January 7, 2002

SEM Instrument Performance Update
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NOAA-12
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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.

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NOAA-14
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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.

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NOAA-15
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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.

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NOAA-16
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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.