1. Introduction This data set has been generated by the Jet Propulsion Laboratory's (JPL) Science Digital Data Preservation Task (SDDPT) by migrating valuable space science data from older, deteriorating magnetic tapes to CD-ROM. The primary goal of the SDDPT is to reduce the amount of data stored on magnetic tapes, preserve valuable science data, and make the data more accessible to the user. This data set (389-MGN-0090) resides on a CD-ROM volume and contains Magellan Synthetic Aperture Radar - Electronic Data Records (SAR-EDR) data. The input for the compact disc was magnetic tape that, in most cases, was at least 15-20 years old. Accompanying each tape on the CD-ROM disc, is a log file which documents the SDDPT processing history. Any problems encountered while recovering the data from tape are documented in the log file. The SDDPT did not reformat the original data. The SDDPT performed a bit copy of the data from tape to CD-ROM. This CD-ROM has been formatted so that a variety of computer systems (e.g., PC, Macintosh, and Sun) may access the data. Specifically, it is formatted according to the ISO-9660 level 1 Interchange Standard. For further information, refer to the ISO-9660 Standard Document: RF#ISO 9660-1988, April 15, 1988. This CD-ROM does not contain any Extended Attribute Records (XARs). Thus, VAX/VMS users on older platforms may have some problems accessing files on this volume. Three copies of each title will be generated: one intended for deep archive at the National Space Science Data Center (NSSDC) in Goddard, MD; one as a backup copy at the JPL Archives; and one to reside with the data user. In the cases where a planetary data set is likely to have many users, the "user" disc will be sent to the cognizant discipline node of the Planetary Data System (PDS). For further information about the SDDPT and the process by which valuable data sets were identified, see the SDDPT Inventory/Evaluation Phase Final Report (JPL Document D-10753), or contact: PDS Operator MS 525-389 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 818-354-4321 Internet: PDS_Operator@jpl.nasa.gov 2. Data Set Information Mission: Magellan (89-033B) =========================== Magellan was a unique mission, the first dedicated U.S. mission to study in detail, using Synthetic Aperture Radar (SAR), the surface of Venus. Because Magellan was intended to be a low cost mission, major components of the spacecraft were obtained from flight spares from other programs including Galileo, Viking, Voyager, Mariner, Skylab, Ulysses, and even the shuttle. Designed as a follow up to the mapping portion of the Pioneer Venus mission, Magellan's purpose was to: (1) obtain near-global radar images of Venus' surface with a resolution equivalent to optical imaging of 1 km per line pair; (2) obtain a near-global topographic map with 50 km spatial and 100m vertical resolution; (3) obtain near-global field data with 700 km resolution and 2-3 milligals (1 gal= 1cm/s**2) accuracy; and, (4) develop an understanding of the geological structure of the planet,including its density distribution and dynamics. The spacecraft consisted primarily of a large (3.7m) high gain antenna dish which served the dual purpose of communications and science instrument for the SAR. The spacecraft was about 6.4m long and, with the solar panels extended, about 9.2m across. Behind the dish was a rectangular section containing the radar sensor electronics, reaction wheels, and batteries. Behind this section lay a decahedral bus, which included the solar panel array, star scanner , a medium-gain antenna, the on-board computer and two tape recorders. Behind the bus lay the propulsion module. The two 5.8m solar panels were used for powering the spacecraft and charging the spacecraft's nickel cadmium batteries. These batteries provided the 28v of power needed during solar occultation to allow normal spacecraft operations. Pointing control was maintained through the use of three electrically powered, orthogonal reaction wheels. Large scale orbital corrections, both in transit to Venus as well as after orbital insertions, was accomplished through the use of monopropellant (hydrazine) thruster system. The thrusters were also used to permit desaturation of the momentum wheels. The coherent X- and S-band radio subsystem was used for communications as well as by the gravity field