Atlas V launches with SBIRS GEO-1 at second attempt

by William Graham

The United Launch Alliance (ULA) have successfully made a second attempt to launch their Atlas V 401 – from Cape Canaveral on Saturday at 2:10pm EDT – following several failed attempts to find a gap in unacceptable weather during the 40 minute launch window on Friday – resulting in a 24 hour scrub turnaround. The Atlas V launched with the first in a new series of early warning satellites to detect missile launches.

Atlas V/SRIRS GEO-1 Overview:

The satellite, SBIRS GEO-1, is the first dedicated spacecraft to be launched as part of the Space Based Infrared System, or SBIRS, although two sensor packages hosted on other satellites are already in orbit. SBIRS is a system of spacecraft which monitor the Earth using infrared sensors in order to detect and track missile launches.

It will consist of satellites in geosynchronous orbit, and sensors on other satellites in highly elliptical orbits. Satellites in low Earth orbit were originally planned as well, however these were later cancelled.

The need to detect missile launches dates back to the Cold War, when both the United States and the Soviet Union perceived a danger that the other could launch a surprise nuclear attack. In the mid 1950s, the United States began development of the first space-based missile detection system; the Missile Defense Alarm System or MIDAS, which used satellites in low Earth orbit equipped with infrared sensors to detect launches.

The first spacecraft, Midas 1, was launched on 26 February 1960 atop an Atlas-Agena, however it failed to reach orbit after the upper stage failed to separate from the Atlas. Midas 2 was successfully launched on 24 May of the same year. The first six satellites were used to test systems, after which operational launches began. Midas 7, launched on 9 May 1963, was the first satellite to detect a missile launch.

In all, twelve MIDAS satellites were launched, of which three were lost in launch failures. In addition, two test flights of the infrared sensors were made, under the designations Discoverer 19 and 21. The last MIDAS satellite, FTV-1353, was launched on 5 October 1966. Although an operational constellation of twelve satellites had originally been planned, by the end of the programme MIDAS was considered an experimental system, and never operated at full capacity.

Following the end of the MIDAS programme, plans to deploy an operational system led to the Integrated Missile Early Warning Satellite programme, or IMEWS. Unlike MIDAS, which was designed to use large numbers of satellites in low Earth orbit, IMEWS consisted of a smaller number of satellites in geosynchronous orbit.

The four first-generation IMEWS satellites were launched aboard Titan III(23)C rockets, beginning on 6 November 1970 with OPS 5960. Despite being left in a lower than planned orbit after its carrier rocket malfunctioned, OPS 5960 was able to raise itself into geosynchronous orbit, and was still able to operate for three years; over twice its 15-month design life.

With the launch of the fourth satellite in June 1973, DSP became the first fully operational missile detection system. Produced by TRW, the first-generation satellites had a mass of around 900 kilograms, generated 400 watts of power, and were designed to operate for fifteen months. Equipped with a 3.5 metre Schmidt telescope with 2000 lead sulphide infrared sensors, the satellites could detect the launches of Soviet and Chinese missile intercontinental and submarine-launched ballistic missiles.

The first three second-generation satellites were launched between 1975 and 1977. They had the same design and instrumentation as the first four spacecraft, however they generated 80 watts more power and were designed to last nine months longer than their predecessors. These satellites were followed by four Multi-Orbit Satellite/Performance Improvement Modification, or MOS/PIM, spacecraft. Around this time, the programme became known as the Defense Support Program, or DSP.

MOS/PIM satellites carried additional attitude control propellant, extending their design lives by another year, and generated 500 watts of power. MOS/PIM was designed to operate in highly elliptical orbits as well as geosynchronous ones, however all four launches went to geosynchronous orbit. They were launched between 1979 and 1984. The third satellite was launched on the final flight of the Titan IIIC rocket, with the fourth satellite being launched instead on a Titan 34D/Transtage.

Due to delays with the development of third-generation DSP satellites, two spare second generation satellites were refitted with sensors being developed for the third-generation spacecraft, and launched in 1984 and 1987. The number of infrared sensors was increased to 6000, and the spacecraft was fitted with a second instrument using mercury cadmium telluride sensors to observe in the mid-infrared.

