Data Set Overview : The Magellan (MGN) Bistatic Radar (BSR) Raw Data Archive (RDA) is a time-ordered collection of raw and partially processed data from bistatic radar experiments conducted using the Magellan spacecraft while it orbited Venus.  The spacecraft radio system was used as the signal source. The spacecraft high-gain antenna (HGA) beamed those signals toward the surface of Venus where they were scattered and then received at stations of the NASA Deep Space Network (DSN) on Earth. Changes in the amplitude, frequency, and polarization of the received signal can be related to the electrical and physical properties of the scattering surface. Bistatic experiments have been described by [SIMPSON1993].  Two types of experiments were conducted using Magellan. In 'spotlight' experiments a point on the surface was selected and, as the spacecraft moved over that point, the HGA was aimed toward it. Experiments conducted on 6 October 1993 over Gula Mons and on 31 May 1994 over Maxwell Montes used the spotlight configuration. In both cases, orbits and targets were chosen so that the backscatter geometry was included in the observation period. The goal was to seek 'enhanced backscatter' [HAPKE&BLEWETT1991] from the target at exactly the time when the Earth, spacecraft, and target were aligned. Predictions were that such a detection would be marginal, at best, given the experiment parameters; but both spot targets were in regions known to have higher reflectivity than the average Venus surface.  In the second type of experiment, the HGA was aimed toward the point on Venus' surface where specular (mirror-like) reflection would be expected. As the spacecraft moved in its orbit, the specular point moved along the ground. Dispersion of the echo signal by reflection from multiple points on the surface, each with its own Doppler shift, is diagnostic of surface roughness. Total power is proportional to the Fresnel reflection coefficient for the surface material. In these experiments, the total echo power is much stronger than in spotlight experiments. S-band detections were predicted for quasi-specular experiments conducted on 9 November 1993 and on 5 June 1994.  Transmitted polarization along the boresight of the spacecraft antenna was linear at the S-band wavelength (13 cm, or 2298 MHz) and circular at the X-band wavelength (3.5 cm, or 8415 MHz). Signals could be received coherently in both right- and left- circular polarizations at both wavelengths when a 70-m antenna was used at the DSN station.  During these experiments, frequency of the spacecraft transmitter was controlled by an onboard crystal oscillator.  Prior to and after most experiments, the high-gain antenna was pointed toward Earth both so that the frequency of the directly propagating signal could be measured and also so that the phase relationship between the two orthogonally polarized S-band receivers could be related to the spacecraft's linearly polarized transmissions.  Spacecraft attitude was not adjusted during the experiments to account for refractive bending in the Venus atmosphere.  Results from the quasi-specular experiments over Maxwell Montes on 5 June 1994 have been published [PETTENGILLETAL1996].  The data set includes Original Data Records (ODRs), which are digitized recordings of baseband receiver output; the ODR is considered to be the primary data type in this archive. Archival Tracking Data Files (ATDFs or TDFs), records of closed-loop receiver output, are also included; they serve as low resolution backup to the ODRs but are not likely to include measures of scattered signal.  Typical users of the data set would compute the expected frequency of the signal from the target point, compute Fourier transforms from the data samples, and sum the power spectra incoherently. The amplitude and spectral width of a detected echo can be related to physical and electrical properties of the scattering surface (and to experimental parameters, such as the illumination footprint of the HGA on Venus' surface). The analysis which has been published [PETTENGILLETAL1996] included inference of surface properties from the polarization of the received echo signal.   