urn:nasa:pds:context:instrument:instrument.pls__vg2
1.0
PLASMA SCIENCE EXPERIMENT for VG2
1.5.0.0
Product_Context
2012-05-21
1.0
extracted metadata from PDS3 catalog and
modified to comply with PDS4 Information Model
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reference.BARNETT-OLBERT1986
Barnett, A., and S. Olbert, Response Function of Modulated Grid Faraday
Cup Plasma Instruments, Rev. Sci. Instr., Vol. 57, p. 2432, 1986.
reference.BRIDGEETAL1977
Bridge, H.S., J.W. Belcher, R.J. Butler, A.J. Lazarus, A.M. Mavretic, J.D.
Sullivan, G.L. Siscoe, and V.M. Vasyliunas, The Plasma Experiment on the
1977 Voyager Mission, Space Sci. Rev., Vol. 21, p. 259, 1977.
reference.BRIDGEETAL1979B
Bridge, H.S., J.W. Belcher, A.J. Lazarus, J.D. Sullivan, F. Bagenal, R.L.
McNutt, K.W. Ogilvie, J.D. Scudder, E.C. Sittler, V.M. Vasyliunas, and
C.K. Goertz, Plasma Observations Near Jupiter: Initial Results from
Voyager 2, Science, Vol. 206, p. 972, 1979.
reference.SCUDDERETAL1981
Scudder, J.D., E.C. Sittler, and H.S. Bridge, Survey of the Plasma
Electron Environment of Jupiter: A View from Voyager, J. Geophys. Res.,
Vol. 86, p. 8157, 1981.
reference.SITTLER1983
Sittler, E.C., Jr., Plasma Electron Analysis: Voyager Plasma Science
Experiment, NASA Tech. Mem. 85037, 1983.
PLASMA SCIENCE EXPERIMENT
Plasma Analyzer
not applicable
not applicable
INSTRUMENT: PLASMA SCIENCE EXPERIMENT
SPACECRAFT: VOYAGER 2
Instrument Information
======================
Instrument Id : PLS
Instrument Host Id : VG2
Principal Investigator : JOHN W. BELCHER
Pi Pds User Id : JBELCHER
Instrument Name : PLASMA SCIENCE EXPERIMENT
Instrument Type : PLASMA INSTRUMENT
Build Date : 1973-01-01
Instrument Mass : 9.900000
Instrument Length : UNK
Instrument Width : UNK
Instrument Height : UNK
Instrument Serial Number : SN001
Instrument Manufacturer Name : MASSACHUSETTS INSTITUTE OF
TECHNOLOGY
Instrument Description
======================
The Voyager Plasma Science experiment consists of four
modulated grid Faraday Cups, three (A,B,C) of which are
positioned about the Telemetry Antenna Axis and generally
point toward the Earth with the fourth (D) at a right angle to
this direction. Ion currents are sampled simultaneously in
all four cups, electrons in the D-cup only. The instrument
has an energy/charge range of 10-5950 V. Data is taken in
four ways, high and low resolution ion modes and high and low
energy electron modes, with energy resolution varying between
3.6 and 29%. The integration time for each energy channel can
be varied are used at Jupiter and Saturn and 0.93 and 0.21
second integration times are used at Uranus and Neptune.
Supersonic flow can be observed only when one of the detectors
points into the flow orientation allows determination of the
plasma density, temperature, and velocity.
Science Objectives
==================
The objective of the Plasma Instrument is to characterize
plasma conditions throughout the Voyager trajectory, in the
solar wind and during the planetary encounters.
Operational Considerations
==========================
Each detector has an effective field of view which is a cone of
half angle 45 degrees falls off quickly at higher angles.
Thus, for the instrument to measure ion parameters in a
Supersonic or Transonic plasma some of the detectors must look
into the plasma flow. Secondary ions and electrons produced
within the detectors can also effect the measurements,
especially if large fluxes of hot ions or electrons are present
and these effects are not well modeled. The instrument does
not measure composition, only energy/charge, so a model of
plasma composition must be adopted to fit the ion data choice
of models can be unambiguous for large Mach number flow (M>3)
but is non-unique for lower Mach numbers. After the Jupiter
encounter the highest channels of the A, B, and C detectors
often contain spurious signal and currents in the upper half of
the energy range should be examined carefully before use.
