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

2. 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 Mini-demo 2 Stanford VLF group image

3. SHOT Design Overview 3

4. Mechanical Results Box intact Thermal isolation between requirements Battery performed nominally (i.e., T batt > -10 °C) PA didn’t exceed nominal temperature (i.e., T heatsink < 140 °C) Cover slightly open Several screws didn’t hold components during landing 4

5. Mechanical Results Box intact with cover slightly opened Components broke free of restraints during landing 5

6. VLF transmitter results – COIL Goal: reception from ground of a VLF (17.319 kHz) signal generated by payload Problems experienced: Lots of VLF noise at launch site Self oscillation of LNA amplifier No properly keyed signal received at transmission frequency Filtering of nearby signals doesn’t show expected keying pattern Correlation may reveal something within noise, but in any case the transmission will not be as efficient as expected! 6

7. VLF transmitter results – PLATES Goal: measure on-board the VLF (34.638 kHz) current transferred to plates in correlation with environment Data loggers recorded a drop in the plates voltage 7 CURRENT INCREASE? ? Baloon telemetry

8. VLF TX – Reasons for Voltage Drop? What this could’ve meant: Increase in current/radiation efficiency at high altitudes What this probably means: The plates (outside the box, T < -56 °C) cooled through copper cables and circuits to the op-amp input, and somehow influenced it Temperatures of 1 MΩ resistor is unlikely to be involved, the transition to/from higher voltage drop is too sudden More investigation needed to confirm this theory! 8

9. Lessons Learned and Future Work Better securing of components inside box in future SHOT launches (only for functionality after recovery, no problems in flight) VLF transmission with “infinitesimally short” antenna is HARD! Focus more on reception equipment for VLF communication: wideband receiver is not optimal in high noise conditions tuned amplifier may help reject noise and stabilize operation Anything outside the box is cold. This will involve additional precautions on the connections. But can we exploit for our goals the low temperature of the high altitude environment? More research needed! 9

10. Thank you! Questions? Comments? 10