Data Set Information
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| DATA_SET_NAME |
P11 HVM 1 MINUTE SATURN ENCOUNTER DATA
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| DATA_SET_ID |
P11-S-HVM-4-SUMM-NEAR-ENC-1MIN-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 ================= This data set consists of magnetic field data recorded by the Vector Helium Magnetometer onboard the Pioneer 11 spacecraft, during the Saturn encounter. Data include 3 field components, 6 covariances, 3 directional cosines, field magnitude, and the magnitude square, in spacecraft-centered PE coordinates. Data Sampling ============== The magnetometer measures the three field components over a frequency range from 0 to 10 Hz. At encounter the data rate was 1024 bits/sec and the magnetometer sampling rate was one vector measurement every 3/16 second, corresponding to 5.33 samples/sec. The NSSDC documentation does not contain information about what data resolution this data set (1 minute) is averaged from. Data Processing =============== No detailed information of data processing is found in the NSSDC documentation pertinent to this data set. Pioneer 11 spacecraft was operating under a spin-stablized condition and had a spin period of 7.7 second. Data Format ============ The Pioneer 11 magnetometer data for Saturn encounters were originally written on a 9-track, 1600 bpi, odd parity, ASCII encoded magnetic tape. The original file was re-formatted into a new ASCII file named P11_HVM_SAT_ENC_1MIN.TAB which contains the following data columns: -------------------------------------------------------------------- Column Column Column Name Format Description -------------------------------------------------------------------- TIME A24 Time in yyyy-mm-ddThh:mm:ss.sssZ DELTA_T I7 Length of data averaging window in millisecond E14.6 Average of the X component of the magnetic field in PE coordinates E14.6 Average of the Y component of the magnetic field in PE coordinates E14.6 Average of the Z component of the magnetic field in PE coordinates E14.6 Average of the square of the X component of the magnetic field in PE coordinates E14.6 Average of the cross product of BX and BY in PE coordinates E14.6 Average of the cross product of BX and BZ in PE coordinates E14.6 Average of the square of the Y component of the magnetic field in PE coordinates E14.6 Average of the cross product of BY and BZ in PE coordinates E14.6 Average of the square of the Z component of the magnetic field in PE coordinates E14.6 Magnetic field vector directional cosine in X E14.6 Magnetic field vector directional cosine in Y E14.6 Magnetic field vector directional cosine in Z <|B|> E14.6 Average of the total magnetic field, evaluated as < SQRT(BX^2 + BY^2 + BZ^2) > E14.6 Average of the square of the total field magnitude, evaluated as < BX^2 + BY^2 + BZ^2 > -------------------------------------------------------------------- Coordinate System for Data =========================== The PIONEER Inertial (PE) coordinates is defined based on two principle directions, the PIONEER spin axis (P), and the direction of north ecliptic pole (E). In this system, the Z is along the direction P, the X is E cross P, and the Y is Z cross X to complete the orthogonal system. Ancillary Data ============== There is no ancillary data associated with this data set. Instrument Calibration ====================== The in-flight calibration consists of impressing eight precisely known currents on the sensor coil system and measuring the resulting fields with the magnetometer. The instrument is designed to carry out a nominal mission with only one instrument-on command. The instrument comes on in the automatic ranging/spectrum analyzer mode and automatically ranges to the proper scale by comparing the +X and |Z| axis outputs with fixed reference voltages. The only function commands sent to this instrument during the Pioneer F&G missions were those to initiate the in-flight calibration sequence periodically during the cruise phase. At the conclusion of this sequence the instrument automatically returned to the automatic ranging mode. A 6-bit digital house-keeping word indicates the operating mode of the instrument. The in-flight calibration onboard the Pioneer spacecraft was done by ground command once or twice a week. The low range sensors were calibrated at field magnitude of 13 GAMMA and 26 GAMMA during the interplanetary cruise period. While the high range sensors were calibrated near planetary encounter where the field magnitude was as high as +- 43,000 GAMMA and 86,800 GAMMA. There are two kind of instrument calibration parameters, sensor scale factor (gain) and offset. The conventional approach to checking the magnetometer scale factors in flight is to apply calibration field changes, dB to the sensors so that the corresponding voltage change dV can be determined. Normally several step changes are applied sequentially so that the linearity can be tested directly. After two years of in-flight calibrations, no change has been detected in the Pioneer 10 or 11 scale factors which were then known to an accuracy of 1 percent or better. The sensor offsets were determined in-flight using two different techniques. For the two sensors in the spin plane, the offset was calculated by averaging the spinning data in a time interval of an integral number of spin period. The offset of the spin axis sensor was determined by an adaptation of a variance technique developed by L. Davis [BELCHER1973]. The essential assumption was made that over short intervals of time (5 minutes), the fluctuations in the interplanetary field are principally changes in direction and tend to conserve the magnitude of the field.
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| DATA_SET_RELEASE_DATE |
3000-01-01T00:00:00.000Z
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| START_TIME |
1979-08-30T12:00:00.000Z
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| STOP_TIME |
1979-09-08T11:59:00.000Z
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| MISSION_NAME |
PIONEER 11
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| MISSION_START_DATE |
1972-03-02T12:00:00.000Z
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| MISSION_STOP_DATE |
1995-09-30T12:00:00.000Z
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| TARGET_NAME |
SATURN
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| TARGET_TYPE |
PLANET
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| INSTRUMENT_HOST_ID |
P11
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| INSTRUMENT_NAME |
HELIUM VECTOR MAGNETOMETER
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| INSTRUMENT_ID |
HVM
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| INSTRUMENT_TYPE |
MAGNETOMETER
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| NODE_NAME |
planetary plasma interactions
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| ARCHIVE_STATUS |
SUPERSEDED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview ========================= The vector helium magnetometer noise spectrum is independent of frequency (white) with a field equivalent power spectral density of 10**-4 GAMMA**2/HZ. For signal bandwidths less than 1 Hz, corresponding for example to values averaged over a few seconds or more, fields smaller than 0.01 GAMMA can be detected. The maximum relative error of the magnetometer sensors is given by dB/B <= dB0/B + dk/k where B0 is the total offset error and dk is the scale factor error. The scale factor accuracy is as good as 1%. And the total offset error is mainly caused by the spin axis sensor error because it is not readily determined as the two in spin-plane sensors. The ratio of the standard deviation of the offset in spinning axis to the field magnitude is about 0.05. Thus, the maximum relative error in the magnetic field measurement is 0.06. There is no flagged values in this data set.
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| CITATION_DESCRIPTION |
, P11 HVM 1 MINUTE SATURN ENCOUNTER DATA, P11-S-HVM-4-SUMM-NEAR-ENC-1MIN-V1.0, NASA Planetary Data System,
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| ABSTRACT_TEXT |
Pioneer 11 Vector Helium Magnetometer (HVM) data from the Saturn encounterperiod between 1979-08-30T00:00:00.000 and 1979-09-08T23:59:00.000. Thedata set provides 1.0 minute averages of 3 magnetic field components, 6field covariances, 3 directional cosines, field magnitude and the fieldmagnitude square, in PE coordinates.
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| PRODUCER_FULL_NAME |
Edward J. Smith
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| SEARCH/ACCESS DATA |
Planetary Plasma Interactions Website
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