New Delhi:

India docked two satellites in space on Thursday, a key milestone for the country’s ambitions of a space station and manned Moon mission. “India docked its name in space history,” said the Indian Space Research Organisation (ISRO) on X. ISRO shared a behind-the-scenes video today to showcase the lead-up to the historic feat – dubbed as SpaDeX, or Space Docking Experiment.

The video shows a packed mission control room for the coverage of the orbital docking.

A man was heard explaining the whole process: “The mission director will be giving a go-ahead for the subsequent motion of spacecraft from 3 meters till docking. The command will be given for the subsequent phase wherein the spacecraft starts at three meters. With a constant velocity of 10 mm per second, it is approaching other spacecraft for docking to take place.”

ISRO successfully completed docking of two SPADEX satellites (SDX-01 & SDX-02) in the early hours of 16 January, 2025.#SPADEX #ISRO pic.twitter.com/UJrWpMLxmh

— ISRO (@isro) January 17, 2025

The satellites, weighing 220 kilograms each, blasted off on December 30, last year, on a single rocket from Andhra Pradesh’s Sriharikota launch site. Later they separated.

The two satellites were manoeuvred back together on Thursday in a “precision” process resulting in a “successful spacecraft capture”.

Back at the control room, the man announced, amid a round of applause, “The capture event is nominal… Both the spacecraft are captured. the capture has been completed.”

Congratulating everyone involved in the mission for accomplishing the “historic docking for the first time in the country”, ISRO chairman V Narayanan said, “During the last 15 days, excellent dedicated activities were carried out and today we have got a historic docking and on this occasion, let me congratulate each one of you. Today, we are a proud nation carrying this technology with us which is required for our future missions, including Chandrayaan-4, crewed mission to moon. This is the first stepping stone towards those important activities”.

The docking experiment is crucial for the smooth conduct of the country’s ambitious future missions, including Chandrayaan-4, Gaganyaan, setting up a space station and landing an astronaut on the moon. Last October, the government announced that India will have its own Space Station by 2035, known as the “Bharatiya Antriksh Station”.

The PSLV C60 rocket carrying two small satellites, SDX01 (Chaser) and SDX02 (Target), along with 24 payloads, had lifted off from the first launchpad of the Satish Dhawan Space Centre, and about 15 minutes after liftoff, the two small spacecraft weighing about 220 kg each were launched into a 475-km circular orbit as intended.

India has become the fourth country to achieve the milestone after Russia, the United States and China.

Two earlier docking attempts by ISRO were postponed due to technical issues.

Photo: YouTube/@isroofficial5866

ISRO has once again postponed the Space Docking Experiment (SpaDEx) involving two satellites, citing excessive drift during a crucial manoeuvre.

The SpaDEx was supposed to take place on January 9.

“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. Stay tuned for updates,” ISRO said in a post on ‘X’ on Wednesday (January 8, 2025).

This is the second time when the ISRO postponed the SpaDEx.

The space agency had initially planned it on January 7, 2025, which was cancelled and postponed to Thursday (January 9, 2025), which again got cancelled.

The Space Docking Experiment (SPADEX) is a pivotal project, which is designed to develop and demonstrate the technology needed for spacecraft rendezvous, docking, and undocking using two small satellites, the space agency said.

“SpaDeX will serve as a milestone in advancing India’s capabilities in space docking, a critical technology for future space missions including satellite servicing, space station operations, and interplanetary missions,” ISRO said in an explainer.

ISRO’s SpaDeX mission, launching with PSLV-C60, will demonstrate in-space docking using two small spacecraft.
| Photo Credit: ANI

The Indian Space Research Organisation (ISRO) will launch its final mission for 2024 on December 30 with the PSLV C60/SPADEX Mission. The launch is scheduled at 9.58 p.m. from the Satish Dhawan Space Centre in Sriharikota.

The space agency, for the first time, will be attempting the Space Docking Experiment (SPADEX) mission which will demonstrate in-space docking using two small spacecraft.

According to ISRO, SPADEX is designed to develop and demonstrate the technology needed for spacecraft rendezvous, docking, and undocking using two small satellites. “SPADEX will serve as a milestone in advancing India’s capabilities in space docking, a critical technology for future space missions, including satellite servicing, space station operations, and interplanetary missions,” the space agency said.

The demonstration of this technology is essential for futuristic missions such as sending an Indian astronaut on the Moon, sample return from the Moon, the building and operation of the Indian Space Station.

The PSLV-C60 will launch the two small spacecraft Chaser and Target also named SDX01 and SDX02 weighing about 220 kg each into a 470 km circular orbit at 55-degree inclination separately.

SDX02 spacecraft will be the first to separate 15 minutes after the launch followed by SDX01 spacecraft a few seconds later.

Incremental velocity

“The demonstrated precision of the PSLV vehicle will be utilised to give a small relative velocity between the Target and Chaser spacecraft at the time of separation from the launch vehicle. This incremental velocity will allow the Target spacecraft to build a 10-20 km inter-satellite separation with respect to the Chaser within a day. At this point, the relative velocity between the Target will be compensated using the propulsion system of the Target spacecraft,” ISRO said.

ISRO added that at the end of this drift arrest maneuver, the Target and Chaser will be in the same orbit with identical velocity but separated by about 20 km, known as Far Rendezvous.

“With a similar strategy of introducing and then compensating for a small relative velocity between the two spacecraft, the Chaser will approach the Target with progressively reduced inter-satellite distances of 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m, ultimately leading to the docking of the two spacecraft,” it added.

The docking is expected to take place in the first week of January 2025.

Twenty-four PS4-Orbital Experiment Module (POEM-4) payloads will be flown onboard the PSLV-C60 SPADEX mission.