Astronomy:SpaDeX

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Space Docking Experiment
SpaDeX Chaser (SDX01) and Target (SDX02) spacecrafts during testing
Mission typeRendezvous and Docking
OperatorISRO
Spacecraft properties
BusModified IMS-1
ManufacturerU R Rao Satellite Centre (ISRO)
Ananth Technologies
Start of mission
Launch date30 December 2024, 10:00 PM IST (16:30 UTC)
RocketPSLV-CA C60[1]
Launch siteSatish Dhawan Space Centre FLP
ContractorISRO
Orbital parameters
Altitude460 kilometres
Inclination45°
 

SpaDeX or Space Docking Experiment is a twin satellite mission developed by the Indian Space Research Organisation (ISRO) to mature and demonstrate technologies related to orbital rendezvous, docking, formation flying, which will have future applications in areas such as human spaceflight, in-space satellite servicing and other proximity operations.[2]

SpaDeX consists of two modified IMS-1 class satellites weighing 220 kg each. During proximity operations one spacecraft acts as a Chaser and other acts as a Target.

Both spacecraft were launched together from the First Launch Pad of Satish Dhawan Space Centre aboard a dedicated Polar Satellite Launch Vehicle on 30 December 2024 at 16:30:15 UTC and subsequently injected into slightly different orbits.[3][4]

After deployment, the two spacecraft then executed manoeuvres to bring them together again. The Chaser (SDX01) approached the target (SDX02) and then carried out precision manoeuvres to complete a successful docking.[5][6] With this success, India became one of the few countries in the world to have achieved a successful in-space docking using indigenous technology.

Objectives

According to ISRO, the SpaDeX mission had the following objectives:

  • To demonstrate an autonomous rendezvous and docking using the V-bar approach.[7]
  • To verify electrical power transfer between two docked spacecraft.[7]
  • To execute a composite spacecraft control using the Attitude Control System of another spacecraft while both are in a docked configuration.[8]
  • To act as independent satellites after undocking, and to operate their payloads for a period of two years.[9][10]

History

The research and development (R&D) needed to complete the project began with preliminary studies in 2016.[11] The Space Docking Experiment (SpaDeX) was approved by the Government of India with an initial funding of ₹10 crore, cleared in 2017.

As of July 2022, SpaDeX was sanctioned ₹124.47 crore (equivalent to ₹124 crore or US$17 million in 2023) in funding.[12]

The Chaser and Target satellites, along with related docking technologies, were designed and implemented for the SpaDeX mission by UR Rao Satellite Centre (URSC) with assistance from Vikram Sarabhai Space Centre (VSSC), Liquid Propulsion Systems Centre (LPSC), Space Applications Centre (SAC), ISRO Inertial Systems Unit (IISU), and Laboratory for Electro-Optics Systems (LEOS).[13]

For the SpaDeX satellites, Ananth Technologies provided Rendezvous Processing Units (RPU) and DC-to-DC converters. Additionally, the company provided 29 essential components for the PSLV-C60 launch vehicle, such as data acquisition units, transmitters, power modules, NavIC chip and control modules.[14][15]

In less than three months, Ananth Technologies completed the satellite assembly, integration, and testing for ISRO, and delivered them to the U R Rao Satellite Centre (URSC).[16] As per the previous head of ISRO, S. Somanath, docking is a crucial component for Chandrayaan-4 and that SpaDeX is intended as a demonstrator and forerunner.[17]

Two future projects of ISRO, the planned Bharatiya Antariksha Station and Gaganyaan human space flights missions depend on the mission's success.[18][19][20]

According to Jitendra Singh Rana, Minister of State for Science & Technology and Earth Sciences, and Prime Minister Narendra Modi, SpaDeX's achievement represents a significant step forward in the establishment of Bharatiya Antariksha Station by 2035.

Mastering docking techniques is essential for future deep space missions, according to Nambi Narayanan. As per Mylswamy Annadurai, the project director of the Chandrayaan-1, the demonstated docking technique will aid in the future management of space debris.[21][22][23]

On 23 May 2025, ISRO declared that the primary mission goal of docking was achieved and the mission is in extended phase. Experiments with the secondary instruments will be conducted with the remaining 5 kg of fuel.[24]

International collaboration

The Italian company Leaf Space, which offers ground segment-as-a-service (GSaaS) solutions, partnered with ISRO to create communication linkages with the POEM-4 platform and the SpaDeX satellites. It made telemetry, command operations, and ongoing SpaDeX mission telemetry monitoring possible.[25]

Description

Render of Chaser (SDX01).

