IUE Dataset Issues This is not comprehensive but is based on things that I encountered while trying to do some science with the IUE Dataset. I was working with the high-dispersion spectra so I have certainly not uncovered possible problems in the low-dispersion products, nor is it likely that I have found all the problems in the high-dispersion data. I note in passing that the ULDA (Uniform Low Dispersion Archive for comets) that is included in the dataset as a document and referred to below, was originally prepared by Michel Festou while the IUE was still taking data and he hopes, in the next year or two, to bring the ULDA up through the end of IUE's life. Mike A'Hearn October 2004 INDEX TABLES Neither index table gives comet names, only new IAU designation. The scientifically useful index should include, for each spectrum, much of the information that is in the ULDA (but also including the high-dispersion spectra, not just the low as in the ULDA), specifically comet name, old IAU provisional designation, new IAU designation, exposure ID including camera ID (e.g. LWR06683), dispersion (High or Low), wavelength range (long or short = first letter of exposure ID, but a separate column to simplify sorting), aperture (large or small), UTC mid-exposure time (including date), exposure time, geometric circumstances (heliocentric and geocentric distances and radial velocities, time from perihelion in days, solar elongation, and phase - all at mid-exposure time), offset from nuclues of slit center (distance & direction), slit orientation (rel to solar direction) A sensible approach might be to actually start with the digitized ULDA, strip out a few columns, calculate the information needed (geometry) for the more recent spectra and the high-dispersion spectra, and then just add the missing lines to that table to make the scientifically useful index. Note that the scientifically useful index would do fine as a fixed width ascii table without delimiters of any sort except blanks, thereby making it easier to read. DIRECTORY STRUCTURE The directory structure, that comes down to one directory per comet, with many directories having only a single spectrum, is rather awkward to work with. Putting all the spectra in one directory would probably also be awkward, but in different ways, so we need to discuss this a little more carefully and consider whether there is a better organization. (I.e. I'm unhappy but I can't figure out how to make it better so I am going to whine.) GEOMETRY It looks as though all the geometric information about the comet is in the ephemeris directory so it can be gotten for the index by interpolation in the ephemerides. The geometry about IUE is probably somewhere in there also, but I haven't searched for it all (it is in the ULDA for the comets that are included there). The slit orientation and aperture type are both given as keywords in the labels for the individual spectra. Ideally the cometary geometrical parameters (distances and velocities and so on) would also be in the labels of the individual spectra, but this would be a fair bit of work. KEYWORDS 1. PDSREAD complains about lack of PDS Version number in both lsi and lmx files, possibly in the labels for the tables at the end of each structure. It may also be a problem with READPDS.PRO rather than with the data since the version ID is given at the beginnning of the label for each compound object (that becomes a structure in IDL such that individual tables within the structure may not have the version ID). 2. Image keywords LINE_DISPLAY_DIRECTION and SAMPLE_DISPLAY_DIRECTION keywords are missing from lsi files. Default assumptions of DOWN and RIGHT seem to work fine, i.e. they give me a representation similar to what we used to get at the IUE control center. 3. Table keywords lmx high-dispersion files include an ascii table for which the columns do not have any column description fields in the label. It turns out that the interpretation of the columns is less than obvious from the names, so column descriptions are definitely needed. Nor are the columns described in the dataset.cat file or in the documents that I looked at in the document directory. I did eventually find the relevant information but the English (apparently copied from some IUE document) leaves ambiguities, which I think I have resolved. WEB PAGES 1. The front page on "Small Bodies Comet Archives" (sbnhtml/comet_index.html) claims that the IUE dataset has 56 comets, whereas the linked page (sbnhtml/comets/comparative.html) claims only 49. I count 49 comets in the subsequent directories. 2. The latter page claims that the IUE spectra are still in lien resolution, even though they were reviewed in 2002, but there is no link to a list of liens anywhere (the liens are available from the corresponding review page). It looks to me as though the liens from the review page have been corrected already. According to Tyler's printout of the datasets at CN, CN thinks these data have been delivered and archived. Thus, I presume, it is our web pages that are badly out of date (of course, I have identified new liens above!) c. The link to the data is still to the jukebox, whereas it should be to the offloaded spectra on some hard drive. ×]yßÝ=ë