With the success of the SpaDex mission, ISRO has lined up a handful of missions. (Express Archives/Partha Paul)
Mylswamy Annadurai
Jan 18, 2025 11:03 IST First published on: Jan 18, 2025 at 11:02 IST
Smartness, diligence and resilience, hallmarks of the Indian space programme, have been once again demonstrated in the early hours of January 16. Two small satellites, each weighing about 220 kgs, were made to dock after a few attempts stretching over a week. There were compelling constraints like smaller and near identical spacecraft, given a limited budget. Having a smaller spacecraft led to use of minimum propellant and hence there was a need for a more optimal number of possible docking attempts. The satellites were monitored and operated by ISRO’s existing ground station network that limits the duration of contact to the spacecraft. The first few attempts of space docking did not meet the desired result. There was a list of obstacles and constraints. Converting all such constraints into challenges to be overcome, ISRO as a team, has shown its grit by successfully docking both spacecraft in space on the fourth attempt. India is now the fourth country to achieve this feat after the US, Russia and China.
Looking ahead, after the successful Space Docking Experiment (SpaDex), ISRO has lined up a handful of missions. Chandrayaan-4, the fourth in the moon mission series, is a sample return mission. The mission profile envisages the lunar-bound lander of Chandrayaan-4 to rise from the lunar surface along with the collected lunar samples to reach an orbit around the moon. In the lunar orbit, the lander will do a rendezvous and dock with another lunar orbiter of Chandrayaan-4 that will be orbiting around the moon before coming back to the earth along with the lunar sample. The latest SpaDex mission is basically a very cost-effective and innovative forerunner for the docking that is envisaged around the moon in Chandrayaan-4 mission.
It is worth noting that after space docking, it is verified that both the satellites’ attitude/orientation is being controlled as a single entity. The electrical power transfer from one satellite to another will be tested and demonstrated in the docked configuration. This power transfer technology is one of the possible scenarios to extend the life of orbit satellites in the future. After a few orbits of testing, both satellites will be de-docked and separated. In the separated configuration again, both the satellites will function as remote sensing satellites for the next few years, as both satellites carry state-of-the-art remote sensing cameras. In addition, the radiation dose monitor in one of the satellites will be used to measure the radiation levels in the 400-km orbit around the earth. This data will be of great use for our own upcoming manned mission Gaganyaan.
The recent past has seen a lot of crowding of active satellites in earth orbits. To safeguard the active satellites from the space debris, controlled orbit maneuvers are being executed. The frequency of such maneuvers is being increased now even for ISRO. There is a possible requirement of removing harmful debris from space. The present space rendezvous and docking/catching mission will be handy in such scenarios.
Beyond all these science and technical outcomes and benefits, it is interesting to note that both the satellites of the SPADEX mission were assembled and integrated by a private entity on their premises at the Bangalore aerospace park. This is the first time that ISRO’s satellites are assembled and integrated outside ISRO, heralding the emergence of a new ecosystem for the space industry in India.
The budget of SpaDex is around Rs 225 crore, far below what any other space agency might have spent. If one looks at the money spent against the list of accomplishments, it will show how cost-effective innovations are being repeatedly brought out by ISRO for its missions, starting from the first spacecraft Aryabhatta to the latest SpaDex. Cost-effective innovation and frugal engineering has been the mantra of ISRO, and it is now poised to spread to Indian industry and the younger generation infectiously, even as the space programme is being opened up to private players.
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While celebrating the success of SpaDex, one can’t stop looking at the road ahead for the Indian space programme. The increasing number of startups in the space sector, good progress and visibility of small satellite launch vehicles like SSLV, Agnikul, Skyroot, the upcoming new launch facility along with a space park near Kulasekarapattinam, open a lot of innovative and commercially-competitive possibilities for the Indian space industry. Considering the need to maintain and replenish the existing Indian earth observation, communication, meteorological and navigation satellites, and new national and international requirements, one can easily foresee a healthy meeting point of supply and demand for space infrastructure.
To conclude, the SpaDex mission is a cost-effective mission for the demonstration of in-space docking using two small spacecraft launched by PSLV. This technology is essential for India’s space ambitions such as putting an Indian on the Moon, bringing back lunar samples, the building and operation of the Bharatiya Antariksh Station (BAS), etc. In-space docking technology is essential when multiple rocket launches are required to achieve common mission objectives. Like major missions such as the Chandrayaans, Mangalyaan and Aditya-L1, the SpaDex mission has inspired 1.4 billion Indians and also boosted India’s image in the space sector.
The writer is former director, ISRO Satellite Centre, Bangalore
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