The designations SDX01 and SDX02 are assigned to the "Chaser" and "Target" satellites, respectively, though both host docking devices capable of active or passive function.[9][26]

The launch vehicle deployed the spacecraft separately in order to create a separation between them of about 20 km (12 mi). After the spacecraft executed manoeuvres to prevent them from drifting further apart and then to begin the rendezvous operation.[27] The satellites were orbiting at about 28,400 km/h when they were 11 km (6.8 mi) apart.[28]

Render of Target (SDX02).

The Chaser then began to approach the Target, gradually lowering the separation between them to a distance of a few metres. After docking was completed, the mission planned to establish and demonstrate the transfer of electrical power between the spacecraft.[27]

The Space Applications Centre developed a miniaturized high-resolution camera with photo and video capability that was carried aboard SDX01. SDX02 was equipped with a Multi-Spectral Payload (MMX) for vegetation and natural resource monitoring. In order to properly plan the Gaganyaan missions, SDX02 has a radiation detector that will collect data on radiation levels in space.[29]

After separation, the two spacecraft will run their payloads for a period of two years.

The Bhartiya Docking System (BDS) was developed by ISRO based on the International Docking System Standard (IDSS) after unsuccessful attempts to import the docking technology from abroad.

Render of Chaser (SDX01) and Target (SDX02) in docked configuration.

For autonomous docking, the relative velocities of SDX01 and SDX02 were reduced to 0.036 km/h or 10 mm/s using retrorockets and a sensor suite. In contrast to the 24 motors used in IDSS, the BDS only uses two. The docking port on SpaDeX is 450 mm in diameter, whereas the docking port at the Gaganyaan and Bharatiya Antariksha Station will be 800 mm.[30][31][32]

The dual-motor actuation design was designed to help ensure secure connections and accurate alignment at low speeds. The real-time alignment and navigation was supported by proximity sensors, laser rangefinders, and rendezvous cameras. During docking operations, an Inter-Satellite Communication Link (ISL) provided smooth data transmission, improving the system's dependability and autonomy.[33] As soon as the satellites were under 5 km apart, they were able communicate via ISL to share orientation and location information.[11]

New process and technologies

  • Instead of being assembled and integrated at Vehicle Assembly and Launching Facility (VALF) and Mobile Service Tower (MST) respectively, the launch vehicle was assembled in a new PSLV Integration Facility (PIF) and transported to the launch pad to reduce the lead-in time between missions.[34][35]
  • A low-impact, androgynous peripheral docking system with an approach velocity of 10 mm/s was developed and employed.[33]
  • Laser rangefinder and corner cube retroreflectors for position vector and velocity in 6,000 to 200 m range. Rendezvous sensor for position vector in 2,000 to 250 m and 250 to 10 m range. Proximity and docking sensor for position vector and velocity in 30 m to 0.4 m range. An image sensor for 20 to 0.5 m range to capture the docking event. Mechanism entry sensor from 8 cm to 4 cm to detect SDX01 entry into SDX02.[7][34][29] Accelerometers for velocity measurement, and star tracker for attitude determination.[36]
  • Integrated processor for Relative Orbit Determination and Propagation (RODP) with differential GNSS-based Satellite Positioning System (SPS) for Positioning, Navigation and Timing (PNT).[13][34] VHF/UHF transceivers to transfer and synchronize position vector and velocity data by Inter-Satellite Communication Link.[33]
  • A trigger mechanism to capture the other satellite and securely hold it in place for docking.[37]
  • Power transfer technology, and built-in artificial intelligence to comprehend satellite conditions.[38]
  • Rendezvous and Docking Algorithms. The Rendezvous Simulation Lab to validate the algorithms through real-time simulation, the Docking Mechanism Performance Test for last stage of docking, and the Vertical Docking Experiment Lab to test the docking mechanisms under controlled settings.[34]

