Virtual ground station for automated spacecraft operations
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Date
2021-01-02
Authors
Parthasarathy, Varsha
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Abstract
Low-earth orbit satellite constellations provide important services over very large areas in a uniform way. Traditional spacecraft communication typically requires manually-staffed ground stations with space systems experts controlling and monitoring bus and payload systems during each pass. These onerous requirements limit the ability to access valuable space assets, more so in the case of large constellations of satellites.
This thesis presents a virtual ground station (VGS) with a real-time virtual satellite model (VSM) and a fault-management system based on industrial statistical process control (SPC) techniques and time-domain feature extraction. The VSM is in continuous view of the VGS at all times and allows the operators to send and receive data as required without waiting for a pass. The operators always interact with the VSM through a graphical user interface (GUI) terminal as opposed to the spacecraft itself such that the VSM mimics the actual satellite as much as possible. The VGS streamlines spacecraft operations by managing every real pass, uploads stored commands when a pass occurs, automatically downloads telemetry and maintains the VSM. This eliminates trivial housekeeping activities and lets the experts focus on complex problems. The VGS also contains a real-time orbit propagator that provides the real-time position and velocity of the satellite and lets the operators visualize the mission in 3D. In this thesis, the VSM uses the power subsystem as an example and takes the form of a real-time power subsystem simulator of the spacecraft. The fault-management system employs custom algorithms to monitor telemetry from the spacecraft and compare it to the predicted telemetry from the VSM to perform early fault diagnosis. The specific faults considered are the loss of a solar string(s), increase in the battery's internal resistance and excessive power consumption onboard the spacecraft.
A unique testbed consisting of a simulation engine with an actual satellite model (ASM) and a serial communication protocol is presented. It is used to demonstrate the functions of the VGS through various scenarios during a typical interaction between the VGS and the satellite. Some of these scenarios include initiation of communication with the spacecraft, automatic telemetry downloading, anomaly detection, real-time data requests and storing and uploading commands to the spacecraft.
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Keywords
Spacecraft constellations, Ground stations, Fault-detection, Real-time health-monitoring, Statistical process control, Virtual model, Power subsystem, CubeSat simulator, Graphical user interface, Operations application, Automation, Virtual satellite model, Automated telemetry analysis, Feature extraction