1. Thermal Modeling of the CX Satellite Jacob Boettcher Thermal Team Lead 4/5/02

2. Overview Brief description of the thermal design process Discuss the reasons for an orbit revaluation Describe the procedure used to perform the orbit revaluation Present the results

3. Thermal Design Philosophy Thermal Control System had to be entirely passive – Places requirement that the spacecraft absorb and emit the right balance of radiation Required accurate model of the thermal environment – Must know if the spacecraft can achieve a steady thermal state

4. Thermal Modeling Process Create 3-D model of the spacecraft for radiation view-factor calculation – SUPVIEW Determine the Beta Angle – FINDB6 Calculate Thermal Inputs – ALBTIME2 & ALBEDO Determine overall radiation model – REFLECT Input thermal conductances and capacitances into model to get temperature profiles – TAK III

5. Reasons for Orbit Revaluation CX was designed to operate in a particular orbit – Altitude: 705 km; Local Time: 10am-10pm Needed to see if other orbits would satisfy: – Power requirements (solar panels) – Science requirements (instruments) – Thermal requirements (radiation budget)

6. Evaluated Orbits Selected based on the following criteria: Must be sun-synchronous (constant beta angle) Science must have pass time between 9am-9pm & 12am-12pm Altitude must be above 500 km (drag effects) Power required local time of 10:30am-10:30 pm or earlier Each ran with hot and cold case values for Solar flux, Earth IR Emission, and Direct Solar Albedo

7. Subsystem Thermal Requirements

8. Results

9. Conclusions No single orbit satisfied all thermal requirements Science subsystem only subsystem not to be satisfied by any other orbit Closer to the original orbit the better – All subsystems, except Science, satisfied with local times between 10am-10pm & 10:30am-10:30pm

10. Questions?