Timeline

Docking and undocking

  • On 30 December 2024, PSLV-C60 launched the SDX01 (Chaser) and SDX02 (Target) spacecraft into a 475-kilometer-high circular orbit with an inclination of 55°.[39]
  • Over subsequent days, ISRO increased the separation between the two spacecraft to greater than 20km. [40]
  • On 6 January, the docking manoeuvre was postponed from 7 January to 9 January after a need for additional validation through ground simulations was found. [41]
  • By 8 January, the two satellites had reduced their separation to 600 meters. To get the chaser satellite closer to the target, ISRO started a drift maneuver that moved it from 500 meters to 225 meters. However, the drift was greater than anticipated after the non-visibility period. The docking was thus was delayed for the second time.[42][43]
  • On 9 January, ISRO placed the chaser on a slow drift trajectory to bring it closer to the target. It was anticipated that the docking sequence would begin on 10 January, however this was subsequently delayed by several days.[44]
  • By 12 January, the SDX01 and SDX02 spacecraft were within 15 metres of one another. ISRO activated imaging sensors allowing the satellites to take pictures and videos of each other.[45]
  • On 13 January, an attempt was made by the chaser to approach within 15 meters and then 3 meters of the target. However, a delay in receiving signals from the proximity and docking sensors was observed during the inter-satellite distance reduction maneuver. For the SDX01 and SDX02 to correctly align throughout the docking process, these sensors were crucial. Because of the delay, an onboard safe mode was automatically activated to prevent any unintentional collision. This aborted the docking attempt and increased the inter-satellite distance between SDX01 and SDX02 to 8 km. [46]
  • On 16 January, a repeat of the docking attempt succeeded as the target captured the chaser for the first time. [47] ISRO also successfully managed to control the two satellites as a single stacked entity after docking.[48]
  • On 13 March, ISRO successfully undocked and separated the SpaDeX satellites.[49][50] The process began with an SDX02 extension, followed by the planned release of capture lever 3, the disengagement of the SDX02 capture lever, and the issuance of the de-capture command for both satellites.[51] All of the capabilities needed for rendezvous, docking, and undocking operations in a circular orbit have by this point been successfully proven by ISRO.[52] Both SDX01 and SDX02 subsequently orbited the Earth independently.[53]
  • ISRO plans to conduct the next series of experiments and another undocking/re-docking by 15 March 2025. The re-docking will take place automatically. Such experiments are only possible in a brief window of 15 days every two months.[54][55]
  • On 20 April 2025, ISRO successfully demonstrated the docking of SDX01 and SDX02 spacecraft for the second time. In contrast to the first docking attempt, which involved manually exercising an additional hold point at an intersatellite distance of 3 metres, the second docking was accomplished in full autonomous mode from an intersatellite distance of 15 metres till docking.[56][57]

Additional experiments

  • On 28 March 2025, V. Narayanan verified that the first docking process had not finished transferring electrical power from one satellite to the other. The experiment was moved to the subsequent round because of a possible small misalignment of the power transmission ports in the first attempt. The SpaDeX satellites still have enough fuel to finish the experiment.[58]
  • The rolling experiment, which involved one satellite circumnavigating the other and returning to its original position while remaining in line of sight, was completed by ISRO on 28 March 2025.[59] Multiple software, sensors, positioning technology, ground station control over satellite maneuvering, etc. were all validated. The experiment will assist ISRO in comprehending the necessary steps to dock satellites from various orientations to a desired location. Additionally, it will assist ISRO in determining whether vertical docking is feasible.[60]
  • On 21 April 2025, the power transfer from SDX02 to SDX01 and vice versa was completed successfully. In the experiment, one of the spacecraft's heating element was powered by the other satellite. Both SDX01 and SDX02 were operating at peak efficiency during the roughly 4-minute power transmission.[56][61] The spacecraft were also undocked to a 460-km circular orbit with a 45-degree inclination.[62]
  • On 3 May 2025, it was reported that ISRO has successfully completed a high-speed satellite rendezvous in space, demonstrating the expertise and readiness for orbital defense. At orbital speed of 28,800 kmph, SDX01 and SDX02 were guided into coordinated, high-speed contact. The satellites tested orbital control, real-time communication, and autonomous control systems as they gradually closed in on one another under controlled conditions, much like in aircraft combat training. The maneuvering accuracy needed in space warfare was emulated in the experiment.[63][64] From an international standpoint, the test was carried out following remarks made by US Vice Chief of Space Operations Gen. Michael Guetlein at the 16th annual McAleese "Defense Programs" Conference in Arlington, regarding China's pursuit of a number of proximity operations in which space objects move in and out of and around one another in unison and under control.[65][66]

Challenges

ISRO did not undertake a trial mission for the space docking experiment due to financial constraints. The two satellites and associated equipment were built by ISRO for ₹125 crore, while the launch vehicle cost an additional ₹250 crore.[67] Before Launch, the rocket was forced to hold to avoid potentially close approach risk with other satellites.[68]

