This program calculates two sets of polynomial coefficients that characterize the jitter in an image acquired by a rolling shutter instrument. One polynomial for the line direction and one for the sample direction. The ISIS camera model for the instrument can then use the coefficients to adjust for the time dependent jitter.

The coefficients are calculated by coregistering lines in the main cube with each line in the check line cube, where each check line was acquired durring the readout of the main cube using the same detector, but at a different time. The registration produces sample and line offsets which are fed into a least squares solution to determin the coeficients of an Nth degree polynomial in time. The coefficients are written to the cube label for use by the ISIS camera model.

The main cube (FROM) is expected to be a full frame image collected by a rolling shutter sensor. The cube must have a table named "Normalized Main Readout Line Times" containing records for each line in the cube where the first column contains the sensor line number used to collect the corresponding image line, and the second column contains the associated exposure time (normalized -1 to 1). A table that meet these requirements is attacted to the cube during ingestion to ISIS (i.e., eis2isis).

The checkline cube is expected to have individual lines (possibly repeated) from the same sensor as the main cube. The checklines must be read during the readout of the main image sequence. A table named "Normalized Main Readout Line Times" containing records for each check line where the first column is the sensor line number used to collect the corresponding check line and the second column contains the normalized time the line was exposed. The same minimum and maximum must be used to normalize these times as was used for the main image times.

      Type   Line    Exp# 
             Number       
                          
      --------------------
      Main   1-10    1-10 
      Check  75      11   
      Main   11-20   12-21
      Check  50      22   
      Main   21-30   23-32
      Check  25      33   
      Main   31-40   34-43
      Check  75      44   
      Main   41-50   45-54
      Check  50      55   
      Main   51-60   56-65
      Check  25      66   
      Main   61-70   67-76
      Check  75      77   
      Main   71-80   78-87
      Check  50      88   
      Main   81-90   89-98
      Check  25      99   
      Main   91-100  100-109
    

In this example the 9 check lines cause the last line of the array to be readout (9 * exposure duration) later than it would have without the check line readouts.

This program was designed around work for the Europa Clipper Europa Imaging System Narrow Angel Camera by Randy Kirk. Since the program relies on the check lines and their spatial and temporal relationship to the main lines, the program will not work with other instruments unless they provide similar data.