7.1.1.2 Mapping of ITF Space to Geometrically Rectified Space

Laboratory measured positions of the fiducial marks (reseaux) are used to map the distortion of the null-subtracted 20% level of the ITF in order to compensate for the geometric distortions in the ITF images. The faceplate of each camera is etched with a square-grid pattern of 169 reseau marks arranged in 13 rows and 13 columns. The reseaux appear on images as occulted areas approximately 2-3 pixels wide, spaced approximately 55 pixels apart for LWP and LWR and 56 pixels apart for SWP. Of the 169 reseau marks embedded in the fiber-optic coupling, approximately 129 fall within the camera target area. According to the design specifications of the scientific instrument (GSFC System Design Report for the IUE, 1976), the placement of the reseau marks in a true square grid is accurate to within ± 0.005 mm, which corresponds to ±  0.138 pixels for LWP/LWR and ± 0.14 pixels for SWP.

In order to refine the true locations of the reseau marks, laboratory measurements were made of the reseau grid on an SEC Vidicon camera which was manufactured about the same time as the IUE cameras; therefore, the same deposition mask was used for the reseaux. The work was performed by the Metrology Department at Rutherford Appleton Laboratory (Didcot, U.K.) in late 1990. The measurements were obtained in an X/Y reference frame in millimeters with a demonstrated repeatability of ± 0.003 millimeters. As a result, it was necessary to derive a scale factor to convert the millimeter measurements to ``true'' pixel locations for the reseaux. Note that the NEWSIPS true reseau positions may be very different from the positions quoted for IUESIPS. The IUESIPS reseau positions are not laboratory measurements, but rather a square grid construct based upon the definitions of a central reseau mark and mean reseau spacing. The NEWSIPS true reseau positions are listed in Tables 7.1-7.6.

The observed positions of the reseau marks are determined per ITF, and the departures of the observed positions from their true locations are used to characterize the geometric distortion of the camera system. A vector field defining the displacement of each pixel in the null-subtracted 20% level of the ITF from geometrically rectified space is derived using a bi-cubic spline interpolation between the reseau marks.

 

  

1 2 3 4 5 6 7

1 80.39 135.37 190.32 245.29 300.11 355.10 410.15

2 80.39 135.35 190.26 245.25 300.17 355.11 410.18

3 80.33 135.32 190.32 245.25 300.17 355.10 410.20

4 80.39 135.39 190.33 245.24 300.20 355.18 410.18

5 80.39 135.40 190.32 245.25 300.20 355.15 410.21

6 80.39 135.30 190.26 245.20 300.17 355.09 410.18

7 80.41 135.33 190.33 245.22 300.20 355.15 410.21

8 80.39 135.24 190.26 245.13 300.13 355.07 410.18

9 80.39 135.25 190.25 245.13 300.09 355.09 410.20

10 80.37 135.22 190.22 245.11 300.09 355.10 410.14

11 80.36 135.20 190.18 245.03 300.02 355.00 410.09

12 80.33 135.26 190.24 245.18 300.10 355.13 410.15

13 80.36 135.26 190.22 245.13 300.07 355.10 410.14

8 9 10 11 12 13

1 465.00 520.00 574.88 629.81 684.67 738.86

2 465.04 520.06 574.88 629.88 684.73 738.93

3 465.04 520.04 574.92 629.84 684.77 739.14

4 465.06 520.06 574.93 629.71 684.76 739.15

5 465.07 520.06 574.99 629.78 684.76 739.25

6 465.03 520.02 574.92 629.70 684.73 739.32

7 465.10 520.10 574.95 629.76 684.67 739.36

8 465.04 520.09 574.91 629.70 684.56 739.29

9 465.03 520.04 574.93 629.70 684.55 739.34

10 465.00 520.04 574.93 629.63 684.52 739.34

11 464.96 519.92 574.81 629.54 684.38 739.32

12 465.04 520.03 574.88 629.70 684.36 739.45

13 465.03 520.03 574.89 629.74 684.51 739.54

 

