Sign of the future: On ISRO’s PSLV C58 mission

The PSLV C58 mission is a symbol of the demands being made of ISRO

Two missions the Indian Space Research Organisation (ISRO) has launched in the five months since its success with Chandrayaan-3 have both been scientific in nature: the Aditya L-1 space probe to study the sun and the X-ray Polarimeter Satellite (XPoSat) to study polarised X-rays emitted in astrophysical phenomena . ISRO launched the XPoSat, in a two-part mission, onboard a Polar Satellite Launch Vehicle (PSLV) on its C58 flight on January 1. The relative timing of these launches may be a coincidence but it is heartening because the ratio of scientific to technological missions ISRO has launched is skewed in favour of the-latter , at the expense of research in the sense of discovery. Those science-oriented missions have all been exceptional in their own-right . For example, XPoSat is only the second space-based experiment to study X-ray polarization , and at higher x-ray energies than the other, NASA’s Imaging X-ray Polarimetry Explorer. Its POLIX payload , realised by the Raman Research Institute, will track X-rays in the 8-30 kilo-electron-volt (keV) energy range and observe emissions from around 50 sources in five years. The XSPECT payload, by ISRO’s U.R. Rao Satellite Centre, will study X-rays of energy 0.8-15 keV and changes in continuous X-ray emissions. Together, they are expected to shed light on intense X-ray sources such as pulsars and black holes.

Then again, the science-technology skew is a reminder that ISRO among the world’s spacefaring organisations has unique needs and priorities. This is exemplified by the second part of the C58 mission. After launching XPoSat in a 650-km circular orbit around the earth, the fourth stage of the rocket lowered itself into a 350-km-high orbit and unfurled solar panels, becoming a rudimentary satellite and orbital testbed for the 10 payloads it carried. These are a radio payload by the K.J. Somaiya Institute of Technology and a device to measure ultraviolet radiation from L.B.S. Institute of Technology for Women; a ‘green’ cubesat propulsion unit, a ‘green’ monopropellant thruster, a tantalum-based radiation shield, a heater-less hollow cathode, and a nanosatellite platform, all from private entities; and an interplanetary dust counter, a fuel-cell power system, and a high-energy cell from ISRO centres. This is only the third time ISRO has operated the PSLV fourth stage in this way. As such, the C58 mission represents a union of the aspirations of professional scientists, aspiring students of science, and India’s private spaceflight sector. This again is a vignette of the demands of ISRO itself as it navigates an era in which a permanent lunar station seems inevitable , drawing as much on technological capabilities as — based on scientific missions — humankind ’s knowledge of the universe.