BENGALURU: In a milestone for India’s space capabilities, Isro completed its first-ever satellite docking manoeuvre early Thursday (Jan 16), marking a crucial step toward multiple future missions — including Chandrayaan-4 and the country’s own space station — in the pipeline.
The final command for the docking was issued from the Isro Telemetry, Tracking and Command Network (Istrac) in Bengaluru.
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Isro termed it a historic moment. Elaborating on the process, it said it first completed the manoeuvre from 15m to 3m hold point. “…Docking was initiated with precision, leading to 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 maneuvers and power transfer tests between the satellites.
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.
PM Narendra Modi, congratulated Isro scientists and the entire space fraternity for the successful demonstration of space docking of satellites. “…It is a significant stepping stone for India’s ambitious space missions in the years to come,” he posted on X.
Union minister Jitendra Singh posted: “…SPADEX has accomplished the unbelievable… docking complete… and it is all indigenous “Bharatiya Docking System”. This paves the way for smooth conduct of ambitious future missions including the Bharatiya Antriksha Station, Chandrayaan 4 & Gaganyaan. PM Sh @narendramodi’s continuous patronage keeps the spirits soaring… here at Bengaluru.”
The Space Docking Experiment (SpaDeX), launched on Dec 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 Jan 6 identified the need for further validation. This crucial input saw Isro postpone the docking procedure from Jan 7 to Jan 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 (Jan 11) morning.” Isro had said. On Jan 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 Dec 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 Jan 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 Jan 9.
And, on Jan 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 (Jan 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 Jan 8.
On Jan 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 (Jan 10), it is expected to reach initialisation conditions,” Isro said Thursday.
And on Jan 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.
