'Requires further validation': ISRO postpones docking experiment by 2 days

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The Indian Space Research Organisation (ISRO) has postponed the historic docking of two satellites in space from January 7 to January 9, confirming "both satellites are safe" and the "process requires further validation through ground simulations based on an abort scenario identified today."


The time of docking is yet to be announced by the space agency.


On December 30, 2024, 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. 


ISRO's SpaDeX mission involved 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.


When 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 happens 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 declared a success once the docking and undocking of the satellites is done, after which the satellites will function independently. 


The system developed indigenously, is named Bhartiya Docking System. The mission's success is crucial for completing future programmes such as Chandrayaan 4 and making the Bhartiya Antariksh Station and Gaganyaan.