Second Attempt: GOCE launched via Russian Rockot

by NSF

A Russian Rockot launch vehicle – a converted SS-19 Russian Intercontinental Ballistic Missile (ICBM) – launched on Tuesday, following a 24 hour delay when Monday’s attempt was scrubbed at T-7 seconds, due to an issue with the Launch Service Tower. The vehicle is carrying the Gravity field and steady-state Ocean Circulation Explorer (GOCE) spacecraft into orbit on Monday.

Attempt One Issue:

“The doors on the launch service tower did not open,” noted ESA. “Due to this anomaly, the tower was held in position and did not move back as required for a launch.”

The launch was resheduled for Tuesday, which resulted in a successful launch.

Mission preview:

The adaptation of the early 1970s nuclear missile launch vehicle, the Rockot uses the original two lower liquid propellant stages of the ICBM in conjunction with a third stage for commercial payloads called Breeze KM – optimised for delivering up to 1950 kg into low Earth orbit. GOCE will be ultimately placed into a Sun-synchronous, near-circular polar.

Around 150 of the SS-19 missiles were declared as excess in military terms by the Strategic Talks on Arms Reduction Treaty (START) agreements signed by the United States and the Soviet Union in 1990 and 1991, but were permitted to be reused as civil launchers.

The SS-19 ICBM has flown over 140 times, with three failures, early on in its operational history. Rockot successfully began commercial launches in 2000 and has since flown eight times, with only one failure.

The overall launch vehicle length is 29 meters; the launch mass is 107 tons. The external diameter of the first, second and third stage is 2.5 m; the payload fairing has an external diameter of 2.6 m and a height of 6.7 m. Rockot is marketed and operated by Eurockot, a German-Russian joint venture.

The GOCE satellite, developed by an industrial consortium of 45 companies distributed over 13 European countries, embodies many world-firsts in its design and use of new technology in space to map Earth’s gravity field in unprecedented detail.

The impressive looking five-metre long satellite is designed to orbit at a very low altitude of just 260 km, due to the gravitational variations are stronger closer to Earth.

GOCE’s main instrument is the Electrostatic Gravity Gradiometer (EGG), a set of six 3-axis accelerometers mounted in a diamond configuration in an ultra-stable structure.

Each accelerometer pair forms a ‘gradiometer arm’ 50 cm long, with the difference in gravitational pull measured between the two ends. Three arms are mounted orthogonally: along-track, cross-track and vertically. The gradiometer will be 100 times more sensitive than any sensor of the same type previously flown in space.

GOCE also carries a GPS receiver to be used as a Satellite-to-Satellite Tracking Instrument (SSTI) to supplement the gradiometer measurements. The SSTI consists of an advanced dual-frequency, 12-channel GPS receiver and an L-band antenna.

GOCE also has a Laser Retroreflector to allow its precise orbit to be tracked by a global network of ground stations through the Satellite Laser Ranging Service. This will provide accurate positioning for orbit determination and data products.

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