There were several radiation alerts issued on 1/30/2001 and 1/31/2001. The highest Acis fluence (3.26e+9) was reported on 1/31/2001, 02:05:01 EST. No Action was taken.
Average of ACIS-I CCDs (MnKa) slope 2.177e-8 CTI/day
Detrended slope 1.484e-8 CTI/day
Day (DOY) Temp (C) Width (DAY)
26.3 -117.0 0.24
29.0 -117.0 0.23
31.0 -118.7 ~1 --- a broad hump
31.4 -118.4
31.7 -116.2 0.52
The peak on day 31 seems to have been affected by the SIM
seeing a bit of the warm Earth.
No new problems were reported, but the following msid was reopened in this period
2LLDIALV (Lower level disc setting) on 2/1/2001. Some regular
threhold crossing MSIDs were removed from the tracking database.
The following msids are keep coming
AOACHIBK, ES2P5CV, ASPEB5CV, 2RSRFALV
All values are in the expected ranges during this period.
| OBSID | DETECTOR | GRATING | TARGET | ANALYSIS | ACA | 2001 | ACIS-S | NONE | CRAB NEBULA | NO ANAL | MISSING | 1655 | ACIS-I | NONE | MACSJ0717.5+3745 | OK | OK | 2160 | ACIS-I | NONE | 2MASSJ095504+1705 | OK | OK | 2223 | ACIS-S | NONE | NGC741GROUP | OK | OK | 1669 | ACIS-S | NONE | A478 | OK | OK | 2198 | ACIS-S | NONE | NGC7331 | OK | OK | 1611 | ACIS-S | NONE | NGC1097 | OK | PROBLEM | 2339 | ACSI-S | NONE | NGC1097 | OK | OK | 1633 | ACIS-S | NONE | NGC660 | OK | OK | 1612 | ACIS-S | NONE | 3C120 | OK | OK | 2240 | ACIS-I | NONE | CADIS01HFIELD | OK | OK | 2155 | ACIS-I | NONE | 2MASSJ015721+1712 | OK | OK | 2154 | ACIS-I | NONE | 2MASSJ012031+2003 | OK | OK | 2153 | ACIS-I | NONE | 2MASSJ010835+2148 | OK | OK | 2158 | ACIS-I | NONE | 2MASSJ034857+1255 | OK | OK | 2266 | ACIS-I | NONE | AGX~J233200+1945 | OK | MISSING | 2157 | ACIS-I | NONE | 2MASSJ023430+2438 | OK | OK | 2152 | ACIS-I | NONE | 2MASSJ005055+2933 | OK | MISSING | 2310 | ACIS-S | LETG | H1821+643 | OK NO GRAT. ANAL. | PROBLEM | 2311 | ACSI-S | LETG | H1821+643 | OK NO GRAT. ANAL. | OK | 988 | HRC-S | NONE | VEGA,HRC-S,AO2 | OK | OK | 992 | HRC-S | NONE | VEGA,HRC-S,AO2 | OK | OK | 995 | HRC-S | NONE | VEGA,HRC-S,AO2 | OK | OK | 990 | HRC-S | NONE | VEGA,HRC-S,AO2 | OK | OK | 994 | HRC-S | NONE | VEGA,HRC-S,AO2 | OK | OK | 986 | HRC-I | NONE | VEGA,HRC-I,AO2 | OK | OK | 1573 | HRC-I | NONE | M31-NORTH2 | OK | OK | 1571 | HRC-I | NONE | M31-NORTH1 | OK | OK | 1569 | HRC-I | NONE | M31-CENTER | OK | OK | 1567 | HRC-I | NONE | M31-SOUTH1 | OK | OK | 1565 | HRC-I | NONE | M31-SOUTH2 | OK | OK | 1973 | HRC-S | NONE | 1RXSJ0203-2438 | No Anal. | OK |
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1. Correlation 'Sum of detector leakage currents' vs '27 V current' Good correlation! As expected. The slope of 35.5 microA/mA is reasonable. On SOHO, we have an extremely stable thermal environment, i.e. no change in leakage current due to temperature variations. However, the E-detector went noisy at some stage with a corresponding leakage current increase. I determined a slope of 31 microA/mA, i.e. a very similar behaviour as you have seen.
2. Correlation 'A leakage current' vs 'temperature' The observed slope is expected. The broadening may be due to higher detector A leakage currents with time. This temporal trend might be due to the annual solar-orbital modulation which you mention, plus a degradation of the thermal blanket. Certainly, there will also be a contribution of radiation effects by solar particles, i.e. even if the temperatures would fall back to the same cooler temperatures, the leakage current would not! This would be most prominent for detector A which is most exposed. The bi-modal correlation (see 3. below) is in support of this.
3. Correlation 'A leakage' vs 'B leakage' It looks as if there are several linear regressions, at least two in the lower part (between 0.03 and 0.1 microA detector B leakage). If we can show that the upper branch is at later times, then the explanation given in 2. above holds.
