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ISRO to launch SpaDeX Mission: Read details about the indigenous in-space docking technology developed for India’s future space programs

The primary objective of SpaDeX is to develop and validate technologies essential for autonomous rendezvous, docking, and undocking of spacecraft.

The Indian Space Research Organisation (ISRO) is set to launch its Space Docking Experiment (SpaDeX) mission on December 30, 2024, at 21:58 IST from the Satish Dhawan Space Centre in Sriharikota. This pioneering mission aims to demonstrate in-space docking technology by deploying two small satellites, designated SDX01 (Chaser) and SDX02 (Target), each weighing approximately 220 kg, into a 470 km circular orbit.

The primary objective of SpaDeX is to develop and validate technologies essential for the autonomous rendezvous, docking, and undocking of spacecraft. These capabilities are crucial for India’s future space endeavours, including lunar missions like Chandrayaan-4, and the construction of the space station Bharatiya Antariksh Station (BAS). The mission also seeks to demonstrate the transfer of electrical power between docked spacecraft, composite spacecraft control, and payload operations post-undocking.

The mission will commence with the PSLV-C60 rocket deploying the Chaser and Target satellites into slightly different orbits. Utilising precise manoeuvres, the Chaser satellite will approach the Target, reducing the inter-satellite distance through stages of 5 km, 1.5 km, 500 m, 225 m, 15 m, and finally 3 m, culminating in docking of the two spacecraft.

After successful docking and rigidization, the mission will demonstrate electrical power transfer between the two satellites. After that, the two satellites perform undocking and separation, and then will initiate their intended operations, with an expected mission life of up to two years.

ISRO has developed indigenous technologies for this mission, including a docking mechanism, a suite of rendezvous and docking sensors, power transfer technology, an autonomous rendezvous and docking strategy, an inter-satellite communication link, and a GNSS-based Relative Orbit Determination and Propagation processor. The space agency also built simulation test beds for both hardware and software design validation and testing.

ISRO said that the SpaDeX mission is challenging due to its small size and mass, as it needed finer precision for the rendezvous and docking manoeuvres compared to docking two large spacecraft.

The docking mechanism is a low-impact docking system with an approach velocity of 10 mm/s, is androgynous which means the docking systems are identical for both spacecraft, and is a peripheral docking system, i.e., a concept similar to the International Docking System Standard used by other agencies for human missions.

ISRO has released an animation illustrating the docking process, providing a visual representation of the mission’s objectives.

The docking mechanism is smaller (450 mm) with one degree of freedom for extension and uses two motors compared to the IDSS (800 mm) on a hexapod with 24 motors. Multiple test beds were established to test the hardware and software simulation of the docking kinematics to verify and finalise the docking approach parameters, ISRO said.

The sensor suite of the mechanism includes Laser Range Finder (LRF) and Corner Cube Retro Reflectors to work for a range of 6000 to 200 m for determining range (R). The set of Rendezvous Sensors (RS) is used in the range of 2000 to 250 m and from 250-10 m. RS provides the relative position (x, y, z) while LRF determines both relative position and velocity independently.

Proximity and Docking Sensor (PDS) provides relative position and velocity over a range of 30 m to 0.4 m. Laser Diodes (LDs) are used as targets for RS & PDS. A video monitor is used in the 20 to 0.5 m range and it will capture the video of the docking event. A Mechanism Entry Sensor (MES) is used from 8 cm to 4 cm to detect chaser entry into the target spacecraft during docking.

Both the SpaDeX spacecraft carry a differential GNSS-based Satellite Positioning System (SPS), which provides PNT (Position, Navigation, and Timing) solutions for the satellites. 

After the docking and undocking demonstration, the two satellites be separated and will begin their pre-planned activities. The spacecrafts are equipped with High-Resolution Camera, Radiation Monitor, Miniature Multi-Spectral Payload for natural resource monitoring and vegetation studies.

The SpaDeX satellites were designed and realized by the UR Rao Satellite Centre (URSC) with the support of other ISRO centres (VSSC, LPSC, SAC, IISU, and LEOS). The spacecraft, in its orbital phase, will be controlled from ISTRAC using ISRO ground stations and other externally hired ground stations.

These advancements position India to become the fourth country globally to possess space docking technology. Till now, only Russia, the US, and China have mastered the complex technology.

The success of SpaDeX is anticipated to enhance India’s capabilities in space exploration, enabling complex missions that require multiple launches and in-orbit assembly. This includes future lunar missions, human spaceflight endeavours, and the development of India’s own space station. By mastering in-space docking technology, ISRO aims to facilitate longer-duration missions and more intricate space operations, marking a substantial leap in the nation’s space program

The satellites are scheduled to be launched at 9:58 PM on 30 December from the Satish Dhawan Space Centre in Sriharikota. For those interested in witnessing this milestone, ISRO has opened registrations for the public to view the launch from the Launch View Gallery at SDSC SHAR, starting December 23, 2024.

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OpIndia Staff
OpIndia Staffhttps://www.opindia.com
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