experiment. The initial phase of the mission (Cycle 1) began shortly after orbital insertion about Venus and lasted for eight months (15 Sept. 1990--15 May 1991). During this cycle, Magellan collected radar images of about 84% of the planet's surface. Cycle 2 lasted from the end of cycle 1 until 15 Jan. 1992, during which the spacecraft obtained images of the southern polar region and filled numerous gaps left in cycle 1 information. Cycle 3 began on 24 Jan. 1992 and lasted until 15 Sept. 1992, during which the remaining gaps from cycle 1 were filled in as well as providing data which, in combination with earlier data, could be used to produce stereo images of the surface. Cycle 4 lasted from 15 Sept. 1992 to the end of the mission (May 1993), during which data for the gravimetry experiment was gathered. By the end of the mission, over 99% of the planets surface had been mapped with a resolution ten times better than that obtained by the earlier Soviet Venera 15 and 16 missions. Instrument: Magellan, Synthetic Aperture Radar (89-033B-01) =========================================================== The purpose of this experiment was to obtain radar images, combined with altimetry and radiometry measurements, over the majority of Venus' surface. The radar sensor unit was contained in a single unit of overall dimensions 1.27 x 0.76 x 0.30 m. The radar system used the 3.7 m diameter high-gain antenna for synthetic aperture radar (SAR) observations and radiometry. A smaller, fan-beam antenna was used for the altimetry measurements. The antennae operated at a wavelength of 12.6 cm and shared common electronics. Between SAR bursts, pulses from the altimeter were transmitted toward the planet's surface. Radiometer data were also interleaved between the SAR burst by having the high-gain in a passive mode during which it measured the amount of radiated thermal microwave energy from the surface. Calibration of the radiometer was performed using an internal source. Thermal noise sources (e.g., the radar sensor, antenna, and cabling) were removed by making physical temperature measurements. The SAR operated at a frequency of 2.385 GHz with a pulse length of 0.0265 ms and a peak output of 325 W. In radar mode , the resolution of the instrument was about 150m. The resolution of the altimeter was 30m and the accuracy of the radiometer was 2K. Mapping took place during a 37.2 minute period centering around periapsis with data transmitted during the time around apoapsis. This resulted in imaging swaths of approximately 25 km by 17,000 km which could then be combined to create a map of Venus' surface. When the radar data was combined with altimeter data, a three-dimensional surface map could be created. The radiometer data were used to determine the electrical conductivity and composition of the surface. Each mapping cycle was designed to allow the surface to rotate by one Venus day (243 Earth days or about eight months) under the space craft, thereby imaging a full 360 degrees longitude in each cycle. Because both experiments required the dedicated use of the high-gain antenna, the first three cycles of operation were dedicated to the SAR with the final cycle dedicated to the gravimetry experiment. The original intent was to provide a map which covered in excess of 70% of the surface. By the end of the first mapping cycle, over 80% of the surface had been mapped. By the end of the second cycle, over 90% of the surface had been mapped at least once. By the completion of the third cycle, approximately 99% of the surface had been mapped by the SAR. Data Set: SAR EDRs on Tape (89-033B-01C) ======================================== This data set consists of engineering data records (EDRs) from the Magellan Synthetic Aperture Radar experiment. The data on these tapes has not been validated by the Planetary Data System and should not be distributed at this time. The file MGN_INFO.TXT located on each CD, correlates the tape ID with the corresponding CD Volume and descriptions of the tapes' contents. The tape descriptions were obtained from the exterior tape labels and available information contained in the MIPS On-line tape database. More detailed descriptions may be available from the analysts' catalogs. 