Parameters : Open loop data records (ODRs) contain 8-bit samples of receiver output. Each block of 4000 data samples is accompanied by a 166 byte header. The ODR is described by a Software Interface Specification (SIS), included as RSC11_11.TXT in the DOCUMENT directory of the data set archival volume.  For experiments in 1993, two X-band (3.5 cm wavelength) open-loop receivers were used, one capturing right-circularly polarized signals and the other capturing left-circularly polarized signals. These are identified in the data stream as Channels 1 and 3, respectively. Two S-band open-loop receivers were also used for 70-m observations in 1993, yielding right- and left-circularly polarized output on Channels 2 and 4, respectively. Failures in the data acquisition equipment make these four-channel 1993 data more difficult to use.  By 1994, capabilities of the sampling equipment had degraded to the point where only two signals from the 70-m antennas could be recorded simultaneously. For these experiments, the usual practice was to record two polarizations at X-band on one orbit, alternating with two polarizations at S-band on the next orbit.  Each ATDF data record contains 117 parameters, stored in records of 288 bytes at rates up to one per second. The parameters include estimates of received signal strength and frequency as well as 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 each archival volume.   Processing : With the following exceptions, open loop data (ODRs) were not edited or otherwise processed before being incorporated into the archival volumes.  (1) A 32-byte label at the beginning of each ODR tape is not included in the data file. The 32-byte label gives the version of the data taking software; this information has been copied to the PDS label that accompanies the data file. The software version recorded in the 'NOTE' keyword is more likely to be accurate than the version recorded with the 'SOFTWARE_VERSION' keyword. Because the 32-byte label is no longer part of the data stream, users can treat the remaining file as an integral number of fixed-length records.  (2) Some tapes were delivered with record lengths truncated to 566 bytes rather than the expected 4166 bytes. The truncation may have occurred during copying at the DSN station; no cause was ever determined and the original (uncorrupted) data were not recovered. Records truncated to 566 bytes have been padded to their original 4166-byte lengths with binary zeroes before being stored in the archival volumes. A list of these files is given in the ERRATA.TXT file at the root of the archival volume.  The DSN Navigation Team sometimes edits ATDF records to remove values clearly outside the nominal range. The extent of editing on Magellan bistatic radar ATDFs is not known.   Data : Original Data Records (ODRs) were the primary data type for this raw data archive. ODRs were generated at stations of the NASA Deep Space Network (DSN) and were distributed on 6250 bpi tape. Those tapes have been copied to disk files, defined as PDS TABLE Objects, and archived on these CD-WO volumes. ODRs are stored on CD-WO volumes in chronological order; ancillary data files (to support analysis) accompany ODRs in the CALIB, GEOMETRY, and DOCUMENT directories. The table FILELIST.TAB in the DOCUMENT directory shows relationships among ODR files and ancillary data.  A nominal ODR contains 24000 records, each record having 166 bytes of header data and 4000 bytes of 8-bit sample data. Each of four receiver channels (X-RCP, S-RCP, X-LCP, and S-LCP) was sampled at 50000 samples per second in 1993; these appear in the output record as channels 1 through 4, respectively [see RSC11_11.TXT in the DOCUMENT directory of the archival volume]. A single file represented 8 minutes of observing time. For most experiments in 1994, only two channels were sampled (usually X-RCP and X-LCP, Channels 1 and 3, respectively; or S-RCP and S-LCP, Channels 2 and 4, respectively). The sampling rates on each channel remained at 50000 per second, but the rate for each analog-to-digital converter was only 25000. A single file usually represented 16 minutes of data.  