Friedman 1 REAL - TIME MODELING OF SPACECRAFT SIMULATORS USING SYSTEMS TOOL KIT

The research presented in this report focuses on the spacecraft simulators, Whorl-I and Whorl-II, in the Space Systems Simulation Laboratory (SSSL) at Virginia Tech. The goal of this research is to develop a program to visualize the attitude of the simulators in real-time through Analytical Graphics Inc.’s Systems Tool Kit (STK). Spacecraft missions are high-risk and highexpense; therefore, extensive hardware testing prior to launch is important to spacecraft missions. Air-bearing systems are often used to simulate spacecraft because of their ability to reduce the friction on the simulator due to gravity. Creation of a program to simulate attitude of a spacecraft in real-time further improves pre-flight testing capabilities. A three-axis accelerometer and a three-axis magnetometer are used to collect data, which is then processed using the TRIAD method for attitude determination. Quaternions are then sent to STK by Connect commands; furthermore, Connect commands are used to propagate an orbit in STK. The simulator attitude is continually sent from the simulator to STK to create a real-time visualization of spacecraft attitude in orbit establishing a more accurate test bed for new spacecraft hardware prior to launch. 1. Spacecraft Simulators The Space System Simulation Laboratory (SSSL) at Virginia Polytechnic Institute and State University (Virginia Tech) houses two spacecraft simulators, formally known as a Distributed Spacecraft Attitude Control System Simulator (DSACSS). The DSACSS uses an air-bearing system with a low-friction sphere and clean, dry air filtered from an air compressor for testing of attitude control hardware and sensors. The first simulator, Whorl-I, depicted in Figure 1, uses a “tabletop” platform with ±360° of rotation in the yaw axis and approximately ±6.5° of rotation in the roll and pitch axes. The second simulator, Whorl-II, depicted in Figure 2, uses a “dumbbell” form with two vertical platforms placed at the end of two circular metal arms which are connected to the low-friction sphere. Whorl-II has ±360° of freedom in the yaw and roll axes and approximately ±15° of freedom in the pitch axis. Figure 1. Distributed spacecraft attitude control system known as “Whorl-I.” Figure 2. Distributed spacecraft attitude control system known as “Whorl-II.”