Instrument Overview
    ===================
      The Interplanetary Magnetic-Field Experiment is
      designed to study macroscopic and microscopic
      structures in the helio-magnetosphere and in the
      cometary magnetosphere, as well as large-amplitude
      low-frequency hydromagnetic waves in the solar
      wind.  The data gathered will be compared with the
      configuration, brightness and variations of
      Halley's corona, which will be imaged by the UV
      camera on Planet-A.  The IMF is to be measured by a
      triaxial, ring-core, fluxgate magnetometer sensor
      mounted on a 2 m-long boom.  This boom was extended
      soon after injection of the spacecraft into orbit.
 
      From a block diagram of the IMF instrument, the
      dynamic ranges of which are +/- 64 nT and +/- 128
      nT.  The table below summarizes the instrument's
      sensitivity, resolution, bit rate, and sampling
      rate.  The dynamic range and conversion output will
      be selected by ground command.
 
      During the initial period of the mission, when the
      telemetry signals are strong enough, the
      high-bit-rate data will be used for the study of
      the ULF hydromagnetic waves.  The low-bit-rate data
      will be used while the spacecraft is closer to
      Comet Halley to study the macroscopic structure of
      the helio-magnetosphere and the cometary
      magnetosphere.
 
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Table. Characteristics of the Interplanetary Magnetic-Field Instrument
 
            Sensitivity                                Sampling rate (s)
 
Dynamic                      Resolution  Telemetry bit           Format-3
range (nT)  Output (bit)     (nT/LSB)    rate (bit/s)  Format-1     & 4
-----------------------------------------------------------------------
                                         h.b.r.        1/8       1/16
+/-  64     12 (high gain)  0.03125      l.b.r.        4         2
(Narrow)    8 (low gain)    0.5          h.b.r.        1/16      1/32
                                         l.b.r.        2         1
-----------------------------------------------------------------------
                                         h.b.r.        1/8       1/16
+/-  128    12 (high gain)  0.0625       l.b.r.        4         2
(wide)       8 (low gain)   1.0          h.b.r.        1/16      1/32
                                         l.b.r.        2         1
-----------------------------------------------------------------------
h.b.r. =  high bit rate (2048 bit/s)   l.b.r.  =  low bit rate (64 bit/s)