PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "C. See, 30 Jan 2007" RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2006-05-05 NOTE = "" END_OBJECT = TEXT END N.B.: The Peer Review of the data set is not fully completed. The review is ongoing, but no major issues are expected. A data set version 2.0 shall be released in the near future, as soon as the review process is complete. This dataset contains data obtained by the Descent Imager Spectral Radiometer(DISR) aboard the Huygens probe, which was released from the Cassini Spacecraft. The data was obtained on January 14 during the primary descent phase of the Cassini-Huygens mission. In addition to the data themselves, the datasets contain a wide variety of supporting files and tools for the Archive user. The organization below the root level is as follows: 1) aareadme.txt (describes an overview of the structure of the dataset.), 2) errata.txt (if present, is a cumulative update of all DISR volumes published thus far), 3) The voldesc.cat is a description of volume contents in PDS format. 4) catalog folder (describes some general information about the mission, 5) document folder (a collection of critical documents relating to the data and, specifically, data reduction), 6) index folder (provides a ready mechanism for data retrieval), 5) data (the actual data from the mission), 7) browse folder (provides a thumbnail of the images). The catalog folder has 7 major sections: 1) catinfo.txt (is an ascii description of the contents of this directory), 2) dataset.cat is gives detailed information about the data, 3) disrinst.cat gives specific information about the DISR instrument, 4) instrument_host.cat gives specific information about the Huygens probe, 5) mission.cat gives specific information about the overall mission itself, 6) person.cat is a listing of the personnel involved in data production, 7) ref.cat is a listing of references in the published literature relating to the DISR instrument, 8) soft.cat relates to software, which is not appropriate for DISR, 9) target.cat has to do with the target of the object of study. There are 7 main components to the document section: 1) bibliography, is a compilation of relevant references, 2) Calibration Documents are critical and will be expounded upon momentarily. 3) docinfo.txt describes the documents within this folder, 4) document_label_file.lbl sepcifies each documentin this directory explicitly, 5) eaicd.doc, provides a description of the data structure in document form and describes the interface between DISR and the PSA/PDS. 6) exp_users_manual_rev_c.pdf despcribes detailed information about the DISR instrument, 7) Header description.doc,provides a description of the header that is associated with each data file. Regarding the Calibration Documents, data from the DISR can be subdivided into 8 major logical types of data: 1) Imagers, 2) Infrared, 3) Solar Aureole, 4) Sun Sensor, 5) Surface Science Lamp, 6) Violet, 7) Violet Flux and 8) Visible. Thus, there is a Calibration report for each of these types of data. In addition to these 8 documents, there is a final category of calibration documents called the calibration standard. This last category is further subdivided into the cal standard review, integrating sphere homogeneity and dark current. The DISR instrument calibration reports contain complete descriptions of each instrument detector system, the calibration data, methods, and algorithms for converting the instrument data numbers into physical units and intensities into data numbers. Reduced mean intensities over the field of view (FOV) are provided for the spectrometers. However for the broad band instruments (imagers, SA camera) the mean intensity over the FOV is not a useful number since the spectral variation is important, and the bandpass changes significantly during the descent. It is felt that the best scientific approach is to create models which reproduce data numbers rather than mean intensities. Although some lines of code exist as examples in the calibration reports, no generic calibration software is available. Interpretation of the DISR data is model dependent and selection of the model parameters (i.e. atmospheric composition, intensity spectrum, surface reflectance, variation over the field of view) is key in deciphering the data. The scientist is encouraged to develop their own software to explore the physical interpretations of the DISR data. There are 3 main parts to the index category: 1) Indexinfo.txt, 2) index.lbl, 3) index.tab Regarding the data folder, the data is organized into 13 different main types, identified as follows (in alphabetical order): Dark, Descent, Hkeeping, Image, Ir, Lamp, Solar, Strip, Sun, Time, Violet, Visible and Visible_ext. Several of these data divisions have further subtypes of data within. The following is a brief description of each of the data subtypes. Dark: provides a measure of the dark current from 4 adjacent columns of the CCD. Descent: Lists hearder information (i.e., cycle types, start times, etc) that are found nowhere else. HKeeping: Engineering data (i.e., Electronics Assembly temperature, Optics temperature, etc. found nowhere else. Image: Contains images of 3 main sizes and resolutions (HRI, MRI, SLI), or half as "tall" of each of these 3 types. Ir: Infrared data, either the uplooking (ULIS), downlooking (DLIS) or a combination (IR combined). Lamp: Current and Voltage information about the internal calibration lamps and the Surface Science Lamp (SSL). Solar: 4 channels of the Solar Aureole (24 by 50) or (4 by 50; summed within each); blue, red, horizontal and vertical. Strip: 2 by 254, a vertical strip from both the right and left side of the SLI imager. Sun: The times of the sun crossing the 3 slits, and the amplitude (measure of brightness) from the Sun Sensor. Time: Compares probe mission time to DISR internal time. Time values are in 10 thousands of a second. Violet: A single number from the violet photometer looking up (ULV) or looking down (DLV). Visible: Visible spectra. If up looking (ULVS) then always 2 by 200. Down is 2, 5, 10 or 20 (unsummed) by 200. Visible_ext: Reference measurements of scattered light for instrument crosstalk, always 2 by 200. Finally, there is a browse directory, within which is the Image_display directory. The Image_display directory contains files which are Thumbnails of all images in slightly modified raw form in PNG format. For more information about the data please contact the PI team: Dr. Elisabeth (Lisa) McFarlane DISR/UA lmcfar@lpl.arizona.edu Charles (Chuck) See DISR/UA csee@lpl.arizona.edu Dr. Martin (Marty) Tomasko DISR/UA mtomasko@lpl.arizona.edu For further information about the dataset and about the PDS please contact the Atmospheres Node of the Planetary Data System: Lyle Huber PDS/UNM lhuber@nmsu.edu For more information about the dataset and about the ESA Planetary Data Archive please contact the European Space Agency at the European Research and Technology Center (ESTEC), Noordwijk, The Netherlands: Olivier Witasse ESTEC/ESA owitasse@rssd.esa.int