Data Set Information
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| DATA_SET_NAME |
CLEM1 LUNAR RADIO SCIENCE RAW BISTATIC RADAR V1.0
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| DATA_SET_ID |
CLEM1-L-RSS-1-BSR-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : The Clementine Bistatic Radar Raw Data Archive (BSR-RDA) is a time-ordered collection of raw and partially processed data from bistatic radar scattering experiments conducted using the Clementine spacecraft while it orbited the Moon. The spacecraft radio system was used as a signal source, and the spacecraft high-gain antenna beamed those signals toward surface targets on the Moon. The transmit polarization along the boresight of the spacecraft antenna was right- circular; the nominal wavelength was 13 cm (S-band). Echo signals were received coherently in both right- and left- circular polarizations using 70-m antennas at stations of the NASA Deep Space Network (DSN) on Earth. The scattering experiments were conducted in two configurations. For 'spotlight' experiments a single target was identified on the Moon; the spacecraft attitude was controlled during the experiment so that the HGA always pointed toward that target location. Spotlight experiments, conducted on polar targets were designed to detect and measure enhanced backscatter from possible ice deposits in areas permanently shaded from solar illumination. Such enhancements have been seen in Earth-based radar studies of the Galilean satellites [CAMPBELLETAL1978], Mars [MUHLEMANETAL1991], and Mercury [HARMONETAL1994]. Although Earth-based radar studies of the Moon [STACY1993] have had considerably better sensitivity and surface resolution than this experiment, the Clementine geometry uniquely allowed measurements as a function of the bistatic angle -- the separation angle between transmitter and receiver when viewed from the target [SIMPSON1993]. The angular variation of any enhancement may be related to the distance the radar signal travels through the ice and, hence, to the thickness and/or clarity of the ice at 13 cm wavelength. For 'quasi-specular' observations, the HGA was aimed toward the point on the lunar surface where mirror-like (specular) reflections were expected. Signals transmitted by the spacecraft would carom from the lunar surface and be received at the DSN stations. Because the (specular) image of Earth moved as Clementine orbited the Moon, the HGA illuminated a swath across the surface as the spacecraft advanced in its orbit. A single quasi-specular track was obtained -- in the southern hemisphere during the last set of bistatic radar observations. The data set includes Original Data Records (ODRs), digitized recordings of baseband receiver output; Archival Tracking Data Files (ATDFs), edited records of closed-loop receiver output and related parameters; Link Monitor and Control log files (LMC logs), the automatic diary of station operator activities; trajectory and attitude data; and relevant documentation. Typical users of the data set would spectrally analyze the echo signals in the ODRs; with trajectory and attitude data, the measured signals could be calibrated and mapped to reflectivity of specific surface areas. Unusual reflectivities in geometries near backscatter [HARMONETAL1994; MUHLEMANETAL1991] might suggest the presence of ice deposits. More general scattering properties of the surface can be investigated; this is the first planetary data set for which scattering from a single target region has been observed over a wide range of bistatic angles. Parameters : Open loop data records contain 8-bit samples of receiver output as noted above. Each block of 4000 data samples is accompanied 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 these experiments two S-band (13 cm wavelength) open-loop receivers were used, one capturing right- circularly polarized signal and the other capturing left-circularly polarized signals. These are identified in the data stream as Channels 1 and 3 respectively. Channel 1 was sampled alternately by analog-to-digital converters (ADCs) #1 and #3; Channel 3 was sampled alternately by ADCs #2 and #4. Each ADC operated at 25000 8-bit samples per second giving an effective sampling rate of 50000 on each channel. The effective bandwidth of the filtered output on each channel was about 20 kHz. Each ATDF data record contains 117 parameters, stored in records of 288 bytes at rates up to 10 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 BSR-RDA volume. LMC files are real-time command logs for operators at DSN stations. Although they contain information on a wide variety of equipment, their primary value for these experiments is their record of configuration changes (ambient load calibrations) and attenuator settings. These are either not available or not nearly as well recorded in other files. LMC files were not available for all observations. LMC file formats are described by file LMC.TXT in the DOCUMENT directory of each BSR-RDA volume. Processing : Open loop data (ODRs) are not edited or otherwise processed before being incorporated in the BSR-RDA. A 32-byte label at