Data Set Information
DATA_SET_NAME GIOTTO RADIO SCIENCE EXPERIMENT DATA V1.0
DATA_SET_ID GIO-C-GRE-3-RDR-HALLEY-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview: The Giotto Radio Science Experiment data set consists of four tables. Each table contains a measurement value listed as a function of time. The measurements are: closed-loop receiver carrier signal amplitude, closed-loop receiver carrier frequency residual, open-loop receiver carrier signal amplitude, and open-loop receiver carrier frequency. 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 : The closed-loop receiver carrier signal amplitude is the measured strength of the spacecraft signal at the DSN 70-m antenna when connected to a closed-loop receiver. The data file GREACL is a table of signal level measurements (in units of dB relative to 1 milliwatt) taken at 1 second intervals starting at 0 h on 14 March 1986. The closed-loop receiver frequency residual is the measured frequency of the spacecraft signal at the DSN 70-m antenna relative to the frequency expected from the spacecraft moving only in response to gravitational forces. The data file GREFCL is a table of residual frequencies (in units of Hz) taken at 0.1 second intervals starting at 0 h on 14 March 1986. The open-loop receiver carrier signal amplitude is the measured strength of the spacecraft signal at the DSN 70-m antenna when connected to an open-loop receiver. The data file GREAOL is a table of signal level measurements (in units of dB relative to 1 milliwatt) taken at 0.128 sec intervals starting at 601.103470 sec past 0 h on 14 March 1986. The open-loop receiver frequency is the measured frequency of the spacecraft signal at the DSN 70-m antenna relative to 8428463000 Hz. The data file GREFOL is a table of frequencies (in units of Hz) taken at 0.128 second intervals starting 601.103470 secs after 0 h on 14 March 1986. Processing : The open-loop original samples have been digitally filtered. The estimates of signal amplitude and frequency are based on the strength and location of the spacecraft signal in power spectra derived from those filtered samples .
DATA_SET_RELEASE_DATE 1992-04-30T00:00:00.000Z
START_TIME 1986-03-14T12:00:00.000Z
STOP_TIME 1986-03-14T12:24:00.000Z
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 Confidence Level Overview: 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.
CITATION_DESCRIPTION Edenhofer, P., GIOTTO RADIO SCIENCE EXPERIMENT DATA V1.0, GIO-C-GRE-3-RDR-HALLEY-V1.0, NASA Planetary Data System, 1992
ABSTRACT_TEXT The Giotto Radio Science Experiment data set consists of four tables. Each table contains a measurement value listed as a function of time. The measurements are: closed-loop receiver carrier signal amplitude, closed-loop receiver carrier frequency residual, open-loop receiver carrier signal amplitude, and open-loop receiver carrier frequency.
PRODUCER_FULL_NAME INTERNATIONAL HALLEY WATCH
SEARCH/ACCESS DATA
  • SBN Comet Website
    		•