Hi Lyle,

I was able to read in the Cassini UVIS data files, and the documentation's
description of the different data products is adequate (even though it is
confusing in places).  

Steffl et al., Icarus in press #1, 2004 describe a complicated background
subtraction for UVIS spectra.  I doubt this data reduction is included in
the current calibration.  A description of the background sources (RTGs,
detector electronics, pinhole light-leak) and non-uniformities (i.e., the
"mesa" feature) is essential for the proper scientific analysis of these
data.  The composite dark image that Steffl states was made from IPM
observations should be provided to display the non-uniformities and aid in
their removal.  A cookbook type example of the background subtraction would
be useful.  

So provided that a composite dark image data file is added, the delivered
data archive meets my standard for acceptance.  Here are comments for
improving the data archive that we can discuss more tomorrow:

1) I like the java-idl procedure for reading in the data and cal images, and
the metadata structure.  Some extra flexibility with this would be useful to
accommodate different scientist's needs and programming styles.  For
example, a command line option to select the idl, java, or none PDS reader
option could be useful for setting up automated analysis codes.  The
DOCUMENT/DATA_OBJECT_READERS_README.TXT file refers to a file
"SOFTWARE/READERS/ObjectReader.jar" that is apparently named
"SOFTWARE/READERS/ReadPDSObject.jar" instead.  It would be nice if the
readme described the -DPDS_DATA option and its potential usefulness.  An
example java command should be included in the UVIS.DOC file, in addition to
the README files.  Also, an IDL example of how to call an external java
program from within an idl program would be useful to many users.  

2) The SOFTWARE/READERS/README file describes the $PDS_HOME location and the
data file name notation <channel><date>.  However, it doesn't indicate that
the filenames passed through the file specified with [a0] require the
<DYEAR_DOY> directory name such that the input file list has the notation: 
	<Dyyyy_ddd>/<channel><date>
This readme file uses option descriptions that are inconsistent with
DATA_OBJECT_READERS_README.TXT, namely -classpath instead of -cp, and
[<arg0>] instead of [a0].  The SOFTWARE/READERS/README.TXT is redundant with
DOCUMENT/DATA_OBJECT_READERS_README.TXT, and may be removed.  Perhaps a
combination of the information in DATA_OBJECT_READERS_README.TXT and the
SOFTWARE/READERS/README file into one file would be most convenient.

3) A plain text version of the comprehensive DOCUMENT/UVIS.DOC, or an Adobe
PDF version of this MSWord file would be more generally useful.  Appendix B
is missing.

4) The metadata entered into the structure is only a fraction of the
information provided in the *.LBL files.  Descriptive information like the
target_name, core_multiplier, and the planet center vectors should be read
in with the data.  Perhaps an additional java option or program could be
provided to read in all the label information when needed, since I imagine
the abbreviated metadata structure has some usefulness.  

5) In the UVIS.DOC section 2.3.3, just state that the software is validated
for Java 1.4 and IDL 5.6 and higher (or the IDL version you used).  In
section 2.3.4 the directory "CALIBRATION" is actually named "CALIB".

6) The CALIB/CALINFO.TXT file refers to a scalar CORE_MULTIPLIER value that
is required for calibration. Is this identical to the
CALIBRATION_SCALE_FACTOR# variable that is set by pds_reader.pro?  The
instructions for calibrating the data in section 2.2.5 should be clearer.
For example, specifically state: 
 calibrated_data = raw_data * calibration_data * calibration_scale_factor
Or I think the CALIB/CALINFO.TXT file paragraph is clearer:
"In order to calibrate a data object contained in the data directory,
multiply each sample of the data Qube by the matrix contained in the
calibration Qube, then multiply each element of the resulting Qube by the
CORE_MULTIPLIER value contained in the label file for the calibration Qube
object."
I suggest including this paragraph in the UVIS.DOC section 2.2.5: 
"In order to calibrate a data object contained in the data directory,
multiply each sample of the data Qube (e.g., d1[*,*,0]) by the matrix
contained in the calibration Qube (e.g., c1[*,*]), then multiply each
element of the resulting Qube by the calibration scale factor value (e.g.,
CALIBRATION_SCALE_FACTOR1).  Thus an example idl command to calibrate the
spectral data is: 
	data = d1[*,*,0] * c1[*,*] * CALIBRATION_SCALE_FACTOR1."

7) The units of the calibrated spectral data are Rayleighs according to
section 2.2.5, not Rayleighs/Angstrom.  I think this is correct since the
IPM observation I think I looked at had a peak Lyman-alpha signal of ~400 R.
Please add a keyword in the metadata structure (and a PDS Qube Object label)
that provides the spectral resolving power for the slit used to assist in
creating spectra in units of Rayleighs/Angstrom.

8) The WAVELENGTH_ARRAY was not assigned for the data I read in, though I
could create arrays using, e.g., the file: 
SOFTWARE/CALIB/VERSION_1/F_FLIGHT_WAVELENGTH.pro.  


Thanks,

Kurt Retherford