Pre-Launch COLA for the PSLV-C60 flight

As per media reports, SpaDeX is having technical difficulties with the undocking procedure that was supposed to take place on 16 January 2024. V. Narayanan announced on 29 January that ISRO is reviewing the undocking procedure because the agency does not want to undock and abandon the satellites. With 60–70% propellant remaining and the project expense being fully utilized, more docking, undocking, and power transfer experiments will be conducted.[69][70] V. Narayanan told Press Trust of India on 8 February 2025, that there are no issues. ISRO intends to take its time, studying, and organize additional experiments before trying the undocking procedure.[71]

Future development

During the SpaDeX mission's post-launch briefing on 30 December 2024, ISRO Chief S. Somanath declared that additional SpaDeX missions with greater size and complexity would be launched, showing larger docking systems, most likely for Gaganyaan and Bharatiya Antariksha Station.[72]

ISRO intends to launch SpaDeX-2 in 2025–2028, pending government approval. It is anticipated that it will take a further 18 months to finish the preparations after approval.[73] The goal of SpaDeX-2 is to dock two satellites in an elliptical orbit rather than a circular one. The reason for this is that in a circular orbit, the satellites' trajectory and velocity stay constant, whereas in an elliptical orbit, they continuously change.[74]

See also

References

  1. ↑ "PSLV-C60 SPADEX Mission". ISRO. https://www.isro.gov.in/media_isro/pdf/Missions/PSLVC60/PSLVC60-mission-brochure-english.pdf. 
  2. ↑ "ISRO PSLV-C60 SpaDeX mission Highlights: Both satellites Chaser and Target deployed successfully!" (in en). 2024-12-30. https://www.cnbctv18.com/india/science/isro-pslv-c60-spadex-mission-live-updates-space-docking-experiment-liveblog-19532008.htm. 
  3. ↑ Chaitanya, SV Krishna (6 December 2024). "ISRO may test space docking on December 26". The New Indian Express. https://www.newindianexpress.com/states/tamil-nadu/2024/Dec/06/isro-may-test-space-docking-on-december-26. 
  4. ↑ Smith, Martin (2024-12-30). "India to launch SPADEX space docking demonstration, begins assembly of human-rated launch vehicle" (in en-US). https://www.nasaspaceflight.com/2024/12/spadex-launch/. 
  5. ↑ "India achieves first space docking, becoming fourth country to achieve major milestone". 16 January 2025. https://www.cnn.com/2025/01/15/india/india-space-docking-attempt-intl-hnk/index.html. 
  6. ↑ "Isro's SpaDeX: India successfully conducts historic space-docking test" (in en-GB). 16 January 2025. https://www.bbc.com/news/articles/c8j89k02py0o. 
  7. ↑ 7.0 7.1 7.2 "SpaDeX Mission". https://www.isro.gov.in/mission_SpaDeX.html. 
  8. ↑ Ramesh, Sandhya (2024-12-30). "ISRO launches SpaDeX onboard PSLV. How it will pave way for Bharatiya Antariksha Station" (in en-US). https://theprint.in/science/isro-set-to-launch-spadex-onboard-pslv-how-it-will-pave-way-for-bharatiya-antariksha-station/2424592/. 
  9. ↑ 9.0 9.1 "PSLV-C60 SPADEX Mission". 2024-12-30. https://www.isro.gov.in/media_isro/pdf/Missions/PSLVC60/PSLVC60-mission-brochure-english.pdf. 
  10. ↑ TA, Johnson; Dutt, Anonna (2025-01-17). "ISRO successfully docks two satellites in space, India fourth country to achieve feat after US, Russia, China" (in en). https://indianexpress.com/article/india/isro-docks-spadex-two-satellites-9781414/. 
  11. ↑ 11.0 11.1 Tripathi, Sibu Kumar (2025-01-06). "Isro to dock SpaDeX satellites on Tuesday, epic space chase in final phase" (in en). https://www.indiatoday.in/science/story/isro-to-dock-spadex-satellites-on-tuesday-epic-space-chase-to-end-soon-2660220-2025-01-06. 
  12. ↑ Fernandes, Jocelyn (2023-10-21). "ISRO Missions: A look at what's up and coming from India's space research agency" (in en). mint. https://www.livemint.com/science/news/isro-missions-a-look-at-whats-up-and-coming-from-indias-space-research-agency-11697863378908.html. 
