New Delhi: After a delay of over two months, the Indian Space Research Organisation (ISRO) Thursday confirmed the successful undocking of its spacecraft, SDX-01 (Chaser) and SDX-02 (Target), as part of its space docking experiment (SpaDeX).
“Congrats team ISRO. And heartening for every Indian! SPADEX Satellites accomplished the unbelievable De-Docking…This paves the way for the smooth conduct of ambitious future missions, including the Bharatiya Antariksh Station, Chandrayaan 4 & Gaganyaan. PM Sh Narendra Modi’s continuous patronage keeps the spirits soaring,” said Union Minister for Science and Technology Jitendra Singh.
The SpaDeX mission, which took flight on 30 December last year, was originally supposed to have displayed the docking and undocking of the two spacecraft in the first week of January. However, while ISRO successfully showcased its docking capabilities, the undocking could not be performed as planned.
ThePrint explains how the undocking experiment was carried out and what caused the delays.
Spadex undocking captured from both SDX-1 & SDX-2! 🛰️🛰️🎥
Watch the spectacular views of this successful separation in orbit.
Congratulations to India on this milestone! 🇮🇳✨ #Spadex #ISRO #SpaceTech pic.twitter.com/7u158tgKSG
— ISRO (@isro) March 13, 2025
The undocking and hurdles
Earlier this week, ISRO was finally able to resolve all glitches and attempt the undocking of SDX-01 and SDX-02.
To undock the two spacecraft, the space agency conducted a manoeuvre to make an extension from SDX-01 to SDX-02. The levers that were holding the two craft were released, and a “de-capture command” was successfully issued.
“Following the command, the two spacecraft moved away. The undocking experiment is now successful,” a senior ISRO official, who wished to not be named, told ThePrint.
ISRO officials said that the primary focus of the space agency for SpaDeX was to ensure that the two spacecraft were healthy. For this reason, the scientists preferred treading cautiously and ensuring a successful outcome.
Another senior ISRO official told ThePrint that after the docking was successfully performed, SDX-01 and SDX-02 were unable to generate enough power for the undocking manoeuvre to be initiated. There was also a struggle with the Attitude Control System (ACS) of the second craft.
“We were also not able to stably capture the two craft for the manoeuvre,” the official said.
The mission
While a milestone mission for India, ISRO’s SpaDeX has been riddled with hurdles from the get-go.
On 30 December 2024, ISRO launched SpaDeX onboard the Polar Satellite Launch Vehicle (PSLV-C60). The in-space manoeuvring was originally scheduled for 7 January, as part of which the two craft were set to display rendezvous, docking, and undocking.
A day before the manoeuvre, however, the space agency announced the postponement of the experiment to 9 January.
“The SpaDeX Docking scheduled on the 7th is now postponed to the 9th. The docking process requires further validation through ground simulations based on an abort scenario identified today,” ISRO said in a statement on 6 January.
While the space agency made multiple attempts to move the craft towards and away from each other, the final docking attempt could not be conducted on 9 January either.
This was because the craft could not stay put at the required position and were drifting away from each other.
“While making a manoeuvre to reach 225 m between satellites, the drift was found to be more than expected, post non-visibility period. The planned docking for tomorrow is postponed. Satellites are safe,” the agency said on 8 January.
Senior ISRO officials told ThePrint in January that while the hiccups were not ideal, the agency was sure of the experiment’s success because the two craft were in good health and had enough fuel to conduct multiple attempts.
Crucial for future missions
By mastering rendezvous, docking, and undocking technologies, ISRO aims to enhance its operational flexibility and expand its mission horizons.
SpaDeX is a milestone in advancing India’s capabilities in space docking. The mission findings will be critical for future space missions, satellite servicing, space station operations, and interplanetary missions.
In its mission document, the space agency said the primary objectives of SpaDeX were to develop and demonstrate the technology for rendezvous and docking using two small spacecraft and to demonstrate controllability in the docked condition, exhibiting the potential for extending the life of the target spacecraft.
“Additionally, the mission aims to test power transfer between the docked spacecraft. The secondary objectives include post-docking activities where the spacecraft will perform independent payload operations,” it read.
(Edited by Radifah Kabir)
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