An illustration of SpaDeX spacecraft rendezvousing in orbit. Credits: ISRO

SpaDeX: India Achives Historic First Docking in Orbit

The Indian SpadeX mission successfully achieved its main objective of rendezvousing, and docking the two small spacecraft in a low-Earth circular orbit

On January 16, 2025, the Indian Space Research Organization (ISRO) performed its first docking between two spacecraft in orbit, reaching the main objective of its Space Docking Experiment (SpaDeX) mission.

The successful maneuver was planned for January 9, then postponed since the drift was more than expected while the two satellites were approaching to reach a relative distance of 225 m.

SpaDeX satellites holding position at 15m. Credits ISRO
SpaDeX satellites holding position at 15m. Credits ISRO

The two satellites designed as SDX01 and SDX02, or the “Chaser” and the “Target”, moved back at a distance of 1,5 Km on January 10th, then to 230 m the day after. In the following days, the SpaDeX spacecraft moved step by step at a closer distance, with a first close rendezvous of about 3 meters on January 12 to continue collecting data.

Finally, on the docking day, the Chaser and the Target began the rendezvous sequence, which ended in a successful spacecraft capture. This was followed by rigidization to stabilize the grip. The mission will continue with additional testing for electric energy transfer and safe undocking.


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India, the fourth nation of the in-orbit docking club

On March 16, 1966, NASA performed the first docking in space of two spacecraft, the Gemini 8 capsule piloted by Neil Armstrong and David Scott, and the Agena target vehicle. If the first manual docking was successful, the rest of the mission was less fortunate due to an uncontrolled roll of the combined vehicle that almost gave us another first man on the Moon.

The Agena target vehicle pictured from the Gemini 8 capsule in space. Credits: NASA
The Agena target vehicle pictured from the Gemini 8 capsule in space. Credits: NASA

One year later, the Soviet Union became the second nation and the first to dock two spacecraft in orbit automatically, the two uncrewed Soyuz test vehicles Kosmos 186 and Kosmos 188.

The two nations remained the only ones able to dock spacecraft in space for over 45 years, until the first in-space docking of the Chinese Shenzhou 8 spacecraft and Tiangong 1 module in 2011. With the SpaDeX mission, India entered the club, becoming the fourth nation to demonstrate this key space capability.


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A milestone for the bold Indian space programs

Docking in space is a strong dependency for a country with significant space ambitions like India. For the Indian Human Spaceflight Programme, the SpaDeX mission is a crucial endeavor since the technology used to dock the “Chaser” and the “Target” satellites will be used to dock the Ganganyaan crewed orbital spacecraft to the Bharatiya Antariksha Station.

Render of the Bharatiya Antariksh Station with two Ganganyaan docked. Credits. ISRO
Render of the Bharatiya Antariksh Station with two Ganganyaan docked. Credits: ISRO

The Chandrayaan lunar exploration program will also leverage all the components used on the SpaDeX spacecraft for its Lunar sample return mission, Chandrayaan 4.

“Chandrayaan-4 has multiple modules, five in total, which will be launched at different times and integrated into two separate modules. These modules need to reach orbit and then dock both in Earth orbit and Moon orbit. Docking is essential for Chandrayaan-4.”

— S Somanath, ISRO chairman


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Giancarlo Albertinazzi

Giancarlo Albertinazzi

Space Ambassador, Terranaut, Future Spacepolitan, Writer of Becoming Spacepolitans Blog

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