Conclusions: As the leakage current increases, so does the voltage drop across the load resistor which is in series with the detector in the bias circuitry. Hence there is less voltage across the detector. To safeguard against this aging effect, we have overdepleted the detectors, i.e. we have applied a higher voltage than is necessary to fully deplete the intrinsic detector volume. The instant when this overdepletion is exhausted is difficult to determine, as the housekeeping measurement of the leakage current is limited in range. The only way I can see is to look at the pulse height distribution for detector A of the INT channel. A shift of the minimum ionizing peak towards lower channels would be indicative for such a case. However, I do not expect this to happen for many years (and solar events) to come. With this explanation of the leakage current increase as a result of radiation damage in the silicon lattice structure, I withdraw my earlier quick and dirty speculation about a pin hole in the aperture foil.
This Week's focus
Most msids are keeping the same trends from the previous reporting period ( 11/03/00 - 11/10/00 weekly).
ACA Thermal ----------- AACCCDRT AC CCD TEMP upward trend, around 289.1 after DOM 400 AAOTALT LENS CELL TEMP upward trend, around 287.4 after DOM 450 AAOTASMT temp 4 - secondary mirror upward trend, 287.1 after DOM 450 AAOTH2MT AC OPT TEL ASSY SECONDARY MIRROR TEMP upward trend, 287.4 after DOM 450 AACH2T AC HOUSING TEMP upward trend, around 287.75 after DOM 430 AACBPPT AC BASEPLATE TEMP mainly around 291.5, but upward scatter after DOM 450 AACBPRT AC BASEPLATE TEMP mainly around 289.7, but upward scatter after DOM 450 AACCCDPT AC CCD TEMP @262.78 AACH1T AC HOUSING TEMP around 287.5, scatter more upward after DOM 450 AAOTAPMT AC OPT TEL ASSY PRIMARY MIRROR TEMP around 286.8, scatter more upward after DOM 450 TEMPCCD temp 1 - CCD flat at 263.15 TEMPHOUS temp 2 - AC housing flat 287.55 but upward scatter after DOM 450 TEMPORIM temp 3 - lens cell around 287.55 after DOM 400 TEMOSEC temp 4 - secondary mirror around 287.15 after DOM 430 IRU Temperature and Electronics ------------------------------- AIRU1G2I IRU-1 GYRO #2 CURRENT downward trend currently around 99 AFSSPC1V FSS POWER CONV 1 VOLTAGE flat @ 3.50 AFSSPC2V FSS POWER CONV 2 VOLTAGE flat @ 0.0 AGWS1V GYRO WHEEL SUPPLY 1 INPUT VOLTAGE almost flat around 2.71 AGWS2V GYRO WHEEL SUPPLY 2 INPUT VOLTAGE flat @0.0 AIRU1BT IRU-1 BASE TEMP flat @313 after a bump finished around DOM 400 AIRU1G1I IRU-1 GYRO #1 CURRENT around 89 after DOM 450 AIRU1G1T IRU-1 GYRO #1 TEMP flat @ 342.26 AIRU1G2T IRU-1 GYRO #2 TEMP flat @ 342.72 AIRU1VFT IRU-1 VFC TEMP flat @ 334.16 AIRU2BT IRU-2 BASE TEMP flat @ 252.59 AIRU2G1I IRU-2 GYRO #1 CURRENT flat @ 9.60 AIRU2G1T IRU-2 GYRO #1 TEMP flat @ 292.59 AIRU2G2I IRU-2 GYRO #2 CURRENT flat @ 9.60 AIRU2G2T IRU-2 GYRO #2 TEMP flat @ 292.59 AIRU2VFT IRU-2 VFC TEMP flat @ 292.58 Pcad Gyro Rates _______________ AOSUNEC1 UNIT VEC. FROM THE SPACECRAFT cycle between -1.0 and 1.0 currently upward cycle AOSUNEC2 UNIT VEC. FROM THE SPACECRAFT cycle between -1.0 and 1.0, bottomed at DOM 520 AOSUNEC3 UNIT VEC. FROM THE SPACECRAFT cycle between -0.4 and 0.4, bottomed at DOM 520 AOTAROT1 TARGET ATTIT cycle between -0.6 and 0.8 bottomed at DOM 500 AOTAROT2 TARGET ATTIT cycle between -1.0 and 1.0,currently downward trend AOATTQT1 AOCMDQT1 cycle between -0.6 and 0.8 bottomed