A standard pattern syntax has been implemented for all HST instruments including NICMOS. During Cycles 7 and 7N, NICMOS patterns (dithering, chopping, mosaicing) were specified as an "Optional Parameter." Patterns are now implemented as a "Special Requirement" with different syntax. Previous Cycles 7 and 7N NICMOS Phase II pattern structures should not be followed when specifying patterns. There are a set of fifteen pre-designed patterns available for NICMOS observations. Users may define their own patterns as well, using the Pattern Parameters Form during Phase II development. The pre-defined patterns include four dithering patterns, four chopping patterns, five dither-chop patterns, and two mapping patterns. See the NICMOS Instrument Handbook for more details on chopping and dithering.
Note that parallels can be obtained at each pattern position, and that the pattern specification is only on the prime exposure.