ULA Atlas V conducts SBIRS-GEO-3 launch from the Cape

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The US Air Force’s third Space-Based Infrared System (SBIRS) geosynchronous missile detection satellite rode to orbit atop United Launch Alliance’s Atlas V rocket on Friday, lifting off from Cape Canaveral Air Force Station, following a scrub of Thursday’s opening attempt.

Atlas V Launch:

Thursday’s attempt was proceeding to plan until a sensor issue resulted in the hold being extended. Once the issue was cleared, the final attempt of the day was scrubbed when the Eastern Range was fouled by an aircraft. ULA opted to scrub for the day, with the next attempt taking place on Friday with a T-0 of 19:52 local time. Friday’s countdown was smooth, resulting in an on-time launch.

Space-Based Infrared System, or SBIRS, is a system of satellite-mounted sensors operated by the United States Air Force, designed to detect missile launches in order to provide an advance warning of any imminent threat.

The satellites can also perform additional infrared surveillance duties. SBIRS is a successor to the earlier Defense Support Program (DSP), whose twenty-three satellites were launched between 1990 and 2007.

SBIRS uses a combination of dedicated satellites in geosynchronous orbit and instrument packages hosted aboard other satellites in highly elliptical Molniya orbits. The payload of this launch, SBIRS-GEO-3, is the third dedicated satellite to launch.

Three hosted, or SBIRS-HEO, payloads are also currently in orbit aboard National Reconnaissance Office signals intelligence spacecraft. A low Earth orbit component to the program was originally planned. However, this was canceled and later evolved into the Space Tracking and Surveillance System (STSS).

The early detection of incoming missiles gives the US military time to react to the threat of a potential nuclear attack, getting key personnel to safety and launching a counterattack. SBIRS also allows missile defense systems to be targeted to intercept the attack.

The SBIRS spacecraft are also tasked with missions described as Technical Intelligence and Battlespace Awareness, using their sensors to identify and analyze the signatures of events producing infrared radiation and to collect data on the conditions of battlefields to aid strategic planning.

The SBIRS program falls under the operation of the US Air Force’s 460th Space Wing, based at Buckley Air Force Base in Colorado.

The United States has operated early warning satellites since the 1960s, beginning with the Missile Defence Alarm System (MIDAS).

The space-based systems augmented ground-based radar systems such as the Ballistic Missile Early Warning System (BMEWS), providing longer range detection which allows missiles to be identified earlier in their flights.

MIDAS was never used operationally; of the first six satellites three were lost to launch failures and the remaining satellites all failed within a day of launch. It was not until MIDAS-7 launched in May 1963 that a missile detection capability could be demonstrated with the satellite tracking various US launches including Atlas, Minuteman, Polaris and Titan missiles.

The operational Defense Support Program (DSP) – originally named Integrated Missile Early Warning System (IMEWS) used geosynchronous satellites in contrast to the low Earth orbit MIDAS. Three generations of DSP satellites were launched – four first-generation spacecraft were launched between 1970 and 1973 using Titan III(23)C rockets.

The second generation, consisting of nine satellites, was deployed between 1976 and 1987; the first six satellites launching atop Titan III(23)C vehicles before its retirement – the final three second-generation spacecraft flew aboard Titan III(34)D/Transtage rockets.

Third-generation DSP satellites were predominantly launched by Titan IV rockets. Exceptions were the third satellite, which was deployed from Space Shuttle Atlantis with the aid of an Inertial Upper Stage (IUS) during 1991’s STS-44 mission, and the final satellite which flew aboard a Delta IV Heavy following the Titan’s retirement.

In total, ten third-generation DSPs were launched, with the first, second and fourth flying aboard the Titan IV(402)A and the Titan IV(402)B being used from the fifth launch onwards. Both of these Titan configurations also made use of an IUS to inject the satellite into geosynchronous orbit.

One of the third-generation satellites, USA-142 – also known as DSP 19, failed to reach its planned orbit as the first and second stages of the Titan IV’s Inertial Upper Stage failed to separate cleanly from each other. The final satellite, USA-197, failed after a few months in service.

The SBIRS program was begun in the 1990s to replace DSP, providing enhanced capabilities. The first satellite, USA-230 or SBIRS-GEO-1, lifted off from Cape Canaveral atop an Atlas V in May 2011. A second satellite, USA-241 or SBIRS-GEO-2, was deployed in March 2013 – also using an Atlas.

SBIRS-GEO-3 was the fourth SBIRS-GEO satellite to be built; the third satellite, which is expected to launch as SBIRS-GEO-4, was completed first and placed into storage. By launching the fourth satellite before the third, the Air Force was able to reduce costs by eliminating the need to swap the spacecraft in to and out of storage. The satellite was ordered in early 2011 – and contracts for two further satellites have since been awarded bringing the SBIRS-GEO constellation up to six spacecraft.

