BENGALURU: India took a giant leap towards becoming part of an elite club of nations after Isro completed its first satellite-docking manoeuvre early Thursday, marking a big step towards multiple future missions, including Chandrayaan-4 and the country’s own space station.
The significant achievement came in Isro’s fourth docking attempt since putting the satellites in orbit on Dec 30 and after a week of suspense.
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After satellites started drifting apart by Jan 7, Isro deployed tough strategies to pull them back as close as just 3 metres from each other, before taking the final step Thursday.
The critical moment of the Space Docking Experiment (SpaDeX) unfolded at 6.30am when commands were issued from Isro Telemetry, Tracking and Command Network (Istrac) in Bengaluru. Tension filled the Mission Operations Complex (MOX) as controllers awaited confirmation of the delicate operation.
Next: Undocking & power transfer test between sats
Isro termed it “a historic moment”. The space agency said it first completed the manoeuvre from 15 metres to 3 metres hold point. “Docking was initiated with precision, leading to (a) successful spacecraft capture. Retraction completed smoothly, followed by rigidization for stability. Docking successfully completed,” Isro said.
Following the docking, Isro demonstrated another crucial capability by controlling the joined satellites as a single unit. The mission will continue in the coming days with planned undocking manoeuvres and power-transfer tests between the satellites.
This achievement moves India closer to joining an exclusive group of space-faring nations of the US, Russia and China. However, Isro would acknowledge that several more successful docking demonstrations will be needed to fully master this complex technology and proudly wear the badge.
The final attempt on Thursday was made possible by multiple teams from UR Rao Satellite Centre (URSC), Istrac, and Laboratory for Electro Optics Systems (LEOS), whose sensors were critical for both rendezvous and docking. The teams were led by URSC director M Sankaran, SpaDeX mission director K Subbarao, and project director N Surendran. Istrac director Anil Kumar led the tracking and control operations.
Thursday was the fourth time ISRO tried attempting docking since putting the satellites in orbit. The launch (Dec 30) created a small velocity difference between the satellites in an orbit of 475km, causing them to drift apart at a rate of 10m/s.
“The maximum distance between the two satellites was 12.8km,” Sankaran told TOI. Initially, Isro planned to have an inter-satellite distance of up to 20km.
Once the maximum distance was achieved, Isro began actively controlling satellite positions using one satellite’s propulsion system to halt the drift and maintain this precise separation. The mission then entered a critical waiting period to achieve optimal solar orientation, ensuring sufficient power generation for the docking procedure.
“We didn’t completely automate everything. Since the launch, there have been 5-6 stages. At each stage, we were monitoring from the ground and giving a go-ahead before proceeding to the next,” Sankaran said. He added that Isro employed a petal-based docking system, aligned with international standards, including the International Docking System Standard.
Isro took a cautious approach to the entire operation, including ground simulations based on an abort scenario that on Jan 6 identified the need for further validation. This crucial input saw Isro postpone the docking procedure from Jan 7 to 9, only to postpone it again. After it put off the docking on Jan 7 and 9, Isro was all set for docking on Jan 12, but conducted only a trial and pushed the actual procedure to later once the analysis of the trial data was complete.
