PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
OBJECT = INSTRUMENT
INSTRUMENT_HOST_ID = "VG2"
INSTRUMENT_ID = "LECP"
OBJECT = INSTRUMENT_INFORMATION
INSTRUMENT_NAME = "LOW ENERGY CHARGED PARTICLE"
INSTRUMENT_TYPE = "CHARGED PARTICLE ANALYZER"
INSTRUMENT_DESC = "
INSTRUMENT: LOW ENERGY CHARGED PARTICLE
SPACECRAFT: VOYAGER 2
Instrument Information
======================
Instrument Id : LECP
Instrument Host Id : VG2
PI Pds User Id : KRIMIGIS
PI Full Name : STAMITIOS M. KRIMIGIS
Instrument Name : LOW ENERGY CHARGED PARTICLE
Instrument Type : CHARGED PARTICLE ANALYZER
Build Date : 1977-08-20
Instrument Mass : 6.652000
Instrument Length : UNK
Instrument Width : UNK
Instrument Height : UNK
Instrument Serial Number : 01
Instrument Manufacturer Name : JOHNS HOPKINS UNIVERSITY
APPLIED PHYSICS LABORATORY
Instrument Overview
===================
The low energy charged particle experiment employs a set of
many solid state detectors arranged to characterize, with
various levels of energy, directional, and compositional
discriminations, the in-situ charged particle environment of
the spacecraft, both within interplanetary and planetary
magnetospheric regions. Electrons can be characterized, with
various electron rate energy channels, between 22 keV and
greater than 10 meV (mode dependent). Ions, without mass
species discriminations, can be characterized with various ion
rate energy channels between 28 keV and greater than 152 keV
(mode dependent). Rate data is telemetered as simple counts
per accumulation time period. The different channels
correspond to different onboard energy discrimination windows
(for ions the discrimination values are mass species
dependent, leading to some ambiguity). Above about 200
keV/nucleon, the ions can be discriminated as to their mass
species composition by the use of multiple parameter
measurements. These measurements consist of the energies that
individual particles deposit in more than one detector. This
information is telemetered both as ion rate data, obtained by
on-board species identification circuitry (with various
channels representing various energy-species combinations),
and as particle multiple parameters data, consisting of pulse-
height-analysis values from each of the affected particle
detectors for each analyzed particle. (A maximum of about 2 to
5 particles per second can be analyzed in this fashion due to
telemetry limitations. A priority scheme avoids saturation by
one species group. there are three such groups defined: atomic
number z = 1,2 each group in a rotating fashion.) Angular
information is obtained through mechanical rotation of the
detectors. The main detectors look within a single scan plane
that is rotated 360 degrees, stopping at 8 different look
sectors (one of the sectors is blocked to obtain a background
measurement: sector 8). The lower energy detectors have full
width viewcones of about 45 degrees. The scan plane is
oriented such that a line that passes exactly between sectors
8 and 1, and also exactly between sectors 4 and 5, is exactly
parallel to the roll axis of the spacecraft (which nominally
points at earth). When the roll orientation of the spacecraft
is such that the star sensor is locked on canopus, the scan
plane is tilted about 30 degrees out of the ecliptic plane,
with sector 3 tilting towards north ecliptic (and also in the
direction that is retrograde with respect to the planetary
orbits). Sectors 1 and 8 point in the general direction of
earth. The scan rate is variable between 48 seconds to 48
minutes per 360 degree scan. There are some electron detectors
(whose properties are not as well established as the others)
that view out of the scan plane described here (see
[KRIMIGISETAL1977]). Some of the data is subject to
substantial contamination depending on the region under
consideration. Before the data from this instrument can be
used, it is vital that the contamination descriptions be
examined ('CONTAMINATION_ DESC') for each contamination type
('CONTAMINATION_ID') and that the contaminations levels be
determined ('DATA_QUALITY_ID' AND 'DATA_QUALITY_DESC'). While
sector 8 is the background sector for most (and generally the
most used) data channels, sector 4 is the background sector
for some channels. Of those channels documented in this
catalog, sector 4 is the background sector for channels: ESA0,
ESB0, AB10, AB12, AB13, PSA1, PSA2, PSA3, PSB1, PSB2, and PSB3.
Science Objectives
==================
Characterize the energy spectra, angular distributions,
species composition, spatial structures, and temporal
variations of the hot plasmas, energetic particles, and
particulate radiation that exist in the vicinity of the outer
planets (Jupiter, Saturn, Uranus, and Neptune) and within the
interplanetary environment. To study the mechanisms by which
such particles are energized and transported throughout such
systems. To study in particular the energization and transport
processes associated with hot plasmas and particulate
radiation in the vicinity of planetary bow shocks,
magnetopauses, magnetotail plasma sheets, inner radiation
zones, the auroral zones, etc., and to study the interaction
of such media with planetary satellites and the planetary
atmospheres and ionospheres.
Operational Considerations
==========================
Instrument operates continuously sampling data over uniform
accumulation intervals. The accumulation intervals are
different for the different channels of information (almost
100 channels). The scan head of the LECP Instrument usually
scans back-and-forth continuously (forward by 315 degrees and
then back by 315 degrees). The scanning head pauses at 8
different scan sectors for periods ranging between 6 seconds
and 48 seconds (for the encounter time periods) and takes
about 0.5 seconds to scan between the sectors. Specially
scanning modes for Voyager 2 at Uranus and Neptune have been
developed whereby 1 or 2 quick scans are performed followed by
6 to 12 minutes of no scanning. Also, for Voyager 2 at Jupiter
there was an extended period of no scanning. The roll
orientation of the spacecraft is of crucial importance as to
the type of data returned since that orientation determines
the orientation of the scan plane of the LECP Instrument. That
orientation also has safety consequences since a poor
orientation could expose the LECP detectors to ring
particulate damage.
