NAME:
    hstjit
 PURPOSE: (one line)
    Read and interpret HST jitter information.
 DESCRIPTION:
    See Tiny Tim User's Manual, Version 6.3, for details.
 CATEGORY:
    Miscellaneous
 CALLING SEQUENCE:
    hstjit, image, xsrc_in, ysrc_in, time, deltax, deltay,
    undistortedx, undistortedy, distortedx, distortedy,
    instr, path=in_path, DISTORT=distort

 INPUTS:
    IMAGE - image name to be fit, must be a string
    XSRC_IN  - x coordinate of object of interest
    YSRC_IN  - y coordinate of object of interest

 OPTIONAL INPUT PARAMETERS:
    PATH     - String, this is the name of the directory where the data are
                stored.  The actual data directory used is PATH+'/'+image.
                The default is '' (blank) and the file would be IMAGE
                which would permit putting a leading path on the root.

 KEYWORD PARAMETERS:
    DISTORT - The input x,y are taken to be in an undistorted reference
              plane and will will be converted to the instrumental (distorted)
              frame.

 OUTPUTS:
    time    - intervals of jitter from start of observation [in seconds]
    deltax  - delta x-axis jitter in pixels
    deltay  - delta y-axis jitter in pixels
    undistortedx  - x coordinate with jitter, undistorted reference frame
    undistortedy  - y coordinate with jitter, undistorted reference frame
    distortedx  - x coordinate with jitter, distorted reference frame
    distortedy  - y coordinate with jitter, distorted reference frame
    instr   - record of which instrument was used for this observation
    rawjitPixelsV2  - raw jitter in pixels, v2 axis
    rawjitPixelsV3  - raw jitter in pixels, v3 axis

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:
    Assumes jitter file is in the same directory as the image file.

 PROCEDURE:

 NOTES: The timestep in the jitter file is one value over 3 seconds
    Currently does not do distortion for ACS images

 MODIFICATION HISTORY:
    Written by S. D. Kern, STScI, September 25, 2007.
    2007/10/18, SDK, added support for camera specifics ACS, WFPC2
    2007/10/24, SDK, conversion of undistorted/distorted coordinates,
        output in pixels    
    2008/04/22, MWB, added support for compressed data files.  Fixed
        bug on reading wrong input quantity from jitter files.