BENGALURU: In a milestone for India’s space capabilities, Isro completed its first-ever satellite docking manoeuvre early Thursday (January 16), marking a crucial step toward multiple future missions — including Chandrayaan-4 and the country’s own space station — in the pipeline.
Multiple sources confirmed that the docking attempt was a success. No official announcement about the same was done at the time of writing this report.
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With this, India has taken the first step towards joining an elite club of nations — the US, Russia and China — that boast of such technology. Isro will need several more docking tests before claiming mastery over the technology.
The Space Docking Experiment (SpaDeX), launched on December 30, saw two satellites that were launched separately unite at an orbital altitude of approximately 475km, with the final commands executed from Isro Telemetry, Tracking and Command Network (Istrac) in Bengaluru.
“We didn’t completely automate everything. Since the launch there have been five to six stages, and at each stage, we were monitoring from the ground and giving a go-ahead before proceeding to the next,” M Sankaran, director URSC, had told TOI explaining the process.
Isro employed a petal-based docking system, aligned with international standards including the International Docking System Standard (IDSS).
The space agency had taken a cautious approach to the entire operation, including ground simulations based on an abort scenario that on January 6 identified the need for further validation. This crucial input saw Isro postpone the docking procedure from January 7 to January 9, only to postpone it again.
By Jan 11, the two satellites achieved a distance of 230m from the distance of 1.5km. “Arrested at Inter Satellite Distance (ISD) of 230 m, all sensors are being evaluated. Spacecraft’s health is normal,” Isro had said.
A day before that Isro had said spacecraft were at a distance of 1.5 km and on hold mode. “Further drift to 500 m is planned to be achieved by tomorrow (January 11) morning.” Isro had said. On January 9, the space agency had put the satellites on a slow drift course after it was forced to put off the docking on the day.
After the launch on December 30, Isro has been preparing for the docking, which requires multiple steps/stages, each of which was monitored from the ground and given a go-ahead before proceeding to the next.
However, it has had to postpone its docking attempt multiple times. On January 6, a day before the first docking attempt was scheduled, Isro had found that the docking process required further validation through ground simulations based on an abort scenario it identified on the day. And the docking was rescheduled for January 9.
And, on January 8, Isro said: “While making a maneuver to reach 225m between satellites the drift was found to be more than expected, post non-visibility period. The planned docking for tomorrow (January 9) is postponed. Satellites are safe.” The space agency had initiated the drift on the chaser spacecraft — the two satellites are designated chaser and target — late on January 8.
On January 9, a day after the drift between satellites caused Isro to postpone SpaDeX for the second time, the space agency managed to put the spacecraft in a slow drift course. “…The drift has been arrested and spacecraft put in a slow drift course to move closer to each other. By tomorrow (January 10), it is expected to reach initialisation conditions,” Isro said Thursday.
And on January 12, it carried out a trial to reach up to 15m and further to 3m and then the satellites were moved to a safe distance.
Docking in space is a complex process and so far, only three other countries have mastered it.