SpaDeX — India Becomes Fourth Nation to Achieve Space Docking
India became the fourth country in the world to successfully demonstrate space docking technology when ISRO's Space Docking Experiment (SpaDeX) spacecraft SDX-01 and SDX-02 docked in orbit on 16 January 2025. India joined an elite group consisting of the United States, Russia and China with the capability to rendezvous and dock spacecraft in space. The indigenous technology is strategically important for India's future space ambitions because docking is required for missions involving multiple spacecraft launches, orbital assembly, satellite servicing, Chandrayaan-4's lunar sample-return architecture and the planned Bharatiya Antariksh Station. ISRO subsequently demonstrated successful undocking in March 2025, followed by a second fully autonomous docking and bidirectional power transfer between the two spacecraft in April 2025.
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Timeline
1 January 2024
SpaDeX mission development advances
ISRO developed the Space Docking Experiment as a cost-effective technology demonstration mission to establish India's indigenous capability for spacecraft rendezvous, docking, formation flying and post-docking operations.
30 December 2024
PSLV-C60 launches SpaDeX
ISRO successfully launched the SpaDeX mission aboard PSLV-C60 from the Satish Dhawan Space Centre at Sriharikota. The mission carried two approximately 220 kg spacecraft, SDX-01 and SDX-02, into orbit.
30 December 2024
Two SpaDeX spacecraft deployed separately
The two SpaDeX spacecraft were deployed independently into orbit so that they could gradually separate and subsequently perform controlled rendezvous and docking manoeuvres.
7 January 2025
First docking attempt postponed
ISRO postponed the initially planned docking operation to allow additional validation and simulation of the rendezvous manoeuvres before proceeding.
9 January 2025
Docking postponed after unexpected drift
A planned docking attempt was postponed after ISRO detected greater-than-expected drift between the two spacecraft while manoeuvring toward a 225-metre separation. Both spacecraft remained safe.
12 January 2025
SpaDeX spacecraft approach within metres
ISRO successfully brought the two SpaDeX spacecraft progressively closer during rendezvous trials, validating navigation, relative positioning and control systems ahead of the final docking operation.
16 January 2025
SpaDeX spacecraft successfully dock
ISRO successfully docked SDX-01 and SDX-02 in orbit. The spacecraft approached from a 15-metre hold point to approximately 3 metres before completing capture, retraction and rigidisation.
16 January 2025
India becomes fourth country to achieve space docking
With the successful SpaDeX docking, India became the fourth country in the world to demonstrate spacecraft docking capability, joining the United States, Russia and China.
16 January 2025
Post-docking control successfully demonstrated
Following docking, ISRO successfully demonstrated control of the two SpaDeX spacecraft as a single combined object, validating another important capability required for future multi-spacecraft missions.
13 March 2025
SpaDeX satellites successfully undock
ISRO successfully undocked SDX-01 and SDX-02 on its first attempt at approximately 09:20 IST. The operation took place in a 460 km circular orbit with an inclination of 45 degrees.
13 March 2025
Complete rendezvous, docking and undocking capability demonstrated
Following the successful undocking, ISRO had demonstrated the major capabilities required for rendezvous, docking and undocking operations between spacecraft in circular orbit.
20 April 2025
SpaDeX satellites dock for second time
ISRO successfully docked SDX-01 and SDX-02 for a second time. Unlike the first experiment, the docking was completed fully autonomously from an inter-satellite distance of 15 metres without the manually exercised 3-metre hold point used during the first docking.
21 April 2025
Power transferred between docked satellites
ISRO successfully demonstrated bidirectional electrical power transfer between SDX-01 and SDX-02. Power from one spacecraft was used to operate a heater element aboard the other spacecraft, with the experiment lasting approximately four minutes.
21 April 2025
SpaDeX completes major mission objectives
The second fully autonomous docking and successful power-transfer experiment completed an important phase of SpaDeX, establishing technologies relevant to future orbital servicing, spacecraft assembly and space-station operations.
29 January 2026
ISRO highlights SpaDeX among major 2025 achievements
ISRO identified SpaDeX as one of the major achievements of India's 2025 space programme, highlighting its successful autonomous docking, undocking and power-transfer demonstrations.
1 July 2026
SpaDeX technology positioned for future Indian missions
India's indigenous docking capability became a foundational technology for future missions requiring spacecraft to rendezvous and connect in orbit, including the Bharatiya Antariksh Station, lunar sample-return missions and future in-orbit servicing and assembly operations.