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THEMIS Instrument PDR 1 UCB, October 15-16, 2003
IDPU Mechanical / Thermal
Preliminary Design ReviewHeath Bersch
University of California - Berkeley
THEMIS Instrument PDR 2 UCB, October 15-16, 2003
IDPU Concept
IDPU Chassis Concept
MASS = 1800 GRAMS EMPTY
4MM WALLS PROVIDE SHIELDINGADDITIONAL SHIELDING PER BOARDAND SPACE CRAFT BUS
Volume = 652 cubic centimeters
THEMIS Instrument PDR 3 UCB, October 15-16, 2003
ICD Drawing
THEMIS Instrument PDR 4 UCB, October 15-16, 2003
LVPS
FGE/PCB
DCB/ETC
DFB
BEB
SST
Card Assignments
THEMIS Instrument PDR 5 UCB, October 15-16, 2003
ALUM SHIELD
PEM SPACER
HEAT SINKS
WEDGE LOC
D-SUB CONNECTOR
Standard Card
THEMIS Instrument PDR 6 UCB, October 15-16, 2003
Wedge Loc Interface
THEMIS Instrument PDR 7 UCB, October 15-16, 2003
ESA Attachment Concept
THEMIS Instrument PDR 8 UCB, October 15-16, 2003
Thermal - IDPU
Heat Transfer
Power Dissipation
•10.74 W
Conduction
•We are trying to keep the bottom deck warm
•Therefore the IDPU is thermally coupled to the bottom deck using a ChoTherm gasket
•ESA conducts heat away and radiates it to space
Radiation
•All surfaces covered with low ε VDA tape or blankets
•IDPU may need radiator, current Swales model includes one
THEMIS Instrument PDR 9 UCB, October 15-16, 2003
Thermal - IDPU
Temperature Limits
•Predictions from Swales
•Cold prediction from 3 hour eclipse orbit
•Hot prediction from hottest orbit and attitude
•Average operating temperature around 30 °C
•Better predictions await more complete instrument thermal models
Survival (°C)Predictions
(°C)
Margin
(°C)Eclipse-Op
Science-Op Cold Hot Cold Hot
-50 -30 40 +65 -16 36 14 4
THEMIS Instrument PDR 10 UCB, October 15-16, 2003
Thermal - IDPU
Temperature Monitoring and Control
•Modified Interface Monitoring
•Probe Bus will monitor the interface temperature near the IDPU
•Instrument Monitoring
•IDPU will process additional thermistors if needed
•Heaters
•No operational heaters are required
•Survival heaters will keep IDPU above Eclipse-Op Limits
•Two heater services provided by the probe bus
•Primary service thermostat closes at -23
•Secondary service thermostat closes at –28
•IDPU may share heater with the ESA, depends on final coupling
