'Ballet In Space': How India Is Planning Historic Docking Experiment

India will conduct a docking experiment in space for the first time. This can also be referred to as "ISRO's Ballet in Space", or an "antariksh jugalbandi". Two small, functioning homegrown satellites will be mated together in space. The complexities of this hugely significant mission are many.

Here are some of the challenges:

Two satellites in space are mated together to make one spacecraft.

On December 30, 2024, India successfully launched the SpaDeX mission using the workhorse Polar Satellite Launch Vehicle (PSLV). The twin 220-kg satellites were released in a precise 470-km circular orbit.

Since then, the chaser and the target satellites - as they are called - have been stabilised in the same orbit, separated by a 20-km difference. Both satellites are equipped with a suite of special homegrown ranging and tracking sensors.

The satellites in orbit will be flying at 28,800 kmph, or 10 times the speed of a bullet. But since both travel together, they appear stationary to each other as the relative velocity is what matters.

When the docking process begins, the satellites will be progressively 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 inch closer to the target at a speed of 10 mm per second. Then the special clasps will hold the satellites together in a tight embrace.

To test if 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.

Once the space-docking experiment is completed, the two satellites will be separated and then each will go on to do independent experiments.

The system, developed indigenously, is named Bhartiya Docking System. India needs to master this docking technology for completing future missions such as Chandrayaan 4 and to make the Bhartiya Antariksh Station and Gaganyaan.

This is such a complex process that only Russia, the US, and China have perfected it till now. No nation shares fine details of this challenging technology, hence the swadeshi effort. If successful, India will become a full-fledged space-faring nation.