Calibration Description
=======================
The instrument was calibrated at MIT using ion and electron
beams and compared to output from other Faraday cups in the
same beam. Current levels are also calibrated in-flight by
injecting known currents into the detectors with the modulators
on and off. Much theoretical modeling has been done on the
response of the detectors to arbitrary plasma conditions.
Contact the PI for more information.
PLS Detectors 'A', 'B', 'C', and 'D'
====================================
Detector Type : FARADAY CUP
Detector Aspect Ratio : 0.000000
Nominal Operating Temperature : 278.000000
The PLS instrument consists of four Faraday cups. Three of
these (A, B, C) are arranged in a cone whose central axis is
parallel to the direction of the telemetry antenna. The look
direction of each of these cups is offset 20 degrees from the
central axis. Detector D has a look direction approximately
perpendicular to the direction of the telemetry antenna. Each
detector consists of three modulator grids, six shield grids
and a suppressor grid in front of the collector. It measures
ion currents in the range 10-5950 V.
Depending on the integration time the detectors measure current
from a minimum of 3.e-14 to 2.e-13 AMPS up to a maximum of
6.e-8 AMPS. Sampling varies from .03 to .93 seconds.
'PLS' Section Parameter 'ELECTRON CURRENT'
------------------------------------------
Sampling Parameter Name : TIME
Section Id : PLS
Instrument Parameter Unit : AMPS
Minimum Instrument Parameter : 0.000000
Maximum Instrument Parameter : 0.000000
Minimum Sampling Parameter : 0.030000
Maximum Sampling Parameter : 0.930000
Sampling Parameter Unit : SECOND
'PLS' Section Parameter 'ION CURRENT'
-------------------------------------
Sampling Parameter Name : TIME
Section Id : PLS
Instrument Parameter Unit : AMPS
Minimum Instrument Parameter : 0.000000
Maximum Instrument Parameter : 0.000000
Minimum Sampling Parameter : 0.030000
Maximum Sampling Parameter : 0.930000
Sampling Parameter Unit : SECOND
Electronics
===========
Currents from the four detectors are amplified, filtered, and
integrated using four different measurement chains. A single
8-bit logarithmic A-D converter samples the four outputs of the
measurement chains and transfers the data to the spacecraft.
The high voltage modulator supplies a DC pedestal and a super-
imposed 400 HZ square wave modulation voltage. For positive
ions the modulator grids of all four detectors are driven in
parallel. A more complete description and block diagram of the
instrument electronics is available in [BRIDGEETAL1977].
Operating Modes
===============
The eight operating modes of Voyager PLS are listed below.
Instrument power consumption is 8.100000 for all modes.
E1-LONG: Low energy electron mode which measures the range
10-140 V with 16 contiguous channels. The
integration time for each channel is 0.93 sec.
E1-SHORT: Low energy electron mode which measures the range
10-140 V with 16 contiguous channels. The
integration time for each channel is 0.21 sec.
E2-LONG: High energy electron mode which measures the range
10-5950 V with 16 contiguous channels. The
integration time for each channel is 0.93 sec.
E2-SHORT: High energy electron mode which measures the range
10-5950 V with 16 contiguous channels. The
integration time for each channel is 0.21 sec.
L-LONG: Low resolution ion mode which measures the range
10-5950 V with 16 contiguous channels. The
integration time for each channel is 0.93 sec.
L-SHORT: Low resolution ion mode which measures the range
10-5950 V with 16 contiguous channels. The
integration time for each channel is 0.21 sec.
M-LONG: High resolution ion mode which measures the range
10-5950 V with 128 contiguous channels. The
integration time for each channel is 0.93 sec.
M-SHORT: High resolution ion mode which measures the range
10-5950 V with 128 contiguous channels. The
integration time for each channel is 0.21 sec.
Instrument Mounting
===================
The PLS instrument is located on the Science Boom. The center
of the main detector cluster (A, B, C) points parallel to the
spacecraft telemetry antenna and detector D is at right angles
to this direction.