ACE News #2: 10/13/97
First Data from the Magnetometer Instrument (MAG)
The MAG sensor was the first ACE instrument turned on, shortly after launch on 8/25/97.
Shown above is the spin-axis component of the magnetic field as measured by
the MAG Primary sensor on the first day of flight. The value of
a zero magnetic field is ~2000 in raw counts. Values greater
than this are increasingly positive and values less than this are
increasingly negative. MAG activation is at ~3000 seconds
after spacecraft activation. Following automated internal checks,
the instrument autoranges to the appropriate range for the ambient
magnetic field. Two automatic range changes can be clearly seen
at other times in the figure. The MAG boom deployment is evident
as the spacecraft transits the quiet magnetosphere. The MAG boom
deployment reverses the direction of the Z-axis of the sensor,
thereby changing the sign of the measured field. Throughout the
transit of the magnetosphere the magnitude of the magnetic field
decreases while range changes provide increased count rates and
increased sensitivity. The subsequent transit of the turbulent
magnetosheath places the spacecraft in the upstream solar wind
near the end of the first day of flight, at which time it was about
10 Earth radii away (~64000 km). Changes in sign of the
solar wind magnetic field are normal and expected. Preliminary
examination reveals an instrument that is functioning as designed
with the onboard FFT and Snapshot buffers working correctly.
.....contributed by Dr. Charles Smith, Bartol Research Institute, Univ. of Delaware.
Last modified 10 October 1997, mrt
Return to ACE homepage.