DISR EAICD Date: 30 Jan. 2007 pg. 1 (of 119 pages) 1 HUYGENS Document : [HP-DISR- NASA PDS and ESA PSA No. EAICD-1] Interface Control Document Issue/Rev . No. : 30 Jan 2007 Date : Page European Space Agency Research and Science Support Department Planetary Missions Division Huygens-DISR NASA PDS and ESA PSA Interface Control Document [HP-DISR-EAICD- 1] ______________________________ Prepared by: Lisa McFarlane __________________________ Approved by: Martin Tomasko __________________________ Approved by: Lyle Huber Table of Contents 1.0 Introduction 1.1 Purpose and Scope 1.2 Contents 1.3 Intended Readership 1.4 Applicable Documents 1.5 Relationships to Other Interfaces 1.6 Acronyms and Abbreviations 1.7 Contact Names and Addresses 2.0 Overview of Process and Product Generation 2.1 Pre-Flight Data Products 2.2 Sub-System Tests 2.3 Instrument Calibrations 2.4 Other Files written during Calibration 2.5 In-Flight Data Products 2.6 Software 2.7 Documentation 2.8 Derived and other Data Products 3.0 Archive Format and Content 3.1 Format and Conventions 3.1.1 Deliveries and Archive Volume Format 3.1.2 Data Set ID Formation 3.1.3 Data Directory Naming Convention 3.1.4 Filenaming Convention 3.2 Standards Used in Data Product Generation 3.2.1 PDS Standards 3.2.2 Time Standards 3.2.3 Reference Systems 3.2.4 Other Applicable Standards 3.3 Data Validation 3.4 Content 3.4.1 Volume Set 3.4.2 Data Set 3.4.3 Directories 3.4.3.1 Root Directory 3.4.3.2 Calibration Directory 3.4.3.3 Catalog Directory 3.4.3.4 Index Directory 3.4.3.5 Browse Directory and Browse Files 3.4.3.6 Geometry Directory 3.4.3.7 Software Directory 3.4.3.8 Gazetter Directory 3.4.3.9 Label Directory 3.4.3.10 Document Directory 3.4.3.11 Extras Directory 3.4.3.12 Data Directory 4. Detailed Interface Specifications 4.1 Structure and Organization Overview 4.2 Data Product Design 4.3 SAMPLE LABELS 4.3.1 DARK LABEL 4.3.2 DESCENT LABEL 4.3.3 HKEEPING LABEL 4.3.4 IMAGE LABEL 4.3.5 IR LABEL 4.3.6 LAMP LABEL 4.3.7 SOLAR LABEL 4.3.8 STRIP LABEL 4.3.9 SUN LABEL 4.3.10 TIME LABEL 4.3.11 VIOLET LABEL 4.3.12 VISIBLE LABEL 4.3.13 VISIBLE_EX LABEL 4.3.14 IMAGE DISPLAY LABEL 4.4 Instrument Temperature (Thermistor Reading) Description 4.5 Solar Aureole Columns, Rows, Filters, and Polarization 4.6 Description of Possible values for Detector_ID keyword 4.7 Description of Possible values for Cycle Type 1. Introduction 1.1 Purpose and Scope The EAICD (Experimenter to Archive Interface Control Document) describes the DISR data and documentation submitted to the ESA PSA and the NASA PDS. 1.2 Contents This document describes the data flow of the DISR instrument on the Huygens Probe. It includes information on how data were processed, formatted, labeled and uniquely identified. The document discusses general naming schemes for data volumes, data sets, data and label files. Standards used to generate the product are explained. 1.3 Intended Readership The staff of archiving authority (Planetary Data System for NASA, Planetary Science Archive for ESA) design team and any potential user of the DISR data. 1.4 Applicable Documents 1.5 Relationships to Other Interfaces This document completely describes the DISR data and documentation as submitted to the NASA PDS and ESA PSA. In the event that there is any conflict between this document and any other Cassini or Huygens data archiving document, this document will take precedence. 1.6 Acronyms and Abbreviations ASCII = American Standard Code for Information Interchange DCT = Discrete Cosine Transformation DDB = Descent Data Broadcast DISR = Descent Imager/Spectral Radiometer DLIS = Downward-looking Infrared Spectrometer DLV = Downward-looking Violet Photometer DLVS = Downward-looking Visible Spectrometer DTWG = Descent Trajectory Working Group EAICD = Experimenter to Archive Interface Control Document ESA = European Space Agency ESOC = European Space Operation Center HRI = High_Resolution Imager IR = Infrared Wavelengths ITAR = International Traffic and Arms Regulations JPL = Jet Propulsion Laboratory MRI = Medium Resolution Imager NASA = National Aeronautics and Space Administration N/A = not applicable or not available PDF = Adobe Acrobat Format Documents PDS = Planetary Data System PNG = Portable Network Grahpics PSA = Planetary Science Archive SLI = Side-Looking Imager SSL = Surface