Tables 5.2 and 5.3 give average detector dark noise
for an entire band for a one second reset interval in column 
.
The
detector noise given is that if some processing has been carried out on the
data, namely throwing away samples affected by glitches. For
comparison, the pre-launch values of detector noise were 0.6 
for
bands 1, 2, 3 & 5 and 0.9
for bands 4 and 6.
Detector dark noise and dark current
values for individual detectors are stored in calibration G files 21_1, 21_2,
21_4 and 21_8, corresponding to the 1, 2, 4 and 8 second
reset interval. Units are 
.
Note that 8
second resets were only used early in the mission.
Checks were made at the start of every revolution for the purpose of characterising the dark current and noise throughout the mission. It was found that they were stable for all bands except band 3. Here, the dark currents increased by up to a factor of three, while the dark noise hardly increased for most detectors. In most cases the increase in dark currents was gradual, but occasionally it was from a sudden jump, e.g. detector 36 (band 3 detector 12) on rev 150. Dark currents also decreased - after 250 revolution of high dark currents, those in detector 36 dropped to one-fifth of their high value.
Which detectors in a band are or are not good can change. For example, at the start of the mission band 3 detector 34 was poor. After PV, when its bias voltage was changed, detectors 30, 31 and 36 were the worst in that band. In general a bad detector has either a high dark current or/and a high noise.
The dark currents were higher at the start of a revolution for all bands, decaying with time so that after about four hours they had reached their nominal values. This was especially the case for bands 2, 4 and 6, with increases of between 15% and 100%. This effect was less important for bands 3 and 5, while for band 1 it was only observed in a few detectors.
The dark noise showed no variation throughout a revolution.
Normally all changes in dark current will be automatically corrected during the OLP processing, see section 8.3.4. Cases where the continuum is weak can cause problems for dark current subtraction in the OLP pipeline, especially when memory effects are included. When the amount of flux falling on the detector is small, there may be cases where the output of the detector from (incident flux plus dark current plus noise) is less than the detector from (dark current plus noise), the end result being negative fluxes in the AAR product. The limiting flux for this is of the order of a few Jy for band 2.