This chapter describes the calibration accuracies that we aim to reach in
Cycle 17. Since the NCS-operated NICMOS represents a new instrument, a full suite of calibrations have been carried out since the installation of the NCS through Cycle 16 to characterize the instrument performance under the new operation conditions. The plans and goals for Cycle 17 are described in this chapter.
In Table 3.5
we summarize the calibration goals for Cycle 17, assuming a 12 month duration of cycle. Observers with science programs that require better calibrations should request and justify additional observing time for any supplemental calibrations necessary to achieve their goals.
The calibration proposals that have been executed during the SMOV
phase, as well as the ones included in Cycle 10 through 16, have been aimed at reproducing and possibly improving the level of calibration accuracy achieved during Cycle 7 and 7N. As discussed in Section 3.3.1
, the temperature of the NICMOS detectors, as measured by the temp-from-bias method, has shown a drift since Cycle 11. The temperature decreased by Δ
T~2K during the period 2002 to 2008. Using the calibration programs from Cycle 11 to 16, the NICMOS team has been able to quantify the effects from this temperature drift on the calibration of the detectors. As a result, new temperature dependent reference files are now available. To continue the investigation of this temperature dependence, as well as the overall detector performances, the monitoring programs continue in Cycle 17.
As shown in Table 3.5
, several programs aim at routinely monitoring the proper operation of NICMOS. Programs to routinely obtained darks, and determine the shading profile of the detectors (11946, 11947), monitor the stability of the flat-fielding in a few broad filters (11948), monitor the photometric stability of the instrument (11950), and to monitor (and correct if necessary) the focus settings of the instrument (11953) are planned. These programs, and the accuracies aimed by these programs are listed in Table 3.5
Cycle 17 includes three special calibration programs that are not part of
the standard monitoring. First, program 11949 will obtain flat-fields for a range of different filters in order to characterize the flat-field behavior at the detector temperature valid for Cycle 17. Program 11951 will extend the flux-dependent non-linearity calibration to fainter limits than previously measured, in order to enable non-linearity corrections to be applied to observations of faint, distant sources. This proposal uses the F160W filter, and is complementary to the Cycle 16 F110W proposal 11799. The purpose of the third special program 11954 is to provide improved spectrophotometric observations for faint IR standards to be used in cross-calibrating to WFC3/IR and JWST.
Two programs in Cycle 17 are intended to verify the behavior of the
NICMOS detectors after Servicing Mission 4. This includes observing standard stars to verify the photometric calibration (11952) as well as the calibration of the NICMOS camera 3 grisms (11955).
If your program requires unique calibrations beyond those that are
planned and listed in Table 3.5
, then you should apply directly for these special calibrations in your Phase I proposal.