On MGN BSR archival volumes, ODR files have names of the form ydddhhmm.ODR where y gives the least significant digit of the year, ddd is the 3-digit day-of-year, hh is the 2-digit hour, and mm is the 2-digit minute on which data acquisition for the file began.  Each ODR data file is accompanied by a full PDS detached label with name ydddhhmm.LBL which completely describes the contents of the ODR file. The format and content of the ODR are also described in RSC11_11.TXT in the DOCUMENT directory of each archival volume.  Archival Tracking Data Files (ATDFs or TDFs) are considered to be primary raw data for many radio science experiments. In this case, they served a backup and ancillary role. ATDFs are generated by the Radio Metric Data Conditioning Team in the DSN. They were delivered either on computer-compatible tape or as electronic files. They have been copied to disk, defined as PDS TABLE objects, and archived on these CD-WO volumes.  A typical ATDF covered several days and had a volume of 35 MBytes. ATDF rates for these Magellan BSR experiments were typically one sample every 60 seconds. Each sample was of 117 items, including measurements of signal amplitude and frequency from closed loop receivers, and was stored as a single record of 288 bytes. Sampling of the signals was limited to one polarization at S-band and one polarization at X-band. Time resolution was more coarse than from the ODR and no information on signal phase was retained. It is unlikely that the closed-loop receivers locked to the echo signal during bistatic maneuvers. The ATDF, from this perspective, provided low-resolution backup to the ODR only during times when the HGA was pointed toward Earth.  Each 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 ydddeeeA.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.  A set of 'browse' files is included on each CD-WO volume. Each file is a composite PostScript file containing plots from three steps in a 'quick-look' processing of the ODR data. Each file will produce a single 8-1/2 x 11 inch page giving results from one 'channel' from an ODR. Plots are: (1) histogram of 8-bit sample values, (2) 60-second average power spectra, and (3) 1-second average values of sample power versus time. Also included in the fourth 'panel' on each page is a text extract from the top of the ODR PDS label. Plots were created as the archive was being assembled. The plots should provide quick low resolution access to the contents of each ODR to users able to display or print PostScript files. The plot files are located in the BROWSE directory.   Ancillary Data : For each ODR, there is a set of ancillary files needed for analysis. These files are stored in the CALIB and GEOMETRY directories, as appropriate. A table FILELIST.TAB in the DOCUMENT directory shows relationships among ODRs and ancillary files.   High-Gain Antenna (HGA) Radiation Pattern ----------------------------------------- The radiation pattern of the high-gain antenna (HGA) is described in a PDS document with both ASCII and PostScript components in the CALIB directory. The HGA pattern would be needed to estimate the illumination of any point on the Venus surface. The HGA calibration document is described in the detached PDS label HGA_XXX.LBL in the CALIB directory; it is included on all CD-WO volumes.   Observing Geometry ------------------ Files describing the observing geometry are stored in the GEOMETRY directory. These include NAIF 'text' format SPK files and NAIF 'transfer' format ephemerides. Files describing spacecraft attitude are also included in the GEOMETRY directory, but are described in the next section.  NAIF (PDS Navigation and Ancillary Information) 'text' format SPK files are available for all observations except those on 1994-05-31. Data for 1994-05-31 are available in NAIF SPK 'transfer' format. SPK files contain the positions of Magellan, Venus, Earth, and the Sun in data modules that can be used readily with NAIF Toolkit software. Each 'text' SPK file has a name ending with the extension 'TSP'; each 'transfer' SPK file name ends with 'XSP'. Each SPK data file is accompanied by a detached PDS minimal label having the same file name but ending with the 'LBL' extension.  