ARISSat-1Critical Design Review

Orlando, Feb 15, 2010

Control Panel

Jerry ZdenekJerry.Zdenek@microchip.com

Feb 15, 2010 ARISSat-1 CDR 2

Introduction• Provides the Control of the Satellite and

indicate Satellite Status• Scope

– Requirements– Design– Safety Considerations– Verification– Operations– Status

Feb 15, 2010 ARISSat-1 CDR 3

Requirements

• Compliant with all ISS safety requirements

• Provide an interface that an Astronaut in a pressure suit can control the satellite

• Indicate status of the Satellite

• Allow the system to be quickly shut down in case of a problem

Feb 15, 2010 ARISSat-1 CDR 4

Design• Provide all timer functions equivalent to Suitsat-1

– One Power switch with LED status– Two Timer switches with LED status

• Same mechanical switch layout as Suitsat-1• Additional LEDs for Operational and Safety

Verification• Solve LED visibility problem reported by

Astronauts• Measure control panel temperature

Feb 15, 2010 ARISSat-1 CDR 5

Control Panel Front

Feb 15, 2010 ARISSat-1 CDR 6

Control Panel Assembly

• Flight units will have wires strain relieved

Feb 15, 2010 ARISSat-1 CDR 7

Design

• Interface Box– Switches and LEDs only– Nearly completely passive assembly

• Control circuitry on ICB

• Safety functions managed by ICB

• LED Brightness circuitry within Control Panel

Feb 15, 2010 ARISSat-1 CDR 8

LED Brightness

• Must balance two conflicting requirements– Minimize power usage– Good visibility to Astronauts, factoring in sun

visor

• Solution: two different brightness modes– LEDs always on dimly (room visible) – If the first timer has not expired, run extra

current through the LEDs for brightness– Using very high efficiency LEDs

Feb 15, 2010 ARISSat-1 CDR 9

Schematic – Timer Control

Feb 15, 2010 ARISSat-1 CDR 10

Schematic – Status LEDs

Feb 15, 2010 ARISSat-1 CDR 11

Safety Considerations

• Activation Switches – False activation due to switch contamination

could create a safety hazard– Using APEM 12000X778 Switches to insure

safety– Switches are designed for high-rel

applications and is QPL certified to MIL-DTL-83731 and MIL-DTL-3950

Feb 15, 2010 ARISSat-1 CDR 12

Safety Considerations

• Access to switches– Metal Finger guards provided so that only one

switch is activated at a time

Feb 15, 2010 ARISSat-1 CDR 13

Verification• Improved design over Suitsat-1

– Switches are now operating with 50% design margin on wetting current

– Suitsat-1 was operating outside spec

• Operating with both low and high voltage inputs• In use during development testing of other

systems• Ran system at real time speed multiple times

– Video Taped one run to verify specified timings

Feb 15, 2010 ARISSat-1 CDR 14

Operations• Integral with ICB Safety Circuitry

– Further details in ICB design review

• To Deploy:– Turn on 28V Power switch

• Verify LEDs in correct state

– Turn on Timer 1 Switch• Verify LEDs in correct state

– Turn on Timer 2 State• Verify LEDs in correct state

• Launch the satellite!

Feb 15, 2010 ARISSat-1 CDR 15

Status• Design and Documentation Complete• Electrical Testing complete• Positioning of Thermistor inside box not

defined yet• Switch set up the same as Suitsat-1, so no

operational problems expected• Quantity of LEDs has been brought up as

a training / ease of use issue• Just need to assemble flight units!