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NASA Space Science Data Coordinated Archive Header



Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1992-11-03 to 1992-12-19


This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= This dataset contains data acquired by the Galileo Magnetometer from the Earth 2 encounter. The data are at the full instrument resolution for the 7.68 kB Low Rate Science (LRS) real time telemetry mode. The data are provided in three coordinate systems: despun spacecraft or inertial rotor coordinates (IRC), Geocentric Solar Ecliptic (GSE) and Geocentric Solar Magnetic (GSM). The IRC coordinate data files also include many of the data processing parameters from the AACS system as well as the sensor zero levels. These data have been fully processed to remove instrument response function characteristics and interference from magnetic sources aboard the spacecraft. The data are provided in physical units (nanoTesla). Processing ========== These data have been processed from the PDS dataset: 'GO-E/V/A-MAG-2-RDR-RAWDATA-HIRES-V1.0' The 'raw data' product was created from the EDR dataset by removing the data processing done by the instrument in space. The raw data dataset contains the raw instrument samples which have been recursively filtered and decimated. In order to generate the IRC processed data, the following procedure was followed: 1) Sensor zero level corrections were subtracted from the raw data, 2) Data were converted to nanoTesla, 3) A coupling matrix which orthogonalizes the data and corrects for gains was applied to the data (calibration applied), 4) Magnetic sources associated with the spacecraft were subtracted from the data, 5) Data were 'despun' into inertial rotor coordinates, For a more detailed description of these proceedures please refer to the file /CALIB/HR_PROC.TXT. For more information regarding data calibration please refer to [KEPKOETAL1996]. Parameters ========== Data Sampling: The Galileo magnetometer samples the magnetic field 30 times per second. These highest rate samples are recursively filtered and then resampled by the instrument at 4.5 vectors per second using a 7,7,6 decimation pattern. Recursive Filter: B(t) = 1/4 Bs(t) + 3/4 B(t-1) B = output field Bs = input field measured by the sensor t = sample time The pattern is generated by doubling the spacecraft clock modulo 10 counter and then applying the decimation scheme. This gives 3 vectors every spacecraft minor frame (about 2/3 second) which are sampled unevenly. The first vector in a minor frame is sampled approximately 0.200 seconds after the last vector in the preceding minor frame. The other two samples are taken approximately 0.233 seconds apart. The time tag associated with a sample is the decimation time. Data Acquisition: The data for this dataset were acquired as part of the normal instrument calibration activities associated with the cruise to Jupiter. As such, the instrument was commonly configured in modes which required calibration even though they may not have been the optimal mode for science data acquisition. The Galileo magnetometer has 8 possible LRS acquisition configurations (modes). There are two sensor triads mounted 7 and 11 meters from the rotor spin axis (inboard and outboard) along the boom. Each of the sensor triads has two gain states (high and low). In addition, the sensor triads can be 'flipped' to move the spacecraft spin-axis aligned sensor into the spin plane and visa versa. Please see the instrument description (/CATALOG/MAGINST.CAT) for full details on the instrument, sensors, and geometries. The combinations of sensor, gain state, and flip direction form modes. -----------------------------------------------------------------Table 1. Mode Characteristics -----------------------------------------------------------------Mode Name Acronym range quantization -----------------------------------------------------------------Inboard, left, high range* ILHR +/- 16384 nT 8.0 nT Inboard, right, high range* IRHR +/- 16384 nT 8.0 nT Inboard, left, low range* ILLR +/- 512 nT 0.25 nT Inboard, right, low range* IRLR +/- 512 nT 0.25 nT Outboard, left, high range* ULHR +/- 512 nT 0.25 nT Outboard, right, high range* URHR +/- 512 nT 0.25 nT Outboard, left, low range* ULLR +/- 32 nT 0.008 nT Outboard, right, low range* URLR +/- 32 nT 0.008 nT -----------------------------------------Table 2. Mode Change History -----------------------------------------s/c clock date/time mode -----------------------------------------00562976:00:0 90-305/16:31 ULHR 00572976:00:0 90-316/17:00 ULLR 00578673:00:0 90-320/17:00 URLR 00586204:00:0 90-325/23:55 URHR 00592915:00:0 90-330/17:01 ILLR 00597439:00:0 90-333/21:15 IRLR 00610156:00:0 90-342/19:33 IRHR 00610509:00:0 90-343/01:30 IRLR 00615701:00:0 90-346/17:00 