According to sources, the Indian Space Research Organization (ISRO) successfully finished docking the SpaDeX satellites on Thursday, days after bringing them as close as three meters to one another. ISRO reported that the two spacecraft were successfully controlled as a single entity after the docking. Through a post on social media platform X, the space agency announced that “undocking and power transfer checks will follow in the coming days.” “The spacecraft docked successfully! A momentous occasion. Let’s examine the SpaDeX docking procedure: The move from the 15-meter to the 3-meter hold point is finished. With careful docking, the spacecraft was successfully captured. Smooth retraction was followed by stability-enhancing rigidization. Earlier in the morning, ISRO had declared that the docking process was successful.
Lauding the achievement, Prime Minister Narendra Modi congratulated the team at ISRO. “Congratulations to our scientists at @isro 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 wrote on X.
Jitendra Singh, Union Minister of State in-charge of science and technology, also congratulated the space agency. “Finally made it. 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,” he wrote.
Due to technical difficulties, ISRO had previously missed two docking dates, on January 7 and 9. On December 30, the space agency launched the satellites. A successful trial attempt to raise the two satellites up to 15 meters and 3 meters apart was announced by ISRO on January 12. “A trial attempt is made to reach up to 15 meters and then 3 meters. retreating spacecraft to a secure distance. After more data analysis, the docking process would be completed, ISRO had stated.
After two successive delays, a senior ISRO official stated that the docking of the two satellites “is on track,” but the space agency will now “dock and inform” the public about the exercise. Previously, ISRO had stated that the docking would be a public event. The news of a change of leadership at ISRO coincided with the postponing of the SpaDex docking schedules. On January 7, the Central government declared that V Narayanan will be the new director of ISRO, and on January 14, he assumed leadership. The goal of the SpaDex (Space Docking Exercise) mission is to demonstrate the technology needed to dock two tiny satellites that the PSLV launched on December 30.
Chandrayaan-4, an Indian mission slated to return lunar samples to Earth, is perhaps the first one that will actually need the docking capability. This mission’s re-entry module, which will be built to survive the heat of re-entry into Earth’s atmosphere, is scheduled for a separate launch. In the Earth’s atmosphere, the re-entry module will dock with the transfer module that is transporting samples from the Moon. In order to build up the Bharatiya Antariksh Station, docking would also be necessary. The launch of the first module is scheduled for 2028. It is anticipated that its five parts will be launched independently and assembled in orbit. The human mission to Moon, which would also require the capability, is not expected to happen before 2040.
ISRO launched two small spacecraft — SDX01, the Chaser, and SDX02, the Target — in a low-Earth circular orbit on December 30 and set them apart at a distance of around 20 km in space to facilitate a gradual rendezvous through the closing of the distance for a final docking.
In the mission, after the initial 20 km inter-satellite separation, the Chaser satellite approaches the Target satellite by reducing the distance to 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m, before the final docking of the two spacecraft.
“After successful docking and rigidisation, electrical power transfer between the two satellites will be demonstrated before undocking and separation of the two satellites to start the operation of their respective payloads for the expected mission life of up to two years,” ISRO had said ahead of the launch of the mission.
After the successful launch and release of the two SpaDex satellites into orbit, ISRO had initially reported that the docking will take place on the morning of January 7.
The agency, however, announced a postponement on January 6 saying, “The SpaDeX docking scheduled on 7th is now postponed to 9th. The docking process requires further validation through ground simulations based on an abort scenario identified today.” The space agency then said on January 8 that it had “initiated the drift on the spacecraft to move closer from 500 m to 225 m”. It, however, also said on the same day that the docking had been postponed to January 9 due to a technical issue.
On Thursday, January 9, the space agency announced: “The drift has been arrested and spacecrafts put in a slow drift course to move closer to each other. By tomorrow, it is expected to reach initialisation conditions.”
“The docking experiment is called for on account of many reasons. The immediate one is Chandrayaan 4 but later for the space station planned for India,” a former ISRO official said.
The Chandrayaan 4 mission involves several docking and undocking exercises, both in the earth orbit and the lunar orbit.
“Two modules launched by two launch vehicles will dock in the GTO and both modules will travel together to the moon and one of the modules will stay in the moon orbit and the others will go to the moon’s surface and collect the sample. One of the modules that lands on the moon will also take off from the moon to the lunar orbit and will dock with the module that is parked in the lunar orbit,” ISRO scientist and project director on the successful Chandrayaan 3 moon landing mission from 2023, P Veeramuthuvel, said in October 2024 at the International Astronautical Conference in Milan.