2.1. Displaying Images To display images originally archived on 7-track tapes use the VICAR program LABEL-CREATE, with inputs of NL = xxx (number of lines) and NS = xxx (number of samples). To display images originally archived on 9-track tapes use the VICAR program DCONVIM with input = record length. 3. Disc Format Each CD-ROM disc has been formatted so that a variety of computer systems (e.g. IBM PC, Macintosh, Sun, VAX) may access the data. Specifically, the discs are formatted according to the ISO 9660 level 1 Interchange Standard, and file attributes are specified by Extended Attribute Records (XARs). For computer software that fully supports XARs, access to the CD-ROM volume will be straightforward; the disc will appear to the user to be identical to a file system of directories, subdirectories and data files. Some computer systems that do not support XARs will ignore them; others will append the XAR to the beginning of the file, in which case the user must read past the first 512 bytes of the file. For further information, refer to the ISO 9660 Standard Document: RF# ISO 9660-1998, 15 April 1988. 4. CD-ROM Contents The files on this CD-ROM are organized in one top-level directory with several subdirectories. The following table shows the structure and contents of these directories. In the table, directory names are enclosed in square brackets ([]), upper-case letters indicate an actual directory or filename and lower-case letters indicate the general form of the directory file names. Top-level directory | |-AAREADME.TXT - This text file containing general information. | |-[INDEX] - Directory containing a text file to simplify searching for | | specific data. | | | |-MGN_INFO.TXT- Text files describing basic information about the input | | data. In these files, tape IDs are correlated with their | corresponding CD Volume and descriptions. | |-[EDR] - The tapes are grouped into directories based on prefix | | sets. This is done in order to minimize delays reading | | the CD due to a large number of directories all appearing at | | the same level of the CD. | | | |-[EDRxxxx] - The data files are arranged into directories based on the | | | INPUT TAPE IDS. The user can locate particular data based on | | | the tape's description by using the MGN_INFO.TXT file on the | | | last CD of the series. | | | | | |-[DATA] - The subdirectory containing the data files. | | | | | | | |-EDRxxxx.yyy;1 - Each data file has a unique name. The file | | | name (EDRxxxx), represents the input tape id, and the file | | | extension (yyy) indicates the file number on the input tape. | | | For example, EDR147A.001 is the file originally located on | | | tape SAR-EDR.00147-1/2;6 file 1. | | | | | |-[LOGS] - The subdirectory containing a log file describing tape | | | | copying history. | | | | | | | |- COPY_LOG.yyy;1 - The tape copying history has been preserved for | | | each data file so that the user can determine if some | | | data has been skipped or lost due to problems reading the | | | input tape. There will be a COPY_LOG in the directory | | | covering each file on the input tape. If there is only one | | | log file in the directory, it covers all files on the tape, | | | otherwise the file extension (yyy) indicates the file number | | | on the input tape. If problems were encountered during the | | | copying process, the entire history will be preserved in | | | this log file. | | | | | | 5. Text Files All document files and copying logs contain a carriage return character (ASCII 13) and a line feed character (ASCII 10) at the end of each record. This allows the files to be read by most operating systems (eg., MacOS, DOS, Unix, and VMS). 6. Recommended CD-ROM Drives and Driver Software (Note that the following list is not inclusive.) VAX/VMS Drive: Digital Equipment Corporation (DEC) RRD40, RRD42, or RRD50. Driver: DEC VFS CD-ROM driver V4.7 or V5.2 and up. Note: The driver software may be obtained from Jason Hyon at JPL (Files are: JPLPDS::DISK$USER1:[JHYON]VFS*.A). It is necessary to use this driver to access the XARs on the CD-ROM. VAX/Ultrix Drive: DEC RRD40, RRD42, or RRD50. Driver: Supplied with Ultrix 3.1. Note: Use the "cdio" software package (in "~ftp/src/cdio.shar" from the "space.mit.edu" server). IBM PC Drive: Toshiba, Hitachi, Sony, or compatible. Driver: Microsoft MSCDEX version 2.2. Note: The newest version of MSCDEX (released in February 1990) is generally available. Apple Macintosh Drive: Apple CD SC (Sony) or Toshiba. Driver: Apple CD-ROM