URLR 00618550:00:0 90-348/17:00 URHR 00624261:00:0 90-352/17:15 ULHR * range is the opposite of gain In addition to exercising the various instrument modes during the first earth encounter, numerous instrument calibration activities were performed. These include using both the internal and external calibration coils. Data corrupted by the use of the calibration coils or by the flipper motor have been removed from the processed data. These data have been archived with the Experimenter Data Records (EDR) and other Magnetometer team raw data archive products. Data ==== The data are provided in three (3) coordinate systems (IRC, GSE, and GSM). Data from the two geophysical coordinate systems are stored in a single file. The IRC data are stored in a separate file, and include some of the AACS and sensor offset parameters which were used in processing the data. The structure and contents of the data files are described below. The coordinate systems are described later in this document in the section entitled 'Coordinate Systems.' Data file structures: -----------------------------------------------------------------Table 3. Data record structure, IRC Coordinates Data Files -----------------------------------------------------------------Column Type Description <units> -----------------------------------------------------------------time char Spacecraft event time, PDS time format sclk char Spacecraft clock (rim:mod91:mod10:mod8) Bx_sc float B-field X component in S/C (IRC) coordinates <nT> By_sc float B-field Y component in S/C (IRC) coordinates <nT> Bz_sc float B-field Z component in S/C (IRC) coordinates <nT> Bmag float |B| Magnitude of B <nT> o1 float Offset subtracted from sensor1 o2 float Offset subtracted from sensor2 o3 float Offset subtracted from sensor3 rotattd float Rotor attitude declination (EME-50) rotattr float Rotor attitude right ascension (EME-50) rotattt float Rotor twist angle (EME-50) spinangl float Rotor spin angle - inertial S/C coordinates spindelt float Rotor spin motion delta <radians/minor frame> screlclk float Rotor-Platform relative clock angle screlcon float Rotor-Platform relative cone angle dqf float Data quality flag (see 'CONFIDENCE_LEVEL_NOTE' for more details) -----------------------------------------------------------------Table 4. Data record structure, GSE/GSM Coordinates Data Files -----------------------------------------------------------------Column Type Description <units> -----------------------------------------------------------------time char Spacecraft event time, PDS time format Bx float B-field X component in GSE or GSM coords. <nT> By_gse float B-field Y component in GSE coordinates <nT> Bz_gse float B-field Z component in GSE coordinates <nT> By_gsm float B-field Y component in GSM coordinates <nT> Bz_gsm float B-field Z component in GSM coordinates <nT> Bmag float |B| Magnitude of B <nT> Ancillary Data ============== Trajectory data for GSE and GSM coordinates are provided separately as part of the GO-E-POS-4-SUMM-E2-GSE/GSM-COORDS-V1.0 data set. Coordinate Systems ================== The data are provided in three coordinate systems. Data are provided in the spacecraft coordinate system in order to aid in the interpretation of particle instrument data. The other two coordinate systems provided for use in Earth magnetospheric studies. The IRC coordinate system takes the basic rotor coordinate system (Y along the boom, Z opposing the high gain antenna) which is spinning, and despins by using the rotor spin angle. In this system, Z still points roughly away from the Earth (with about +/- 10 degree accuracy) along the rotor spin axis, X is approximately parallel to the downward ecliptic normal, and Y completes the right-handed set. Geocentric Solar Ecliptic (GSE) and Geocentric Solar Magnetic (GSM) are related earth centered coordinate systems. Both the GSE and GSM X directions are taken along the Earth - Sun line, positive towards the Sun. The GSE Z direction is parallel to the ecliptic normal, positive northward, and Y completes the right-handed set (towards dusk). For GSM, the X-Z plane contains the Earth's dipole moment vector, positive northward, and Y completes the right-handed set. GSE coordinates are commonly used for analyzing the solar wind near the Earth and GSM coordinates are used when analyzing data inside the Earth's bow shock.

These data are available on-line from the Planetary Data System (PDS) at:

Alternate Names



  • Planetary Science: Fields and Particles

Additional Information



Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II



NameRoleOriginal AffiliationE-mail
Dr. Margaret Galland KivelsonData ProviderUniversity of California, Los
Dr. Margaret Galland KivelsonGeneral ContactUniversity of California, Los
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