January 7, 2002 SEM Instrument Performance Update ********** NOAA-12 ********** Total Energy Detector (TED) on NOAA-12 Beginning early in 1998 the logic that identified the 'characteristic energy channel number' and the sensor response within that channel began to operate in a sporadic fashion for the TED 30§ electron sensor. It appears that the telemetered energy channel number and the response within that channel were consistent with one another but that information was not from the energy channel that contained the maximum in the 30§ electron sensor response during each sweep. This problem has continued in a sporadic manner since that time. Care should be taken in using the identification of the 'characteristic energy' and the sensor response within that energy channel for the 30§ electron channel. Apart from this anomaly, the NOAA-12 TED continues to operate nominally. Medium Energy Proton and Electron (MEPED) Telescopes on NOAA-12 The solid state detector in the 90§ proton telescope became noisy beginning July 15, 2000 and produced invalid high count rates in the lowest energy (30-80 keV) channel. Since that date this detector has degraded still further. Radiation damage to the solid state detectors in both the 0§ and 90§ telescopes has become severe and has the effect of increasing the particle energy thresholds well above their nominal value. It is advised that after 1996 data from those instruments should be treated with caution and after 1999 not used at all. The performance of the MEPED electron telescopes continues to be nominal although after 1996 radiation damage to the solid state detectors in the electron telescopes may have increased the electron energy thresholds above their nominal value. Omni-directional Energetic Ion Detectors on NOAA-12 The omni-directional detectors continue to operate nominally. ********** NOAA-14 ********** Total Energy Detector (TED) on NOAA-14 NOAA-14 TED observations between 1212 UT on October 25, 1998 and 1626 UT on November 10, 1998 should be discarded because the channeltron high voltage was not set properly. The 300-20,000 eV electron channels in the TED on NOAA-14 had been plagued by a spurious count problem that began about July 1, 1995. This problem stabilized by early 1996 and never became severe enough to render the NOAA-14 TED non-operational. However, TED observations from NOAA-14 between July 1, 1995 and February 4, 2001 should be treated with caution. Beginning on January 12, 2001 an additional source of spurious counts, having the character of electo-magnetic interference (EMI), appeared in the NOAA-14 TED. After investigation, the detector pulse threshold discriminator levels were increased to their highest levels. Surprisingly, this step not only mitigated the new spurious count problem but also eliminated the long-standing and separate spurious count problem. Raising the pulse discriminator thresholds did not have any negative impact on the instrument's to natural auroral particle fluxes. Consequently, the TED data after February 4, 2001 may be utilized with confidence. There were a number of intervals between January 12 and February 4, 2001 when the EMI problem rendered data from the NOAA-14 TED unusable. These periods are: January 12 0700 UT to January 12 2030 UT January 15 0800 UT to January 16 1000 UT January 16 1430 UT to January 17 0730 UT January 17 1500 UT to January 18 1130 UT January 20 1530 UT to January 22 0315 UT January 22 2330 UT to January 23 0400 UT January 24 1300 UT to January 24 2030 UT January 26 0630 UT to January 26 1830 UT January 27 2000 UT to January 28 2400 UT January 29 1030 UT to January 30 1400 UT January 31 0900 UT to February 1 1800 UT February 2 0230 UT to February 4 2130 UT Medium Energy Proton and Electron (MEPED) Telescopes on NOAA-14 Beginning at instrument turn-on the 90§ proton telescope displayed no response and is regarded as failed. The solid state detectors in the 0§ proton telescope and both the 0§ and 90§ electron telescopes were noisy from instrument turn-on. This noise affected only the lowest particle energy channels (30-80 keV for the proton telescope, >30 keV for the electron telescope) and the data from the higher energy channels are usable up to 2000 (with the exception noted below.) At that point radiation degradation in the solid state detectors had become significant enough that the effective particle energy thresholds would have increased significantly above their nominal values. Beginning in late 1997 (on or about October 1, 1997) the multiplexer that governed the telemetry time-sharing of sensor responses in the >300 keV energy channels from the 0§ and 90§ electron telescopes began to malfunction in an intermittent fashion. The telemetered response from both of the highest energy electron energy channels often became 0 although there were lengthy periods when the multiplexer functioned properly. By early 1999 the multiplexer was malfunctioning more often than not and by mid-1999 seems to have failed entirely. Care should be taken in using the >300 keV electron data from the MEPED electron telescopes after October 1, 1997 - especially when the telemetered sensor responses are zero. Omni-directional Energetic Ion Detectors on NOAA-14 The omni-directional detectors continue to operate nominally. ********** NOAA-15 ********** Total Energy Detector (TED) on NOAA-15 The TED in the Space Environment Monitor-2 on NOAA-15 is operating nominally as of January 1, 2002. Medium Energy Proton and Electron (MEPED) Telescopes on NOAA-15 The MEPED in the Space Environment Monitor-2 on NOAA-15 is operating nominally as of January 1, 2002 although, after 3.5 years of operation the solid state detectors in the proton telescopes are showing signs of radiation degradation. This degradation leads to an increase in the nominal energy thresholds over their original values. Omni-directional Energetic Ion Detectors on NOAA-15 The omni-directional detectors in the Space Environment Monitor-2 on NOAA-15 are operating normally. ********** NOAA-16 ********** Total Energy Detector (TED) on NOAA-16 The TED in the Space Environment Monitor-2 on NOAA-16 is operating nominally as of January 1, 2002. Medium Energy Proton and Electron (MEPED) Telescopes on NOAA-16 The MEPED in the Space Environment Monitor-2 on NOAA-16 is operating nominally as of January 1, 2002 Omni-directional Energetic Ion Detectors on NOAA-16 The omni-directional detectors in the Space Environment Monitor-2 on NOAA-16 are operating normally. The definitive archived data from NOAA-16 for the short period between 86370 seconds and 86400 seconds UT (2359:30 to 2400:00 UT) on August 22, 2001 should be discarded.