Science Lamp T0 = time in the mission when pyros fire and the DDB is reset to 0 ULIS = Upward-looking Infrared Spectrometer ULV = Upward-looking Violet Photometer ULVS = Upward-looking Visible Spectrometer XDR = External Data Representation Standard 1.7 Contact Names and Addresses Name Affiliation Phone # email address Lisa McFarlane DISR +1 520 621-8686 lmcfar@lpl.arizona.edu Marty Tomasko DISR +1 520 621-6969 mtomasko@lpl.arizona.edu Lyn Doose DISR +1 520 621-2127 ldoose@lpl.arizona.edu Chuck See DISR +1 520 621-1097 csee@lpl.arizona.edu Lyle Huber PDS +1 505 646-1862 lhuber@nmsu.edu Diane Conner JPL +1 818 354-8586 Diane.Conner@jpl.nasa.gov Jean-Pierre Lebreton ESA +31 71 565-3600 Jean- Pierre.Lebreton@rssd.esa.int 2. Overview of Process and Product Generation The following chart describes the data flow from the Cassini spacecraft to the archive. FIG2-1.GIF DISR data is first processed on-board by the flight software. Various operations are performed (depending on the source of the data) to group the data into DISR data sets. This is explained in greater detail in the Experiment Users Manual (in the DOCUMENT folder called EXP_USERS_MANUAL_REV_C.PDF). For more information see also SP1177.PDF (in the DOCUMENTS folder) and Space Science Reviews 104: 469-551, 2002. A data set is a single exposure of a single data product (data products are as defined in this document). A data cycle is a grouping of a set of measurements associated with a science goal. Thus, a group of data sets comprises a data cycle, which constitutes an organized group of measurements in close proximity of time and altitude. These sets are formatted into telemetry packets and delivered to the probe for transmission on one or both of the Huygens Probe's telemetry streams. The Huygens Probe transmits the data to the Cassini Orbiter, which relays the data to the ground. The combined telemetry streams are delivered to ESOC, where they are distributed to the DISR team at the University of Arizona. At the University of Arizona the telemetry is processed to reconstruct DISR data sets, which are expressed as data numbers The data we will provide is at the 1b level, defined `as data that have been sorted by instrument data types and instrument modes. Data are in scientifically useful form, such as images or individual spectra. These data are still uncalibrated'. DISR will include the raw data from the data stream converted into ASCII files when appropriate. Thus, the archive will contain the decompressed data numbers and calibration reports. The calibration reports will contain all information necessary to obtain calibrated data. For detailed information see also SP1177.PDF (in the DOCUMENTS folder) and Space Science Reviews 104: 469- 551, 2002. Individuals involved in the generation of DISR data products are listed below. * Note that all the below are in the Kuiper Space Sciences Building (#92) at the University of Arizona, Tucson Arizona Name Room Responsibilities Marty Tomasko 233 PI Lyn Doose 239 Co-I Bashar Rizk 213 Co-I Chuck See 214 Engineering Operations Mike Bushroe 235C Telemetry Processing Lisa McFarlane 235D Analysis and Documentation Steffi Engel 212 Data Analysis Andrew Eibl 219 Data Analysis Mike Prout 237 Management 2.1 Pre-Flight Data Products No pre-flight data products or flight checkout data will be provided in accordance with this EAICD. All relevant information will be included in the calibration reports and/or white paper summaries. 2.2 Sub-System Tests All relevant Sub-System Test data appear in the calibration reports or white paper summaries. No additional Sub-system data will be included. 2.3 Instrument Calibrations The DISR PI will deliver calibration documents that clearly describe how to calibrate the raw data, approximately one per major instrument system. There is a calibration document for each major system listed below: 1) Imagers 2) Infrared Spectrometers 3) Solar Aureole 4) Sun Sensor 5) Surface Science Lamp 6) Violet Photometers 7) Visible Spectrometers and, 8) Calibration Standard 2.4 Other Files written during Calibration The calibration reports and white paper summaries will contain all information necessary to obtain calibrated data. 2.5 In-Flight Data Products Data will be organized as per the following categories and will be converted to ASCII, with the exception of the images. The images will be converted to 16 bit PNG format which should be identical to the 16 bit XDR images in use by the DISR team. Each image for the Image_Display product will be further converted to 8 bit PNG format, enlarged (x2), rotated and stretched for easier general viewing and access. Data Product Type Comments 1) Dark Text object Dark exposures for each data cycle used to predict dark currents for items 4,7,8,12 and 13. 