India successfully orbited its heaviest commercial mission

On July 10, 2015, Indian Space Research Organization (ISRO) conducted successful launch of PSLV-XL launch vehicle with three DMC3, CBNT-1, and De-OrbitSail satellites into a sun-synchronous orbit (SSO) from Satish Dhawan Space Center, Sriharokota.

With the overall lift-off mass of five satellites amounting to near 1440 kg, the mission has become the heaviest commercial mission undertaken by ISRO and its commercial wing, Antrix Corporation.

CBNT-1 (left) and three DMC3 satellites (right) in the cleanroom at Sriharikota. Credit: ISRO
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Three DMC3 satellites, each weighting 447 kg and having 1 meter resolution imagery, are optical Earth observation spacecraft on SSTL-300S1 platform built by Surrey Satellite Technology Ltd. (SSTL) of the UK. They were made by SSTL under near $165 million contract, signed in 2011, with its subsidiary, satellite imaging provider DMC International Imaging (DMCii), which stands for Disaster Monitoring Constellation, operated by DMCii.

The latter, in turn, leased all DMC3 satellites capacity to Chinese company 21AT (Twenty First Century Aerospace Technology Co. Ltd.), under near $170 million contract on a term for at least 7 years. This approach is new for Earth observation industry, where previously data was sold on a sq.km of imagery basis, and is very similar to business models used in telecommunications.

“I am very glad that the three satellites are in orbit and have started communication with the ground station. It is the first step of our long march and we are looking forward to the commencement of our BJII [another name for the Constellation is Beijing-2] data services following the completion of the commissioning of the DMC3/TripleSat Constellation.” Wu Shuang, CEO & President of 21AT

PSLV-C28 mission, meaning the 28th flight of Polar Satellite Launch Vehicle (excluding three development PSLV-D missions), orbited 2 other British spacecraft as well. The first is CBNT-1 Earth observation technology demonstrator, weighting 91 kg, also built by SSTL. The second is Surrey Space Center-operated De-OrbitSail 3U CubeSat that have a 4-by-4-meter deployable sail to demonstrate rapid de-orbiting.

According to ISRO, in order to accommodate all this payload it had to design a unique circular launch vehicle adaptor (L-adaptor) and a triangular deck called Multiple Satellite Adaptor-Version 2 (MSA-V2).

Location of British payloads on the launcher's adaptor and sequence of their separation. Credit: ISRO
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PSLV family of Indian launchers currently has 3 configurations. PSLV, standard version of the rocket that has four stages and six strap-on boosters, PSLV-CA ('core alone') without strap-on boosters, and PSLV-XL, updated version of rocket's standard configuration boosted by more powerful, stretched strap-on boosters. Payload capacity of the most powerful PSLV-XL, used recently, is 1800 kg to a altitude sun-synchronous orbit.

PSLV-C28/DMC3 mission was the second Indian space launch in 2015, after successful mission to orbit IRNSS-1D navigation satellite on March 28. According to ISRO launch kit, three DMS3, СBNT-1, and De-OrbitSail satellites have become 41-45th foreign spacecraft, launched aboard a PSLV rocket. As it was later reported, India is planning to launch 28 satellites belonging to six or seven other countries in the next three years.

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