ISRO's SpaDeX Mission

Context (IE): ISRO successfully completed the docking of two satellites as part of the SpaDeX Mission, thus making India the fourth country to dock satellites, after the USA, Russia & China.

About Space Docking Experiment (SpaDeX) Mission

SpaDeX Mission is a cost-effective technology demonstrator mission that will demonstrate in-space docking using two small spacecraft (‘Chaser’ and ‘Target’) designed to be launched from a single PSLV class vehicle and to dock at an altitude of about 700 kilometres.
Objective: SpaDeX mission aims to demonstrate rendezvous, docking, and undocking technologies, focusing on key technologies like electrical power transfer between the docked spacecraft, in-space robotics, and conducting payload operations after undocking.
First Experiment: SpaDeX is ISRO’s first satellite docking experiment.
Launch Details: Launched on December 30, 2024, from Sriharikota by ISRO’s PSLV-C60, placing two 220-kg satellites in a 475-km circular orbit.
Duration: The mission will run for 2 years.
Docking Process: The spacecraft will reduce the distance from 20 km to 3 m.
Biological Research: SPADEx will support biological studies on plant growth and bacteria, green propulsion systems and artificial intelligence labs in microgravity.

Orbital docking is joining two space vehicles together in space. The docking process can be temporary or semi-permanent. For e.g., space station modules can dock with International Space Station (ISS).
This process, whether manned or unmanned, allows those to operate as a single unit for critical tasks such as refuelling, repair, and crew exchange.

The first docking was achieved in 1966 when Gemini 8, under the command of American astronaut Neil Armstrong, docked with Agena Target Vehicle (it was uncrewed).

Sensor Suite: Laser Range Finder, Rendezvous Sensor, and Proximity & Docking Sensors were used for precise measurements during the docking process.
SpaDeX A (Chaser) is equipped with a high-resolution camera for monitoring & imaging, SpaDeX B (Target) carries a multispectral payload, radiation monitor & other scientific tools.
Robotic Experimentation: Robotic arms will be validated for satellite servicing.
Docking Mechanism: Androgynous, using identical systems on both satellites.
POEM (PS4 Orbital Experiment Module): The fourth stage of PSLV will be repurposed to test critical in-orbit technologies, including docking and power transfer.
- CROPS mission utilised the PSLV Orbital Experiment Module (POEM)-4 platform to cultivate cowpea seeds in a controlled environment with active thermal management.

Inter-Satellite Communication Link (ISL) for autonomous communication.
GNSS-based Relative Orbit Determination Processor for determining spacecraft positions & velocities.
Autonomous Rendezvous and Docking Strategy developed for precise operations.

Space Docking is crucial for future space missions such as:
- Chandrayaan-4 for Moon sample return.
- Bharatiya Antariksh Station planned for 2028.
- Satellite Servicing and Maintenance to extend operational lifespans of satellites.
- In-space Robotics and future satellite missions for resource monitoring.
Paves Way for the Third Launch Pad at Sriharikota: Approved for the Next Generation Launch Vehicle (NGLV), supporting future space missions and enabling heavier satellite launches.
Enhanced Indian Position: Only the US, Russia & China have successfully demonstrated space docking.
Precision and Coordination: The SpaDeX mission demonstrates India’s ability to control spacecraft at high velocities, which is essential for future deep space missions.
Self-Reliance: The mission showcases India’s growing space capabilities, moving closer to autonomous space operations.
Need for Space Weather Monitoring: The mission underscores the importance of real-time space weather forecasts to ensure safe space operations, especially during solar maximum phases.

Favorable Solar Conditions: The mission occurred during solar cycle 25 with reduced solar disturbances, avoiding interference from solar flares and coronal mass ejections (CMEs), and fewer sunspots, ensuring smooth docking operations.
Space Weather Risks: Solar flares and CMEs can disrupt spacecraft operations, blinding sensors and causing communication breakdowns.
Magnetic Storms: High-speed solar winds can lead to positional errors, complicating docking.