In 1989, the first third-generation satellite was launched, on the maiden flight of the Titan IV rocket, flying in the 402 configuration which incorporated an Inertial Upper Stage (IUS). Three launches using Titan IV(402)A rockets took place between 1989 and 1994, with another satellite being deployed from Space Shuttle Atlantis during the STS-44 mission in 1991, also with the aid of an IUS. A further five satellites were launched by Titan IV(402)B rockets between 1997 and 2004.

The final satellite, USA-197, which incorporated an additional sensor to detect small-scale nuclear tests, was launched on a Delta IV Heavy on 11 November 2007. It had originally been expected to launch on a Titan IV, however it was moved to the Delta IV to allow for a later launch. In September 2008, just after just ten months in service, it failed.

No details on the cause of the failure have been released, however the USA-187 and 188 satellites were used to inspect it, making passes on 23 December 2008 and 1 January 2009. USA-187 and 188 were launched in 2006 as part of the MiTEx programme, and were approaching the ends of their operational lives.

In 1999, the launch of the sixth third-generation satellite ended in failure after the upper and lower stages of the IUS failed to separate fully from each other. The upper stage still completed its burn, leaving the payload, USA-142, spinning out of control in a highly elliptical orbit. Control of the satellite was established after it separated from the IUS, however the satellite could not raise its own orbit, and within a few weeks of launch a fuel leak developed as a result of damage sustained from the out-of-control ascent.

The satellite never entered service, however it was used until July 2008 to study the Van Allen belts, and their effects upon spacecraft systems.

Like the earlier spacecraft, third generation satellites were produced by TRW, which became part of Northrop Grumman in 2002. They had a mass of 2,387 kilograms, a design life of five years, and could generate 1,274 watts of power. Ten third-generation satellites are in orbit; an eleventh satellite was built, however it will never be launched.

DSP satellites have become known for their reliability and longevity; only USA-197 failed to remain operational for its full design life, and most survived for many more years than expected.

SBIRS will begin to replace DSP, with three more geosynchronous satellites under construction and another planned. Unlike DSP, SBIRS satellites are launched into geosynchronous transfer orbit, which eliminates the need for a heavy-lift launch system such as the Titan IV or Delta IV-H to take them all the way to geosynchronous orbit. DSP will be kept in service as long as possible to provide a backup to SBIRS, and to provide additional capacity.

Two SBIRS-HEO payloads are already in orbit, aboard the US National Reconnaissance Office’s ‘Improved Trumpet’ electronic intelligence spacecraft. The first, USA-184, was launched aboard a Delta IV-M+(4,2) on 28 June 2006, and the second, USA-200, was placed into orbit by an Atlas V 411 on 13 March 2008. These sensors are believed to be working well, and two more are currently under construction. They remain attached to the NRO spacecraft, which are located in Molniya orbits.

The SBIRS programme was originally intended to include a low Earth orbit element, with satellites detecting launches, tracking missiles and identifying the type of missile in flight. This element grew out of the SDIO Space Surveillance and Tracking System, later known as Brilliant Eyes. In 2002 it was spun off from SBIRS as separate programme named the Space Tracking and Surveillance System (STSS), under the control of the Missile Defense Agency.

SBIRS GEO satellites are built by Lockheed Martin, based around the A2100M bus, whilst Northrop Grumman is responsible for producing the instruments. Each satellite is equipped with two sensors, one of which scans the whole of the visible part of the Earth, whilst the other focuses on one particular area, such as a known missile base.

The A2100M bus is also used for several other military satellite programmes, including the Advanced Extremely High Frequency communications satellites. The first AEHF satellite, USA-214, was launched last year and is still making its way into geosynchronous orbit after its apogee motor malfunctioned. Lockheed are confident that the SBIRS satellite will not be affected by the same problem.

USA-205, a risk-reduction satellite for the STSS programme, was launched atop a Delta II rocket from Vandenberg in May 2009. It was followed by two demonstration satellites, USA-208 and 209 in September of the same year. An additional demonstration satellite, SBIRS-LADS, was never launched.

SBIRS GEO-1 will be launched by United Launch Alliance using an Atlas V 401 carrier rocket. This features a four metre payload fairing, no solid rocket motors, and a Centaur upper stage with a single RL10 engine.

