Low cost TU Delft built Satellite Positioning System in Indian nanosatellites
On February 15, 2017 the Indian Space Research Organization (ISRO) launched 104 nanosatellites. Two out of these 104 satellites were equipped with a Satellite Positioning System, built by researchers of the Embedded Software Group that is part of the Software Technology Department (Delft University of Technology).
Use of Global Navigation Satellite System (GNSS) receivers in Low Earth Orbit (LEO) satellites for orbit determination has appealed many researchers in the space industry. However, commercial off the shelf GNSS receivers that are optimized for terrestrial intentions are not suitable for space applications. To achieve precise position, velocity, and time resolution while circumventing the doppler effect due to high orbital velocity (approx 7.8 km/s) of satellites, the development of GNSS receivers for space is a major challenge to researchers.
The Delft University of Technology has built low cost GNSS receiver modules in cooperation with ISRO, ISRO-TU Delft Standard Positioning System (SPS), for the two Indian nanosatellites INS-1A and INS-1B as experimental payloads. The modules house a COTS modified GNSS receiver chip supporting both GPS and GLONASS, and a low power ARM based microcontroller to execute algorithms. They communicate with their respective On-Board Computers (OBC) of the satellites. The GNSS receiver in the module estimates position and velocity at 20Hz and sends the information to OBC when there is a request. Apart from this, the modules also send information about the time difference between the location fix and time of data request from OBC to ensure proper synchronization of On Board Time (OBT) in the OBC by GNSS modules.
We achieved a resolution of 10m (3σ) using rigorous test facilities provided by ISRO. The tests included multiple orbit emulation as well as the actual speeds involved. The modules went through vibration, thermal and vacuum tests. The modules were handed over to Dr. M. Annadurai, the Director, ISRO Satellite Centre (ISAC) by Dr. R. R. Venkatesha Prasad (VP), Assistant Professor in the Embedded Software Group of the Delft University of Technology. VP’s PhD-student at Delft, Sujay Narayana, was able to design, develop, and configure the modules duly in time along with on-site support for module testing on the satellites at ISRO.
The twin satellites INS-1A and INS-1B were launched by PSL-C37 launcher in ISRO’s record breaking rocket launch on February 15, 2017. The video of PSLC-C37 launch as well as the launcher stage/satellite separation event can be watched here:
Apart from providing low cost GNSS modules, the Delft University of Technology also offered support to ISRO with its Ground Station at the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS)to track both the nano-satellites. Since the launch, the ground station received telemetry from both the satellites for specific orbit passes. The Delft University of Technology also helped ISRO with decoding the telemetry packets as the telemetry recording was in raw format. The support with tracking is still being continued.
Recently, Dr. R. Venkatesha Prasad had an opportunity to meet Mr. Kiran Kumar, the Chairman of ISRO, and presented the vision of the Delft University of Technology on space robotics (Zebro developed by Dr. Chris Verhoeven), radio interferometry, On-Board Computer, micro-thrusters, inter-satellite communication, and Space IoT. We expect close co-operation with ISRO in the near future on various research aspects.