  We summarize the results of a monitoring program which was executed following
the cryogen exhaustion of the Near Infrared Camera and Multi-Object
Spectrometer (NICMOS) onboard the Hubble Space Telescope. During the subsequent
warm-up, detector parameters such as detective quantum efficiency, dark
current, bias offsets, and saturation levels have been measured over the
temperature range 62K to about 100K. The measurements provide a unique database
of the characteristics of PACE-I HgCdTe detector arrays in the space
environment. A surprising result of the analysis is the fact that all three
NICMOS detectors showed an enhanced dark current in the temperature range
between 77K and 85K. However, a subsequent laboratory experiment designed to
replicate the on-orbit warm-up did not reproduce the anomaly, despite the fact
that it employed a flight-spare detector of the same pedigree. The mechanism
behind the on-orbit dark current anomaly is therefore believed to be unique to
the space environment. We discuss possible explanations for these unexpected
observational results, as well as their implications for future NICMOS
operations.
