SCM
The Goembel Instruments Spacecraft Charge Monitor (SCM) was designed and built to monitor low level charge (~+/-30 volts) which is typically expected on the International Space Station (ISS). In fact, it is believed that such low level charge could be responsible for the death of an astronaut during an extra-vehicular activity, so it is important to monitor for such charging on craft such as the ISS [Ferguson, 2002] .
Potential Uses for the SCM Include:
- monitor for S/C charge reduction devices (such as the plasma contactor unit on the ISS)
- monitor 'S/C charge high: yes or no' (even in GEO, it may be that most of the time the S/C charge will be below +/-30 volts).
- determine the effectiveness of the electron-spectroscopic method of charge measurement.
The flight-ready SCM-1 has been designed and built with the assistance of NASA Phase I and II Small Business Innovative Research (SBIR) funds.
It is ready for flight today.
SCM Specifications:
Floating Potential Range |
-20 to +45 volts with 0.1 volt precision. |
Size |
6.5”x 3.75”x 2.75” |
Mass |
650 grams |
Vibration Qualification level |
14.5 G’s (rms) for 3 minutes each orthogonal axis |
Calibrated operating temperature |
-24˚C to 40˚C |
Expanded operating temperature |
-24˚C to +61˚C |
Storage temperature |
-55˚C to 105˚C |
Power |
< 2Watts, 28V (unregulated) |
S/C Interface |
RS422 two-wire differential |
Data rate |
2kbits/second (raw data output) |
References:
Ferguson, Dale C., Charging of the International Space Station Due to Its High Voltage Solar Arrays, NASA Technical Report Server Document ID: 20030000606, 2002.