present on the satellite to assist with control and maneuvering.
The AEHF-5 satellite cost approximately 1.1 billion dollars. The program’s next satellite’ AEHF-6, is currently slated for launch in March 2020.
The AEHF-5 launch, which made use of United Launch Alliance’s workhorse Atlas V rocket, is the first that the US Air Force’s Space and Missile Systems Center has conducted since introducing its SMC 2.0 business model, a major reorganisation of the way the Air Force procures space missions aimed at making the process more efficient which was initiated at the end of July.
SMC have also integrated a Multi-Manifest Space Vehicle (MSV) rideshare into the launch mission, with the TDO satellite mounted to the aft bulkhead of the Centaur upper stage. TDO, a twelve-unit CubeSat carrying a space debris investigation and tracking experiment, will share AEHF-5’s ride into orbit, separating before the primary – or anchor – payload.
Atlas V is one of two rockets operated by United Launch Alliance (ULA) under the US Air Force’s National Security Space Launch (NSSL) program – formerly the Evolved Expendable Launch Vehicle (EELV) program. Along with its stablemate, Delta IV, Atlas conducts critical national security launches for the US military, while also being used for commercial and scientific launches outside of the auspices of NSSL.
ULA was formed in 2006 to offer launch services to the US Government, taking over operations of Lockheed Martin’s Atlas V program and Boeing’s Delta II and Delta IV vehicles.
Atlas V is one of the most reliable rockets in service. First flown in August 2002, it has conducted seventy-nine missions prior to Thursday’s launch without ever failing and losing a payload.
The only blemish on its record is a June 2006 partial failure, where a pair of National Reconnaissance Office ocean surveillance satellites were placed into an off-target orbit, however, these satellites were able to maneuver to the correct orbit with minimal impact upon their mission.
The two-stage rocket consists of a Common Core Booster (CCB) first stage with a Centaur upper stage. Depending on the size and mass of its payload, the target orbit and other mission requirements, Atlas can fly in several different configurations.
These use varying numbers of solid rocket boosters to augment the first stage, single and dual-engine versions of the Centaur and four or five meter (13.1 or 16.4 foot) diameter payload fairings to accommodate different satellites.
Thursday’s launch used the 551 configuration, with a five-meter fairing, five solid rocket boosters and a single-engine Centaur. This is the most powerful version of Atlas V to have been developed. The rocket that performed Thursday’s launch has tail number AV-083.
Atlas launched from Space Launch Complex 41 (SLC-41) of the Cape Canaveral Air Force Station on Florida’s Space Coast. This is one of two launch pads available for the Atlas V, along with Space Launch Complex 3E at California’s Vandenberg Air Force Base. Launching from Florida instead of California is necessary in order to reach the near-equatorial orbit that AEHF-5 will operate in.
SLC-41 was built in the 1960s as part of the Titan Integrate-Transfer-Launch (ITL) complex, which also included nearby Space Launch Complex 40 (SLC-40) which SpaceX now use to launch their Falcon 9 rocket. The ITL Complex initially supported Titan IIIC rockets before SLC-41 was modified for the Titan IIIE configuration in support of NASA’s deep space missions in the 1970s. The pad was later used by Titan IV rockets, with its last Titan mission lifting off in April 1999. The first Atlas launch from the complex was the maiden flight of Atlas V in August 2002.
During Titan IIIE’s occupancy of SLC-41, the pad served as a launch site for NASA’s Voyager probes to the outer planets, the Viking missions to Mars and the Helios solar research spacecraft. Atlas V launches from the pad have continued this legacy of exploration, carrying missions bound for the Moon, Mars, Jupiter, near-Earth asteroid (101955) Bennu and Pluto and the Kuiper Belt.
When launching from SLC-41, Atlas rockets are assembled in the nearby Vertical Integration Facility (VIF) before being transported the short distance to the launch pad atop a mobile launch platform.
AV-083 was moved to the launch pad on Tuesday ahead of the AEHF-5 launch. With Atlas in position, on Wednesday RP-1 propellant, a form of rocket-grade kerosene was loaded into its first stage tanks.
The first stage burns RP-1, oxidized by liquid oxygen, while Centaur uses liquid hydrogen and liquid oxygen. Because of their extremely low boiling points, these cryogenic liquids were not loaded onto the rocket until Thursday’s countdown was well underway.
Thursday’s launch began with ignition of the RD-180 main engine at the base of Atlas’ Common Core Booster, which roared to life 2.7 seconds before the countdown reaches zero. Atlas lifted off at T+1.1 seconds, with the five Aerojet AJ-60A solid rocket motors clustered around the first stage igniting.
Atlas quickly cleared its launch pad, beginning a series of pitch and yaw maneuvers to attain its proper trajectory 3.9 seconds after liftoff.
Climbing to the east over the Atlantic Ocean, Atlas reached the speed of sound, Mach 1, 34.4 seconds into her flight. Atlas passed through the area of maximum dynamic pressure – Max-Q – 11.8 seconds later. When flying with a five-meter fairing Atlas follows a steep ascent path, climbing to get above the atmosphere while the first stage is still burning.
The five AJ-60A solids burned for about 90 seconds, providing additional thrust to augment the RD-180 in the early stages of flight. After burning out the motors remained attached awaiting more favorable aerodynamic conditions for them to separate – minimizing the risk of the spent casings colliding with the rest of the rocket. The first two boosters separated 105.8 seconds after liftoff, with the other three following about a second later.
