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Hubble Space Telescope
ACS pointing patterns

ACS-HRC-DITHER-LINE
pointing patterns

This is a one-dimensional dither pattern, with the following allowable parameter ranges:

     Pattern_Number: 1 
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 2-9
      Point_Spacing: 0.01 - 10.0  (arcseconds)
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 0.0 - 360.0  (degrees)     
Angle_Between_Sides: 0.0 - 360.0  (degrees) 
     Center_Pattern: ?            (YES or NO)
The following versions of this Pattern_Type are projected onto the detector pixel space in the graphic above.
The default pattern is a 5x5 pixel shift designed to allow for the rejection of most HRC detector artifacts.
     Pattern_Number: 21
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 2
      Point_Spacing: 0.198
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 44.39
Angle_Between_Sides: N/A
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      0.142,  0.139


The following 2-point occulting finger dither pattern shifts over the HRC occulting finger, which is permanently fixed in the HRC field-of-view. Without this dither, there will be missing data behind the finger in any HRC frame. See this graphic from the VTT.
     Pattern_Number: 28
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 2
      Point_Spacing: 1.90
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 5.85
Angle_Between_Sides: N/A
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      1.890,  0.194


The following 2-point hot pixel dither pattern alows for the simultaneous rejection of both hot pixels cosmic rays -- it is a better alternative to CR-SPLIT.
     Pattern_Number: 20
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 2
      Point_Spacing: 0.079
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 44.39
Angle_Between_Sides: N/A
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      0.057,  0.055


The 2-point sub-pixel dither pattern.
     Pattern_Number: 22
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 2
      Point_Spacing: 0.084
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 32.14
Angle_Between_Sides: N/A
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      0.071,  0.044


The 3-point sub-pixel dither pattern...
     Pattern_Number: 23
       Pattern_Type: ACS-HRC-DITHER-LINE
    Pattern_Purpose: DITHER
   Number_Of_Points: 3
      Point_Spacing: 0.092
       Line_Spacing: N/A
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 44.35
Angle_Between_Sides: N/A
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      0.066,  0.065
                      0.132,  0.129


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