NICMOS Patterns

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 Chapter 11 of the NICMOS Instrument Handbook for more details on chopping and dithering.

The following Phase II example includes the "Pattern_Data" for a four position dither pattern and the exposure line containing the pattern "Special Requirement". Note that parallels can be obtained at each pattern position, and that the pattern specification is only on the prime exposure.

Pattern_Data:


  Pattern_Number: 1
  Primary_Pattern:
    Pattern_Type: NIC-SPIRAL-DITH
 Pattern_Purpose: DITHER
Number_Of_Points: 4
   Point_Spacing: 1.3
Coordinate_Frame: POS-TARG
  Pattern_Orient: 0
  Center_Pattern: NO



     Exposure_Number: 10
         Target_Name: NGC6681
              Config: NIC1
              Opmode: MULTIACCUM
            Aperture: NIC1-FIX
          Sp_Element: F170M
          Wavelength: 1.70
 Optional_Parameters: SAMP-SEQ=STEP8,NSAMP=9
Number_of_Iterations: 1
   Time_Per_Exposure: DEF
Special_Requirements:
                PAR 11,12 WITH 10
                PATTERN 1 10-12
            Comments: exp=31.963s


     Exposure_Number: 11
         Target_Name: ANY
              Config: NIC2
              Opmode: MULTIACCUM
            Aperture: NIC2
         Sp_Element: F160W
          Wavelength: 1.600
 Optional_Parameters: SAMP-SEQ=STEP1,NSAMP=7
Number_of_Iterations: 1
   Time_Per_Exposure: DEF
Special_Requirements:
            Comments: exp=4.987s


     Exposure_Number: 12
         Target_Name: ANY
              Config: NIC2
              Opmode: MULTIACCUM
            Aperture: NIC2
          Sp_Element: F171M
          Wavelength: 1.71
 Optional_Parameters: SAMP-SEQ=STEP8,NSAMP=8
Number_of_Iterations: 1
   Time_Per_Exposure: DEF
Special_Requirements:
            Comments: exp=23.969s