2) Descent Text object Header information for an entire cycle that is found nowhere else. 3) Hkeeping Text object Engineering data describing the internal function of the instrument and provide temperatures which are necessary for calibration. 4) Image image object Contains images of three main different types and sizes (High Resolution HRI: 160 by 256, Medium Resolution MRI: 176 by 256, Sidelooking SLI: 128 by 256) 5) Ir Multiple Table Infrared spectra (either the uplooking ULIS, objects downlooking DLIS or both in one) 6) Lamp Text object Information about the internal calibration lamps and the surface science lamp (SSL). 7) Solar Table object Solar Aureole data (24 or 4 by 50) divided into 4 channels (blue and red polarized horizontally and vertically) 8) Strip Table object A vertical strip from the right and left side of the sidelooking Imager (2 by 254). 9) Sun Table object Sun Sensor data (three time pulses and an amplitude, to determine spin rate, solar azimuth and solar zenith angles). 10) Time Table object Clock values (2 by 20) comparing probe mission time to DISR internal time. 11) Violet Table object Violet Photometer (either uplooking ULV or downlooking DLV). A single number. 12) Visible Table object Visible Spectra (either uplooking ULVS: always 2 by 200; or downlooking DLVS: variable by 200) 13) Visible_Ext Table object Reference measurements of stray light used with the visible data (always 2 by 200) Elsewhere: Image_Display: Contains the same files as the Image directory, but converted to 8 bit PNG format, enlarged (x2) and stretched for easy viewing. 2.6 Software N/A (No special software is needed since the data is provided in ASCII form or in industry standard TIFF or PNG files and the calibration documents do not require software). All information that is necessary to obtain calibrated data are provided in the calibration reports or white paper summaries. No special software is required to use the calibration documents or white paper summaries. 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. 2.7 Documentation The calibration reports or white paper summaries will contain all information necessary to obtain calibrated data. Calibration reports for each major DISR system will be provided in Adobe Acrobat PDF format with incorporated tables and figures as follows: 1) Imagers; 2) Solar Aureole; 3) Sun Sensor; 4) Surface Science Lamp; 5) Calibration Standard. White paper summaries will be provided in Adobe Acrobat PDF format with incorporated tables and figures for the following: 1) Infrared; 2) Violet; 3) Violet flux; 4) Visible. The folder CALIBRATION_STANDARD contains the following three reports: 1) CALIBRATION_STANDARD_REVIEW, deals primarily with the monochrometer used in the absolute calibration of the DISR; 2) DARK_CURRENT, explains the method for determining dark current at a given time; 3) INTEGRATING_SPHERE_HOMOGENEITY, explores the uniformity of the light used for calibration. Other documents include: DOCINFO.TXT, describes all the documents in this section; EAICD.PDF, which is this document; EXP_USERS_MANUAL_REV_C.PDF, provides a detailed description of the DISR instrument (including, e.g., Science Overview, Instrument Overview, Operations, Instrument Commands, Software Architecture, Buffer Allocations, Bit Numbering, Telemetry Formats, etc. This document also provides an explanation of housekeeping information, e.g., ccd_flag, proc_flag, etc); HEADER_DESCRIPTION.PDF, provides a description of the information that is associated with each data file in the header of the data; IR_SW_AND_DATA_COLLECTION.DOC, provides a detailed explanation of the organization of the infrared data (including locations of shutter time, sample time, operation time, region, rotation, etc.). The structure of the document section is shown below, and later in this document. | - DOCUMENT | - BIBLIOGRAPHY | - DISR_CALIBRATION_DOCUMENTS | - CALIBRATION_STANDARD | - CALIBRATION_STANDARD_REVIEW | - DARK_CURRENT | - INTEGRATING_SPHERE_HOMOGENEITY | - IMAGERS | - INFRARED_SPECTROMETERS | - SLI_STRIPS | - SOLAR_AUREOLE | - SUN_SENSOR | - SURFACE_SCIENCE_LAMP | - VIOLET_PHOTOMETERS | -VIOLET_FLUX_DETERMINATION | -VIOLET_PHOTOMETER_CAL_DOC | - VISIBLE_SPECTROMETERS | - DISR SUPPORTING DOCUMENTS | - EAICD | - ESA_SP1177 | - DISR_INSTRUMENT | - SUNLIGHT_PENETRATION_MODEL | - EXPERIMENT_USERS_MANUAL | - HEADER_DESCRIPTION | - SPACE_SCIENCE_REVIEW | - DOCINFO.TXT 2.8 Derived and other Data Products Derived data products and schedules in support of the Descent Trajectory Working Group are presented in the DTWG archive. The average intensity over the field of view is provided for the violet, visible and infrared systems. Also, mosaic presentations of the DISR images are provided as posters. 3. Archive Format and Content 3.1 Format and Conventions 3.1.1 Deliveries and Archive Volume Format DISR will deliver the data to a PSA archive in electronic form within 18 months of the descent. Simultaneously the DISR team will deliver the data to the PDS in identical form. The proprietary period will extend for 18 months after the descent. During the proprietary period the data will not be disseminated without the approval of the DISR PI. We anticipate that the DISR data will fit on one CD, and the calibration reports on another 2 CDs. Thus the logical archive volume would fit on one DVD. DISR will deliver the data to the PDS archive in electronic form and the archiving authority will write the physical volumes. 3.1.2 Data Set ID Formation HP-SSA-DISR-2/3-EDR/RDR-V1.0 --- -- We will provide Level 2 data as defined in the table below: Level Type Data Processing Level Description 2 Edited Data Corrected for telemetry errors and split or decommutated into a data set for a given instrument. Sometimes called Experimental Data Record. Data are also tagged with time and location of acquisition. Corresponds to NASA Level 0 data. 3.1.3 Data Directory Naming Convention The subdirectories will be named according to the data product. Data products are listed in section 2.5 of this document. 3.1.4 Filenaming Convention 1) DARK_0286_012044_2903.TAB 2) DESCENT_0286_012044_2903.TXT 3) HKEEPING_0286_012044_2903.TXT 4A) IMAGE_0286_012044_2903.IMG 4B) IMAGE_0286_012044_2903.TAB 5) IR_0286_012044_2903.TAB 6) LAMP_0286_012044_2903.TXT 7) SOLAR_0286_012044_2903.TAB 8) STRIP_0286_012044_2903.TAB 9) SUN_0286_012044_2903.TAB 10) TIME_0286_012044_2903.TAB 11) VIOLET_0286_012044_2903.TAB 12) VISIBLE_0286_012044_2903.TAB 13) VISIBLE_EX_0286_012044_2903.TAB (27.3) In browse: IMG_DISPLY_0286_012044_2903.PNG ___. Where .TAB refers to a table, .TXT refers to text, .PNG refers to portable network graphics and .IMG is a non-compressed image file. 3.2 Standards Used in Data Product Generation 3.2.1 PDS Standards We intend to comply with the PDS standards to the extent as defined in this document. 3.2.2 Time Standards All start times are referenced to the probe on-board software mission time, T0. DISR mission time is synchronized to the Huygens probe mission timer T0. An exception to this is for the first couple of message data products (which are generated before synchronization and are relative to when DISR was turned on. These first few messages are time stamped. Mission time is measured to 10 thousandths of a second. 3.2.3 Reference Systems DISR derives azimuth information from the Sun Sensor instrument subsystem. The azimuth is measured relative to the sun in the instantaneous plane of the probe and is thus labeled an apparent solar azimuth angle. All angles are measured within a right-handed system aligned to the Huygens Probe system, which is defined in the EID, Part A. Quoting from Issue 1, Rev 0, Sect. 3.1, page 3: "The Probe axes form a right-handed orthogonal system Xp, Yp, Zp that is fixed relative to the Probe geometry. The Probe Reference Frame has the same orientation as the Orbiter Reference Frame (i.e., no tilt angle). The -Xp axis is pointing along the Probe centerline towards the nose of the Probe. The -Zp axis is pointing in the direction of the top SED strut. The origin of the Probe Reference Frame is on the lower side of the experiment platform (i.e., the side facing the Probe nose)." The DISR mechanical system within which the apparent solar azimuth angle above is measured, is aligned to the Huygens Probe system described above but the origin of the DISR system is displaced from that of the Huygens system. 