Simulator for Functional Verification and Validation of a Nanosatellite

Abstract

The introduction of CubeSats in the space industry has opened the frontiers of space to educational institutions. This surge of new organizations in the industry calls for a better process to test and validate the operations of a satellite before it is launched. The process should be flexible to include a variety of payload and should be compatible with the existing popular systems in the industry. The paper discusses one such process devised by the members of Team Anant, the Student Satellite Team of BITS Pilani. The team is currently working on a 3U nanosatellite with a hyperspectral camera as its primary payload. Being a research-based project, the members developed a Satellite Simulator by themselves rather than utilizing similar platforms for the validation of their satellite's operation. Apart from the various modules present in any general satellite, the program offers the utility of adding an independent Operations module, specific to the interests of the user. The user can then easily program the planned FSM of the modes of operation of their satellite and use the developed platform to perform tests comprising the satellite's hardware as well as software-logic. The program has been developed in MATLAB, making it convenient as well as economical to integrate it with hardware for a Hardware-in-loop (HIL) simulation. The program is essentially a virtual replica of the actual space environment experienced by the satellite with the ability to generate 3D visualizations of the satellite in orbit. Currently, processes like HIL simulations are able to accurately determine the response of the satellite independent of any other celestial body in its vicinity. A team can use the developed program in association with the HIL simulation to enhance the accuracy of that process. The Physics module determines the position of the satellite in Earth's orbit and its current attitude. The Telemetry module can estimate how much data can be downlinked/uplinked during each pass over the ground station, depending on the launch time and location. The Power module is used to estimate the instantaneous power levels of the satellite in each mode of its operation, considering the changing position of the Sun and the satellite's attitude. The program also features a replaceable Payload module, which in our case, replicates the function of the imager. The modular approach in the development of this program makes it feasible to add more functions depending on the requirement of the project. The use of MATLAB also makes it compatible with most platforms used for testing the operations of a satellite. All aspects of the program can be easily modified according to the various specifications of the satellite, its orbit, and the mission. The program, in collaboration with a hardware-in-loop simulation, is an efficient and accurate way to verify the physical operations of the satellite. The flexibility, compatibility, and accuracy of this process make it a viable alternative to traditional HIL testing.