SpaDeX is a cost-effective technology demonstrator mission designed to showcase in-space docking using two small spacecrafts launched by 62nd PSLV flight. This mission is pivotal for India's future space ambitions, including lunar missions, sample returns, and the development of the Bharatiya Antariksh Station (BAS). Objectives Develop and demonstrate technology for rendezvous and docking using two small spacecrafts. Showcase controllability in the docked condition. Demonstrate the potential for extending the life of the target spacecraft. Test power transfer between docked spacecraft. SpaDeX Spacecrafts The SpaDeX mission involves two small satellites, SDX01, which is the Chaser and SDX02, the Target, each weighing approximately 220 kilograms. These spacecrafts are androgynous in nature i.e. either of the spacecraft can act as chaser (active spacecraft) during docking. They are equipped with solar panels, lithium-ion batteries, and a robust power management system. The Attitude and Orbit Control System (AOCS) includes sensors such as star sensors, sun sensors, magnetometers and actuators like reaction wheels, magnetic torquers and thrusters. The satellites will execute a series of complex manoeuvres to demonstrate the docking process in orbit. Post-docking, the two satellites will operate as a single spacecraft. Electrical power will be transferred from one satellite to the other to confirm the success of the docking. After successful docking and undocking, the spacecraft will separate and be used for application missions. During undocking, the spacecraft will separate to begin individual payload operations. These payloads will provide high resolution images, natural resource monitoring, vegetation studies and on orbit radiation environment measurements which find numerous applications. Indigenous technologies in SpaDex Mission Docking mechanism. A suite of four rendezvous and docking sensors. Power transfer technology. Indigenous novel autonomous rendezvous and docking strategy. Inter-satellite communication link (ISL) for autonomous communication between spacecrafts, incorporated with inbuilt intelligence to know the state of the other spacecraft. GNSS-based Novel Relative Orbit Determination and Propagation (RODP) processor to determine the relative position and velocity of the other spacecraft. Simulation test beds for both hardware and software design validation and testing. Achievements and future plans In a historic achievement, the Space Docking Experiment (SpaDeX) mission’s docking operation was successfully completed on 16th January, 2025 marking India’s entry into the elite group of nations capable of executing space docking operations. With this success, India becomes the fourth country in the world to achieve this technological feat. Space docking is a critical prerequisite for upcoming space missions, such as lunar exploration and the operation of space stations. By successfully executing this mission, ISRO is laying the foundation for autonomous docking—a vital capability for future missions like Chandrayaan-4. Additionally, the SpaDeX mission will play a key role in supporting India's ambitious space goals, such as the Gaganyaan mission, sending an Indian astronaut to the Moon and setting up the Bharat Antariksh Space Station. Source : ISRO