ISRO's first New Year day launch success, PSLV-C58/XPoSat mission to study black holes accomplished

Sriharikota, (Andhra Prdesh): In a first, the Indian Space agency heralded 2024 with the successful first ever New year day launch, when PSLV-C58, carrying XPoSat, X-ray Polarimeter Satellite, and ten other payloads, was successfully injected into the orbit after a fine take off from the spaceport of Sriharikota on Monday morning.

After a smooth 25 hour countdown that began at 0810 hrs yesterday, the workhorse launch vehicle of ISRO took off from the First Launch Pad at 0910 hrs, amid loud cheers from the audience and after a 20-minute flight duration and the ignition and separation of all the four stages of the vehicle, the 469 kg satellite was injected into the orbit.

Scientists at the Mission Control Centre burst into jubilation after the satellite was injected into the precise orbit as the space agency ringed in the new year with a bang.

"PSLV-C58/XPOSAT mission was accomplished", ISRO Chairman S.Somanath said, addressing the scientists after the successful mission.

"Happy New Year to all. Yet another PSLV mission was accomplished successfully and placed in 650 km orbit (with just 2-3 km difference)", he said, adding, it will take some more time (about 4,000 secs) as the Orbit will be lowered to 350 km by switching off and starting the fourth stage PS4 engine of launch vehicle twice experimenting POEM-3 for scientific experiments.

"We are really happy and we are having exciting times ahead', he said.

The solar panels on board the spacecraft were deployed and the ground stations have

started monitoring by taking control of it.

Mission Director Jayakumar also expressed happiness over the success of the Mission.

The 44.4m tall PSLV-C58, in its 60th flight and fourth under DL variant with two strap-on motors and with a lift off mass of 260 tonnes, took off from the First Launch Pad at 0910 hrs from the SHAR Range as scheduled.

After an eventful, successful and a landmark 2023 with Chandrayaan-3 and Sun exploratory missions, ISRO ushered in 2024 with this successful mission--a first on the New Year day--setting the tone for a series of upcoming missions, including Aditya spacecraft (Sun mission) landing on L1 point a few days from now, and the prestigious INDO-US NASA collaboration NISAR Satellite launches this month.

About 20 minutes after the lift off, the 469 kg XPoSat was injected into an Eastward low inclination orbit of 650 kms.

ISRO posted in X "PSLV-C58/XPoSat Mission: Lift-off normal. xPoSat satellite is launched

successfully".

"PSLV-C58 vehicle placed the satellite precisely into the intended orbit of 650 km with

6-degree inclination", it said.

The POEM-3 is being scripted ..., it said.

After injection of XPOSAT, the PS4 stage is being restarted twice to reduce the orbit into 350 km circular orbit to maintain in 3-axis stabilized mode for Orbital Platform (OP) experiments.

The PSLV Orbital Experimental Module-3 (POEM-3) experiment was executed meeting the objective of 10 identified payloads, supplied by ISRO and IN-SPACe.

With a mission life of five years, XPoSat (X-ray Polarimeter Satellite) is the first dedicated scientific satellite from ISRO to carry out research in space-based polarisation measurements of X-ray emission from celestial sources.

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

It carries two payloads namely POLIX (Polarimeter Instrument in X-rays) and XSPECT (X-ray Spectroscopy and Timing). POLIX is realized by Raman Research Institute and XSPECT is by

Space Astronomy Group of URSC.

The objectives of the mission are 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, to carry out long term spectral and temporal studies of cosmic X-ray sources in the energy band 0.8-15keV by XSPECTpayload and 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 emission mechanism from various astronomical sources such as blackhole, neutron stars, active galactic nuclei, pulsar wind nebulae etc. originates from complex physical processes and are challenging to understand.

While the spectroscopic and timing information by various space based observatories provide a wealth of information, the exact nature of the emission from such sources still poses deeper challenges to astronomers, it said.

The polarimetry measurements add two more dimension to our understanding, the degree of polarization and the angle of polarization and thus is an excellent diagnostic tool to understand the emission processes from astronomical sources.

