TERSat Massachusetts Institute of Technology Eric Peters, Danilo Roascio,
description
Transcript of TERSat Massachusetts Institute of Technology Eric Peters, Danilo Roascio,
TERSatMassachusetts
Instituteof Technology
Eric Peters, Danilo Roascio, Leonard Tampkins, Kezi
Cheng
July 1st, 2012
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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 techniqueSHOT 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
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Stanford VLF group image
SHOT Design Overview
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Mechanical Results
• Box intact• Thermal isolation between requirements
• Battery performed nominally (i.e., Tbatt > -10 °C)• PA didn’t exceed nominal temperature (i.e., Theatsink < 140 °C)
• Cover slightly open• Several screws didn’t hold components during landing
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Mechanical Results
Box intact with cover slightly opened
Components broke free of restraints during landing
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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!
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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
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CURRENT INCREASE?
?
Baloon telemetry
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
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!
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Thank you!
Questions? Comments?
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