around DOM 500 AOATTQT2 AOCMDQT2 cycle between -0.6 and 0.6 bottomed around DOM 550 AOCMDQT1 AOCMDQT1 cycle between -0.6 and 0.8 bottomed around DOM 500 AOCMDQT2 AOCMDQT2 cycle between -0.6 and 0.6 bottomed around DOM 550 AOATTQT3 AOCMDQT3 scattered between -0.6 and 0.6 AOATTQT4 AOCMDQT4 scattered between 0.0 and 1.0 AOCMDQT3 AOCMDQT3 scattered between -0.6 and 0.6 AOSCPOS2 COMMANDED SPACECRAFT ATT scattered between -1.2e5 to -2.0e5 AOSCVEL1 SPACECRAFT POSITION VEL scattered between -1.5 and 1.0 more around 0.9 AOSCVEL2 SPACECRAFT POSITION VEL scattered between -1.5 and 1.5 AOSCVEL3 SPACECRAFT POSITION VEL scattered between -1.0 and 1.0 AOTAROT3 TARGET ATTIT scattered between -0.8 and 0.6, slightly upward trend. AOSCPOS3 COMMANDED SPACECRAFT ATT around 5 in log scale AOSCPOS1 COMMANDED SPACECRAFT ATT around 5 in log scale AI1AX1X IRU-1 AXIS 1X ANALOG RATE flat @ 0.0 AI1AX1Y IRU-1 AXIS 1Y ANALOG RATE flat @ 0.0 AI1AX2X IRU-1 AXIS 2X ANALOG RATE flat @ 0.0 AI1AX2Y IRU-1 AXIS 2Y ANALOG RATE flat @ 0.0 AI2AX1X IRU-2 AXIS 1X ANALOG RATE flat @ -3.72 AI2AX1Y IRU-2 AXIS 1Y ANALOG RATE flat @ -3.72 AI2AX2X IRU-2 AXIS 2X ANALOG RATE flat @ -3.72 AI2AX2Y IRU-2 AXIS 2Y ANALOG RATE flat @ -3.72 FTS Temp and Gradient ---------------------- OHRTHR43 RT 134: PERISCOPE slight upward trend 293.0 to 293.1 OOBAGRD3 RT 505 TO RT 504: PERISCOPE GRADIENT slight downward trend 1.0 to 0.95 OHRTHR27 RT 20 : PERISCOPE tightly scattered around 297.10 OHRTHR42 RT 133: PERISCOPE tightly scattered around 294.10 OOBAGRD6 RT 507 TO RT 506: PERISCOPE GRADIENT flat @0.03 PCAD Reaction Wheel Rates -------------------------- AORWCMD1 REACTION WHEEL TORQUE COMMANDS 1 flat @ 0.0 AORWCMD2 REACTION WHEEL TORQUE COMMANDS 2 flat @ -0.01 AORWCMD3 REACTION WHEEL TORQUE COMMANDS 3 flat @ 0.0 AORWCMD4 REACTION WHEEL TORQUE COMMANDS 4 flat @ -0.01 AORWCMD5 REACTION WHEEL TORQUE COMMANDS 5 flat @ 0.0 AORWCMD6 REACTION WHEEL TORQUE COMMANDS 6 flat @-0.01 AORWCNT1 TACH PULSE COUNT 1 scattered between -60 and 60 AORWCNT2 TACH PULSE COUNT 2 scattered between -40 and 40 AORWCNT3 TACH PULSE COUNT 3 scattered between -60 and 60 AORWCNT4 TACH PULSE COUNT 4 scattered between -60 and 60 AORWCNT5 TACH PULSE COUNT 5 scattered between -60 and 60 AORWCNT6 TACH PULSE COUNT 6 scattered between -60 and 60 AORWMC1 COMMANDED REACTION WHEEL ANGULAR MOMENTUM scattered between 16 and 28 AORWMC4 COMMANDED REACTION WHEEL ANGULAR MOMENTUM scattered between -28 and -16 AORWMC5 COMMANDED REACTION WHEEL ANGULAR MOMENTUM scattered between 16 and 26 AORWMC6 COMMANDED REACTION WHEEL ANGULAR MOMENTUM scattered between 140 and 260 AORWSPD2 REACTION WHEEL RATES scattered between -240 and -120, slight downward trend AORWSPD3 REACTION WHEEL RATES scattered between 140 and 280, slight downward trend AORWSPD4 REACTION WHEEL RATES scattered between -260 and -140 AORWSPD5 REACTION WHEEL RATES scattered between 140 and 240 AORWSPD6 REACTION WHEEL RATES scattered between -260 and -140 Drift rate updated to Gyros ---------------------------- AOGBIAS1 GYRO DRIF REATE EMSIMATED (ROLL) flat @0.0 AOGBIAS2 GYRO DRIF REATE EMSIMATED (PITCH) flat @0.0 AOGBIAS3 GYRO DRIF REATE EMSIMATED (ROLL) flat @0.0 AOGYRCT1 ACCUM. GYRP PULSE COUNTS scattered between -1500 and 1000 AOGYRCT2 ACCUM. GYRP PULSE COUNTS scattered between -2000 and 200 AOGYRCT3 ACCUM. GYRP PULSE COUNTS scattered between -2000 and 300 AOGYRCT4 ACCUM. GYRP PULSE COUNTS scattered between -4000 and 400