NAME: 
  getstrip
 PURPOSE: 
  Extract a 2-d rectangular strip image from a OSIRIS XD image.
 DESCRIPTION:
 CATEGORY:
  Spectroscopy
 CALLING SEQUENCE:
  getstrip,calib,root,frno,strip,hdr
 INPUTS:
  calib- Anonymous structure containing all pertinent calibration
           information.  This structure is usually loaded beforehand using
           the routine, "ldcalir"
  root - string containing the root of the file name (with leading path
         if desired).
  frno - Frame id (integer) of image to read.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  OFF_CHIP - Value to assign to output array for pixels that do not map
                to the original array (default=0.0)
 OUTPUTS:
  strip - 2-d rectangular strip image pulled from raw data (see getstrip).
  hdr   - FITS header for image.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:

 PROCEDURE:
 MODIFICATION HISTORY:
  95/03/24, Written by Marc W. Buie, Lowell Observatory
  95/09/15, MWB, added usage of calib structure and return of header.
  98/06/08, MWB, added OFF_CHIP keyword
  98/08/17, MWB, added fix to get actual Exposure time from image.