the beginning of each ODR tape is not included in the data file; it gives the software version of the data taking equipment and is saved instead as the value of the keyword SOFTWARE_NAME in the PDS label that accompanies the data file. DSN NAV performs editing on data during conversion from the Intermediate Data Record (IDR) to ATDF formats; this function serves mostly to remove anomalous (out of nominal range) values. LMC files are ASCII files and are not processed before being included in the BSR-RDA. Data : During the observations on 1994-04-09 and 1994-04-10 the Earth was nearly in the Clementine orbit plane; the spacecraft appeared to move from north to south across the lunar disk, as viewed from Earth. Spotlight experiments were conducted on revolutions 233-236 using target points near the lunar south pole, where a large shaded region [SHOEMAKERETAL1994] potentially containing permanent deposits of water ice may exist [NOZETTEETAL1994]. These experiments were conducted at new moon; periselene was on the far side of the Moon at approximately 30 degrees S latitude. NB: The revolution number refers to an observational pass over the Moon. The revolution number was incremented by one each time the spacecraft passed over the south pole prior to the beginning of data acquisition. REVOLUTION_NUMBER was used in lieu of orbit number because of the way the orbit number was defined by the mission. The orbit number was incremented each time the spacecraft passed through the equatorial plane on the sunlit side of the Moon. Thus, the orbit number generally changed in the middle of an observational pass. This proved to be awkward in defining the data acquired by a single pass over the Moon. During the observations of 1994-04-23 and 1994-04-24 Earth was also nearly in the spacecraft orbit plane. The spacecraft appeared to move from south to north across the lunar disk, as viewed from Earth. Spotlight experiments were conducted on revolutions 299, 301, and 302 using targets near the lunar north pole. A single track of quasi-specular data was obtained in the southern hemisphere during one revolution, and at least three ingress and one egress occultations were recorded. These experiments were conducted at full Moon; periselene was on the near side of the Moon at approximately 30 degrees N latitude. The primary data are Original Data Records (ODRs) -- the sampled output from open-loop receivers at stations of the NASA Deep Space Network (DSN). Calibrations preceded and followed most bistatic radar observations and were recorded on the same ODRs. Bistatic radar data collection included the science events shown in the table below. The column labeled DSS contains the value of the PDS label keyword DSN_STATION_NUMBER (the primary ground antenna). Revolution Date Number DSS UTC Observation ---------- ---------- --- ----------- ------------------- 1994-04-09 233 14 18:13-19:50 Spotlight (90S, 0W) 234 43 23:28-01:17 Spotlight (90S, 0W) 1994-04-10 235 43 04:33-06:16 Spotlight (90S, 0W) 236 63 09:16-10:02 Spotlight (90S, 0W) 1994-04-23 299 43 08:42-09:46 Spotlight (90N, 0W) 299 43 09:56 Occultation Ingress 301 63 18:35-19:45 Spotlight (90N, 0W) 301 63 19:52 Occultation Ingress 301 63 21:04 Occultation Egress 301 63 21:22-22:33 Specular Point 302 63 22:33-23:23 Specular Point (cont) 302 63 23:26-00:42 Spotlight (90N, 0W) 1994-04-24 302 63 00:52 Occultation Ingress ATDFs are files of radiometric data produced by the Network Operations Control Center (NOCC) Navigation Subsystem (NAV). They are derived from Intermediate Data Records by NAV and contain all radiometric measurements received from the DSN station including signal levels, antenna pointing angles, Doppler, range, and residuals. Doppler data are often used to infer spacecraft radial motion relative to the tracking antenna. Data values in ATDFs are reported at rates no higher than 10 per second. A single ATDF covers all but the last 90 minutes of the Clementine bistatic radar observations. Link Monitor and Control log files provide accurate diaries of station activities, including changes in configuration and changes in attenuator settings. Hand-written logs also provide records of configuration changes, and attenuator settings are checked periodically and saved in ODR headers; but the LMC log files are by far the most accurate for times at which changes were made. LMC logs have been obtained for the DSS 63 coverage on 1994-04-10 and 1994-04-23. SPICE CK files allow reconstruction of spacecraft attitude; SPICE SPK files give the spacecraft trajectory as well as planetary positions and velocities. The SPICE system is described in files TK_FTP.TXT, TK_DESCR.TXT, and TK_INSTL.TXT in the DOCUMENT directory of each BSR-RDA volume. Documentation includes real-time notes, stored as text files in the CALIB directory. Coordinate System : SPK ephemeris files and CK attitude files are produced for the J2000 inertial reference frame. SPICE 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. The Stanford software has not been prepared for general distribution and is not included with the 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.
