ISRO to perform unique experiment in PSLV-C56 mission launched today

SRIHARIKOTA: Scientists at ISRO, after successfully launching seven Singaporean satellites on Sunday's mission, will attempt a unique experiment using the fourth stage of the PSLV-C56 rocket.

While the mission is a follow-up to the PSLV-C55 TeLEOS-2 mission launched in April this year, scientists in today's mission will place the fourth stage of the PSLV rocket in a lower orbit.

After injecting all the Singapore satellites into the intended orbit at an altitude of about 536 km, the upper stage of the rocket will be placed in lower orbit to ensure its reduced orbital life at an altitude of about 300 km, ISRO said. ISRO Chairman S Somanath said, ''We are going to have many exciting further activities on the PS4 stage after this (successful launch). The PSLV fourth stage, which is currently in the orbit of the satellite which is at almost 535 km circular orbit in a 5-degree inclination, will be brought back to a lower orbit of 300 km''.

He said the reason for bringing back the PS4 stage to a lower orbit was to mitigate space debris problems.

''(The experiment is being done) with an intent to have a lower lifespan of the stage being spent in space, primarily to make sure that the space debris mitigation problems are addressed through our conscious efforts to bring back the PSLV upper stage in a controlled manner, and to demonstrate that in this mission.'' Somanath, who is also Secretary, Department of Space, said at the Mission Control Centre.

PSLV Mission Director S R Biju said, ''As our Chairman indicated, we have not completed the mission. The primary mission, the primary objective of the mission is completed (to place the seven Singapore satellites into intended orbits) and it has become a habit for PSLV (sic) to doing some experiments (in the fourth stage of rocket).'' ''Because as you know, last time also we have done this, that is we have written 'POEMS', we have sung melodies in space, we have taken startups to orbit, all those things we have done with spent PS4 stage and this time we thought we will do something different,'' Biju explained.

''We are embarking on it after the completion of the primary mission because we are taking the PS4 stage back to another orbit, because this orbit of 536 km-570km orbit is very much in demand for many satellites. So, we thought we will not be wandering there and we decided that we will take the PS4 stage or the spent stage to another orbit, to another objective for two purposes.'' he said.

''One, our chairman has told to do whatever is best possible to mitigate the menace of debris in orbit and another thing, this precious orbit will not be occupied with spent ps4 stage as a debris and we will give space for future satellites. These are two objectives with which we are doing this experiment, and that experiment is in progress'' he said.

In April, ISRO undertook a similar exercise during the launch of the PSLV-C55 mission.

Scientists successfully performed another unique experiment where the fourth stage of the PSLV rocket was utilised as an orbital platform to carry out scientific experiments using the PSLV Orbital Experimental Module (POEM) in the rocket. ''POEM is going to write some more poems with seven payloads,'' Somanath had said then after the successful launch of PSLV-C55. Those payloads belong to ISRO, Bellatrix, Dhruva Space and Indian Institute of Astrophysics.