SpaDeX
ISRO's twin satellite mission demonstrating in-space docking.
SpaDeX (Space Docking Experiment) is a twin satellite mission developed by ISRO to mature and demonstrate technologies for orbital rendezvous, docking, and formation flying. The mission consists of two modified IMS-1 class satellites, each weighing 220 kg, launched together on a PSLV from the Satish Dhawan Space Centre on 30 December 2024. With the successful docking of the Chaser (SDX01) and Target (SDX02), India became one of the few countries to achieve in-space docking using indigenous technology.
Quick Facts
- Operator
- ISRO
- Spacecraft bus
- Modified IMS-1
- Manufacturer
- U. R. Rao Satellite Centre; Ananth Technologies
- Launched
- 30 December 2024, 10:00 PM IST (16:30 UTC)
- Launch rocket
- PSLV-CA C60
- Launch site
- Satish Dhawan Space Centre FLP
- Orbit altitude
- 460 kilometres
- Orbit inclination
- 45°
Facts from the source article.
History
The Space Docking Experiment, or SpaDeX, took shape after initial groundwork in 2016, with the Indian government giving it the green light the following year and setting aside ₹10 crore to start. The U. R. Rao Satellite Centre led the design and implementation of the Chaser and Target satellites and their docking systems, drawing on support from several other ISRO centres, including the Vikram Sarabhai Space Centre and the Liquid Propulsion Systems Centre. Ananth Technologies supplied key hardware like Rendezvous Processing Units and DC-to-DC converters for the satellites, plus 29 parts for the PSLV-C60 rocket, and managed to finish assembly, integration, and testing of the satellites in under three months before handing them over. Former ISRO chief S. Somanath pointed out that docking is vital for Chandrayaan-4 and that SpaDeX serves as a testbed and precursor. Minister Jitendra Singh Rana and Prime Minister Narendra Modi highlighted the mission’s role in paving the way for the Bharatiya Antariksh Station by 2035. Nambi Narayanan stressed that mastering docking is key for future deep-space work, while Mylswamy Annadurai noted the technique could help with managing space debris.
Satellite description
SDX01 (Chaser) and SDX02 (Target) both host docking devices capable of active or passive function, built on the IMS class satellite bus. Sensor suites include a Laser Range Finder (LRF) and Corner Cube Retro Reflectors for ranges of 6000 to 200 m, two sets of Rendezvous Sensors covering 2000 to 250 m and 250 to 10 m, a Proximity and Docking Sensor (PDS) for 30 to 0.4 m, a video camera for 20 to 0.5 m, and a Mechanism Entry Sensor from 8 cm to 4 cm. Both spacecraft use Laser Diodes as targets for the RS and PDS sensor suits. A NAVIC-based Satellite Positioning System provides Position, Navigation, and Timing services, and VHF/UHF transceivers are carried. The Space Applications Centre developed a miniaturized high-resolution camera with photo and video capability aboard SDX01. SDX02 carries a Multi-Spectral Payload (MMX) for vegetation and natural resource monitoring and a radiation detector for data collection relevant to Gaganyaan. The Bhartiya Docking System (BDS), based on the International Docking System Standard (IDSS), uses only two motors compared to IDSS's 24. The docking port on SpaDeX is 450 mm in diameter.
Challenges
ISRO skipped a practice run for its space docking experiment to save money. The two satellites and their hardware cost ₹125 crore to build, and the rocket added another ₹250 crore. Before liftoff, the launch was delayed to avoid getting too close to other satellites. Media reports say the undocking step, planned for 16 January 2024, hit technical snags. On 29 January, V. Narayanan said ISRO is rethinking the undocking plan because it doesn't want to let the satellites go and lose them. With 60–70% of the fuel left and the full budget already spent, the agency will run more tests on docking, undocking, and power transfer. On 8 February 2025, Narayanan told Press Trust of India everything is fine. ISRO plans to move slowly, study the situation, and set up extra experiments before trying to undock.
Future development
ISRO plans to follow up its SpaDeX mission with two more complex ones. During a briefing on 30 December 2024, Chairman S. Somanath said future missions will use larger docking systems, likely for Gaganyaan and the Bharatiya Antariksh Station. SpaDeX-2, pending government approval, is expected to launch between 2025 and 2028, with 18 months of preparation needed after approval. Its goal is to dock two satellites in an elliptical orbit, where speed and path change constantly, unlike a circular orbit. SpaDeX-3, planned for the late 2020s, will demonstrate sample transfer and remote robotic operations with scaled-up hardware, supporting the Bharatiya Antariksh Station and Chandrayaan-4.
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