1 2 3 4 5 6 7

1 60.40 60.32 60.29 60.39 60.32 60.33 60.29

2 115.35 115.22 115.44 115.44 115.39 115.40 115.33

3 170.20 170.21 170.30 170.50 170.30 170.36 170.18

4 225.21 225.22 225.41 225.46 225.41 225.30 225.24

5 280.18 280.13 280.36 280.43 280.32 280.36 280.21

6 335.20 335.13 335.32 335.32 335.30 335.21 335.11

7 390.14 390.07 390.24 390.32 390.22 390.14 390.04

8 445.04 445.09 445.18 445.35 445.29 445.28 445.07

9 500.21 500.09 500.18 500.33 500.17 500.21 500.10

10 555.10 555.13 555.22 555.30 555.25 555.15 554.98

11 610.00 610.07 610.04 610.29 610.15 610.09 609.93

12 664.93 665.05 665.03 665.30 665.14 665.13 664.98

13 719.96 720.15 720.13 720.20 720.04 720.11 719.98

8 9 10 11 12 13

1 60.36 60.26 60.32 60.30 60.29 60.29

2 115.26 115.29 115.32 115.25 115.22 115.22

3 170.33 170.30 170.33 170.13 170.24 170.17

4 225.30 225.20 225.26 225.17 225.11 225.32

5 280.29 280.20 280.24 280.18 280.25 280.33

6 335.29 335.22 335.21 335.14 335.17 335.29

7 390.18 390.11 390.17 390.06 390.15 390.24

8 445.22 445.11 445.18 445.17 445.14 445.29

9 500.15 500.13 500.25 500.13 500.09 500.22

10 554.98 555.04 555.18 555.03 555.06 555.29

11 610.09 609.99 610.03 609.99 609.92 610.17

12 665.04 665.00 664.93 664.89 664.92 665.13

13 720.04 719.93 719.87 719.93 719.98 720.20

 

  

1 2 3 4 5 6 7

1 80.39 135.37 190.32 245.29 300.11 355.10 410.15

2 80.39 135.35 190.26 245.25 300.17 355.11 410.18

3 80.33 135.32 190.32 245.25 300.17 355.10 410.20

4 80.39 135.39 190.33 245.24 300.20 355.18 410.18

5 80.39 135.40 190.32 245.25 300.20 355.15 410.21

6 80.39 135.30 190.26 245.20 300.17 355.09 410.18

7 80.41 135.33 190.33 245.22 300.20 355.15 410.21

8 80.39 135.24 190.26 245.13 300.13 355.07 410.18

9 80.39 135.25 190.25 245.13 300.09 355.09 410.20

10 80.37 135.22 190.22 245.11 300.09 355.10 410.14

11 80.36 135.20 190.18 245.03 300.02 355.00 410.09

12 80.33 135.26 190.24 245.18 300.10 355.13 410.15

13 80.36 135.26 190.22 245.13 300.07 355.10 410.14

8 9 10 11 12 13

1 465.00 520.00 574.88 629.81 684.67 738.86

2 465.04 520.06 574.88 629.88 684.73 738.93

3 465.04 520.04 574.92 629.84 684.77 739.14

4 465.06 520.06 574.93 629.71 684.76 739.15

5 465.07 520.06 574.99 629.78 684.76 739.25

6 465.03 520.02 574.92 629.70 684.73 739.32

7 465.10 520.10 574.95 629.76 684.67 739.36

8 465.04 520.09 574.91 629.70 684.56 739.29

9 465.03 520.04 574.93 629.70 684.55 739.34

10 465.00 520.04 574.93 629.63 684.52 739.34

11 464.96 519.92 574.81 629.54 684.38 739.32

12 465.04 520.03 574.88 629.70 684.36 739.45

13 465.03 520.03 574.89 629.74 684.51 739.54

 