For all orbits, predicted Keplerian orbital elements for the Magellan spacecraft are available in the file KEPELEMS.TAB.  A single NAIF 'transfer' format file (PEPH8996.XSP) contains solar system ephemerides. For reconstruction of observing geometry, this file may be used in conjunction with KEPELEMS.TAB as an alternative to the NAIF SPK files.  Before using either 'text' or 'transfer' NAIF files, the user should convert ASCII carriage-return line-feed delimiters on each record to the default delimiter for text files on the local system, then use the NAIF utility SPACIT to convert the archival file to local binary.  Information on acquisition, installation, and use of the NAIF software can be found in TK_FTP.TXT in the DOCUMENT directory.   Spacecraft Attitude (Quaternions) --------------------------------- Since maneuvers were executed to point the HGA toward the surface during each bistatic radar experiment, information on the spacecraft attitude is required for proper analysis and interpretation of the results.  Attitude data are available as spacecraft quaternion polynomial coefficients during maneuvers and as fixed quaternions prior to and after the maneuvers (during Earth point). Quaternion files are in the GEOMETRY directory and have names of the form yydddeee.QPC where 'yy' gives the 2-digit year and 'ddd' and 'eee' give the start and end day-of-year for which the file applies.   Coordinate System : SPK ephemeris files and quaternion files were produced for the J2000 inertial reference frame. NAIF reader routines may be used to convert these to other coordinate systems.  Other data types are not dependent on definition of a coordinate system.   Software : Software for parsing, reducing, and analyzing data such as these has been developed at Stanford University and elsewhere. Because such software must usually operate at the bit-level and is written for a narrow range of platforms, it is not suitable for general distribution. No software is included with this archival data set.   Media/Format : The archival data set is written on CD-WO media using the Young Minds CD Studio authoring system. The CD-WO volumes conform to ISO 9660 standards.

Overview : With the exception of the quasi-specular track across Maxwell Montes [PETTENGILLETAL1996], relatively little analysis had been performed on the raw data at the time they were archived.   Review : This archival data set was reviewed by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review was conducted in accordance with PDS procedures.  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, the experiment investigator, and others, as appropriate.  Data on the CD-WO volumes were checked using Stanford parsing and reduction software to ensure that they were both complete and accurate replicas of the data contained in the original tape files.   Data Coverage and Quality : The times covered by ODR tapes are given in FILELIST.TAB in the DOCUMENT directory. The experiments are summarized briefly here.  6 October 1993 (Orbits 9331, 9335, and 9336) -------------------------------------------- This was a set of three spotlight experiments with Gula Mons as the target. The summit of Gula Mons appears brighter than average in radar backscatter. The objective was to detect enhanced backscatter in the bistatic configuration and to compare it with scatter at other angles. Chances of bistatic detection were predicted to be marginal because of the rapidly changing bistatic geometry and the relatively small area at the summit of Gula Mons with enhanced reflectivity.  Orbit 9331 was observed using the 70-m Goldstone antenna; X-RCP, S-RCP, X-LCP, and S-LCP were recorded. A malfunction in the data acquisition equipment resulted in loss of about two-thirds of the records. It may be possible to recover the remainder, but considerable care will be required in handling the remainder since sampling coherence has been lost -- at least at some record-to-record boundaries and possibly within single records.  