| DATA_SET_DESCRIPTION |
Data
====
HET data record format
----------------------
Column 1: Date/time in format yyyy-mm-ddThh:mm:ss.sssZ
Column 2: Accumulation time (second) for H1-H9
Column 3: H1 counting rate (c/s)
Column 4: H2 counting rate (c/s)
Column 5: H3 counting rate (c/s)
Column 6: H4 counting rate (c/s)
Column 7: H5 counting rate (c/s)
Column 8: H6 counting rate (c/s)
Column 9: H7 counting rate (c/s)
Column 10: H8 counting rate (c/s)
Column 11: H9 counting rate (c/s)
[please note that time-stamp and record format have been
changed by the PDS/PPI Node for the sake of consistency with
other data sets found on this volume]
A caveat is that during most of the Jupiter flyby, the counting
rate logic was swamped by the extremely high intensity of
electrons contained in the magnetosphere. As a result, we
believe that the most reliable interpretation of the counting
rates is that they become effectively measures of the integral
intensity above the minimum energy required for an electron to
penetrate to the most deeply buried detector required by the
counting rate logic. For example, the H4 counting rate, which
is nominally defined by the coincidence D1 D2 D4 K1 N[K4 A S
(H)] becomes the integral intensity of all electrons with
sufficient energy to reach K1, which, by the table below, based
on the Berger and Seltzer tables and the thicknesses of the
D1-D6 detectors, is ~2.7 MeV.
The minimum electron energies required to trigger the counting
rates, based simply on energy required to penetrate to the
deepest detector and trigger its discriminator are as follows.
For detectors beyond the midpoint of the telescope, we have
assumed that there is sufficient material (instrument and
spacecraft) behind the telescope that the easiest access to
the detector is still through the front of the telescope. This
may not be a good assumption.
H1 ~0.5 MeV
H2 ~2.6 MeV (higher level discriminators on D1 and D2
H3 ~1.5 MeV required)
H4 ~2.7 MeV
H5 ~8.9 MeV
H6 ~1.2 MeV
H7 ~2.7 MeV
H8 ~1.5 MeV
H9 ~16 MeV
The detailed coincidence logic defining these counting rates
is given in [SIMPSONETAL1992A]. As indicated by the ~, these
energies are very approximate. Our assumption is that
essentially all the counting rates, even those such as H2
designed to discriminate against electrons, were dominated by
electrons inside the magnetosphere.
One additional word of explanation is required. In an
ill-advised attempt to configure the HET to a mode to minimize
the effects of the expected high counting rates on our slow
logic, from approximately 1206 UT day 32 until approximately
0018 UT day 34, the HET S detector High Voltage was turned off,
effectively turning off S, and the D1 detector was replaced by
D3 in the counting rate logic. (Commands C1 and C9 as
described in Table 8 of [SIMPSONETAL1992A].) The intent was to
remove from the logic those detectors expected to be in near-
saturation throughout the flyby, and thus to make the counting
rates more interpretable. The change was effected before
crossing the bowshock and magnetopause in order to establish a
base-line in the new configuration prior to encountering the
expected high fluxes in the magnetosphere. The actual effect
turned out to be to increase the background in most of the
counting rates to such a high level that features such as up-
stream particles escaping from the magnetosphere were
completely obscured. After about a day and a half in this
mode, it was decided to return to normal mode, and we remained
in normal mode for the remainder of the flyby.
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