India ushers in 2024 orbiting XPoSat successfully

X-ray Polarimeter Satellite (XPoSat) is the first space mission for the Indian Space Research Organisation (ISRO) on January 1.
India ushers in 2024 orbiting XPoSat successfully
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For the first time in its history, the Indian Space Research Organisation's (ISRO), on Monday, January 1, ushered in the New Year in a grand manner by orbiting its X-ray Polarimeter Satellite (XPoSat). At about 9.10 a.m. on the first day of the calendar year 2024, India's Polar Satellite Launch Vehicle-C58 (PSLV-C58) standing 44.4-metre tall, with a lift off mass of 260 ton blasted off from the first launch pad at the Satish Dhawan Space Centre. The rocket carried XPoSat and 10 other experimental payloads on its fourth stage.

Interestingly, this is the first space mission for the Indian Space Research Organisation (ISRO) on January 1.

At about 21 minutes into its flight, the rocket ejected XPoSat at an altitude of about 650 km. Speaking after the launch ISRO Chairman S Somanath said, "The orbit accomplished for XPoSat is excellent as the deviation is just three kilometres. The solar panels of the satellite have been deployed."

The XPoSat is the first dedicated scientific satellite from the ISRO to carry out research in space-based polarisation measurements of X-ray emission from celestial sources. It carries two payloads, namely POLIX (Polarimeter Instrument in X-rays) and XSPECT (X-ray Spectroscopy and Timing). The POLIX is realised by the Raman Research Institute and XSPECT is by the Space Astronomy Group of the UR Rao Satellite Centre (URSC).

According to the ISRO, the three objectives of XPoSat are: (a) To measure polarisation of X-rays in the energy band 8-30keV emanating from about 50 potential cosmic sources through Thomson Scattering by POLIX payload. (b) To carry out long-term spectral and temporal studies of cosmic X-ray sources in the energy band 0.8-15keV by XSPECT payload and (c) To carry out polarisation and spectroscopic measurements of X-ray emissions from cosmic sources by POLIX and XSPECT payloads, respectively, in the common energy band.

The 10 payloads are from TakeMe2Space, LBS Institute Technology for Women, K J Somaiya Institute of Technology, Inspecity Space Labs Private Ltd, Dhruva Space Private Ltd, Bellatrix Aerospace Private Ltd (two payloads) and three payloads from the ISRO.

In its normal configuration, the PSLV is a four-stage/engine expendable rocket powered by solid and liquid fuels, alternatively, with six booster motors strapped onto the first stage to give higher thrust during the initial flight moments.

The ISRO has five types of PSLV rockets -- Standard, Core Alone, XL, DL, and QL. The major difference between them is the use of strap-on boosters which, in turn, largely depends on the weight of the satellites to be orbited. The PSLV uses 6,4,2 solid rocket strap-on motors to augment the thrust provided by the first stage in PSLV-XL, QL & DL variants, respectively. However, strap-ons are not used in the core-alone version (PSLV-CA).

The satellite configuration is modified from the IMS-2 bus platform. The configuration of the mainframe systems is derived based on the heritage of IRS satellites. 

After orbiting the XPoSat in 650km, the rocket's fourth stage -- PS4 stage -- will be lowered to 350km, about 9.6 deg orbit, by restarting it twice. The left-out propellant in the PS4 will be disposed of through the main engines as a precursor to enabling the safety of the PS4 stage in atmosphere reentry experiments planned in future.

The oxidiser will be let out first followed by fuel in a predetermined sequence of operations. The existing scheme of spent stage passivation by venting the tank pressure will also be active. Post passivation of PS4, the control of the stage is transferred to the PSLV Orbital Experimental Module-3 (POEM-3) avionics, the ISRO said.

The POEM is configured as a 3-axis stabilised orbital platform for conducting experiments to space qualify systems with novel ideas. The orbital platform's electrical power requirements are catered by a Flexible Solar Panel in conjunction with 50Ah Li-Ion battery in battery tied configuration.

The orbital platform consists of avionic systems to take care of navigation, guidance, control and telecommands and Orbital Platform Attitude Control System to cater to control of the platform to test the payloads, the ISRO added.

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