Orbits 9335 and 9336 were observed using the 70-m Canberra antenna. Signals recorded included X-RCP, S-RCP, X-LCP, and S-LCP. For both orbits, the data acquisition equipment functioned normally for several minutes, but then a 2-second modulation on all channels began. There is some evidence that pairs of samples were being lost on a regular basis, effectively toggling RCP and LCP on both the X- and S-band channels every two seconds. These data may be recoverable; but care will be required if the effects of the modulation are to be properly characterized and removed.  From an early analysis, no clear echo signal was identified on any channel from any of the three orbits on 6 October.  DSS Start Time Stop Time Channels Archive Notes --- ---------- ---------- -------- ------- ------------------ 14 13:24:14 13:32:31 XRSRXLSL MG_2301 Lost records 14 13:39:35 13:43:35 XRSRXLSL MG_2301 Post-maneuver data -- -------- -------- -------- ------- 43 19:42:46 19:50:45 XRSRXLSL MG_2301 43 19:50:46 19:58:40 XRSRXLSL MG_2301 Modulation -- -------- -------- -------- ------- 43 21:17:26 21:25:25 XRSRXLSL MG_2301 Modulation 43 21:25:26 21:33:20 XRSRXLSL MG_2301 Modulation   9 November 1993 (Orbits 9846 through 9848) ------------------------------------------ Parts of three quasi-specular tracks were observed using the 70-m DSN antenna near Madrid. The tracks extended from near (27S, 67E), crossed the equator at 67E, passed near (76N, 167E), and ended at approximately (57N, 210E). Incidence angle was minimum (73 deg) near (41N, 73E) and increased to about 75.5 deg at both ends of the ground track, in all cases including a preliminary adjustment for atmospheric refraction. Signals were received in X-RCP, S-RCP, X-LCP, and S-LCP polarizations. The objective was to observe variations in reflected signal amplitude and bandwidth as the specular point moved across the surface. Predicted signal strengths were more than adequate for detection at S-band; because of increased atmospheric attenuation and frequency dispersion during the surface scattering process, predicted performance at X-band was uncertain.  Fifteen of 22 digital tapes that were received contained good data; the other 7 contained records from which about 90 percent of the data samples had been truncated. The cause for this was never determined, but there are suggestions that an incorrect record length may have been entered during copying. The original tapes were recycled at the DSN station before the error was discovered. Records in the archive have been padded to the correct length with binary zeroes to allow processing, albeit with artifacts in the output from the padding.  S-band echoes were observed in both polarizations in real time, though amplitudes and echo widths varied considerably -- and the signal disappeared entirely at times. No X-band echoes have been seen in preliminary reductions of the data, though confusion over monitor display settings led to early belief that both S- and X-band echoes were being seen in real time.  DSS Start Time Stop Time Channels Archive Notes --- ---------- ---------- -------- ------- ---------- 63 09:17:32 09:25:31 XRSRXLSL MG_2302 Orbit 9846 63 09:25:32 09:33:31 XRSRXLSL MG_2302 Orbit 9846 63 09:33:32 09:41:31 XRSRXLSL MG_2302 Orbit 9846 -- -------- -------- -------- ------- 63 10:03:12 10:11:11 XRSRXLSL MG_2302 Orbit 9846 63 10:11:12 10:17:40 XRSRXLSL MG_2302 Orbit 9846 -- -------- -------- -------- ------- 63 10:51:41 10:59:40 XRSRXLSL MG_2303 Orbit 9847 63 10:59:41 11:07:40 XRSRXLSL MG_2303 Orbit 9847 63 11:07:41 11:15:40 XRSRXLSL MG_2303 Orbit 9847 63 11:15:41 11:22:41 XRSRXLSL MG_2303 Orbit 9847 63 11:23:09 11:31:08 XRSRXLSL MG_2303 Orbit 9847 63 11:31:09 11:39:08 XRSRXLSL MG_2304 Orbit 9847 63 11:39:09 11:47:08 XRSRXLSL MG_2304 Orbit 9847 63 11:50:32 11:53:02 XRSRXLSL MG_2304 Orbit 9847 -- -------- -------- -------- ------- 63 12:26:11 12:34:11 XRSRXLSL MG_2304 Orbit 9848 63 12:34:12 12:42:11 XRSRXLSL MG_2304 Orbit 9848 63 12:42:12 12:50:11 XRSRXLSL MG_2304 Truncated records 63 12:50:12 12:51:37 XRSRXLSL MG_2305 Truncated records 63 12:53:24 12:58:35 XRSRXLSL MG_2305 Truncated