PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2005-06-21, Version 1.4; 20150402 RChen/EN work around catalog ingest. Delete this line next time." RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "CO-SSA-RADAR-5-BIDR-V1.0" OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = CO INSTRUMENT_ID = RADAR END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_INFORMATION ABSTRACT_DESC = "N/A" ARCHIVE_STATUS = "ARCHIVED - ACCUMULATING" CITATION_DESC = "N/A" DATA_OBJECT_TYPE = IMAGE DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_SET_NAME = " CASSINI ORBITER SSA RADAR 5 BIDR V1.0" DATA_SET_RELEASE_DATE = 2015-02-25 DATA_SET_TERSE_DESC = " The Cassini Basic Image Data Record product is a gridded map of Titan produced from synthetic aperture radar data. " DETAILED_CATALOG_FLAG = "N" PRODUCER_FULL_NAME = "Bryan W. Stiles" START_TIME = 2004-300T10:20:10.828 STOP_TIME = "NULL" CONFIDENCE_LEVEL_NOTE = " * Confidence Level Overview The BIDR data set contains synthetic aperture radar (SAR) images and coregistered backplanes of geometry and beam mask. (See DATA_SET_DESC below.) The data has been calibrated and empirical range and doppler corrections have been applied in order to minimize image artifacts due to errors in pointing and emphemeris knowledge. The images are elongated strips. The long (along track) dimension corresponds to the motion of the spacecraft during the observation. The short (cross track) dimension corresponds to the combined width of the 5 radar beams. * Review BIDR data will be validated internally by the Cassini Radar Team prior to each release of data to the PDS. The overall data set organization will also be peer reviewed once by the PDS prior to the release of the first volume. * Data Coverage and Quality Currently 20 SAR observations comprising roughly 20% of the surface of Titan are planned for the nominal Cassini mission. BIDR data will be obtained for each such observation. SAR observations of Titan occur at irregular intervals throughout the mission. Each observation is nominally 40 minutes long. Shorter-duration cases occur whenever RADAR shares a Titan observation with another Cassini instrument. The BIDR data set contains SAR image data only. Other Cassini RADAR data such as altimetry, scatterometry, and radiometry are available in the SBDR, LBDR, and ABDR data sets. The SAR image pixel values are normalized radar cross-section, a unitless quantity related to the slope, roughness, and composition of the observed surface. We currently estimate the accuracy of this quantity to be + or - 3 dB absolute and + or - 2 dB relative for the majority of image pixels. (See image artifacts discussion in the Limitations section.) The full resolution BIDRs are oversampled to insure no loss of information content. The intrinsic spatial resolution of the data varies from 300 m for the portion of the swath obtained at closest approach to 1 - 2 km at the extreme ends of the swath. Location error of the pixels is dominated by ephemeris and pointing knowledge errors and is expected to be less than 5 km throughout the mission. * Limitations Ephemeris error is expected to improve throughout the mission. Since there is no plan to recompute the ephemeris of previous observations as new measurements are obtained, however, earlier observations may have poorer location accuracy. The dominant calibration error term is error in our knowledge of the gain of the attenuators in the receiver. Engineering tests are currently planned to improve our knowledge of the attenuator gains. SAR images are prone to artifacts such as: 1) poor calibrations at the edge of the beams 2) extreme noisiness in regions with a small number of overlapping measurements (looks) 3) scalloping and antenna calibration misalignment due to errors in ephemeris and pointing knowledge 4) distorted imagery near the ends of the swath due to non-optimal pointing while turning to make altimeter measurements. Artifacts of type 2 and 4 are unavoidable. Types 1 and 3 can be minimized by empirically correcting range and doppler biases in the data. We have sought to minimize the occurrence of these artifacts in the BIDR images, but there are still noticeable seams between beams and poor calibration near the edges of the swath. The artifact minimization algorithm does not attempt to use the estimated range and doppler biases to correct ephemeris or pointing. For this reason location errors of a few kilometers are possible. The TA Titan Observation on October 25, 2004, was the first SAR observation. It has some special features. The first (earliest) third of the swath has noticeable scalloping in the along track dimension and is noisier than the rest of the image. This portion of the swath has non-optimal viewing geometry and a small number of looks due to pointing constraints for other Cassini instruments. A substantial portion of the last (latest) third of the swath is in low resolution SAR mode. This mode coarsens the cross track resolution of the image by a factor of 2. It was used on TA in order to accommodate conservative SNR expectations. In the same region of the image, an experiment was performed in which the data compression technique typically used by SAR was turned off. Due to data volume and data rate constraints this resulted in fewer looks and noisier data. " DATA_SET_DESC = " * Data Set Overview Full resolution basic image data records (BIDR) consist of SAR (synthetic aperture radar) normalized backscatter data (sigma0) at 13.78 GHz (Ku band) acquired in one pass of the Cassini spacecraft near