  13. ↑ 13.0 13.1 "ISRO to launch its SpaDeX mission tomorrow". ANI. 29 December 2024. https://www.aninews.in/news/national/general-news/isro-to-launch-its-spadex-mission-tomorrow20241229134535/. 
  14. ↑ "Hyderabad-based ATL congratulates ISRO on PSLV-C60, Spadex" (in en-IN). The Hindu. 2024-12-31. ISSN 0971-751X. https://www.thehindu.com/news/national/telangana/hyderabad-based-atl-congratulates-isro-on-pslv-c60-spadex/article69043857.ece. 
  15. ↑ Siddiqui, Huma (2024-12-31). "India's PSLV-C60 launch: A milestone in space docking and private industry collaboration" (in en). https://www.financialexpress.com/life/science/indias-pslv-c60-launch-a-milestone-in-space-docking-and-private-industry-collaboration/3704342/. 
  16. ↑ MP, Sidharth (2024-10-18). "ISRO gears up for 'Space handshake' SPADEX; private firm delivers two satellites" (in en-us). https://www.wionews.com/india-news/isro-gears-up-for-space-handshake-spadex-private-firm-delivers-two-satellites-768653. 
  17. ↑ Upadhya, Harish; Sen Gupta, Pathikrit (25 December 2024). "Two 200 Kg Spacecraft At Rs 125 Cr: A Lot Is Riding On ISRO's SpaDeX Mission; Here's Why | Exclusive" (in en). https://www.news18.com/india/two-200-kg-spacecraft-at-rs-125-cr-a-lot-is-riding-on-isros-spadex-mission-heres-why-exclusive-9167171.html. 
  18. ↑ Kumar, Chethan (2024-10-14). "Docking test likely before Dec 15; Gaganyaan G1: Vyomitra on 1 seat, ECLSS on 2nd, rocket gets new cryo stage". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/city/bengaluru/docking-test-likely-before-dec-15-gaganyaan-g1-vyomitra-on-1-seat-eclss-on-2nd-rocket-gets-new-cryo-stage/articleshow/114205782.cms. 
  19. ↑ "Isro launches space docking satellites, India on path to elite club; PSLV last stage has 24 payloads". The Times of India. 2024-12-31. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/isro-launches-space-docking-satellites-india-on-path-to-elite-club-pslv-last-stage-has-24-payloads/articleshow/116805228.cms. 
  20. ↑ C.S, Hemanth (2024-12-30). "PSLV-C60 launch: ISRO launches SpaDeX mission for space docking" (in en-IN). The Hindu. ISSN 0971-751X. https://www.thehindu.com/sci-tech/science/pslvc60-lifts-off-with-spadex-spacecraft-from-sriharikota/article69044491.ece. 
  21. ↑ Bajwa, Harpreet (2025-01-17). "SpaDex docking a step towards Indian Space Station by 2035: Minister Jitender Singh" (in en). https://www.newindianexpress.com/nation/2025/Jan/17/spadex-docking-a-step-towards-indian-space-station-by-2035-minister-jitender-singh. 
  22. ↑ Tripathi, Sibu Kumar (2025-01-16). "A stepping stone: PM Modi congratulates Isro over Spadex docking success" (in en). https://www.indiatoday.in/science/story/a-stepping-stone-pm-modi-congratulates-isro-over-spadex-docking-success-2665679-2025-01-16. 
  23. ↑ Singh, Surendra (2025-01-17). "Isro's SpaDeX op success stepping stone for India's ambitious space missions: PM Modi". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/isros-spadex-op-success-stepping-stone-for-indias-ambitious-space-missions-pm-modi/articleshow/117312695.cms. 
  24. ↑ ""7,200 Tests Completed": ISRO Declares 2025 As Gaganyaan Year" (in en). 23 May 2025. https://www.ndtv.com/india-news/we-have-declared-2025-as-gaganyaan-year-isro-chief-v-narayanan-8484208. 
  25. ↑ Faleti, Joshua (2025-01-03). "Leaf Space Provides Support to ISRO SpaDeX LEO Mission" (in en-US). https://spacewatch.global/2025/01/leaf-space-provides-support-to-isro-spadex-leo-mission/. 
  26. ↑ "Isro integrates two Spadex satellites with PSLV-C60 for launch" (in en). 2024-12-26. https://www.indiatoday.in/science/story/isro-integrates-two-spadex-satellites-with-pslv-c60-for-launch-2655643-2024-12-26. 
  27. ↑ 27.0 27.1 Singh, Surendra (2024-12-25). "Isro to launch SpaDex mission on Dec 30 for developing space docking tech". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/isro-to-launch-spadex-mission-on-dec-30-for-developing-space-docking-tech/articleshow/116641609.cms. 
