The following table gives the legal TPG expose times (TPG_TIME) in seconds, needed to calculate legal exposure times in
ACCUM and
ACQ Modes. These values are approximated for simplicity, so that exposure times derived from them may be reduced by up to 1 msec.
Each camera has two apertures defined near the center of the FOV. Only exposures using the corresponding configuration (
NIC1,
NIC2,
NIC3) may use a given camera’s apertures. The
CAMERA-FOCUS optional parameter may be used to select a compromise focus position not optimized for either
NIC1 or
NIC2, but intended to work well with both.
One of the two FOV-center apertures (NIC1,
NIC2,
NIC3) is an optimal location near the center of the FOV considering detector efficiency and pixel quality, which will be updated by the STScI as the detectors change on orbit. One aperture in each camera (
NIC1–FIX,
NIC2–FIX,
NIC3–FIX) corresponds to a fixed pixel at or near the center of the detector array, which will not change on orbit.
The aperture NIC2–CORON is the location of the coronagraphic spot in the
NIC2 camera. It will be used by science exposures which have been preceded by a target acquisition exposure using the
NIC2–ACQ aperture or by a real-time acquisition image obtained using the
NIC2-CORON aperture. The acquisition aperture will be slightly offset from the coronagraphic aperture, but within the acquisition detector subarray.
The following Spectral Elements in Table 12.5, including filters, polarizers, and grisms, are available for the three NICMOS cameras. Only exposures using the corresponding configuration (
NIC1,
NIC2,
NIC3) may use a given camera’s spectral elements. The
CAMERA-FOCUS optional parameter may be used to select a compromise focus position not optimized for either
NIC1 or
NIC2, but designed to work well for both. See the
NICMOS Instrument Handbook for details.
