United Launch Alliance (ULA) has launched a new satellite for NASA’s Tracking and Data Relay Satellite System (TDRSS) on Friday, with an Atlas V carrying the TDRS-M satellite into orbit. Liftoff from Space Launch Complex 41 (SLC-41) at Cape Canaveral was late in a 40-minute window, with liftoff occurring at 08:29 local time (12:29 UTC).
The Tracking and Data Relay Satellite System, or TDRSS, is a fleet of geosynchronous communications satellites that form part of NASA’s Space Network.
Introduced in the 1980s to support the Space Shuttle, TDRSS continues in service today, providing a relay for communications, scientific data, telemetry and commands between operators on the ground and spacecraft in Earth orbit – including the Hubble Space Telescope and the International Space Station.
The constellation consists of spacecraft stationed in three regions of operation: TDRS-East over the Atlantic, TDRS-West over the Pacific and TDRS-Z – covering the blind spot, or “zone of exclusion”, between the other satellites over the Indian Ocean.
The TDRS-6, TDRS-9 and TDRS-12 satellites are currently operating in the Atlantic region, with TDRS-3 as a backup, while TDRS-10 and TDRS-11 are in service over the Pacific with TDRS-5 as a backup. The TDRS-7 and TDRS-8 satellites serve the Indian Ocean region.
In addition to providing communications for spacecraft already in orbit, TDRSS also supports rockets ascending towards orbit. As it carries the TDRS-M satellite into orbit on Friday, Atlas V will communicate to the ground via both the Atlantic and Indian Ocean regions of the system.
The TDRS-12 satellite, which was itself deployed by an Atlas V in January 2014, will provide tracking while the rocket is over the Atlantic from the TDRS 41 slot at 41 degrees West. The later stages of the flight, including spacecraft separation, will be performed in sight of TDRS-7 in the TDRS 275 slot at 85 degrees east (275 degrees west).
Tracking and Data Relay Satellite M (TDRS-M) is the last of three satellites that comprise the third generation of the TDRSS constellation. The name TDRS-M is temporary, as spacecraft in the series are given an alphabetical designation before launch which is then changed to a numeric one once on station in orbit. TDRS-M is expected to become TDRS-13 once in orbit.
The third-generation satellites have been constructed by Boeing, based around the BSS-601HP bus. Originally announced by Hughes Satellite Systems in 1987, and transferred to Boeing in the latter’s merger with Hughes in 2000, the BSS-601 series – formerly the HS-601 – was one of the most widely-produced satellite platforms of its era. The BSS-601HP is an upgraded model, announced in 1995 and first flown two years later.
Over seventy-five BSS-601s have been launched, using a fleet of rockets that has included the Atlas I, II, III and V, the Delta III and Delta IV, Europe’s Ariane 4, China’s Chang Zheng 2E, Russia’s Proton and the Zenit-3SL of Sea Launch. With the BSS-601 now replaced by Boeing’s BSS-702 platform, and NASA declining to exercise an option for an additional third-generation TDRS spacecraft, TDRS-M may be the last Boeing 601 to launch.
The third-generation TDRS spacecraft succeed the three second-generation satellites, which were also built around the BSS-601 platform – although the standard version rather than the HP model. The constellation’s seven first-generation spacecraft were built by TRW using a bespoke platform.
First-generation satellites were launched aboard the Space Shuttle, using an Inertial Upper Stage (IUS) to reach their operational orbits. TDRS-1 was deployed in this manner during Space Shuttle Challenger’s maiden flight, STS-6, in April 1983.
An IUS failure left the satellite in a lower-than-planned orbit, which was corrected using TDRS-1’s manoeuvring thrusters. The spacecraft remained in service for twenty-six years, finally being retired in October 2009 and decommissioned the following June.
The launch of the second TDRS spacecraft, TDRS-B, was delayed from 1984 while an investigation into the IUS failure was conducted. It was eventually reassigned to Challenger’s STS-51-L mission and was lost along with Challenger and her crew when the Shuttle disintegrated seventy-three seconds into her ascent to orbit.
The TDRS-2 designation, which would have been assigned to TDRS-B after deployment, was not reassigned.
When the Space Shuttle returned to flight in September 1988, TDRS-3 was the payload of Discovery’s STS-26 mission. Further satellites were deployed by Discovery during STS-29R, Atlantis during STS-43 and Endeavour during STS-54.
The final TDRS satellite to be deployed by the Shuttle, and the last first-generation spacecraft, was TDRS-7. This was launched aboard Discovery during the STS-70 mission in July 1995.
Aside from TDRS-B, all of the first-generation spacecraft have long exceeded their seven-year design lives – with the oldest operable spacecraft, TDRS-3, nearing its thirtieth anniversary in orbit. Only TDRS-1 and TDRS-4 have been decommissioned – after twenty-six and twenty-three years of service respectively.
The second-generation satellites, TDRS-8, 9 and 10 were launched aboard Atlas IIAS rockets from Cape Canaveral, between 2000 and 2002.
The first two spacecraft of the third generation, TDRS-11 and TDRS-12 (launched as TDRS-L and TDRS-K), flew aboard Atlas V rockets in January 2013 and 2014 respectively.
