31st December 2024 : Ananth Technologies Pvt. Ltd. (ATL), a pioneer in aerospace innovation, congratulates ISRO on the triumphant launch of the PSLV-C60 vehicle, which successfully deployed the Space Docking Experiment (SPADEX) satellites into low-Earth orbit at an altitude of 470 km. The SPADEX mission features two identical satellites, SDX01 (Chaser) and SDX02 (Target), each weighing 220 kg, designed to demonstrate advanced space technologies. For the first time in Indian Space Programme Spacecraft was realized beyond ISRO facility. The Front Runner Ananth Technologies (ATL) , Bengaluru realized these Twin-Spacecraft in its state of art clean room, under the technical guidance of ISRO team, in record time meeting the project schedule for launch by PSLV from SHAR. Well trained and experienced engineers and technicians of ATL have put enormous effort almost 24×7, in realizing these spacecraft and meeting all technical specifications.
After the successful launch, on 30th December, 2024, has created a Golden Mark in the history of Indian Space Programme, where ‘ATL took the challenge and build the spacecraft, outside ISRO and performed with great satisfaction under the leadership of Dr. Subba Rao, CMD’. ATL is now confident and ready to take new such space challenges to meet country’s growth and development.
Dr. Subba Rao Pavuluri, CMD of ATL, remarked, “Being a part of this milestone mission highlights ATL’s commitment to India’s human space program and our evolving contributions, from subsystem manufacturing to full satellite and launch vehicle integration. PSLV-C60 is the 10th launch vehicle ATL has assembled, integrated, and tested.”
Headquartered in Hyderabad, ATL operates advanced facilities in Thiruvananthapuram for the fabrication, assembly, and testing of launch vehicle subsystems and satellites. To date, ATL has contributed to the success of 102 satellites and 82 launch vehicles for India’s space programs. With its dedication to precision engineering, innovation, and reliability, ATL continues to play a vital role in India’s space missions, furthering the nation’s vision for technological excellence and leadership in space exploration.
SpaDeX is a mission for the demonstration of in-space docking (Chaser & Target in LEO ~470km) using two small spacecraft (of ~220kg class) launched by PSLV. Docking aims for futuristic India’s space ambitions such as ‘Man on Moon’, ‘Sample Return missions’ and ‘Building and Operation of Bharatiya Antariksh Station (BAS)’, etc. Secondary beehives includes Demonstration of the transfer of electric power between the docked spacecraft (an essential application for in-space robotics), Composite spacecraft control, and Payload operations after undocking.
With small relative velocity between the Target and Chaser at the time of separation from the launch vehicle, will allow the Target spacecraft to build a 10-20 km inter-satellite separation (using propulsion system of the Target spacecraft). At the end of this drift arrest maneuver, the Target and Chaser will be in the same orbit with identical velocity but separated by about 20 km, known as Far Rendezvous. With a similar strategy of introducing and then compensating for a small relative velocity, the Chaser will approach the Target with progressively reduced inter-satellite distances of 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m, ultimately leading to the docking of the two spacecraft. After successful docking and rigidization, electrical power transfer between the two satellites will be demonstrated before undocking and separation of the two satellites to start the operation of their respective payloads for the expected mission life of up to two years.
Both the SpaDeX spacecraft carry a differential GNSS-based Satellite Positioning System (SPS), which provides PNT (Position, Navigation, and Timing) solutions for the satellites. In SpaDeX, a novel RODP processor is included in the SPS receiver, which allows accurate determination of the relative position and velocity. The VHF/UHF transceivers in both satellites aid this process by transferring the GNSS satellite measurements from one satellite to the other.
Up to an inter-satellite distance (ISD) of 5 km, standard orbit maintenance and attitude control algorithms employed. As the spacecraft are in circular orbit, and any addition or reduction of velocity to the satellites will result in orbit change. The V-bar strategy using n-Pulse, Glideslope and PV guidance algorithms are employed to reduce the ISD, hold at fixed ISDs to evaluate the sensors and software, and finally docking. These algorithms were converted into software for achieving the rendezvous and docking. These software solutions were tested and validated in multiple digital, hardware-in-loop, onboard-in-loop, software-in-loop, and robotic simulations.
After the docking and undocking events, the spacecrafts will be separated and used for application missions.
• A High-Resolution Camera (HRC) with a 4.5 m IGFOV and a swath of 9.2 x 9.2 km (snapshot mode) and 9.2 x 4.6 km (video mode) from a 450 km altitude is mounted in SDX01 (Chaser).
• A Miniature Multi-Spectral Payload (MMX) is mounted in SDX02 (Target). This has four VNIR bands (B1/B2/B3/B4) at 450 nm to 860 nm and a 25 m IGFOV with a swath of 100 km from a 450 km altitude. The imaging is useful for natural resource monitoring and vegetation studies.
• A Radiation Monitor (RadMon) payload in SDX02, will measure radiation dose encountered in space. This will help in generation of a radiation database for future Total Ionization Dosimeter (TID) and Single Event Upset (SEU) measurements for space science studies, with applications in human spaceflight.
The indigenous technologies developed for enabling this docking mission are as follows:
• Docking mechanism with rendezvous and docking sensors and autonomous rendezvous and docking strategy.
• Power transfer technology,
• Inter-satellite communication link (ISL,
• GNSS-based Novel Relative Orbit Determination and Propagation (RODP) processor,
• Simulation test beds for both hardware and software design validation and testing.