SRIHARIKOTA: The Indian Space Research Organisation (Isro) on Saturday successfully placed two Singapore satellites — TeLEOS-2 (a synthetic aperture radar satellite) and Lumelite-4 (a technology demonstration nano-satellite) — in their desired orbits. A Polar Satellite Launch Vehicle (PSLV-C55), which carried these satellites, also carried out scientific experiments with seven payloads attached to its PS4 upper stage.
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The rocket lifted off from the first launch pad at Satish Dhawan Space Centre in Sriharikota at 2.19pm. It was PSLV’s 57th flight. It was also the 16th flight of PSLV with a CA (core-alone) variant, which is the lightest version of launch vehicle as it has only four core stages and no strap-on boosters to give an added thrust.
Around 19 minutes after the lift-off, PSLV-C55 placed 741kg TeLEOS-2 in a 586km orbit. Fifty seconds later, the rocket placed 16kg Lumelite-4 also in the desired orbit.
Around two minutes after the last satellite was separated, the upper stage of PSLV underwent passivation (a chemical process) with mixed oxides of nitrogen (MON) followed by mono methyl hydrazine (MMH) – the propellants that power PSLV’s upper stage. The operation was to reduce the compression in the tanks to prevent an explosion. Given that there would be exposure to high temperatures, the fuel could expand and cause an explosion.
After this process, the PS4 upper stage of the rocket turned into an orbital platform (PSLV Orbital Experimental Module-2 or POEM-2) to perform in-orbit scientific experiments with payloads attached to it. Seven non-separable payloads were mounted on a multi-satellite adapter (MSA).
Isro chairman S Somanath said PSLV has once again proved its reliability. “The upper stage of the rocket is going to write a summer poem. Seven payloads are mounted on top of the upper stage. If everything goes well, it will function for the next one month. It is for the first time that we are deploying a solar panel in PS4. We’ll update on the performance of POEM through our social media handles,” he said.
Isro officials said payloads were powered on by a command, after all satellites were separated. The platform had a solar panel mounted around the PS4 tank which was deployed through a ground command after confirmation of the stage achieving stabilization.
The platform ensured that the deployed solar panel pointed towards the sun, optimally using an appropriate sun pointing mode to increase its power generation capability. The power was provided to the payloads and the avionic packages based on their requirements. Throughout this part of the mission, the platform remained in the same orbit achieved at the end of PS4 tank passivation after the primary mission.
This is the third time that PS4 was used after satellite separations as a platform for experiments.
POEM-2 carried seven experimental non-separable payloads. They included PiLOT (PSLV In orbitaL Obc and Thermals), an OBC package from IIST; ARIS-2 (Advanced Retarding Potential analyser for Ionospheric Studies) experiment from IIST; HET-based ARKA200 Electric Propulsion System from Bellatrix; DSOD-3U and DSOD-6U deployer units along with DSOL-Transceiver in S- & X- bands from Dhruva Space and Starberry Sense Payload from Indian Institute of Astrophysics (IAP).
The two Singapore satellites
The TeLEOS-2, developed under a partnership between DSTA (representing the Government of Singapore) and ST Engineering, will be used to support the satellite imagery requirements of various agencies of the Singapore government. TeLEOS-2 carries a Synthetic Aperture Radar (SAR) payload. TeLEOS-2 will be able to provide all-weather day and night coverage. It is capable of imaging at 1m full-polarimetric resolution.
Lumelite-4 is co-developed by the Institute for Infocomm Research (I2R) of A*STAR and Satellite Technology and Research Centre (STAR) of the National University of Singapore. Lumelite-4 is an advanced 12U satellite developed for the technological demonstration of the High-Performance Space-borne VHF Data Exchange System (VDES). Using the VDES communication payload developed by I2R and STAR’s scalable satellite bus platform, it aims at augmenting Singapore’s e-navigation maritime safety and benefit the global shipping community.
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