Lockheed Martin is the prime contractor for the SBIRS program, under a contract originally awarded in 1996, with the SBIRS-GEO spacecraft based around the company’s A2100M platform. Each satellite has a mass of about 4.5 tons (4.4 Imperial tons, 5.0 US tons) and has a design life of at least twelve years.

The satellites are equipped with a pair of infrared imagers, one of which scans the disc of the Earth while the other is able to focus on specific areas of interest. The imaging payload was developed by Northrup Grumman, who in 2002 acquired TRW Incorporated, the prime contractor of the earlier DSP program.

The SBIRS satellite carries a Moog Incorporated LEROS-1C apogee motor for orbit-raising operations. SBIRS-GEO-3’s launch was delayed from the last quarter of 2016 to allow further inspections of this engine after the same model of engine aboard the commercial Intelsat 33e spacecraft failed to operate.

Like the two SBIRS-GEO satellites launched ahead of it, SBIRS-GEO-3 rode an Atlas V rocket into orbit. This vehicle, designated AV-066, flew in the 401 configuration with a four-metre (13.1-foot) payload fairing, no solid rocket boosters and a single-engine Centaur upper stage.

The 401 is the smallest configuration in the Atlas V fleet, and is the same version that was used for the two previous SBIRS launches.

The launch was the sixty-ninth flight of an Atlas V and the thirty-fourth to use the 401 configuration.

A workhorse of the US space program, the Atlas V first flew in August 2002 with the successful deployment of Eutelsat’s Hot Bird 6 satellite.

One of two rockets developed for the US Air Force’s Evolved Expendable Launch Vehicle (EELV) programme, alongside Boeing’s Delta IV, the Atlas V was developed to the requirements of the US military as a unified replacement for the existing rockets used by the Air Force, including the Atlas II, Delta II and Titan IV. An Atlas V Heavy, which would have carried the heaviest Titan IV-class payloads, was proposed but never developed.

Since December 2006 both the Atlas V and Delta IV – along with the Delta II – have been operated by United Launch Alliance, a joint venture between Boeing and Lockheed Martin – the developers of the Delta and Atlas respectively.

Atlas V launches from Cape Canaveral take place at Space Launch Complex 41, a former Titan launch complex which previously hosted Titan IIIC, Titan IIIE, Titan IVA and Titan IVB missions. The rocket is assembled atop a mobile launch platform in the Vertical Integration Facility (VIF), 550 meters (600 yards) southeast of the pad itself. Atlas was rolled out to the launch pad on Wednesday morning in preparation for the SBIRS mission.

The first stage of the Atlas V, the Common Core Booster (CCB), is powered by a single NPO Energomash RD-180 engine. This ignited 2.72 seconds before the launch countdown reached zero, with liftoff taking place at T+1.121 seconds. Atlas began a pitch and yaw maneuver to attain the correct attitude for the ascent to orbit at 17.9 seconds elapsed time.

Flying east downrange on an azimuth of 95.9 degrees, AV-066 reached a speed of Mach 1, the speed of sound, at 80.7 seconds into flight, passing through the area of maximum dynamic pressure, Max-Q, 9.9 seconds later.

The RD-180 powered Atlas for the first four minutes and 3.18 seconds of flight before cutting off – a mission event designated Booster Engine Cutoff (BECO). The spent Common Core Booster was jettisoned six seconds after cutoff, with the Centaur second stage igniting its RL10C-1 engine two-hundredths less than ten seconds after staging. Eight seconds into the Centaur’s first burn, the payload fairing separated from the nose of the vehicle.

Centaur conducted two burns during the mission; the first of these lasted eleven minutes and 3.497 seconds, establishing an initial parking orbit. Following a nine-minute, 37.463-second coast Centaur restarted for its second burn, firing its RL10 engine for a further three minutes and 38.184 seconds. Spacecraft separation occurred at 43 minutes and 48.320 seconds mission elapsed time, fifteen minutes and 10.016 seconds after the end of powered flight.

At separation, SBIRS-GEO-3 is expected to be in a 185-by-35,786-kilometer (115 x 22,237 miles, 100 x 19,323 nautical miles) orbit inclined at 23.29 degrees to the equator. The satellite will maneuver to geosynchronous orbit under its own power.

The launch was the first of the year for United Launch Alliance and the second overall for the United States following SpaceX’s successful Falcon 9 mission from Vandenberg Air Force Base on Saturday.

The next Atlas mission is currently slated for 9 February and will see an Atlas V 401 fly from Vandenberg on a mission for the National Reconnaissance Office designated NROL-79 – which is believed to be the deployment of a pair of naval intelligence satellites into low Earth orbit.

The next SBIRS launch – officially – is of the GEO-4 satellite in November atop an Atlas V. However, the NROL-42 mission, scheduled for launch in June, may carry the fourth SBIRS-HEO payload. SBIRS-HEO launches are not announced until their host satellites are in orbit, but the NROL-42 mission is likely to be the same type of satellite that has played host to the three HEO sensors already in orbit.

(Images via ULA, Lockheed Martin and L2 Historical).

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