3.2.4 Other Applicable Standards N/A 3.3 Data Validation The internal validation of the scientific content will be performed by the science team. All DISR packets include Cyclic Redundancy Check codes. Packets with invalid codes are discarded. We will ensure data values are in the expected range and are valid numbers. We agree to a peer review of the EAICD by a committee chaired by the Project Scientist and the PSA manager and consisting of the members of the HSWT, members of the DISR team and PSA and PDS personnel and to abide by their recommendations within the resources available. 3.4 Content 3.4.1 Volume Set The DISR data set will be part of the Huygens Volume Set. 3.4.2 Data Set All of the raw DISR data products (listed in section 2.5 of this document) will be combined to form one data set. 3.4.3 Directories ROOT | - BROWSE || - PNG | - CATALOG || - CATINFO.TXT || - DATASET.CAT || - DISRINST.CAT || - INST_HOST.CAT || - MISSION.CAT || - PERSON.CAT || - REF.CAT || - (SOFT.CAT) || - (TARGET.CAT) | - DATA || - DARK || - DERIVED_DATA_PRODUCTS ||| - DLIS ||| - DLV ||| - DLVS ||| - ULIS ||| - ULV ||| - ULVS || - DESCENT || - HIGHER_LEVEL_DATA ||| - POSTERS || - HKEEPING || - IMAGE ||| - IMG_FORMAT ||| - TABLE_FORMAT || - IR || - LAMP || - SOLAR || - STRIP || - SUN || - TIME || - VIOLET || - VISIBLE || - VISIBLE_EXT | - DOCUMENT || - BIBLIOGRAPHY || - DISR_CALIBRATION_DOCUMENTS ||| - CALIBRATION_STANDARD |||| - CALIBRATION_STANDARD_REVIEW |||| - DARK_CURRENT |||| - INTEGRATING_SPHERE_HOMOGENEITY ||| - IMAGERS ||| - INFRARED_SPECTROMETERS ||| - SLI_STRIPS ||| - SOLAR_AUREOLE ||| - SUN_SENSOR ||| - SURFACE_SCIENCE_LAMP ||| - VIOLET_PHOTOMETERS |||| -VIOLET_FLUX_DETERMINATION |||| -VIOLET_PHOTOMETER_CAL_DOC ||| - VISIBLE_SPECTROMETERS || - DISR SUPPORTING DOCUMENTS ||| - EAICD ||| - ESA_SP1177 |||| - DISR_INSTRUMENT |||| - SUNLIGHT_PENETRATION_MODEL ||| - EXPERIMENT_USERS_MANUAL ||| - HEADER_DESCRIPTION ||| - SPACE_SCIENCE_REVIEW || - DOCINFO.TXT | - EXTRAS || - MOSAICS || - MOVIES ||| - NARRATION_SCRIPTS ||| - TECH_MOVIE ||| - TITAN_DESCENT_MOVIE || - POSTERS || - PROBE_ATTITUDE ||| - DATA_AT_SOLAR_CROSSING ||| - HUYGENS_DESCENT_PARAMETERS || - PROCESSED IMAGES ||| - DISRSOFT_E_IMAGES ||| - DISRSOFT_G_IMAGES ||| - UNSMOOTHED_IMAGES || - RENDERINGS | - INDEX || - INDEXINFO.TXT || - INDEX.LBL || - INDEX.TAB | - AAREADME.TXT | - ERRATA.TXT | - VOLDESC.CAT 3.4.3.1 Root Directory AAREADME.TXT Volume Contents and format info in ASCII text format. ERRATA.TXT Cumulative listing of updates for all DISR volumes published thus far. VOLDESC.CAT Description of volume contents in a PDS format. 3.4.3.2 Calibration Directory Detailed calibration reports will be provided for all the DISR Science instruments, approximately one per major instrument system as follows: 1) Imagers; 2) Infrared; 3) Solar Aureole; 4) Sun Sensor; 5) Surface Science Lamp; 6) Violet; 7) Visible; 8) Calibration Standard 3.4.3.3 Catalog Directory CATINFO.TXT ASCII description of the contents of this directory. DATASET.CAT Data set catalog object. DISRINST.CAT Instrument catalog object. INST_HOST.CAT Space craft catalog object (to be provided by ESA) MISSION.CAT Mission catalog object (to be provided by the Cassini Project) PERSON.CAT Listing of personnel involved in data production. REF.CAT References (published literature) catalog object. SOFT.CAT A placeholder since no software is archived. (TARGET.CAT) (to be provided by the ESA or the Cassini Project) 3.4.3.4 Index Directory Index table of all label files this archive. 3.4.3.5 Browse Directory and Browse Files We provide Thumbnails of all images in slightly modified raw form, in PNG format. The files are same images as are in the Image directory, but converted to 8 bit PNG format, enlarged by a factor of two and stretched for easy viewing. The directory contains about 600 images. 3.4.3.6 Geometry Directory There is no Geometry Directory. Geometry data is included in the instrument calibration reports. 3.4.3.7 Software Directory N/A - There is no software in the DISR archive. See section 2.6 for further discussion. 