The polarimetric observations along with spectroscopic measurements are expected to break the degeneracy of various theoretical models of astronomical emission processes. This would be the major direction of research from XPoSat by Indian science community.

The POLIX payload serves as an X-ray Polarimeter designed for astronomical observations within the energy band of 8-30 keV. The instrument comprises a collimator, a scatterer, and four X-ray proportional counter detectors surrounding the scatterer.

The scatterer, constructed from low atomic mass material, induces anisotropic Thomson scattering of incoming polarized X-rays. The collimator plays a crucial role in restricting the field of view to 3 degrees by 3 degrees, ensuring that only one bright source is within the field of view for most observations.

POLIX's primary objective is to observe bright astronomical sources across various categories during the planned 5-year lifetime of the XPoSat mission. Notably, POLIX stands out as the first payload in the medium X-ray energy band specifically dedicated to polarimetry measurements.

XSPECT is an X-ray Spectroscopy and Timing instrument, designed to offer fast timing and excellent spectroscopic resolution in soft X-rays (0.8-15 keV). XSPECT also monitors changes in line flux and profile, offering simultaneous, long-term temporal monitoring of soft X-ray emission. The instrument employs an array of Swept Charge Devices (SCDs) with an effective area exceeding 30 cm² at 6 keV and an impressive energy resolution of less than 200 eV at 6 keV.

XSPECT employs passive collimators to reduce background by narrowing its field of view. This payload is anticipated to observe a variety of sources, including X-ray pulsars, black hole binaries, low-magnetic field neutron stars (NS), active galactic nuclei (AGNs), and magnetars.

With these two payloads--POLIX and XSPECT--the XPoSat mission is capable of simultaneous studies of temporal, spectral, and polarization features of the bright X-Ray sources. The mission objectives include measurement of X-Ray polarization in the energy band of 8-30 keV emanated from X-Ray sources, long-term spectral and temporal studies of cosmic X-Ray sources in the energy band of 0.8-15 keV.

The payloads onboard XPoSat will observe the X-Ray sources during its transit through the Earth’s shadow, i.e., during the eclipse period.

The Scientific goals of the mission are to study the distribution of magnetic field, geometric anisotropies, alignment w.r.t line of sight, nature of accelerator in galactic cosmic X-Ray sources by measuring degree of polarization and its angle; Structure and geometry of magnetic field of neutron stars, mechanism of X-Ray beaming and its relation with luminosity and mass of accretion rate of powered pulsars; Detailed understanding of galactic black hole binary sources; To study and confirm about production of X-Rays is either from polar cap of neutron star or outer cap of pulsar magnetosphere and to distinguish the synchrotron mechanism as dominant over thermal emission in Supernova remnants.

ISRO said after injection of XPoSat in 650km, 6 deg orbit, PS4 stage will be lowered to 350km, 9.6 deg orbit, by restarting PS4 twice. The left out propellant in the PS4 will be disposed through the Main engines as a pre cursor to enabling safety of PS4 stage in atmosphere re-entry 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 stage is transferred to POEM Avionics.

About POEM, it said PS4 stage is configured as a 3-axis stabilized Orbital platform for conducting experiments to space qualify systems with novel ideas. The PS4 Stage Orbital Platform Electrical power requirements are catered by 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 & telecommands and Orbital Platform Attitude Control System to cater to control of the platform to test the 10 payloads.

The 10 payloads developed by start-ups, education institutions and ISRO centres are the Radiation Shielding Experimental Module (RSEM) by TakeMe2Space, Women Engineered Satellite (WESAT) by LBS Institute of Technology for Women, BeliefSa-t0 Amateur radio satellite by K.J. Somaiya Institute of Technology, Green Impulse TrAnsmitter (GITA) by Inspecity Space Labs Private Limited, Launching Expeditions for Aspiring Technologies -Technology Demonstrator (LEAP-TD) by Dhruva Space Private Limited, RUDRA 0.3 HPGP by Bellatrix Aerospace Private Limited, ARKA-200 by Bellatrix Aerospace Private Limited, Dust Experiment (DEX) by PRL, ISRO Fuel cell Power System (FCPS) by VSSC, ISRO and Si-based High Energy cell by VSSC, ISRO. (UNI)