The Indian Space Research Organisation (ISRO) on Wednesday deferred the space docking experiment of satellites, for a second time, citing an excessive drift between the mission satellites.
The mission, known as the Space Docking Experiment (SpaDeX), was originally scheduled for Tuesday. However, it was later postponed to Thursday.
In a post on X on Wednesday, the Bengaluru-based space agency announced the latest delay but did not provide the next date for docking.
“While making a maneuver 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,” it wrote on the micro-blogging site.
On Tuesday, Isro had deferred the experiment, saying the “process requires further validation through ground simulations based on an abort scenario identified today.”
The 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.
On December 30, ISRO’s workhorse, the Polar Satellite Launch Vehicle (PSLV), lifted off with twin 220-kg satellites for space and released in a 470-km circular orbit. Docking is a complex manoeuvre perfected only by China, the US, and Russia.
The mission involves two satellites separated by 20 km in a 470 km circular orbit. A chaser and target satellite move at a speed of 28,800 kmph, or 10 times the speed of a bullet, but they appear to be stationary due to zero relative velocity.
Whenever the docking process begins, the satellites will be brought closer. 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 precise docking of the two spacecraft.
When the docking takes place, the chaser will move closer to the target at a speed of 10 nm per second and hold onto the target.
Earlier, ISRO chief S Somanth said: “They will do the docking exercise only when all sensors have been fully calibrated and tested to satisfaction before it is attempted. All algorithms and scenarios are also tested on the ground before commands are sent to the spacecraft to autonomously do the docking.”
To check if the docking is successful, electrical power will be transferred from one satellite to the other. After docking, the satellites will be controlled as a single spacecraft. The process will be declared a success once the docking and undocking of the satellites is done, after which the satellites will function independently.