driver. Note: The Toshiba drive requires a separate driver, which may be obtained from Toshiba. Sun Micro Drive: SUN Microsystems (Sony). Driver: SUN CD-ROM Driver. Note: There is a patch to support structured files. >the following error, when >trying to do a "ls" on its directory contents: > 'hsfs: filetype(0X8) not supported'. > The files that cause the error message are structured files. They are organized in records (fix or variable length). Applications need to retrieve additional file attributes (fix or variable length, and maximum record length) from these files in order to access the contents correctly. Unfortunately, UNIX can only handle stream files (unstructured byte stream). There is currently no application interface to access the extended file attributes and data records in a record format file. (Note: Philips is coming up with an X/Open specification (XCDR) to provide an API to access the ISO 9660 CD-ROM format Disc. It is too early to tell whether it will be approved or not). The design decision when implementing the CD-ROM file system was to ignore all record format files stored in a CD-ROM. This is obviously a mistake. The best way is at least to allow users to access these files. The following is a patch for SunOS 4.1 Sun4c (SPARCSTATION) to correct the above problem: acuraintegra# adb -w vmunix >>>> hs_parsedir+9c?X _hs_parsedir+0x9c: ba0da0ee >>>> hs_parsedir+9c?Wba0da0e6 _hs_parsedir+0x9c: 0xba0da0ee = 0xba0da0e6 >>>> hs_parsedir+14c?X _hs_parsedir+0x14c: ba0da0ee >>>> hs_parsedir+14c?Wba0da0e6 _hs_parsedir+0x14c: 0xba0da0ee = 0xba0da0e6 >>>> $q Note: you can also patch hsfs_node.o with the above patch. The patch for SunOS 4.0.3c (SPARCSTATION) is similar: hs_parsedir+9c?X _hs_parsedir+0x9c: ba0de0ee hs_parsedir+9c?Wba0de0e6 _hs_parsedir+0x9c: 0xba0de0ee = 0xba0de0e6 hs_parsedir+14c?X _hs_parsedir+0x14c: ba0de0ee hs_parsedir+14c?Wba0de0e6 _hs_parsedir+0x14c: 0xba0de0ee = 0xba0de0e6 $q The following is the patch for the sun3: adb -w hsfs_node.o hs_parsedir+56?X _hs_parsedir+0x56: ee6612 hs_parsedir+56?We66612 _hs_parsedir+0x56: 0xee6612 = 0xe66612 hs_parsedir+e4?X _hs_parsedir+0xe4: ee6612 hs_parsedir+e4?We66612 _hs_parsedir+0xe4: 0xee6612 = 0xe66612 $q 6. Disclaimer Although considerable care has gone into making this volume set, errors are both possible and likely. Users of the data are advised to exercise the same caution as they would when dealing with any other unknown data set. Reports of errors or difficulties would be appreciated. Please contact one of the persons listed below. A. For questions about how to read CD-ROMs: Jason J. Hyon MS 171-264 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 818-354-0730 Electronic mail addresses: SPAN: JPLPDS::JHYON Internet: jhyon@pop.jpl.nasa.gov NASAmail: jhyon B. For questions concerning detailed information about the Magellan SAR-EDR Data contact: Sue LaVoie MS 168-514 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 818-354-5677 Electronic mail addresses: Internet: sue.lavoie@jpl.nasa.gov 7. Reference Documentation 1. JJPL-0006-0001, JPL SFDU Description and Usage. Issue 5, March 7,1988. 2. JPL D-1350, Module TIM-I, JPL Standard for Time Code Formats, Issue 1, July 1986 (or later edition) 3. RF #ISO 9660-1988, ISO 9660 Standard Document, April 15, 1988 4. SFOC-1-MHR-MGN-SCIEDR, Magellan Software Interface Specification, SAR and Altimeter EDR/TEDR Tapes, J. Springer and B. Wilson, JPL. November 28, 1988. 5. VRM-SE-001-002, Venus Radar Mapper (VRM) System and Subsystem Design Book, Section VRM-2-280. 6. SFOC-2-DPS-CDB-Ephemeris, NAIF Ephemeris File, JPL Navigation Ancillary Information Facility, July 15, 1988. 7. JPL D-4683, Standards for the Preparation and Interchange of Data Sets, T.Z. Martin et al., JPL PLanetary Data System, Version 1.1, October 3, 1988. 8. MGN 630-79, Rev. C, Magellan Planetary Constants and models, D.T. Lyons, Magellan Mission Design, JPL, April 11, 1988. 9. JPL D-10945, Automated Tape Conversion System (ATCS) Design Document, D.P. Bernath, J. Hyon, K. Rengarajan, Sept. 1, 1993. 10. Portable Archive Conversion System (PACS) Overview Document, K. Rengarajan, D.P. Bernath, J. Hyon, Sept 1,1993 11. Document 820-13; Rev. A, DSN System Requirements, Detailed Interface Design, TLM-3-17, DSN Telemetry Interface with SFOC-Magellan Effective Date: February 1, 1988, Release Date: February 1, 1988, Reissue Date: March 1,1989