Indian PSLV successfully launches SPOT-6 for France

by William Graham

The Indian Space Research Organisation (ISRO) have launched a Polar Satellite Launch Vehicle on Sunday, carrying the French SPOT-6 Earth observation satellite, along with a 15-kilogram Japanese microsatellite.

Liftoff from the Satish Dhawan Space Centre was on schedule at 04:23 UTC (09:53 local time).

ISRO Launch:

The sixth satellite in France’s Système Probatoire d’Observation de la Terre, or SPOT, programme, SPOT-6 is an optical imaging satellite capable of imaging the Earth with a resolution of 1.5 metres.

Constructed by EADS Astrium, it is based on the AstroSat-500 Mk.II bus, has a mass of 712 kilograms (1,600 lb) and is expected to operate for ten years. Another satellite, SPOT-7, is scheduled for launch in 2014.

The first SPOT satellite, SPOT-1, was launched in February 1986 on the final flight of the Ariane 1 carrier rocket, and operated until December 1990. It was subsequently reactivated in 1997 to replace a failed satellite, before finally being decommissioned in 2003. SPOT-2 was launched by an Ariane 4 in January 1990, operating for 19 years until it was retired in July 2009.

SPOT-3 was also launched by an Ariane 4, in September 1993; however it failed four years after launch in 1997, necessitating the reactivation of SPOT-1. The SPOT-4 and SPOT-5 satellites, launched in March 1998 and May 2002 respectively, remain in service.

In addition to SPOT-6, Sunday’s launch carried the Project of OIT Electric-Rocket-Engine Onboard Small Space Ship, or PROITERES, satellite for Japan’s Osaka Institute of Technology (OIT).

A 15-kilogram microsatellite equipped with a boom for gravity gradient stabilisation, PROITERES will be used for experiments investigating the propagation of radio signals, testing communications systems, and demonstrating electric propulsion for small satellites. It also carries a high resolution camera for earth imaging.

The mini Redundant Strapdown Inertial Navigation System, or mRESINS, payload is also being flown aboard the PSLV. This is a technology demonstration payload operated by ISRO, testing new avionics for future PSLV missions; similar to the AAM payload launched by PSLV C8. Like AAM, it will remain bolted to the rocket’s upper stage following launch.

The spacecraft was launched by the Indian Space Research Organisation, ISRO, using a Polar Satellite Launch Vehicle, or PSLV. First flown in 1993, the PSLV is the most flown and most successful Indian orbital launch system yet developed. The launch will use the Core Alone configuration, the smallest PSLV variant in use.

The first flight of the PSLV in September 1993 carried the IRS-1E satellite; however a guidance problem resulted in the rocket failing to achieve orbit. Another failure occurred on the first operational launch in September 1997.

This failure resulted in the payload being placed into a lower-than-planned orbit, from which it expended a significant quantity of its onboard fuel in an effort to recover.

The launch of SPOT-6 was the second mission for India’s PSLV this year, following the deployment of RISAT-1 in April. Overall, it marked the twenty-second flight of the PSLV, and the eighth of the Core Alone configuration.

The vehicle that flew on Sunday is PSLV C21. Its Core Alone configuration consists of the same core vehicle as a standard PSLV, however without the six solid rocket motors attached to the first stage.

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The PSLV-CA configuration was first used in April 2007, on the C8 flight, to deploy the AGILE spacecraft for the Italian Space Agency; a mission which also carried ISRO’s AAM avionics experiment. Its next launch came in January 2008, deploying Israel’s TecSAR radar imaging spacecraft, with another launch in April carrying CartoSat-2A, IMS-1, seven CubeSats and the Rubin-8 payload. A year later, the fourth flight launched RISAT-2 and ANUSAT.

In September 2009, the next PSLV-CA deployed OceanSat-2 and four CubeSats, also carrying the Rubin-9 payload, which like Rubin-8, remained intentionally attached to the upper stage. The sixth launch, in July 2010, orbited CartoSat-2B, AlSat-2A, and three CubeSats. The most recent flight before C21 occurred in October 2011, when PSLV C18 deployed the Franco-Indian Megha-Tropiques satellite, along with the VesselSat-1, SRMSAT and Jugnu spacecraft.

PSLV C21’s first stage was the PS1, a solid-fuelled stage powered by an S-138 motor, which produces 4.8 meganewtons (1.1 million pounds) of thrust, with an expected burn time of around 101.5 seconds. It ignited upon the countdown reaching zero, and powered the rocket until burnout.

The first stage separated from the vehicle 115.5 seconds after liftoff, with second stage ignition occurred two tenths of a second later.

The second stage of PSLV C21 was a PS2, powered by a hypergolically-fuelled L40 Vikas engine, which used unsymmetrical dimethylhydrazine as fuel, and dinitrogen tetroxide as oxidiser. Intended to burn for 148 seconds, the second stage was jettisoned 267.1 seconds into the flight.

During the second stage burn, the payload fairing, or “Heat shield” as ISRO describe it, separated from around the spacecraft. Fairing separation occurred 195.7 seconds after liftoff.

Following second stage separation, the PSLV’s third stage took over. This was the PS3, a solid-fuelled stage with an S-7 motor, which burns for 110 seconds. Following depletion of the third stage, the PSLV coasted for a few minutes, before stage three separation 521.9 seconds after liftoff. Then, 11.6 seconds after staging, the fourth stage ignited.

Powered by two L-2-5 engines burning monomethylhydrazine and mixed nitrogen oxides, the PS4 fourth stage was the final stage of the PSLV-CA vehicle. It can burn for up to 526 seconds, and for this mission it burned for 508.3 seconds.

Following cutoff, 1,041.8 seconds after launch, the vehicle prepared for spacecraft separations. SPOT-6 was the first payload to separate from the upper stage, 37 seconds after cutoff. PROITERES was deployed fifty seconds later.

The launch is targeted to an orbit with a perigee of 654.9 kilometres, and an apogee of 656.5 kilometres, with 98.233 degrees of inclination.

The Satish Dhawan Space Centre’s First Launch Pad was the site of Sunday’s launch. The centre, formerly named the Sriharikota High Altitude Range, was named after the former chairman of ISRO upon his death in 2002.

All of India’s orbital launches have occurred from Satish Dhawan, with the First Launch Pad being the older of its two active orbital launch complexes.

PSLV C21 was the second Indian launch this year. One more is scheduled, which currently planned for early December carrying the SARAL spacecraft and several other satellites. In addition to this, two Indian satellites are expected to launch on European Ariane 5 rockets in the next few months.

The Geosynchronous Satellite Launch Vehicle’s return to flight mission and the test flight of the GSLV Mk.III, however, have been delayed to 2013.

(Images via ISRO).

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