  28. ↑ Kumar, Chethan (2025-02-20). "No mega rocket for crewed Moon mission, Isro to rely on docking". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/no-mega-rocket-for-crewed-moon-mission-isro-to-rely-on-docking/articleshow/118398404.cms. 
  29. ↑ 29.0 29.1 MP, Sidharth (2024-12-29). "Explainer: Why SPADEX is India's most sophisticated mission around Earth" (in en). https://www.wionews.com/india-news/isro-spadex-explainer-indias-most-sophisticated-mission-around-earth-8576199. 
  30. ↑ Bagla, Pallava (26 December 2024). "'SpaDeX' Mission: How ISRO Will Dock Two Satellites In Space" (in en). https://www.ndtv.com/india-news/spadex-mission-how-isro-will-dock-two-satellites-in-space-7332909. 
  31. ↑ Indian Space Research Organisation (2022-09-09). ISRO's patent filing for SPADEX docking interface. https://archive.org/details/SPADEX_docking_system_patent/Complete%20Specification/. 
  32. ↑ "Patent Drawings for Autonomous vehicle docking system 200 (r/ISRO)" (in en). 30 September 2022. https://imgur.com/a/patent-drawings-autonomous-vehicle-docking-system-200-r-isro-UJ1V1fW. 
  33. ↑ 33.0 33.1 33.2 Singh, Abhinav (23 December 2024). "PSLV-C60 POEM-4: Pioneering space research with cutting-edge payloads from ISRO, startups, and universities" (in en). https://www.theweek.in/news/sci-tech/2024/12/23/pslv-c60-poem-4-pioneering-space-research-with-cutting-edge-payloads-from-isro-startups-and-universities.html. 
  34. ↑ 34.0 34.1 34.2 34.3 Dutt, Anonna (2024-12-30). "Why ISRO's 'docking' mission today is critical for India's space ambitions" (in en). https://indianexpress.com/article/explained/explained-sci-tech/isro-docking-mission-significance-space-9751091/. 
  35. ↑ Ramesh, Sandhya (2024-03-02). "How ISRO's PSLV Integration Facility launch at Sriharikota will help India's space ecosystem" (in en-US). https://theprint.in/science/how-isros-pslv-integration-facility-launch-at-sriharikota-will-help-indias-space-ecosystem/1985181/. 
  36. ↑ Singh, Abhinav (1 January 2025). "India's SpaDeX mission: Mastering the precision of autonomous space docking" (in en). https://www.theweek.in/news/sci-tech/2025/01/01/india-spadex-mission-mastering-the-precision-of-autonomous-space-docking-isro.html. 
  37. ↑ Kumar, Chethan (2025-01-20). "Isro preps for more docking trials with same SpaDeX sats to perfect precision in Space". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/science/isro-preps-for-more-docking-trials-with-same-spadex-sats-to-perfect-precision-in-space/articleshow/117378839.cms. 
  38. ↑ Kumar, Santosh; S, Gouri; Srivastava, Vatsla (16 January 2025). "SpaDeX Mission: Revolutionising Space Exploration". Department of Space, Government of India. Press Information Bureau. https://pib.gov.in/PressReleasePage.aspx?PRID=2093369. 
  39. ↑ Jones, Andrew (2024-12-30). "India launches space docking experiment with PSLV rocket, advancing major ambitions" (in en-US). https://spacenews.com/india-launches-space-docking-experiment-with-pslv-rocket-advancing-major-ambitions/. 
  40. ↑ "Epic chase to begin in space as distance between Isro's SpadeX satellites grow" (in en). 2025-01-02. https://www.indiatoday.in/science/story/epic-chase-to-begin-in-space-as-distance-between-isros-spadex-satellites-grow-2658491-2025-01-02. 
  41. ↑ "ISRO's SpaDeX docking experiment postponed to January 9" (in en-IN). The Hindu. 2025-01-06. ISSN 0971-751X. https://www.thehindu.com/sci-tech/science/spadex-docking-experiment-postponed-to-january-9/article69067681.ece. 
  42. ↑ Tripathi, Sibu Kumar (2025-01-08). "Isro's SpaDeX satellite begins drift to move closer for docking" (in en). https://www.indiatoday.in/science/story/ready-to-dock-isros-spadex-satellites-now-separated-by-just-600-meters-2661641-2025-01-08. 
  43. ↑ Kumar, Vivek; Joshi, Poorva (2025-01-08). "Isro postpones SpaDeX docking again, says satellites are safe" (in en). https://www.indiatoday.in/science/story/isro-postpones-spadex-docking-excess-drift-satellites-are-safe-2661786-2025-01-08. 