Once Atlas was clear of Earth’s atmosphere it shed the payload fairing that has encapsulated and protected AEHF-5 and Centaur during their ascent through the atmosphere.
Separating three minutes and 23.3 seconds into the flight, the fairing split into two parts and fell away from the vehicle, exposing AEHF-5 to space for the first time.
Just under 63 seconds after fairing separation, the Common Core Booster concluded its burn with Booster Engine Cutoff (BECO), when the RD-180 shut down having exhausted its supply of propellant. Stage separation six seconds later saw the spent booster discarded: Centaur then began its prestart sequence, igniting ten seconds after staging.
Centaur is powered by a single RL10C-1 engine, a cryogenic powerplant capable of making multiple burns to inject its payload into the planned orbit. For Thursday’s launch, the Centaur is equipped with a Geosynchronous Orbit Kit, allowing it to perform an extended mission and place AEHF-5 into a higher orbit than would otherwise be possible.
Centaur will make three burns to place AEHF-5 in a high-perigee geosynchronous transfer orbit. The first of these established an initial parking orbit – with the RL10 burning for 0.7 seconds short of seven minutes before main engine cutoff 1 (MECO-1).
After coasting for eleven minutes and 8.4 seconds Centaur restarted for its second burn, firing for six minutes and 3.4 seconds to raise the orbit’s apogee – the point farthest from Earth – to about 35,300 kilometers (21,900 miles, 19,100 nautical miles). TDO separated in this orbit, with the satellite deploying from Centaur’s aft bulkhead carrier 31 seconds after the burn ended.
Once TDO separated, Centaur’s mission entered an extended coast phase as the stage climbed towards apogee. Five hours and thirty-six minutes after liftoff it will reach apogee and the RL10 restarted for its third burn. This lasted one minute and 46.6 seconds, raising the perigee – or lowest point – of Centaur’s orbit. This burn reduces the amount of fuel AEHF-5 must burn to reach geostationary orbit, giving the satellite increased prospects for an extended mission.
At five hours, 40 minutes and 35.7 seconds mission elapsed time – two minutes and 49.1 seconds after the end of the third Centaur burn, AEHF-5 separated to begin its mission. The target separation orbit is 14,435.3 by 35,298.7 kilometers (8969.66 by 21933.6 miles, 7794.42 by 19,059.8 nautical miles) at an inclination of 9.95 degrees and with an argument of perigee of 180 degrees.
About 26 minutes and 20 seconds after AEHF-5 has separated, a blowdown of Centaur’s tanks will be performed to reduce pressure and minimize the danger of the stage exploding in orbit. With this complete, the Atlas mission will officially end six hours, thirty-eight minutes and 35.7 seconds after lifting off from Cape Canaveral.
Once on orbit, AEHF-5 will receive a designation under the USA series, assigned to most US military satellites. It is expected to become USA-292 on orbit. The satellite will use its own propulsion systems to climb out of its initial deployment orbit and reach geostationary orbit. After determining its position and orientation relative to the Earth, the satellite will execute a series of three burns with its liquid apogee motor, raising the perigee of its orbit.
With these complete AEHF-5’s electric propulsion system will take over, firing continuously for about seventy days to bring the spacecraft into geostationary orbit. It is expected to arrive on station in October to begin on-orbit checkout and commissioning. The use of Centaur’s extended mission kit and its perigee-raising third burn are expected to have reduced the duration of this process by about 40 days, compared to previous AEHF spacecraft.
Thursday’s launch was the first Atlas V mission since the launch of AEHF-4 last October – an unusually quiet period for America’s workhorse rocket.
The AEHF-5 mission had previously been scheduled to launch in late July, however, ULA opted to delay after a test on an upper stage component from one of their suppliers failed an acceptance test a few weeks before the expected launch date.
This required that suspect hardware be removed from the vehicle, inspected, modified and reinstalled. The same component concern also resulted in a Delta IV launch being delayed from July to 22 August. These delays and appropriate due diligence stem from ULA’s commitment to ensuring the success of their launches.
The Atlas and Delta launches form part of the Space and Missile Systems Center’s Summer of Launch 19 campaign, a series of four launches from the Eastern range originally scheduled over a one-month period. This campaign began with the successful launch of a SpaceX Falcon Heavy rocket carrying the STP-2 multi-satellite mission at the end of June, continuing with the Orion Ascent Abort 2 (AA-2) mission using a booster derived from the first stage of a decommissioned Peacekeeper missile.
The launch window for AEHF-5 opens 34 hours and 21 minutes after SpaceX’s Falcon 9 lifted off from the adjacent launch pad, SLC-40, to deploy Israel’s Amos 17 satellite. The Eastern Range’s fast turnaround between the two launches comes as part of their goal to build up an ability to support at least 48 launches per year.
United Launch Alliance will next be in action with the Delta IV on 22 August. This will be the final flight of the Delta IV Medium+ rocket, deploying a Block III Global Positioning System (GPS) navigation satellite. The next Atlas V launch is currently scheduled no earlier than 17 September, with the uncrewed Orbital Test Flight (OTF) of Boeing’s CST-100 Starliner spacecraft.