Titan. The primary image data and the additional 'backplanes' of geometry and beam mask are provided at 256 pixels per degree on Titan's surface (approximately 175 m per pixel). The USGS will produce 128-pixel/degree versions of all the floating point BIDR images (backplanes and primary image). USGS will also produce 8-bit versions of primary (incidence angle corrected sigma0) image BIDRs at 256, 128, 32, 8, and 2 pixel per degree resolutions. The primary image data and the backplanes are provided on a rectangular grid which is an oblique cylindrical coordinate system whose equator is the nadir track of the spacecraft on the current pass and the zero of longitude is the point of closest approach. Two of the backplanes are longitude and latitude in standard Titan coordinates. A particular index pair specifying a location in the data grid provides data for the same point for each full resolution file and similarly for the averaged 128 pixel per degree files (primary image and backplanes). For more information about the format and content of the BIDR files, see the Cassini Radar Basic Image Data Record Software Interface Specification, JPL D-27889. A copy of the document is located on this volume as file BIDRSIS.PDF in the DOCUMENT directory. * Parameters The original image data and the 128 pixel per degree data are floating- point values of sigma0 in linear units (not dB). Lower resolution images are 1-byte scaled values in dB. The data are (1) Primary dataset (e.g., incidence angle corrected sigma0) in 32-bit floating-point format (linear scale values, not in dB). (2) Sigma0 without incidence angle correction in 32-bit floating point format (linear scale values, not in dB). (3) Incidence angle, floating point values in degrees. (4) Latitude, floating point values in degrees. (5) Longitude (positive-west), floating point values in degrees. (6) Beam mask, 8 bit values. (7) Number of looks, 32 bit integer values. * Processing The encoded raw active mode data in the Burst Ordered Data Product (LBDR) files is decoded and processed into SAR images by the Cassini RADAR Instrument Team. Each of the five beams is treated separately by typical SAR processing (azimuth and range compression). The image strip is then produced by selecting the best beam for each pixel. The selection is performed by choosing the beam with the most looks. In the event of a tie the highest SNR beam is chosen. The pixel values in the primary BIDR images will be normalized backscatter cross-section values corrected for incidence angle effects. The incidence angle correction algorithm is TBD and will be determined jointly by the Cassini RADAR Instrument and Science Teams after enough data is acquired to estimate the variation of sigma0 due to incidence angle over the surface of Titan. Until the final correction algorithm is determined, the primary BIDR image will be computed with a preliminary incidence angle correction. The exact form of this correction can be found in the PDS label for the primary BIDR image file. These files will be converted into 8-bit formats at various resolutions by members of the Astrogeology Team of the U. S. Geological Survey (USGS) in Flagstaff, Arizona. The processing used to produce the 8-bit formats is the same as that done for the Cassini Radar Digital Map products as described in the Cassini Radar Digital Map Software Interface Specification. * Data See Parameters. * Ancillary Data No ancillary data beyond the collection of BIDR files is needed to interpret the images. * Coordinate System The oblique cylindrical coordinate system is fully described in the data set map projection catalog DSMAP.CAT, which is located in the CATALOG directory on this volume. * Software No software is provided within this volume. Cassini BIDR files can be read using PDS image handling software or by using the Integrated Software for Imagers and Spectrometers (ISIS) developed by the Astrogeology Team of the U.S. Geological Survey. ISIS may be of use for scientists wishing to read, display, manipulate, and analyze BIDR data. ISIS including C and FORTRAN source code is in the public domain and versions configured to run under Solaris or Red Hat Linux may be obtained by qualified researchers from (http://astrogeology.wr.usgs.gov/Projects/ISIS). Documentation for the system is available from the same website. * Media/Format The data are provided on media as determined by PDS. The BIDR data files are ZIPPED as described in the PDS standard. Detached labels are provided for the ZIPPED files; the ZIPPED files also include their attached labels. Detailed formats are defined within the attached labels of the files and in the Cassini Radar Basic Image Data Record Software Interface Specification. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_MISSION MISSION_NAME = "CASSINI-HUYGENS" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ELACHIETAL2005" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ELACHIETAL2004" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "ELIASON1997" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GADDISETAL1997" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "TORSON&BECKER1997" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SEIDELMANNETAL2002" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BUGAYEVSKIY&SNYD1995" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "YANGETAL2000" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "GREELEY&BATSON1990" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = TITAN END_OBJECT = DATA_SET_TARGET END_OBJECT = DATA_SET END