BENGALURU: The two satellites — SDX01 and SDX02 — that formed the core of the Indian Space Research Organisation’s (Isro) Space Docking Experiment (SpaDeX) re-entered Earth’s atmosphere on Oct 12 and 13, bringing the mission to an end after nearly 21 months in space.A senior scientist from the Isro Telemetry, Tracking and Command Network (Istrac) in Bengaluru independently confirmed the development to TOI.According to Space-Track, a US Space Force catalogue of space objects, SDX01 re-entered at 9.38 pm on Oct 12 over the southern Indian Ocean, west of Australia, while SDX02 followed at 4.35 am on Oct 13 over the North Pacific, south of the Aleutian Islands.Launched aboard a PSLV rocket from Sriharikota on Dec 30, 2024, the spacecraft were designed to demonstrate technologies required to bring two satellites together in orbit, dock them, separate them and transfer electrical power between them. Each weighed approximately 220 kg.Isro achieved the mission’s first docking on Jan 16, 2025, followed by undocking on March 13. On April 20, the satellites completed a second docking, this time autonomously from a distance of 15 metres. The space agency said it had demonstrated power transfer between the spacecraft a day later, with electricity from one satellite powering a heater on the other.These capabilities are important for future missions that require spacecraft to join up in orbit, including Chandrayaan-4, India’s planned lunar sample-return mission, and the proposed Bharatiya Antariksh Station. The technology could also support future human spaceflight missions involving complex orbital operations.The satellites’ eventual return was preceded by a sustained decline in their orbital altitude. After undocking, they orbited at around 460 km above Earth. Their mean altitude had dropped to approximately 413 km by Jan 1, 2026, and to 312 km by Sept 1. By Oct 12, their final recorded orbital elements placed them at around 155 km.The rapid descent in their final days marked the end of a mission that established India’s capability to demonstrate autonomous docking and power transfer in space. India is only the fourth country to achieve this.