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| DATA_SET_RELEASE_DATE |
1999-02-28T00:00:00.000Z
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| START_TIME |
1994-04-09T12:00:00.000Z
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| STOP_TIME |
1994-04-23T11:59:59.000Z
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| MISSION_NAME |
DEEP SPACE PROGRAM SCIENCE EXPERIMENT
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| MISSION_START_DATE |
1991-11-19T12:00:00.000Z
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| MISSION_STOP_DATE |
1994-05-07T12:00:00.000Z
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| TARGET_NAME |
MOON
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| TARGET_TYPE |
SATELLITE
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| INSTRUMENT_HOST_ID |
CLEM1
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| INSTRUMENT_NAME |
RADIO SCIENCE SUBSYSTEM
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| INSTRUMENT_ID |
RSS
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| INSTRUMENT_TYPE |
RADIO SCIENCE
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| NODE_NAME |
Geosciences
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Overview : At the time the raw data were archived relatively little analysis had been performed, though all ODRs had been checked and some 'quick-look' results had been reported. The primary weakness in the data set is likely to be in the calibration of signal amplitudes for absolute echo powers. The experiment involved signals which were both very strong and very dynamic. Calibration measurements are included in the ODR collection; but it is not clear as of this writing whether the calibrations were performed at the remote sites as the experimenters had intended or whether the results captured on tape can be interpreted. During some portions of the experiment, signals propagating directly from the spacecraft to the ground station were strong enough that the response of the maser was suppressed. The quantitative effect on the signals being measured has not been estimated. Since the interfering signal was not always within the recorded passband, the times at which maser performance was degraded cannot necessarily be determined from simple examinations of the data. Secondarily, the frequency of the spacecraft transmitter was controlled by a simple crystal oscillator. Its frequency is known only approximately (and confirmed through these observations); its drift characteristics both as a function of operating time and as a function of temperature are not known. After these raw data were originally archived, a group of Clementine investigators published results of their analysis [NOZETTEETAL1996], concluding that there was evidence for enhanced backscatter (and, thus, ice) at the South Pole. A subsequent reanalysis of the South Pole data at Stanford University was unable to reproduce those results. A Stanford paper by R.A. Simpson and G.L. Tyler was expected to appear in Journal of Geophysical Research in early 1999. Review : This archival data set was distributed to a peer review panel prior to its acceptance by the Planetary Data System (PDS). The review panel was appointed by the Manager of the PDS Geosciences (GEO) Discipline Node (DN); the review was conducted in accordance with PDS GEO 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 Principal Investigator, and others, as appropriate. Data on the CD-WO volumes was checked using Stanford parsing and reduction software to ensure that it was both complete and an accurate replica of the data contained in the original tape files. Data Coverage and Quality : The times covered by ODR tapes are given below: Revolution Start Time (ERT) Stop Time (ERT) Number DSS Obsn ------------------- ------------------- ---------- --- -------- 1994-04-09T17:48:45 1994-04-09T18:04:44 233 14 1994-04-09T18:04:45 1994-04-09T18:20:44 233 14 S Pole 1994-04-09T18:20:45 1994-04-09T18:36:44 233 14 S Pole 1994-04-09T18:36:45 1994-04-09T18:52:44 233 14 S Pole 1994-04-09T18:52:45 1994-04-09T19:08:44 233 14 S Pole 1994-04-09T19:08:45 1994-04-09T19:24:44 233 14 S Pole 1994-04-09T19:24:45 1994-04-09T19:40:44 233 14 S Pole 1994-04-09T19:40:45 1994-04-09T19:56:44 233 14 S Pole 1994-04-09T19:56:45 1994-04-09T20:05:09 233 14 1994-04-09T23:00:55 1994-04-09T23:16:54 234 43 1994-04-09T23:16:55 1994-04-09T23:32:54 234 43 S Pole 1994-04-09T23:32:55 1994-04-09T23:48:54 234 43 S Pole 1994-04-09T23:48:55 1994-04-10T00:04:54 234 43 S Pole 1994-04-10T00:04:55 1994-04-10T00:20:54 234 43 S Pole 1994-04-10T00:20:55 1994-04-10T00:36:54 234 43 S Pole 1994-04-10T00:36:55 1994-04-10T00:52:54 234 43 S Pole 1994-04-10T00:52:55 1994-04-10T01:08:54 234 43 S Pole 1994-04-10T01:08:55 1994-04-10T01:24:54 235 43 S Pole 1994-04-10T01:24:55 1994-04-10T01:33:55 235 43 1994-04-10T04:02:22 1994-04-10T04:18:21 235 43 1994-04-10T04:18:22 1994-04-10T04:34:21 235 43 S Pole 1994-04-10T04:34:22 1994-04-10T04:50:21 235 43 S Pole 1994-04-10T04:50:22 1994-04-10T05:06:21 235 43 S Pole 1994-04-10T05:06:22 1994-04-10T05:22:21 235 43 S Pole 1994-04-10T05:22:22 1994-04-10T05:38:21 235 43 S Pole 1994-04-10T05:38:22 1994-04-10T05:54:21 235 43 S Pole 1994-04-10T05:54:22 1994-04-10T06:10:21 235 43 S Pole 1994-04-10T06:10:22 1994-04-10T06:26:21 236 43 S Pole 1994-04-10T06:26:22 1994-04-10T06:42:21 236 43 1994-04-10T06:42:22 1994-04-10T06:46:54 236 43 1994-04-10T08:52:22 1994-04-10T09:08:21 236 63 1994-04-10T09:08:22 1994-04-10T09:24:21 236 63 S Pole 1994-04-10T09:24:22 1994-04-10T09:40:23 236 63 S Pole 1994-04-10T09:40:24 1994-04-10T09:56:23 236 63 S Pole 1994-04-10T09:56:24 1994-04-10T10:12:23 236 63 S Pole 1994-04-10T10:12:24 1994-04-10T10:28:23 236 63 1994-04-10T10:28:24 1994-04-10T10:44:23 236 63 1994-04-10T10:44:24 1994-04-10T10:53:05 236 63 1994-04-23T08:19:08 1994-04-23T08:35:07 299 43 1994-04-23T08:35:08 1994-04-23T08:51:07 299 43 N Pole 1994-04-23T08:51:08 1994-04-23T09:07:07 299 43 N Pole 1994-04-23T09:07:08 1994-04-23T09:23:07 299 43 N Pole 1994-04-23T09:23:08 1994-04-23T09:39:07 299 43 N Pole 1994-04-23T09:39:08 1994-04-23T09:55:07 299 43 N Pole 1994-04-23T09:55:08 1994-04-23T10:11:07 299 43 Occ In 1994-04-23T10:11:08 1994-04-23T10:27:07 299 43 1994-04-23T10:27:08 1994-04-23T10:43:07 299 43 1994-04-23T10:43:08 1994-04-23T10:46:01 299 43 1994-04-23T18:15:14 1994-04-23T18:31:13 301 63 1994-04-23T18:31:14 1994-04-23T18:32:23 301 63 1994-04-23T18:35:32 1994-04-23T18:51:31 301 63 N Pole 1994-04-23T18:51:32 1994-04-23T19:07:31 301 63 N Pole 1994-04-23T19:07:32 1994-04-23T19:23:31 301 63 N Pole 1994-04-23T19:23:32 1994-04-23T19:39:31 301 63 N Pole 1994-04-23T19:39:32 1994-04-23T19:55:31 301 63 Occ In 1994-04-23T19:55:32 1994-04-23T20:11:31 301 63 1994-04-23T20:11:32 1994-04-23T20:27:31 301 63 1994-04-23T20:27:32 1994-04-23T20:43:31 301 63 1994-04-23T20:43:32 1994-04-23T20:59:31 301 63 1994-04-23T20:59:32 1994-04-23T21:15:31 301 63 Occ Eg 1994-04-23T21:15:32 1994-04-23T21:31:31 301 63 Q-Spec 1994-04-23T21:31:32 1994-04-23T21:47:31 301 63 Q-Spec 1994-04-23T21:47:32 1994-04-23T22:03:31 301 63 Q-Spec 1994-04-23T22:03:32 1994-04-23T22:19:31 301 63 Q-Spec 1994-04-23T22:19:32 1994-04-23T22:35:31 302 63 Q-Spec 1994-04-23T22:35:32 1994-04-23T22:51:31 302 63 Q-Spec 1994-04-23T22:51:32 1994-04-23T23:07:31 302 63 Q-Spec 1994-04-23T23:07:32 1994-04-23T23:23:31 302 63 Q-Spec 1994-04-23T23:23:32 1994-04-23T23:39:31 302 63 N Pole 1994-04-23T23:39:32 1994-04-23T23:55:31 302 63 N Pole 1994-04-23T23:55:32 