Magnetic Field Investigation (MFI) on WIND

The main purpose of the Wind spacecraft is to measure the incoming
solar wind, magnetic fields and particles, although early on it will
also observe the Earth's foreshock region. Wind, together with
Geotail, Polar, SOHO, and Cluster projects, constitute a cooperative
scientific satellite project designated the International Solar
Terrestrial Physics (ISTP) program which aims at gaining improved
understanding of the physics of solar terrestrial relations.

The magnetic field experiment on WIND provides data for studies of a
broad range of scales of structures and fluctuation characteristics of
the interplanetary magnetic field throughout the mission, and, where
appropriate, relate them to the statics and dynamics of the
magnetosphere. The basic instrument of the Magnetic Field
Investigation (MFI) on the WIND Spacecraft is a boom-mounted dual
triaxial fluxgate magnetometer and associated electronics. The dual
configuration provides redundancy and also permits accurate removal of
the dipolar portion of the spacecraft magnetic field. The instrument
provides:

(1) near real-time data at nominally one vector per 92 s as key
parameter data for broad dissemination,
(2) rapid data at 10.9 vectors/s for standard analysis,
(3) occasionally, snapshot (SS) memory data and Fast Fourier Transform
data (FFT), both based on 44 vectors/s.

These measurements are precise (0.025%), accurate, ultra-sensitive
(0.008 nT/step quantization), and where the sensor noise level is <
0.006 nT r.m.s for 0-10 Hz. The digital processing unit utilizes a
12-bit microprocessor controlled analogue-to-digital converter. The
instrument features a very wide dynamic range of measurement
capability, from 4 nT up to 65 536 nT per axis in eight discrete
ranges. (The upper range permits complete testing in the Earth's
field.) In the FFT mode power spectral density elements are
transmitted to the ground as fast as once every 23 s (high rate), and
2.7 min of SS memory time series data, triggered automatically by
pre-set command, requires typically about 5.1 hours for
transmission. Standard data products are the following vector field
averages: 0.0226-s (detail data from SS), 0.092 s ('detail' in
standard mode), 3 s, 1 min, and 1 hour, in both GSE and GSM
coordinates, as well as the FFT spectral elements.