Data Set Information
DATA_SET_NAME GIOTTO RADIO SCIENCE ORIGINAL EXPERIMENT DATA V1.0
DATA_SET_ID GIO-C-GRE-1-EDR-HALLEY-ADDENDA-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : The Giotto Radio Science Original Experiment Data Set was generated by ground equipment connected to the Canberra 64-m antenna of the NASA Deep Space Network (DSN) in Australia. It includes two types of data -- an Archival Tracking Data File (ATDF) from closed loop receivers and Original Data Records (ODRs) from open loop receivers. These should be considered 'raw' data which much be processed before being applied to science problems. The data in 'GIO-C-GRE-3-RDR-HALLEY-V1.0' have been partially processed and may be more suitable for immediate science application. 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 -- in this case to determine the reduction in velocity when Giotto passed through the dust and gas surrounding Comet Halley. Data values in ATDFs are reported at rates no higher than 10 per second. One ATDF is included in this data set. It covers the time interval 1986-03-13T15:32:47 to 1986-03-14T05:10:00. ODRs are files of digitally sampled medium-bandwidth receiver output. In conjunction with gain settings and receiver tuning information (contained in the ODR header) these files allow the investigator to derive the amplitude and frequency of the Giotto radio signal to highest accuracy with post-experiment processing. For the Giotto Radio Experiment an open-loop receiver bandwidth of 25 kHz was selected, and 8-bit sampling was performed on each of four channels. The channel assignments were: (1) S-RCP, (2) S-LCP, (3) X-RCP, and (4) X-LCP where S-Band signals are at 13 cm wavelength, X-Band signals are at 3.6 cm wavelength, RCP denotes right circular polarization, and LCP denotes left circular polarization. During the Giotto experiment only X-RCP was transmitted by the spacecraft, so channels (1) and (2) should contain only noise and channel (4) should contain, at most, a leakage signal. Two ODR files are included in this data set; each covers eight minutes. Together they cover the Giotto Halley encounter. Their start times (UTC) are 1986-03-13T23:56:02 and 1986-03-14T00:04:02 The measurements of frequency and frequency residual may be converted to changes in spacecraft velocity during the Halley encounter. The changes in velocity may then be interpreted in terms of mass fluence (dust and gas) within Halley's coma [EDENHOFERETAL1986A], [EDENHOFERETAL1986B], [EDENHOFERETAL1986C], [EDENHOFERETAL1986D], [EDENHOFERETAL1987A]. More detailed analyses of the dynamics of the spacecraft as inferred from the GRE data have been published by [BIRDETAL1988], [PAETZOLDETAL1988], [PAETZOLDETAL1990], [PAETZOLDETAL1991A], [PAETZOLDETAL1991B], and [PAETZOLDETAL1991C]. Parameters : Each ATDF data record contains 117 parameters. These 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, included as TRK_2_25.TXT in the DOCUMENT directory of the data set archival volume. A complete list of parameters is given in Table 3 of that document. Open loop data records contain 8-bit samples of receiver output as described above. Each block of 4000 data samples is accompanied an 80 byte header, a 300 byte trailer of Precision Power Monitor data, and a 10 byte trailer of operator-entered timing and frequency offsets. The ODR is described by a Software Interface Specification, included as RSC_11_9.TXT in the DOCUMENT directory of the data set archival volume. A complete list of header parameters is given in Figure RSC-11-9-1 in that document. Processing : DSN NAV performs editing on data during conversion from the IDR to ATDF formats; this function serves mostly to remove anomalous (out of nominal range) values. Open loop data are not edited or otherwise processed.
DATA_SET_RELEASE_DATE 1994-07-31T00:00:00.000Z
START_TIME 1986-03-13T03:32:47.000Z
STOP_TIME 1986-03-14T05:10:00.000Z
MISSION_NAME GIOTTO
MISSION_START_DATE 1985-07-02T12:00:00.000Z
MISSION_STOP_DATE 1992-07-10T12:00:00.000Z
TARGET_NAME HALLEY
TARGET_TYPE COMET
INSTRUMENT_HOST_ID GIO
INSTRUMENT_NAME GIOTTO RADIOSCIENCE EXPERIMENT
INSTRUMENT_ID GRE
INSTRUMENT_TYPE RADIO SCIENCE
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE [EDENHOFERETAL1987B] reported that 'The maximum frequency offset in the one-way data was 16.9 Hz. But the two-way data acquired before and after the encounter are consistent with a maximum of only 4.64 Hz.' Two explanations have been offered [EDENHOFERETAL1987B]. First is that the drag forces amplified the oscillator drift through acoustic, electrical, or thermal energy deposition. In this case, the measurements differ from the actual values by only a scale factor. The analysis presented by [EDENHOFERETAL1987B] adopts this assumption. The second explanation is that transients during the encounter (possibly associated with failure of the NMS experiment and switching of the TWT amplifier tubes) also induced a frequency offset in the on-board oscillator. In this case, both an offset and a scale factor may be needed to correct the data. No applicable pre-launch tests were conducted on the radio system to allow choosing between these assumptions. There is no other information on quality of the data. It is believe that operations during data acquisition were nominal and that these two data types represent the highest quality raw data that could be obtained under the circumstances.
CITATION_DESCRIPTION McDonnell, J. A. M, GIOTTO RADIO SCIENCE ORIGINAL EXPERIMENT DATA V1.0, GIO-C-GRE-1-EDR-HALLEY-ADDENDA-V1.0, NASA Planetary Data System, 1994.
ABSTRACT_TEXT The Giotto Radio Science Original Experiment Data Set includes two types of data -- an Archival Tracking Data File (ATDF) from closed loop receivers and Original Data Records (ODRs) from open loop receivers.
PRODUCER_FULL_NAME INTERNATIONAL HALLEY WATCH
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