Modified PSLV places three foreign satellites in orbit

ISRO uses PS-4 stage, which normally ends up as debris, as an orbital platform for experiments

June 30, 2022 07:02 pm | Updated July 01, 2022 12:08 pm IST - Sriharikota

Polar Satellite Launch Vehicle (PSLV) launched the PSLV-C53 mission with three payloads from Singapore at Sriharikota, around 100 kilometres from Chennai on June 30, 2022. 

Polar Satellite Launch Vehicle (PSLV) launched the PSLV-C53 mission with three payloads from Singapore at Sriharikota, around 100 kilometres from Chennai on June 30, 2022.  | Photo Credit: S.R. Raghunathan

On a hot summer evening accentuated by clear blue skies, the Indian Space Research Organisation’s (ISRO) workhorse launch vehicle on its 55th mission, the PSLV-C53, rose into the sky, painting it with a pencil-shaped plume of smoke before it curved away and injected three Singaporean satellites into their intended orbits in the second dedicated mission for the commercial arm of ISRO, New Space India Limited (NSIL).

The mission also served an additional purpose for ISRO, which decided to use the fourth stage, the PS4, as a stationary platform in orbit to conduct scientific experiments. ISRO Chairman, S. Somanath, described the manoeuvre as “a poem in orbit”.

The modified PSLV-C53 took off from the second launchpad at the Satish Dhawan Space Centre, Sriharikota Range (SHAR), at 6.02 p.m. and placed the three satellites — a 365 kg Singaporean Earth Observation Satellite, DS-EO, a 155 kg small commercial satellite with a Synthetic Aperture Radar (SAR) payload, the NeuSAR; and a 2.8 kg satellite from Nanyang Technological University (NTU) and SCOOB-1 — into orbit 19 minutes after lift-off.

This was also the first time since December 2019 that a launch was allowed to be witnessed by the media and the general public allowed to the Visitors Gallery, marking a sense of normalcy at the space port since the COVID-19 pandemic struck the world and lockdown restrictions were placed.

“After the primary mission, the PSLV-4th stage is going to write some poems in orbit. The PSLV Orbital Experimental Module (POEM) is going to be functional after this [placing of satellites into orbit] taking over the control of the primary mission computer to another computer. The fourth stage will be powered, generating power on board and will be stabilised with altitude control and host some experiments by some of young startups enabled by InSpace,” Mr. Somanath said from Mission Control.

Mr. Somanath said that, normally, the fourth stage would end up as debris in space. But ISRO had repurposed the fourth stage and introduced a computer control system to fire its thrusters, sensors such as star sensors that will enable it look at the stars, find its own position, and also send commands from the ground. The fourth stage can be used in missions where the load is light, like on the PSLV-C53. On missions with higher payloads, such as an upcoming launch with a 1.5 tonne satellite, there will be too little propulsion left to operate the POEM.

S.R. Biju, Mission Director, said the PSLV was in a different configuration this time with the core-alone version being used after a long time. “We had to introduce some changes to improve the production of PSLV so that we can meet the growing demand of customers, which we have implemented, and it has yielded results,” he said.

Explaining about the fourth stage and POEM, Mr. Biju said ISRO would take over the PS-4 stage and give it some energy to do some cost-effective experiments in orbit that can satisfy the growing demand from startups, and the student and scientific communities. “Left to itself, it [PS-4] would have taken its own course, tumbled, wobbled, or it would have somersaulted. But given some more energy, probably we will be able to continue the active PS-4 for some more time, so that the platform is available, all the resources are available, you keep some scientific payloads there so that it can serve a secondary purpose also,” he said.

D. Radhakrishnan, Chairman and Managing Director, NSIL, said the agency was gearing up for more commercial launches for international customers.

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