With a mass of approximately 3,770 kilograms (8,310 lb), TDRS-M is slightly heavier than the previous satellites of its generation. It was originally one of two contract options in the contract signed between NASA and Boeing in December 2007 for the latter to build two spacecraft – TDRS-11 and 12.
The TDRS-M option was converted to a firm order in 2011, while the second option, TDRS-N, has not been taken up.
TDRS-M carries a communications payload that consists of S, Ku and Ka-band transponders. The satellite has a pair of steerable antennae, each capable of tracking a single spacecraft and providing communications in all three supported bands. These are used for major missions such as Hubble and the ISS. Additional antennae allow TDRS-M to support multiple spacecraft.
The satellite is powered by a pair of solar arrays, with an R-4D-11-300 engine providing propulsion for orbit-raising and on-orbit manoeuvres. TDRS-M is expected to give NASA at least fifteen years of service.
TDRS-M was launched Friday from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station in Florida. This launch pad, which was originally built for the Titan IIIC rocket in the 1960s, was also used by the Titan IIIE rocket, which deployed the Viking missions to Jupiter and the Voyager probes to the outer planets.
It was later used by the Titan IV, before being demolished and rebuilt as the East Coast home of the Atlas V between 1999 and 2002.
The TDRS-M launch had earlier been scheduled for the beginning of August, re-opening the Eastern Range following a period of downtime maintenance, or recapitalization, which was conducted in July.
The launch was delayed after the satellite’s omni S-band antenna was damaged during the final stages of processing, necessitating that it be removed and replaced. As a result of the delay, SpaceX’s Falcon 9 launch, conducted on Monday to deploy the CRS-12 Dragon spacecraft, was the first after this downtime.
Friday’s launch made use of United Launch Alliance’s Atlas V rocket, which was flying in the 401 configuration. The Atlas V, tail number AV-074, consists of a Common Core Booster (CCB) first stage, with a single-engine Centaur (SEC) upper stage and a four-metre payload fairing fitted atop the Centaur. Although the Atlas V can fly with up to five Aerojet AJ-60A solid rocket motors boosting the first stage, AV-074 will use none.
The Atlas V first flew in August 2002, with Friday’s launch occurring three days before the fifteenth anniversary of its maiden flight – which deployed Eutelsat’s Hot Bird 6 communications satellite. Prior to the TDRS-M launch, Atlas V has made seventy-one launches with seventy of these having been completed successfully.
The only blemish on its record is the June 2007 NROL-30 mission, which reached a lower-than-planned orbit due to a faulty valve in one of the Centaur’s engines leaking propellant as the vehicle coasted between burns. Despite the anomaly, the spacecraft – a pair of Intruder ocean surveillance satellites – were able to manoeuvre into their correct orbits under their own power.
The Atlas’ Common Core Booster, or CCB, is powered by a single RD-180 engine. This burns RP-1 kerosene propellant oxidised by liquid oxygen. The RD-180 is produced by Russian manufacturer NPO Energomash, and is a two-chamber derivative of the four-chamber RD-170 series developed for the Zenit rocket.
The RD-180 ignited with about 2.7 seconds remaining until Friday’s countdown reached zero. At about 1.1 seconds after the T-0 mark, the thrust generated by the engine exceeded the vehicle’s weight and AV-074 lifted off, beginning her ascent towards orbit.
At 17.7 seconds mission elapsed time, the rocket began a series of pitch and yaw manoeuvres to align itself with its planned trajectory downrange. Flying out to the East over the Atlantic Ocean, Atlas reached Mach 1, the speed of sound, eighty seconds after liftoff. Eleven and eight-tenths of a second later the rocket experienced maximum dynamic pressure, or Max-Q.
The RD-180 powered AV-074 for the first four minutes and 2.2 seconds of the journey to orbit. At this point in the mission the engine ceased burning, an event designated booster engine cutoff, or BECO. The spent stage was jettisoned six seconds later, with second stage ignition taking place ten seconds after stage separation. Eight seconds after second stage ignition, the payload fairing separated from around TDRS-M.
Centaur is powered by a single RL10C-1 engine. Burning liquid hydrogen and liquid oxygen, it made two burns in order to insert TDRS-M into geosynchronous transfer orbit. The first burn, beginning after stage separation and continuing for thirteen minutes and 39.5 seconds, injected the spacecraft and upper stage into an initial parking orbit. Following an extended 90-minute, 6-second coast, Centaur restarted for its second burn, this time firing for 56.4 seconds.
TDRS-M separated from the Centaur four minutes and 46 seconds after the end of the second burn. The orbit at spacecraft separation is expected to have a perigee – or point closest to Earth – of 4540.2 kilometres (2,883.3 miles, 2505.5 nautical miles). Its apogee, the point farthest from Earth, will be 35,787.7 kilometres (22,237.4 mi, 19,323.8 nmi), while the orbit will be inclined to the equator at 26.2 degrees with an argument of perigee of 180.0 degrees.
Following Friday’s launch, United Launch Alliance and their Atlas V rocket will next be in action on 11 September, deploying a classified national security payload – NROL-42 – from Vandenberg Air Force Base in California. This is expected to be a signals intelligence satellite, bound for a highly-elliptical Molniya orbit. The TDRS launch is the second of three planned from Florida’s Space Coast in August – the next, using a Minotaur IV rocket, will take place on 26 August.
(Images via ULA and Boeing)