Subsequent to the DEA shutoff on day 259 (DOM 2247) the ACIS focal plane temperature readout appears to be about 1 degree warmer than the actual temperature. See figure focalplaneT.ps attached. This was diagnosed by noting the cti decreased after temperature correction whereas the raw data cti remained constant through this period, and by noting that the apparent difference between focal plane and radiator temperature also increased by one degree at this time. No mechanism for this change is currently identified. The implication is that the focal plane temperature can now bounce around between about -118.5 (depending on earth illumination) and -120.9, since the control heater will not turn on until the temperature sensor reads -119.9.
The minimun temperature reading after the doy 278 test is -118.40 F.
| Day (DOY) | Temp (C) | Width (Days) | |
|---|---|---|---|
| 281.78 | -116.64 | >0.51 | |
| 284.19 | -116.15 | >0.25 | |
| 284.54 | -116.96 | >0.22 |
Weekly focal plane temperature with sun angle, earth angle, and altitude overplotted. Sun angle is the solar array angle, that is the angle between the sun and the optical axis (+X axis). The earth angle is the angle between earth and the ACIS radiator (+Z axis). Altitude varies from 29 kkm to 120 kkm.
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