Isro, which recently undocked the two satellites part of its Space Docking Experiment (SpaDeX) mission on March 13, has successfully completed another experiment — the “rolling” or “rotating” experiment — which involved circumnavigation of one of the satellites and bringing it back to the same spot....Isro chairman V Narayanan confirmed to TOI that the experiment was carried out last week [week of Mar 21], and said: “We’ve completed the rolling experiment. The satellites have a lot of propellant… I have only told [the teams] one thing, please do everything [on] simulation on ground [first]. Let us be very careful. Let us not make any mistakes as a wealth of data can be generated [through various experiments]....During the whole time, the satellite performing the experiment was in the line of vision of the other satellite. The experiment was to help Isro validate its control over satellite manoeuvring from ground — that means a slew of softwares, sensors, positioning tech etc. There is no immediate confirmation if the satellite did the circumnavigation (do the full circle) horizontally or vertically (somersault)....With a lot of fuel left in the satellite, Isro is expected to carry out more experiments. Afterall, SpaDex is an experimental mission and Isro is hoping to make the most of it. Also, once the next docking is complete, there will be another attempt to do power transfer between the satellites, learning from which — some lessons have already been learnt from the first attempt — will be crucial for future mission design and development.
On the flip side, there was one crucial experiment in the SpaDeX mission - to transfer electrical power from one satellite to the other - that was not completed in the first round of docking, ISRO chief Dr V Narayanan confirmed...."In the first attempt there was a suspicion of a minor mis-alignment of the power transfer ports (and) hence this was postponed to the next round," Dr Narayanan confirmed.
On December 30, 2024, ISRO’s PSLV-C60 launched twin SPADEX satellites and after injecting satellites at 475 km altitude, the specially configured upper stage (PS4) of PSLV-C60 (called PSLV Orbital Experimental Module in short POEM-4) was also almost in the same orbit. Subsequently, POEM-4 was de-orbited by engine restarts to a nearly circular orbit at 350 km altitude with 55.2 degree inclination. PS4 was then passivated by venting the leftover fuel to minimise any potential risk for accidental break-up. During its mission life, POEM-4 hosted altogether 24 payloads (14 payloads from ISRO and 10 from various NGEs) and all payloads worked as expected yielding valuable science data.While the POEM-4 was in orbit, it was continuously tracked by ISRO’s Radar Facilities and United States Space Command (USSPACECOM) facilities as well. The tracking data was in turn utilised in the re-entry prediction process. It was observed that POEM-4’s orbit had decayed to 174 km x165 km and the platform was predicted to re-enter the Earth’s atmosphere on April 04, 2025.The atmospheric re-entry event of POEM-4 was then closely monitored by ISRO System for Safe and Sustainable Space Operations Management (IS4OM) and regular updates in predictions were made. Finally, the POEM-4 module re-entered the atmosphere and impacted at 02:33 UTC (08:03 IST), April 04, 2025, in the Indian Ocean. The safe re-entry of POEM-4 is yet another accomplishment to ISRO’s commitment to contain the growth of space debris, reaffirming the prominent role of ISRO in the long-term sustainability of outer space environment and Debris Free Space Mission (DFSM).
#ISRO SPADEX Update:Glad to inform that the second docking of satellites has been accomplished successfully.As informed earlier, the PSLV-C60 / SPADEX mission was successfully launched on 30 December 2024. Thereafter the satellites were successfully docked for the first time on 16 January 2025 at 06:20 AM and successfully undocked on 13 March 2025 at 09:20 AM. Further experiments are planned in the next two weeks.
In the SPADEX mission, India has already "successfully demonstrated docking and undocking twice over", ISRO Chairman Dr V Narayanan told NDTV.After these extended docking and undocking maneuvers, the ISRO chief said, there was still 50% of the fuel left on the two satellites.A precision rocket launch and frugal orbital management has left the two satellites with nearly 2.5 kilograms of fuel each, said the ISRO chief, adding that this helps extend the mission life.
After successfully demonstrating space docking this year, Isro chairman V Narayanan said the agency is planning to conduct a second phase of space-docking experiment, which will pave the way for setting up India's own space station, Bharatiya Antariksha Station. Narayanan said space-docking experiments involving two satellites launched by a PSLV rocket in Dec were successful and Isro was planning SpaDeX-2. A proposal on this second phase will be presented to govt soon, he said. SpaDeX-2 may be launched in the coming three years, subject to govt approval.
“Docking in a circular orbit is much easier than docking in an elliptical orbit. This is because the trajectory and velocity of the satellites remain constant in a circular orbit, whereas they keep changing on an elliptical orbit. What this essentially means is that calculations done for one point will not be relevant after a few minutes,” said a scientist in the know of the matter. “This is, however, what the SpaDeX 2 experiment will attempt.”This capability is likely to play a vital role in future missions, such as Chandrayaan-4, where multiple modules may be launched separately, and docking and undocking will be required in both Earth and lunar orbits.