The rocket that will launch GEO-1 has the tail number AV-022. It will be the twenty-sixth Atlas V to fly, and the eleventh flight of the 401 configuration.

The Atlas V is a two stage rocket, with a Common Core Booster (CCB) first stage, and a Centaur second stage. A single Russian-built RD-180 engine powers the CCB. The RD-180, a derivative of the RD-170 engine developed for the Zenit boosters of the Energia rocket, is fuelled by RP-1 propellant and oxidised by liquid oxygen.

Ignition of the RD-180 will occur 2.7 seconds before the countdown reaches zero, and at T-0 the engine will be ready for flight, before liftoff occurs 1.1 seconds later. The engine will reach full thrust a second after liftoff as AV-022 heads straight up.

At T+17.7 seconds, at an altitude of around 240 metres, AV-022 will pitch over, and perform roll and yaw manoeuvres to establish the correct trajectory for its ascent to orbit.

Heading East over the Atlantic Ocean on an azimuth of 98.82 degrees, AV-022 will pass through Mach 1 around 80.8 seconds into its flight, before passing through Max-Q, the area of maximum dynamic pressure, 9.8 seconds later. As fuel drains from the first stage, the vehicle’s acceleration will increase, and around 215 seconds after launch the RD-180 will be throttled back to limit the force caused by acceleration to 5g.

Booster Engine Cutoff, or BECO, will occur 243 seconds after launch, the RD-180 engine shutting down having completed its role in the launch. Six seconds later the Atlas first stage will separate from the Centaur. The Centaur is powered by a single RL10A-4-2 engine, which is fuelled by liquid hydrogen and oxidised by liquid oxygen. The RL10 will ignite ten seconds after stage separation, and will be followed eight seconds later by the separation of the payload fairing.

Eleven minutes and 12.9 seconds after igniting, the Centaur’s engine will shut down, having completed the first of its two burns. After coasting for eight minutes and 45.1 seconds, the engine will restart for its second burn, which will last three minutes, fifty two and a half seconds. The rocket will then coast for fifteen minutes an ten seconds.

Forty three minutes and 19.5 seconds after lifting off, the payload will separate from the upper stage into a geosynchronous transfer orbit with a perigee of 185 kilometres, an apogee of 35,786 kilometres, 21.64 degrees inclination, and an argument of perigee of 178 degrees. Over the next nine days, the satellite will raise itself into geosynchronous orbit through six burns of its apogee motor.

AV-022 will lift off from Cape Canaveral Air Force Station’s Space Launch Complex 41, or SLC-41. Originally built as a Titan IIIC launch complex, it was first used in December 1965. In the 1970s the Titan IIIE rocket, which deployed the Helios, Viking and Voyager probes, launched from Complex 41.

Titan IV launches from SLC-41 began in June 1989. Whilst the complex was being used by the Titan IV, three DSP launches took place from the pad, most recently the failed launch of USA-142 on 9 April 1999, which was the final Titan launch from the complex. Six months later the fixed and mobile towers at the pad were demolished by controlled explosions, ahead of the complex being renovated for use by Atlas V rockets. The Atlas V made its maiden flight from SLC-41 in 2002, carrying the Hot Bird 6 spacecraft for Eutelsat.

AV-022 was assembled in the Vertical Integration Facility, a tower located 550 metres southeast of SLC-41 and used to integrate all Atlas rockets launched from the pad. The rocket, atop its mobile launch platform, was transported to the launch pad on Thursday. The rollout began at 14:18 UTC, and ended with the arrival of AV-022 at the pad, which occurred at 14:59.

The launch of AV-022 will be the twentieth orbital launch attempt of 2011, and the third Atlas V launch of the year. It is the first time the Atlas V 401 configuration has flown since February last year when one deployed the Solar Dynamics Observatory. The next Atlas V launch is currently planned for 5 August, when the Juno probe is scheduled to be dispatched to the planet Jupiter.

The next launch by United Launch Alliance is expected to be of a Delta II rocket, carrying the SAC-D spacecraft for CONAE, the Argentine space agency. That launch is currently scheduled to occur no earlier than 9 June. A Delta IV will also launch next month with a GPS satellite.

(Images via ULA and Pat Corkery, United Launch Alliance and Lockheed Martin).

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