1 2 3 4 5 6 7

1 60.40 60.32 60.29 60.39 60.32 60.33 60.29

2 115.35 115.22 115.44 115.44 115.39 115.40 115.33

3 170.20 170.21 170.30 170.50 170.30 170.36 170.18

4 225.19 225.22 225.41 225.46 225.41 225.30 225.24

5 280.18 280.13 280.36 280.43 280.32 280.36 280.21

6 335.20 335.13 335.32 335.32 335.30 335.21 335.11

7 390.14 390.07 390.24 390.32 390.22 390.14 390.04

8 445.04 445.09 445.18 445.35 445.29 445.28 445.07

9 500.21 500.09 500.18 500.33 500.17 500.21 500.10

10 555.10 555.13 555.22 555.30 555.25 555.15 554.98

11 610.00 610.07 610.04 610.29 610.15 610.09 609.93

12 664.93 665.05 665.03 665.30 665.14 665.13 664.98

13 719.96 720.15 720.13 720.20 720.04 720.11 719.98

8 9 10 11 12 13

1 60.36 60.26 60.32 60.30 60.29 60.29

2 115.26 115.29 115.32 115.25 115.22 115.22

3 170.33 170.30 170.33 170.13 170.24 170.17

4 225.30 225.20 225.26 225.17 225.11 225.32

5 280.29 280.20 280.24 280.18 280.25 280.33

6 335.29 335.22 335.21 335.14 335.17 335.29

7 390.18 390.11 390.17 390.06 390.15 390.24

8 445.22 445.11 445.18 445.17 445.14 445.29

9 500.15 500.13 500.25 500.13 500.09 500.22

10 554.98 555.04 555.18 555.03 555.06 555.29

11 610.09 609.99 610.03 609.99 609.92 610.17

12 665.04 665.00 664.93 664.89 664.92 665.13

13 720.04 719.93 719.87 719.93 719.98 720.20

 

   

1 2 3 4 5 6 7

1 74.41 130.48 186.50 242.55 298.45 354.51 410.65

2 74.41 130.45 186.45 242.51 298.50 354.53 410.68

3 74.36 130.42 186.50 242.51 298.50 354.51 410.69

4 74.41 130.49 186.52 242.50 298.53 354.60 410.68

5 74.41 130.51 186.50 242.51 298.53 354.57 410.70

6 74.41 130.41 186.45 242.45 298.50 354.50 410.68

7 74.44 130.44 186.52 242.48 298.53 354.57 410.70

8 74.41 130.34 186.45 242.38 298.46 354.48 410.68

9 74.41 130.35 186.43 242.38 298.42 354.50 410.69

10 74.40 130.32 186.40 242.37 298.42 354.51 410.63

11 74.39 130.30 186.36 242.29 298.35 354.41 410.58

12 74.36 130.36 186.42 242.44 298.43 354.54 410.65

13 74.39 130.37 186.40 242.38 298.41 354.51 410.63

8 9 10 11 12 13

1 466.57 522.65 578.60 634.61 690.55 745.80

2 466.61 522.71 578.60 634.68 690.61 745.87

3 466.61 522.69 578.64 634.64 690.65 746.08

4 466.63 522.71 578.66 634.51 690.63 746.10

5 466.64 522.71 578.71 634.58 690.63 746.19

6 466.60 522.66 578.64 634.50 690.61 746.26

7 466.67 522.75 578.67 634.55 690.55 746.31

8 466.61 522.73 578.63 634.50 690.44 746.24

9 466.60 522.69 578.66 634.50 690.42 746.29

10 466.57 522.69 578.66 634.43 690.39 746.29

11 466.53 522.57 578.53 634.33 690.25 746.26

12 466.61 522.68 578.60 634.50 690.23 746.40

13 466.60 522.68 578.62 634.54 690.38 746.49

 

1 2 3 4 5 6 7

1 54.43 54.34 54.32 54.41 54.34 54.36 54.32

2 110.45 110.32 110.55 110.55 110.49 110.51 110.44

3 166.38 166.39 166.49 166.68 166.49 166.54 166.36

4 222.47 222.48 222.68 222.72 222.68 222.57 222.50

5 278.52 278.46 278.70 278.77 278.66 278.70 278.55

6 334.61 334.54 334.74 334.74 334.72 334.62 334.53

7 390.63 390.56 390.73 390.82 390.72 390.63 390.54

8 446.61 446.66 446.75 446.92 446.87 446.85 446.64

9 502.86 502.73 502.83 502.99 502.82 502.86 502.75

10 558.83 558.85 558.95 559.04 558.98 558.88 558.70

11 614.81 614.88 614.85 615.10 614.96 614.89 614.74

12 670.82 670.93 670.91 671.19 671.03 671.01 670.86

13 726.92 727.12 727.09 727.16 727.01 727.08 726.94

8 9 10 11 12 13

1 54.39 54.29 54.34 54.33 54.32 54.32

2 110.37 110.39 110.42 110.35 110.32 110.32

3 166.52 166.49 166.52 166.31 166.42 166.35

4 222.57 222.45 222.52 222.43 222.37 222.58

5 278.63 278.53 278.57 278.52 278.59 278.67

6 334.71 334.64 334.62 334.55 334.58 334.71

7 390.68 390.61 390.66 390.55 390.65 390.73

8 446.80 446.68 446.75 446.74 446.71 446.87

9 502.80 502.78 502.90 502.78 502.73 502.87

10 558.70 558.77 558.91 558.76 558.78 559.02

11 614.89 614.79 614.83 614.79 614.72 614.97

12 670.93 670.89 670.82 670.77 670.80 671.01

13 727.01 726.89 726.82 726.89 726.94 727.16