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6.1.2 LWR ITF

As is the case with the LWP camera, two ITFs were acquired for the LWR. The first ITF (1978 epoch) was acquired with no constraints placed on camera temperature (THDA). Hence, a viable raw space ITF could not be constructed from the 1978-epoch dataset (i.e., the individual UV-Flood images in a given ITF level did not align geometrically with one another). The second ITF (1983 epoch) was taken under more controlled spacecraft conditions; however, an ITF constructed purely using the 1983-epoch images (LWR83R94A or ITF A) did not correlate well with pre-1984 science images. As a result, a ``hybrid'' 1983-epoch ITF (LWR83R96A or ITF B) was generated where all levels (except the null) of the ITF were constructed from UV-Flood images taken during the 1983 ITF acquisition and the null level is composed of six null images taken during the 1978-1983 time period. LWR science images show a marked bimodality as far as ITF preference is concerned. For the most part, the majority of low-dispersion images taken prior to 1984 tend to correlate well with ITF B; while images taken after this date register well with the ITF A.

LWR ITF selection in NEWSIPS low-dispersion processing is made on an image-by-image basis. Each low-dispersion LWR image is processed twice through the image registration (CROSS-CORR) step; once using ITF A and another time utilizing ITF B. NEWSIPS then chooses the ITF which yields a higher median cross-correlation coefficient for subsequent processing of the image. High-dispersion LWR images do not go through such a selection process; only ITF A is used. This is because no clear improvement in image quality was seen when using ITF B over ITF A in high dispersion.


next up previous contents
Next: 6.1.3 SWP ITF Up: 6.1 Construction of the Previous: 6.1.1 LWP ITF
Karen Levay
12/4/1997