3.4.3.8 Gazetter Directory N/A - There are no named features at this time. 3.4.3.9 Label Directory There is no Label Directory. Label files are located with their targets in the DATA and DOCUMENT directories. The Index table shows the location of all label files. 3.4.3.10 Document Directory Documents are provided in ASCII format. In most cases MS Word and Adobe PDF files are also available. The Calibration Reports are located in the Document directory. Other documents included in this directory are the DISR EAICD, Header Description, Users Manual, mission description documents and Bibliography. 3.4.3.11 Extras Directory The Extras Directory contains six subdirectories: 1) MOSAICS: Assemblages of the DISR images to create views of Titan's surface. Filenames with numbers represent the resolution in meters/pixel (i.e. 4.png is a mosaic with 4 m/pixel resolution). These depictions were made using FORTRAN by Erich Karkoschka. The other 3 files (HIGH..., MEDIUM..., & TITAN.PNG) are earlier, hand made mosaics. 2) MOVIES: Two types of movies inhabit this directory. The Titan Descent Movies are an extension of Erich's mosaic work. There are sequenced frames of mosaics at increasingly higher resolution (starting out with frames which orient the viewer from the Mees Solar Observaroty). A detailed description exists in the TITAN_DESCENT_MOVIE directory(TITAN_DESCENT_MOVIE.TXT). The Narration Scripts also describe these movies. The Tech Movie combines all of the DISR data into one graphic dynamic display (with sound). A detailed description exists in the TECH_MOVIE directory as DESCRIPTION_OF_TECH_MOVIE.TXT. 3) POSTERS: This directory contains a variety of views of Titans surface as seen by the Huygens probe during the descent. Various projections at distinct altitudes are presented. There is more detailed description in the file TITAN_POSTERS_DESCRIPTION 4) PROBE_ATTITUDE: Measurements of the sun's position, and movement of features on Titan's surface allowed us to make of estimates of the Huygens probe's attitude and position during the descent. This information is provided in tabular form in this directory. 5) PROCESSED_IMAGES: The individual images taken by the DISR are presented in this directory with 3 levels of processing. The most basic (Unsmoothed Images) just have camera defects removed. The next step (E-Images) includes compressor artifact removal and some smoothing, while the G-Images also have geometric distortions removed and are photometrically normalized. 6) RENDERINGS: Movies of stereographic renderings of Titan's surface created by USGS using the DISR images. 3.4.3.12 Data Directory The data directory will is organized according to the directory levels as listed in section 2.5 of this document. 4. Detailed Interface Specifications 4.1 Structure and Organization Overview See preceding section. 4.2 Data Product Design The data products will be in ASCII format, with the exception of the Image and Image_Display which will be in PNG format. Software will not be provided. There are often several types of data files within each data product type (such as with a different number of columns). The following lists each data product type, followed by a brief description, with dimensions shown in parentheses where appropriate. For more specific details see the disrinst.cat, the Experiment Users Manual or the Space Science Reviews paper listed in the Bibliography. 1) Dark: Dark exposures for each data cycle (2 by 256) are from 4 adjacent columns on the CCD covered by an opaque coating. The first dark column is DN values for columns 7 and 8 summed, and the second dark column is DN values for columns 9 and 10 summed. 2) Descent: Header information for an entire cycle that is found nowhere else. Lists cycle types, start times, etc. The altitude entry is from real-time data and is not necessarily correct. 3) Hkeeping: Engineering data to check the internal function of the instrument. This is the only place where some types of temperature data exist (e.g. Electronics Assembly (EA) or Optics temperature specifically). 