  44. ↑ "ISRO's SpaDex mission back on track after satellite drift, docking may be achieved on Friday" (in en). 2025-01-09. https://indianexpress.com/article/india/isros-spadex-mission-back-on-track-after-satellite-drift-docking-may-be-achieved-on-friday-9770309/. 
  45. ↑ "SpaDex satellites now at a distance of 15 metres from each other: ISRO" (in en). https://www.deccanherald.com/science/spadex-satellites-now-at-a-distance-of-15-metres-from-each-other-isro-2-3351553. 
  46. ↑ Tripathi, Sibu Kumar (2025-01-13). "Isro aborted SpaDeX docking after satellites triggered safe mode in space" (in en). https://www.indiatoday.in/science/story/isro-aborted-spadex-docking-after-satellites-triggered-safe-mode-in-space-2663956-2025-01-13. 
  47. ↑ C.S, Hemanth (2025-01-16). "ISRO successfully executes SpaDeX docking experiment; India joins elite club of nations" (in en-IN). The Hindu. ISSN 0971-751X. https://www.thehindu.com/sci-tech/science/isro-successfully-executes-spadex-docking-experiment-india-joins-elite-club-of-nations/article69103462.ece. 
  48. ↑ "ISRO successfully docks SpaDeX satellites in space, creates history" (in en-us). Hindustan Times. 2025-01-16. https://www.hindustantimes.com/india-news/isro-successfully-docks-spadex-two-satellites-in-space-101737003035346.html. 
  49. ↑ Vibhavari, Prisha (2025-03-13). "ISRO Aces 'Unbelievable De-docking' Of SpaDeX Satellites, Shares Viral 'Spectacular View' Post" (in en). https://www.news18.com/india/isro-accomplishes-unbelievable-de-docking-of-spadex-satellites-posts-spectacular-view-watch-9260878.html. 
  50. ↑ "ISRO undocks SpaDex satellites, making India the 4th country to achieve this historic feat" (in en-IN). The Hindu. 2025-03-13. ISSN 0971-751X. https://www.thehindu.com/sci-tech/science/isro-undocks-spadex-satellites/article69325035.ece. 
  51. ↑ "ISRO SpaDex successfully completes undocking, sets stage for Chandrayaan-4". Hindustan Times. 13 March 2025. https://www.hindustantimes.com/india-news/isro-spadex-successfully-completes-undocking-sets-stage-for-chandrayaan4-101741849976151.html. 
  52. ↑ Kumar, Chethan (2025-03-13). "Isro undocks SpaDex satellites, could try more docking trials". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/science/isro-undocks-spadex-satellites-could-try-more-docking-trials/articleshow/118971376.cms. 
  53. ↑ Dutt, Anonna (2025-03-14). "Isro undocks SpaDeX satellites 2 months after docking them in space" (in en). https://indianexpress.com/article/india/isro-undocks-spadex-satellites-2-months-after-docking-them-in-space-9884658/. 
  54. ↑ "ISRO to resume SpaDeX experiments from March 15: V. Narayanan". The Times of India. 2025-02-28. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/isro-to-resume-spadex-experiments-from-march-15-v-narayanan/articleshow/118625225.cms. 
  55. ↑ "Isro to begin undocking of SpaDeX craft". The Times of India. 2025-02-28. ISSN 0971-8257. https://timesofindia.indiatimes.com/city/thiruvananthapuram/isro-to-begin-undocking-of-spadex-craft/articleshow/118634331.cms. 
  56. ↑ 56.0 56.1 "SPADEX Mission: Successful demonstration of Second Docking and Power Transfer". 21 April 2025. https://www.isro.gov.in/Spadex_Successful_demonstration_of_Second_Docking_and_Power_Transfer.html. 
  57. ↑ "SpaDeX Mission: ISRO successfully executes docking of satellites for second time" (in en-IN). The Hindu. 2025-04-21. ISSN 0971-751X. https://www.thehindu.com/sci-tech/science/spadex-mission-isro-successfully-executes-second-docking-of-satellites/article69473419.ece. 
  58. ↑ Bagla, Pallava (2025-03-28). "India's Satellites In Space Dance, 500km Above Earth At 28,800 Kmph" (in en). https://www.ndtv.com/india-news/isro-news-spadex-docking-mission-news-indias-satellites-in-deep-space-dance-500km-above-earth-at-28-800-kmph-8033529. 
  59. ↑ Tripathi, Sibu (2025-03-28). "Isro successfully rolls SpaDeX satellites, pushes them to the limit" (in en). https://www.indiatoday.in/science/story/isro-successfully-rolls-spadex-satellites-chandrayaan-3-hop-test-moon-rolling-rotating-experiment-2700423-2025-03-28. 
