Data Set Overview :  This data set contains raw radio tracking data from the Galileo (GLL) Venus Range Fix Observations conducted during the GLL Venus flyby centered on 10 February 1990.  The data set includes one NASA Deep Space Network (DSN) Archival Tracking Data File (ATDF or TDF), media calibration data, and documentation.   Parameters : Each 288-byte ATDF data record contains 117 parameters, stored at rates of up to 10 records per second. The parameters include outputs from the DSN ranging system, estimates of Doppler offsets, estimates of received signal strength, and status information on components of the DSN system. The ATDF is described by a Software Interface Specification (SIS), included as TRK_2_25.TXT in the DOCUMENT directory of the archival volume.   Processing : Radiometric data are received by the DSN Network Operations and Control Center (NOCC) Navigation Subsystem (NAV) in the form of Intermediate Data Records (IDRs). These IDRs are processed to generate ATDFs. An ATDF contains all radiometric data received from the Deep Space Communications Complexes (DSSCs) tracking a single spacecraft for one or more passes or days.   Data : ATDFs contain precise radio range and Doppler measurements made between DSN ground stations and a spacecraft. During the Galileo Venus encounter, coded waveforms were transmitted from the Earth, relayed by the on-board Galileo telecommunications system, and received back on Earth. Cross correlation between the transmitted and received waveforms yielded a measurement of the round trip distance, which could then be related to the Earth-Venus distance during the flyby. Doppler shift from the same measurements could be interpreted as relative velocity along the propagation path.  An ATDF has a file name of the form ydddeeeX.TDF where y is the least significant digit of the year and ddd is the day-of-year for the first ATDF record. The eee gives day-of-year for the last data record in the ATDF, and X is set to 'A'.  Each ATDF is accompanied by a full PDS detached label with name ydddeeeX.LBL which completely describes the contents of the ATDF. The format and contents are also described in TRK_2_25.TXT in the DOCUMENT directory of each archival volume. Both the ATDF and its label are stored in the TDF directory of an archival volume.   Ancillary Data :  The ancillary files are stored in the CALIB directory. Each ancillary file is accompanied by a detached PDS label having the same file name except for the extension 'LBL'.  Low-Gain Antenna (LGA) Radiation Pattern ----------------------------------------- The radiation pattern of the low-gain antenna (LGA) is described in files LGA1_DL.TAB and LGA1_UL.TAB. These files provide the radiation patterns for downlink and uplink, respectively.  Media Calibration Files ----------------------- Media calibration files give model and measurement results which can be used to correct radiometric tracking data for effects of the Earth's ionosphere and troposphere. Ionosphere Calibration files have names of the form ydddeeeV.ION where y is the least significant digit in the year, ddd is the 3-digit day-of-year at the start of the file, eee is the 3-digit year at the end of the file, and V indicates version of the file ('A' is first, 'B' is second, etc.). Troposphere Calibration files have file names of the form ydddeeeV.TRO where meanings are the same. Each file is accompanied by a minimal detached PDS label with the name ydddeeeV.LBL. Media Calibration files and labels are ASCII files with records delimited by an carriage-return (ASCII13) line-feed (ASCII 10) pair. Files are described by TRK_2_23.TXT in the DOCUMENT directory.  Documentation ------------- Text and 59 TIFF files are included to provide users with background on the general objectives and procedures for Galileo radio Science observations. The material is from Radio Science Handbook, Volume 4, written several years after the Venus Range fix data were collected. The document which would have been applicable to the Venus Range Fix data acquisition was not available in electronic form when the data set was archived. A detached PDS label HANDBK4.LBL in the DOCUMENT directory of the archival volume points to the text and TIFF files. It also gives a complete citation for document which does describe the Venus Range fix observation. Also included in the DOCUMENT directory are Software Interface Specifications (SIS) for the ATDF and Media Calibration files and an (incomplete) abstract mentioning the Venus Range Fix results.  Coordinate System : Most data types are not dependent on definition of a coordinate system; for those that are, the user should consult the appropriate SIS for information.   Software : Software for parsing, reducing, and analyzing data such as these has been developed at the Jet Propulsion Laboratory and elsewhere. Because parsing must be done at the bit level, its implementation may be very sensitive to platform and operating system. No parsing has been written and tested on a variety of platforms, so none has been included with the archival data set. Users are referred to PDS labels and to Software Interface Specifications for detailed information on file formats.   Media/Format : The archival data set is written on CD-WO media using GEAR software and a Yamaha CRW4260tx writer. The CD-WO volume conforms to ISO 9660 standards.

Overview : There are no known limitations to use of these data, subject to signal-to-noise considerations which would be typical for systems of this type.   Review : Prior to creation of the final version of the archival data set, key elements of the archive were distributed for preliminary review. These included electronic versions of example PDS labels, CATALOG files, and Software Interface Specifications. These materials were distributed to PDS personnel and the PDS Radio Science advisor.   Data Coverage and Quality : The data covers the Venus encounter period around 10 February 1990. There are no known quality issues which would limit use of these data other than the normal signal-to-noise constraints.   Limitations : None.