records 63 12:59:08 03:02:45 XRSRXLSL MG_2305 Truncated records 63 13:07:08 13:15:07 XRSRXLSL MG_2305 Truncated records 63 13:15:08 13:23:07 XRSRXLSL MG_2305 Truncated records 63 13:23:08 13:27:02 XRSRXLSL MG_2305 Truncated records   31 May 1994 (Orbits 12955 through 12958) ---------------------------------------- Spotlight experiments were carried out over a target in the south- eastern part of Maxwell Montes; all receiving was done using the 70-m DSN antenna near Madrid. The objective was to detect enhanced backscatter in the bistatic configuration and to compare it with scatter at other angles. Chances of bistatic detection were predicted to be poor because of the rapidly changing bistatic geometry and the low radar cross section for Maxwell at the highly oblique viewing angles -- despite its enhancement relative to nearby areas. Quasi-specular observations were planned over the same target five days later.  Data were collected from four consecutive orbits. The first orbit was observed using all four receiver channels (X-RCP, S-RCP, X-LCP, and S-LCP). The second and fourth orbits were observed using only S-RCP and S-LCP; the third orbit was observed using only X-RCP and X-LCP.  Tapes generally contained good data, but no signal was detected during preliminary processing. Modulation was noticed on the X-RCP carrier prior to the first spotlight maneuver; its cause was not determined.  DSS Start Time Stop Time Channels Archive Notes --- ---------- ---------- -------- ------- ---------------- 63 11:31:38 11:39:37 XRSRXLSL MG_2306 Pre-cal 63 11:39:38 11:47:30 XRSRXLSL MG_2306 Pre-cal -- -------- -------- -------- ------- 63 12:15:34 12:23:01 XRSRXLSL MG_2306 X-RCP modulation 63 12:23:36 12:31:06 XRSRXLSL MG_2306 X-RCP modulation 63 12:31:21 12:39:04 XRSRXLSL MG_2306 Orbit 12955 63 12:40:06 12:42:21 XRSRXLSL MG_2306 Orbit 12955 63 12:49:16 12:54:58 XRSRXLSL MG_2306 Orbit 12955 63 12:55:31 13:03:30 XRSRXLSL MG_2307 Orbit 12955 63 13:03:31 13:10:33 XRSRXLSL MG_2307 Orbit 12955 -- -------- -------- -------- ------- 63 13:50:11 14:06:02 SRSLSRSL MG_2307 Orbit 12956 63 14:06:17 14:22:02 SRSLSRSL MG_2307 Orbit 12956 63 14:26:23 14:35:53 SRSLSRSL MG_2307 Orbit 12956 -- -------- -------- -------- ------- 63 15:25:10 15:41:09 XRXLXRXL MG_2308 Orbit 12957 63 15:41:10 15:57:09 XRXLXRXL MG_2308 Orbit 12957 63 15:57:10 16:03:01 XRXLXRXL MG_2308 Orbit 12957 -- -------- -------- -------- ------- 63 17:00:11 17:16:10 SRSLSRSL MG_2308 Orbit 12958 63 17:16:11 17:32:10 SRSLSRSL MG_2308 Orbit 12958 63 17:32:11 17:45:57 SRSLSRSL MG_2308 Orbit 12958   5 June 1994 (Orbits 13032 through 13040) ---------------------------------------- Eight quasi-specular tracks were observed using two 70-m DSN antennas. Each track extended from south of the Venus equator to beyond Maxwell Montes in the north. The objective was to observe changes in reflected signal amplitude and dispersion as the specular point moved over different surface units. Of particular interest was Maxwell Montes, targeted five days earlier in a spotlight bistatic experiment. Predictions were for real-time observation of echoes at S-band and possible detection (with intense non-real-time processing) of X-band echoes.  Six orbits were captured using DSS 63 near Madrid; four were captured using DSS 14 near Goldstone. Madrid began with S-RCP and S-LCP on the first orbit, switched to X-RCP and X-LCP on the second, and continued to alternate on successive orbits thereafter. On the fifth orbit, DSS 14 began with X-RCP and X-LCP (while DSS 63 collected S-RCP and S-LCP), and alternated thereafter.  Tuning predictions for the open-loop receivers were calculated at Stanford; owing to a sign error, the predictions failed to achieve the desired result, but real-time corrections to the tuning were sufficient to keep the S-band signal within the passband for all but the first of the DSS 63 observations.  At DSS 14 an error in ground antenna pointing reduced signal levels considerably; those data probably have very little value when compared with the DSS 63 results.  