  60. ↑ Kumar, Chethan (2025-03-28). "Isro attempts & succeeds in 'rolling' SpaDeX satellites, learning key for future docking". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/india/isro-attempts-succeeds-in-rolling-spadex-satellites-learning-key-for-future-docking/articleshow/119613052.cms. 
  61. ↑ Kumar, Chethan (2025-04-22). "In big breakthrough, Isro docks 2 SpaDeX satellites for 2nd time". The Times of India. ISSN 0971-8257. https://timesofindia.indiatimes.com/science/isro-achieves-second-docking-with-spadex-satellites/articleshow/120475563.cms. 
  62. ↑ "ISRO's SpaDeX mission completes second docking of satellites" (in en-us). Hindustan Times. 2025-04-21. https://www.hindustantimes.com/india-news/isros-spadex-mission-completes-second-docking-of-satellites-101745210871441.html. 
  63. ↑ Bagla, Pallava (3 May 2025). "Indian Satellites Practising "Dogfights" In Space. What It Means" (in en). https://www.ndtv.com/india-news/indian-satellites-practising-dogfights-in-space-what-it-means-8320645. 
  64. ↑ "ISRO performs space 'dogfight' with twin satellites 500 kilometres above Earth, showcasing advanced orbital control". The Times of India. 2025-05-08. ISSN 0971-8257. https://timesofindia.indiatimes.com/science/isro-performs-space-dogfight-with-twin-satellites-500-kilometres-above-earth-showcasing-advanced-orbital-control/articleshow/120990430.cms. 
  65. ↑ Gordon, Chris (2025-03-19). "China Practicing 'Dogfighting in Space,' US Space Force Says" (in en-US). https://www.airandspaceforces.com/china-practicing-dogfighting-space-force/. 
  66. ↑ Dinner, Josh (2025-03-21). "China now has a 'kill mesh' in orbit, Space Force vice chief says" (in en). https://www.space.com/space-exploration/space-force-general-warns-of-adversaries-surpassing-us-abilities-in-orbit-we-are-at-an-inflection-point. 
  67. ↑ Gupta, Pathikrit Sen; Upadhya, Harish (25 December 2024). "Two 200 Kg Spacecraft At Rs 125 Cr: A Lot Is Riding On ISRO's SpaDeX Mission; Here's Why | Exclusive" (in en). https://www.news18.com/india/two-200-kg-spacecraft-at-rs-125-cr-a-lot-is-riding-on-isros-spadex-mission-heres-why-exclusive-9167171.html. 
  68. ↑ "Indian Space Situational Assessment Report (ISSAR) for 2024 Released". https://www.isro.gov.in/ISSAR_2024.html. 
  69. ↑ "After successful space docking, Isro's SpaDex satellites face delay in undocking exercise" (in en). 2025-02-06. https://indianexpress.com/article/cities/bangalore/isro-spadex-satellites-space-docking-delay-undocking-exercise-9818712/. 
  70. ↑ Tripathi, Sibu Kumar (2025-01-21). "Isro yet to attempt undocking as SpaDeX satellites remain docked to each other" (in en). https://www.indiatoday.in/science/story/isro-yet-to-attempt-undocking-as-spadex-satellites-remain-docked-to-each-other-2667965-2025-01-21. 
  71. ↑ "No glitches in SpaDex, we are going step by step: ISRO chief V Narayanan" (in en). https://www.deccanherald.com/india/no-glitches-in-spadex-we-are-going-step-by-step-isro-chief-v-narayanan-3396575. 
  72. ↑ "ISRO set to launch NVS-02 satellite in Jan 2025, with more missions planned for upcoming year: ISRO Chief". ANI. 31 December 2024. https://www.aninews.in/news/national/general-news/isro-set-to-launch-nvs-02-satellite-in-jan-2025-with-more-missions-planned-for-upcoming-year-isro-chief20241231043355/. 
  73. ↑ Choudhary, Srishti (2025-05-06). "ISRO To Plan Second Space Docking Mission Soon, To Approach Govt For Approval" (in en). https://www.news18.com/india/isro-to-plan-second-space-docking-soon-to-approach-govt-for-approval-ws-l-9325834.html. 
  74. ↑ Dutt, Anonna (2025-06-22). "ISRO readies SpaDeX-2 mission to dock satellites in elliptical orbit" (in en). https://indianexpress.com/article/india/isro-readies-spadex-2-mission-to-dock-satellites-in-elliptical-orbit-10080630/. 



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