4) Image: Contains images of three main different types and sizes (HRI: 160 by 256 pixels, MRI: 176 by 256, SLI: 128 by 256). In addition, some images can be half this size, that is the number of columns by 128 (or half of 256 rows). The top and bottom row are copies of adjacent rows as the total number of rows needed to be a multiple of 16 to work with the data compressor. These will be provided in PNG format. Data will be in DN and will include exposure time. 5) Ir: Infrared spectra, either the ULIS (2 by 150), DLIS (2 by 150) or IR combined (24 by 150). Data will be a table of DN and will include sufficient information to compute effective exposure times. 6) Lamp: Current and Voltage Information about the internal calibration lamps and the SSL. 7) Solar: Solar Aureole data (24 or 4 by 50) divided into 4 channels (blue and red horizontal and vertical). The 4 by 50 array is summed within each of the 4 channels. Data will be in DN and will include exposure time. 8) Strip: A vertical strip from the right and left side of the SLI Imager (2 by 254). Data will be in DN and will include exposure time. 9) Sun: Sun Sensor data (three time pulses and an amplitude). Pulse time is in seconds, amplitude is in DN. There are three slits in the Sun Sensor, and so as the image of the sun crosses the slit, one pulse per slit. This data is used to determine the azimuth and rotation rate of the probe, as well as the zenith angle of the sun. There are a variable number of measurements in a file. 10) Time: Time values (2 by 20) comparing probe mission time to DISR internal time. It is used to record the correlation between mission time from the probe that is sent to DISR in the probe broadcast messages and the master time which is kept by a hardware clock. Broadcast time is mission time from the DDB in 0.0001 second increments from the beginning of the mission. The master time corresponds to mission time and is also in 0.0001 second increments. Since the DISR is powered-on post T0, the broadcast time from the probe is always the larger value. 11) Violet: Violet Photometer (either ULV or DLV). A single number. data will be in DN. The violet photometers are instruments that are reading continuously, so there is no exposure time or integration time. 12) Visible: Visible Spectra (either ULVS: always 2 by 200; or DLVS: 2, 5, 10 or 20 by 200). For DLVS, the 20 by 200 is unsummed. Otherwise, 10, 5 and 2 adjacent columns are summed for arrays with 2, 5 and 10 DLVS columns. Data will be in DN and will include exposure time. 13) Visible_Ext: Reference measurements of scattered light used with the visible data. This measures instrument crosstalk. This uses otherwise unused columns between the ULVS/DLVS and DLVS/Imagers. The dimensions are always 2 by 200. Data will be in DN and will include exposure time. In the Browse directory: Image_Display contains the same files as the Image directory, but converted to 8 bit PNG format enlarged (x2) and stretched. FIG4-1.PNG Some of the labels include a temperature array, referred to as the keyword INSTRUMENT_TEMPERATURE. The following is a description of each of the positions within this array, referred to as INSTRUMENT_TEMPERATURE_POINT. 4.4 Instrument Temperature (Thermistor Reading) Description ccd_t1 CCD Chip - On edge of CCD chip (part of the chip). ref_t2 Near CCD chip - MPAE reference. irb_t3 IR Chip, beginning - Near the thermal strap to detector lug (biased +10C)* ire_t4 IR Chip, ending - Near the thermal strap to detector lug (biased +10C)* ccdlug_t5 CCD Lug - Where the thermal strap meets the CCD. strap_t6 Strap - At strap split (IR/CCD), near DISR Strap Heater (not powered). optics_t7 Optics - On fiber optic conduit, about 1/3 way from CCD to Optics. violet_t8 Violet - Towards the Front of the optical bench, near cover (cooler). sh_aux_t9 Aux Board - On SH Aux. Circuit Card, near heater (not powered). sh_box_t10 SH Box - On Sensor Head (SH) back cover (facing EA), warm part of SH. ea_box_t11 EA Box - In Electronics Ass'y (EA), on Motherboard (warm, lags housing) * The temperature (thermistor reading) in this keyword is too high by +10 K because of the sensor bias. Note that these are all thermistor readings and not calibrated temperatures. A value of 47 corresponds to Absolute Responsivity Calibration. FIG4-1.PNG 4.5 Solar Aureole Columns, Rows, Filters, and Polarization For DISR#3 the correspondence between columns and rows in a Solar Aureole data set and a Full data set are as follows: Rows 0:49 in a Solar Aureole data set correspond to rows 204:253 in a Full data set.