1. TERSat Massachusetts Institute of Technology Eric Peters, Danilo Roascio, Leonard Tampkins, Kezi Cheng June 29, 2012 1

2. Mission Background Radiation in Earth orbit harms satellites –Natural radiation: High energy particles from solar wind are trapped in Van Allen Belts –Man-made: high altitude nuclear activity Gap in radiation belts is caused by lightning Can we scatter radiation particles by emitting VLF waves, like lightning? 2 SOHO composite image by Steve Hill (NASA) Van Allen Belts Stanford VLF group image

3. Mission Overview Satellite Goals: -Demonstrate wave-particle interaction within the inner Van Allen belts -Transmit VLF waves at LEO altitude -Demonstrate science behind potential radiation remediation technique SHOT II Goal: -Use VLF wave transmitter to demonstrate ability to transmit signal to a receiver on the ground Connection: -Demonstrates payload concept of operations, tests prototype VLF receiver parts Example TERSat Interaction with DSX Mini- demo 3

4. SHOT Design Overview 4

5. Payload Design Structure Foam Box Two antennas: 17 kHz copper coil along perimeter 34 kHz aluminum plates on long sides Structure: Foam box with high impact foam on bottom to mount electronics Weight: 1.45 kg Dimensions: 8.5” x 11” x 5” Mylar for thermal insulation Balloon attachment cord runs through middle of payload 5

6. 6 Payload Design Electronics Circuit design includes: Crystal oscillator for frequency stability Payload Amplifier Morse code keyer 2 Voltage Data Loggers with peak detector conditioning to evaluate power going into aluminum plates +

7. Ground Station Design Ettus USRP SDR Receiver –Low-frequency daughter boards –Sampling between 0 and 125 kH Custom Low Noise Amplifier tuned to operate between 1kHz and 80 kHz Attached to square loop antenna 7

8. SHOT Functional Testing 8 Received signal Lot of noise in VLF band Morse Keying helps identify signal Morse code: Hello World Cooling Test First prototype – not insulated enough Second prototype – Thicker foam + Mylar sheet show better thermal insulation

9. Mechanical Testing Drop Test Whip Test Stair Test Drop Test Successful! Battery held down Box maintained shape Screws were set 9

10. Demonstration 10