Some of the tapes received from DSS 63 had truncated records; for the archive, those have been padded with binary zeroes, as was done with the truncated records from 31 May 1994.  About half the tapes received from DSS 14 were unreadable; the unreadable tapes are not included in the archive.  S-band echoes were observed in real time from DSS 63; no X-band echoes were seen. A paper based on this set of experiments has been published [PETTENGILLETAL1996].  DSS Start Time Stop Time Channels Archive Notes --- ---------- ---------- -------- ------- ----------------- 63 13:09:31 13:25:30 SRSLSRSL MG_2309 63 13:25:31 13:41:30 SRSLSRSL MG_2309 63 13:41:31 13:48:39 SRSLSRSL MG_2309 -- -------- -------- -------- ------- 63 14:25:09 14:41:08 XRXLXRXL MG_2309 Truncated records 63 14:41:09 14:57:08 XRXLXRXL MG_2309 63 14:57:09 15:13:08 XRXLXRXL MG_2309 63 15:13:09 15:21:26 XRXLXRXL MG_2310 Truncated records -- -------- -------- -------- ------- 63 15:58:12 16:14:11 SRSLSRSL MG_2310 63 16:14:12 16:30:11 SRSLSRSL MG_2310 63 16:30:12 16:46:11 SRSLSRSL MG_2310 63 16:46:12 16:54:17 SRSLSRSL MG_2310 -- -------- -------- -------- ------- 63 17:31:12 17:47:11 XRXLXRXL MG_2310 Truncated records 63 17:47:12 18:03:11 XRXLXRXL MG_2311 63 18:03:12 18:19:11 XRXLXRXL MG_2311 63 18:19:12 18:28:06 XRXLXRXL MG_2311 Truncated records -- -------- -------- -------- ------- 63 19:10:25 19:26:24 SRSLSRSL MG_2311 63 19:26:25 19:42:24 SRSLSRSL MG_2311 63 19:42:25 19:58:24 SRSLSRSL MG_2311 63 19:58:25 20:00:23 SRSLSRSL MG_2311 -- -------- -------- -------- ------- 63 20:37:11 20:53:10 XRXLXRXL MG_2312 Truncated records 63 20:53:11 21:09:10 XRXLXRXL MG_2312 63 21:09:11 21:21:07 XRXLXRXL MG_2312 -- -------- -------- -------- ------- 14 18:52:34 19:01:20 XRXLXRXL MG_2312 Pre-cal 14 19:02:27 19:10:01 Tape unreadable -- -------- -------- -------- ------- 14 19:33:44 19:49:43 XRXLXRXL MG_2312 Bad Pointing 14 19:49:44 20:01:25 Tape unreadable -- -------- -------- -------- ------- 14 20:36:10 20:52:09 SRSLSRSL MG_2312 Bad Pointing 14 20:52:10 20:55:38 Tape unreadable 14 20:55:54 21:11:53 SRSLSRSL MG_2313 Bad Pointing 14 21:11:54 21:27:53 Tape unreadable 14 21:27:54 21:36:11 SRSLSRSL MG_2313 Bad Pointing -- -------- -------- -------- ------- 14 22:09:09 22:25:08 XRXLXRXL MG_2313 Bad Pointing 14 22:25:09 22:41:08 Tape unreadable 14 22:41:09 22:57:08 XRXLXRXL MG_2313 Bad Pointing 14 22:57:09 23:06:53 Tape unreadable -- -------- -------- -------- ------- 14 23:39:53 23:55:52 SRSLSRSL MG_2313 Bad Pointing 14 23:55:53 00:11:52 Tape unreadable -- -------- -------- -------- ------- 14 00:11:53 00:27:37 SRSLSRSL MG_2313 Bad Pointing  Orbit numbers are not uniquely identified with the data collection intervals listed above; the table below may provide guidance. Times after 11:00:00 are for 5 June 1994; times before 02:00:00 are for 6 June 1994.  Orbit Number Start Time (UTC) Stop Time (UTC) ------------ ---------------- --------------- 13032 11:48:08 13:21:04 13033 13:21:05 14:54:02 13034 14:54:12 16:26:59 13035 16:27:00 17:59:56 13036 17:59:57 19:32:54 13037 19:32:54 21:05:51 13038 21:05:52 22:38:48 13039 22:38:49 00:11:46 13040 00:11:46 01:44:43   12 December 1995 ---------------- A test of the DSN equipment was carried out in December 1995 to measure the phase shift introduced by attenuators on open-loop receivers. The test was intended to show whether adding attenuation could change the inferred phase on one S-band channel with respect to the other. Such a differential phase shift could lead to errors in reconstruction of linear received polarizations from the circulars that are actually recorded on the ground. Attenuator settings are included with the DSP header information, but the test data were never analyzed to the precision required to answer the question posed. Data were collected at the DTF 21 DSN-equivalent site at JPL; sample rate was 200 Hz, so data records have lengths of 566 bytes.  DSS Start Time Stop Time Channels Archive Notes --- ---------- ---------- -------- ------- ------------------- 06 17:13:13 17:39:59 XRSRXLSL MG_2313 Phase vs atten test   Limitations : The limitations in this data set follow from the quality of the execution, which is described above under Data Coverage and Quality.