| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This dataset contains results from the Implanted Ion
Sensor (IIS) 4DH mode and the Fast Ion Sensor SW and
HAR modes of the Three- Dimensional Particle Analyzer
(JPA) experiment on the GIOTTO spacecraft for the
mission to comet Halley. The results of the Fast Ion
Sensor (FIS - inbound) and IIS (outbound) have been
merged with results from other Giotto instruments.
In the first submitted table, magnetometer
measurements are included. Values are given for
protons.
JPA FIS data are from two sources:
- up to March 13, 19:24:55 SCET, data are from the
solar wind mode at 8 seconds time resolution. The
moments are derived from data in a 45 x 45 degree
field of view, centered on the nominal solar wind
direction. There is continuous coverage in energy
and angle. The peak remains within this reduced
field of view.
- March 13, 19:24:55 to 22:38:17 SCET, data are from
the HAR mode at 24 second time resolution. This mode
has an angular field of view accepting ions from all
directions except a 20 deg cone in the ram direction.
Energy-angle coverage is not contiguous in this mode
so an assumption is made to boost the counts in each
bin to make the distribution appear contiguous. The
peak of the solar wind flux alternates between the
last two 26 deg bins during this period. Moments are
calculated for the regions of space sampled by the
detector, i.e. up to the 20 deg ram cone, with no
assumption to increase the range beyond this.
The following assumptions hold: FIS is an
electrostatic analyzer and so cannot distinguish mass
- except in the solar wind mode where the protons and
alpha particles are cold enough that they separate in
energy/charge; in HAR mode the moment is over the
full FIS energy range so includes anything (all
protons).
The temperature profile from solar winds to HAR mode
is not continuous due to the different bin sizes
involved, so the sudden temperature jump at 19:24:55
should not be take to be correct.
JPA IIS data is from the 4DH mode. In this mode,
the Time of Flight measurement is combined with the
energy level information provided by the IIS to
separate mass groups, e.g., 0-1.7 amu/q (presumably
protons). The moments are derived from data
collected during one spacecraft spin, i.e., 128 s, at
each of 32 energy levels to obtain a complete
distribution. Pickup protons are included in the
numbers but this is only a small effect.
The 'JPAMERGE' file includes both FIS and IIS data.
The JPA data up to 22:38:17 are from FIS given every
8 s. (At this time the sampling changes to every 64
s; only magnetometer values are listed in this
interval.) The JPA data starts again at approx 0104
on March 14 (MJD 13221 or day 73), and is from the
IIS 4DH mode. This data has a time resolution of 128
seconds - in the merge file it is combined with 64s
magnetometer data, which is why there are two MAG
points for every JPA data repeated twice here. (The
last 16 lines are again only magnetometer values.)
In the second table, the results from the FIS have
been merged with data from the magnetometer, the
RPA-Copernic plasma experiment, and the Ion Mass
Spectrometer (IMS) HERS instrument to form this file.
The original file was called GIOMERGE and its
explanation follows below:
The file contains data for the period between March
12, 06:09:30 to March 13, 23:36:34 SCET for the MAG,
RPA and IMS/HERS experiments and the JPA experiment,
which ended earlier (at approximately 22:38 SCET).
MAG 8s averaged data
RPA 8s averaged data
JPA 8s data up to March 13, 19:24:55, 24s after this
time
IMS/HERS 16s proton samples after March 13, 18:30:00
64s averaged alpha data
MAG and RPA data are available for all of the above
given intervals.
JPA FIS data are from two sources:
- up to March 13, 19:24:55 SCET, data are from the
solar wind mode at 8 seconds time resolution. The
moments are derived from data in a 45 x 45 degree
field of view, centered on the nominal solar wind
direction. There is continuous coverage in energy
and angle. The peak remains within this reduced
field of view.
- March 13, 19:24:55 to 22:38:17 SCET, data are from
the HAR mode at 24 second time resolution. This mode
has an angular field of view accepting ions from all
directions except a 20 deg cone in the ram direction.
Energy-angle coverage is not contiguous in this mode
so an assumption is made to boost the counts in each
bin to make the distribution appear contiguous. The
peak of the solar wind flux alternates between the
last two 26 deg bins during this period. Moments are
calculated for the regions of space sampled by the
detector, i.e. up to the 20 deg ram cone, with no
assumption to increase the range beyond this.
The temperature profile from solar winds to HAR mode
is not continuous due to the different bin sizes
involved, so the sudden temperature jump at 19:24:55
should not be taken to be correct.
IMS proton and alpha data have been processed
differently:
- Proton data were obtained during ~1 s intervals
every 16 s. Since the measurement intervals happened
to fall approximately midway between the 8 s times at
which the other data in this file are given, each
proton parameter is given twice -- ~4 s before the
measurement and ~4 s after the measurement was made.
Up until ~1830 on March 13, the solar wind was close
to or slightly beyond the proton field of view of the
HERS so V[z] could not be determined. We recommend
using JPA proton data for this time interval, and so
have not included IMS proton data in the merged file
for this early period.
- Alpha data were also obtained during ~1 s
intervals every 16 s, but the parameters have been
calculated for averages over 4 such measurements;
each value is therefore repeated 8 times in this data
file.
|
| CITATION_DESCRIPTION |
Coates, A., K.H. Glassmeier, H. Reme, M. Neugebauer, E. Grayzeck,
and A.C. Raugh, GIOTTO JOHNSTONE PARTICLE ANALYZER MERGED DATA
V1.0, GIO-C-JPA-4-DDR-HALLEY-MERGE-V1.0, NASA Planetary Data
System, 1992
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