DATE-OBS = START_TIME
INSTRUME = INSTRUMENT_ID

EXPOSURE = EXPOSURE_DURATION <ms>
RA = RIGHT_ASCENSION <deg>
DEC = DECLINATION <deg>
TWIST = TWIST_ANGLE <deg>
TARGET = TARGET_NAME
DISTANCE = TARGET_CENTER_DISTANCE <km>

All files are 32-bit PC_REAL images.
All files are 1022 lines by 1024 samples.

From the PDS label: 
 o Remove LABEL_RECORDS
 o Change ^IMAGE pointer
 o Add FITS_HEADER
 o Change SAMPLE_TYPE
 o Add AXIS_ORDER_TYPE
 o Remove CHECKSUM

Problems:

TARGET_NAME is inconsistent - why are some "N/A"?

MISSING_CONSTANT is looking like invalid syntax and it doesn't seem to 
reflect what's in the images anyway.  Should we set everything not actually
in the image windows to some fixed value, like 0.0 or -1.0?

These are PC_REAL images.  They would have to be byte-swapped to make FITS 
images.

Also, we'll have to swap the axes in order to get the FITS images to display
correctly (column- vs. row-major).

There are checksums in the label that become instantly invalid as soon as 
we touch anything, so the existing PDS Labels need more than just pointer 
editing.


RECIPE
======
o Use "spltimg" to split data out from PDS .img file (pipe in and out)

o Use "swpinv"  to swap bytes and invert axes (pipe in and out)

o Use "fitspad -n" to pad data segment to integral FITS blocks.

o Concatenate data segment to header.