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Instrument: FGM : CLUSTER-II Fluxgate Monitor |
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Associated Platforms CLUSTER-II Related Data Sets View all records related to this instrument Description The fluxgate magnetometers on Cluster-II are similar to many previous instruments flown in Earth-orbit and on other, planetary and interplanetary missions. In order to minimise the magnetic background of the spacecraft, one of the magnetometer sensors (the outboard, or OB sensor) is located at the end of one of the two 5.1 m radial booms of the spacecraft, the other (the inboard, or IB sensor) at 1.5 m inboard from the end of the boom. In flight, either sensor can be designated as the Primary Sensor, for acquiring the main data stream of magnetic-field vectors. Selection of the sensors as Primary or Secondary is made by ground command; in the default configuration, the OB sensor is used as the Primary Sensor. Data can also be acquired simultaneously from the other, Secondary Sensor, albeit at a lower rate. The magnetometers have eight possible operating ranges; of these, five are used on the Cluster magnetometers. These ranges were selected to provide good resolution in the solar wind (with expected field magnitudes between 3 and 30 nT), and up to the highest field values expected in the magnetosphere along the Cluster orbit (up to about 1,000 nT). The highest range (* 65,500 nT) is used only to facilitate background testing. Range selection can be automatic (controlled by the instrument DPU) or commanded from the ground. When in the automatic mode, a range selection algorithm running in the DPU continuously monitors each component of the measured field vector. If any component exceeds a fraction (set at 90 %) of the range, an up-range command is generated and transmitted to the magnetometer. If all three components are smaller than 10 % of the range for more than a complete spin period (in fact for more than the telemetry frame period of 5.15222 s), an automatic down-range command is generated to the magnetometer. The instrument uses two 16-bit Analogue-to-Digital Converters (ADC), normally in cold redundancy. The most significant 14 bits of the converted field-component values are used for generating the output of the instrument. The digital resolution, corresponding to the five ranges of the magnetometers. See: http://www.sp.ph.ic.ac.uk/Cluster/ Online Resources http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=33024&fbodylongid=1104 http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=2000-041B&ex=4 http://www3.imperial.ac.uk/spat/research/space_magnetometer_laboratory/spacemissionpages/clusterhomepage/clustermagnetometerinstrument/ Instrument Logistics Instrument Start Date: 2007-07-16 Instrument Owner: NASA/GSFC Space & Atmospheric Physics Group Imperial College, London Institut fur Weltraumforschung, Austrian Academy of Sciences, Austria Institute for Geophysics and Extraterrestrial Physics, Technical University, Germany |
