PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2016-10-10 INTERCHANGE_FORMAT = ASCII NOTE = "N/A" END_OBJECT = TEXT END EARTH-BASED RADAR OBSERVATIONS OF VENUS 1. Introduction This archive contains Earth-based, polarimetric radar image data for Venus collected from 1988 onwards, using the Arecibo Observatory 12.6-cm (2380 MHz) transmitter and receivers at either Arecibo or the Green Bank Telescope in West Virginia. One sense of circular polarization is transmitted, and both senses of the reflected echo are recorded in amplitude and phase. These data have a horizontal spatial resolution of 1-2 km in the highest-resolution mode, and about 8 km in a lower-resolution mode used to increase the signal-to-noise performance for some polarimetric analyses. The first data products archived are complex-valued images of the backscatter from Venus for individual coherent looks five minutes in duration. Up to about thirty such looks for the north and south portions of the planet's disk visible at each inferior conjunction are collected. The maps are in un-calibrated, delay-Doppler format, and thus require additional processing to normalize the echoes to the background noise and convert the spatial sampling to a latitude-longitude format. Once those steps are completed, users may sum the images as they choose to create multi-look (reduced speckle, higher SNR) dual-polarization maps of the surface or Stokes-vector values for polarimetric studies. Future PDS releases may include such calibrated and summed maps produced by the data providers. Please see VENUS_RADAR.PDF in the DOCUMENT directory for further details. It describes the data products, including information on how to read the data files. 2. File Formats Files with names ending in IMG are image files. Each image file in the archive is a simple binary array with pixels stored in order from left to right, top to bottom of the image. The radar backscatter images in this archive have pixels that are complex numbers. Each complex value consists of a 4-byte floating-point number representing the real part of the value, followed by a 4-byte floating-point number representing the imaginary part. Please note that the standard PDS-3 data product reader, NASAView, cannot open these IMG files. VENUS_RADAR.PDF in the DOCUMENT directory details the math needed to generate a browse image. Files with names ending in PDF are Adobe Portable Document Format files (www.adobe.com). Files with names ending in LBL, CAT, TXT, HTM, and TAB are ASCII text files with a carriage return (ASCII 13) and line feed (ASCII 10) at the end of each record. LBL files are PDS labels. Every data and documentation file in the archive is accompanied by a PDS label that describes its contents and format. 3. Archive Contents Files in this archive are organized into a series of subdirectories below the top-level directory. The archive organization and the contents of each directory are described below. Top-level Directory ------------------- AAREADME.TXT The file you are currently reading. VOLDESC.CAT This text file contains a description of the volume contents as a PDS catalog object. It is a required file on PDS archive volumes. ERRATA.TXT This text file contains comments and errata concerning the archive volume. CATALOG Directory ----------------- Files in the CATALOG directory are text files containing documentation formatted in PDS object description language. The files contain information about the observatories and instruments involved in acquiring the data, the data set, references, and personel involved in archiving the data. See the file CATINFO.TXT for details. DATA Directory -------------- The data files and associated PDS labels are stored in the DATA directory. INDEX Directory --------------- The INDEX directory contains a PDS index file for this archive. An index file is an ASCII table with each record (or line) in the table containing information about a single data product in the archive. See the file INDXINFO.TXT for additional details. DOCUMENT Directory ------------------ The DOCUMENT directory contains document files relating to this archive. See DOCINFO.TXT for a description of the files in the DOCUMENT directory. 4. Whom to Contact for Information For questions related to the data collection and calibration, contact: Bruce Campbell Smithsonian Institution MRC 315, Center for Earth and Planetary Studies PO Box 37012 Washington, DC 20013-7012 202-633-2472 E-mail: campbellb@si.edu For questions concerning this volume set, contact: PDS Geosciences Node Washington University 1 Brookings Drive, Campus Box 1169 St. Louis, MO 63130 314-935-9295 Website: http://pds-geosciences.wustl.edu/ E-mail: geosci@wunder.wustl.edu For general information related to the PDS, contact: Planetary Data System, PDS Operator M/S 202-101 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109-8099 818-354-4321 Website: http://pds.jpl.nasa.gov/ E-mail: pds_operator@jpl.nasa.gov 5. Cognizant Persons This archive volume designed and produced at the PDS Geosciences Node, Washington University, St. Louis, Missouri by Jennifer Ward.