1994-04-24T00:11:31 302 63 N Pole 1994-04-24T00:11:32 1994-04-24T00:27:31 302 63 N Pole 1994-04-24T00:27:32 1994-04-24T00:43:31 302 63 N Pole 1994-04-24T00:43:32 1994-04-24T00:59:31 302 63 Occ In 1994-04-24T00:59:32 1994-04-24T01:15:31 302 63 1994-04-24T01:15:32 1994-04-24T01:31:31 302 63 1994-04-24T01:31:32 1994-04-24T01:47:31 302 63 1994-04-24T01:47:32 1994-04-24T01:54:40 302 63 Both before and after observations of the echo signal, calibrations were scheduled. These typically included a few minutes' observation of the zenith sky to obtain a baseline characterization of the receiving system with no spacecraft signal present. Ambient loads were then switched in and the receiver attenuators were adjusted for approximately the same rms output noise level. From the actual change in the noise power, the attenuator differential, and the physical temperature of the ambient load, it should be possible to calculate the system temperature. It was not clear during the calibrations that the ambient loads were being switched in and out as requested -- on both channels -- and it was not always possible to obtain the physical temperatures of these devices from the remote sites. After the ambient load tests at zenith, the 70-m antenna was slewed to track the spacecraft briefly. As the spacecraft began its maneuver to point toward the target on the surface of the Moon, the ground antenna was moved to the center of the lunar disk. This yielded a measurement of the thermal microwave emission of the Moon, which was recorded on the ODR tapes. In some cases, however, the signal from the spacecraft may have corrupted these measurements. Finally, the ground antenna was moved to point at the target region on the lunar surface. Again, there were instances in which a strong signal propagating directly from the spacecraft to the ground may have overloaded the front end of the receiving system and corrupted the recording. After observing the echo signal for typically one hour, the procedure was reversed (another calibration at the center of the Moon, an ambient load test, and a clear sky measurement). Limitations : See section Data Coverage and Quality above. Although spotlight coverage on revolution 236 (1994-04-10) was nominally the South Pole, negative quaternions were generated and the high-gain antenna commanding was in error. The times during which the error occurred were approximately 09:23-09:50; the 'target' location under those conditions was approximately (-70.73, 274.38). During revolution 235 a shorter period of negative quaternions occurred during approximately 04:38-04:41. It appears from subsequent analysis that a single antenna feed was connected to both receivers during data collection at DSS 43 on 1994-04-23. Although attenuators on each channel were operated independently, the RCP signal was recorded on both. Thus there is no polarization in formation in the DSS 43 data from this date.
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| CITATION_DESCRIPTION |
Simpson, R. A., CLEM1 LUNAR RADIO SCIENCE RAW BISTATIC RADAR V1.0, CLEM1-L-RSS-1-BSR-V1.0, NASA Planetary Data System, 1999
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| ABSTRACT_TEXT |
The Clementine Bistatic Radar Raw Data Archive (BSR-RDA) is a time-ordered collection of raw and partially processed data from bistatic radar scattering experiments conducted using the Clementine spacecraft while it orbited the Moon.
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| PRODUCER_FULL_NAME |
RICHARD A. SIMPSON
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| SEARCH/ACCESS DATA |
Lunar Orbital Data Explorer
Geosciences Web Services
Geosciences FTP Resource
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