Calibration
===========
The instrument was calibrated on the ground by placing it into
beam chambers (e.g. Van DeGraf machines) and firing calibrated
beams of known composition at it. Also, a radioactive source
is positioned behind the 'sunshield' positioned at sector 8
for in-flight calibration of some detector-electronic gains.
Also, the instrument has a calibration mode whereby pulses of
known strength are sent into the pre-amplifier chains
following the detectors. Information about calibration can be
found in: [KRIMIGSETAL1977], [KRIMIGISETAL1981],
[ARMSTRONGETAL1981], and [HAMILTONETAL1981].
'LECP' Detector
===============
Total Fovs : 8
Data Rate : 600
Scan Mode Id : UNK
Sample Bits : 10
Detector Type : SOLID STATE
Detector Aspect Ratio : 0.000000
Nominal Operating Temperature : 273.000000
The LECP Instrument consists of a variety (about 28) of 'Solid
State Detectors' that are used individually and in
combinations (using coincidence and anti-coincidence
criterion) to detect and characterize nuclear particles. The
detector thicknesses range from 2 to 2450 microns to cover a
very broad range of particle energy and mass characteristic.
Detectors count particles that have appropriate discriminated
characteristics with an efficiency that approaches 1.
Therefore the sensitivity is strictly a function of the
geometric factors of the detectors (geometric factors
associated with different data channels are documented
elsewhere in this catalog) and the energy and species band-
widths of the data channels (also documented elsewhere). The
geometric factors have units of area X Steradians (CM^2 X
STR).
'LECP' Section Parameter 'ELECTRON RATE'
----------------------------------------
Instrument Parameter Name : ELECTRON RATE
Sampling Parameter Name : ENERGY PER NUCLEON
Instrument Parameter Unit : COUNTS/SECOND
Minimum Instrument Parameter : 0.000000
Maximum Instrument Parameter : 0.000000
Minimum Sampling Parameter : 0.022000
Maximum Sampling Parameter : 20.000000
Noise Level : 0.000000
Sampling Parameter Interval : 0.000000
Sampling Parameter Resolution : 0.000000
Sampling Parameter Unit : MEV PER NUCLEON
A measured parameter equaling the number of electrons hitting
a particle detector per specified accumulation interval. The
counted electrons may or may not be discriminated as to their
energies (e.g. greater than E1, or between E1 and E2).
'LECP' Section Parameter 'ION RATE'
-----------------------------------
Instrument Parameter Name : ION RATE
Sampling Parameter Name : ATOMIC NUMBER
Instrument Parameter Unit : COUNTS/SECOND
Minimum Instrument Parameter : 0.000000
Maximum Instrument Parameter : 0.000000
Minimum Sampling Parameter : 1.000000
Maximum Sampling Parameter : 26.000000
Noise Level : 0.000000
Sampling Parameter Interval : 0.000000
Sampling Parameter Resolution : 0.000000
Sampling Parameter Unit : ATOMIC NUMBER
A measured parameter equaling the number of ions striking a
particle detector per specified accumulation interval. The
counted ions may or may not be discriminated as to their
energies (e.g. energy/nucleon or energy/charge between E1 and
E2 or greater than E1) and/or as to their ion composition
(atomic number Z or mass number greater than Z1 or M1, or
between Z1 and Z2 or M1 and M2).
'LECP' Section Parameter 'PARTICLE MULTIPLE PARAMETERS'
-------------------------------------------------------
Instrument Parameter Name : PARTICLE MULTIPLE PARAMETERS
Sampling Parameter Name : ATOMIC NUMBER
Instrument Parameter Unit : MEV X MEV
Minimum Instrument Parameter : 0.000000
Maximum Instrument Parameter : 0.000000
Minimum Sampling Parameter : 1.000000
Maximum Sampling Parameter : 26.000000
Noise Level : 0.000000
Sampling Parameter Interval : 0.000000
Sampling Parameter Resolution : 0.000000
Sampling Parameter Unit : ATOMIC NUMBER
A set of measured parameters which yield multiple pieces of
information about each particle (generally ions) that Q enters
the system. These pieces of information can, for example,
consist of the energy deposited by a single particle in two or
more separate detectors, or the time-of-flight between two
different detectors plus the energy deposited in a third, etc..
The multiple pieces of information can be used to perform mass,
atomic number, and/or charge state discriminations on ions. The
information can be discriminated on-board and telemetered in
the form of ion rate channels, or the multiple information
about each particle analyzed can be telemetered for obtaining
the finest species discriminations.
(the following table is excerpted from: [MAUKETAL1991])
TABLE 1. Voyager 2 LECP Channel Characteristics
----------------------------------------------------------
Effective
Field
of Energy
Channel Species, View, Passband,* [epsilon]G,
Designation Z deg MeV/nucleon cm^2 sr
----------------------------------------------------------
Ion/Proton Channels
PL01 Z❯=1 45 0.028-0.043 1.13x10^-1
PL02 Z❯=1 45 0.043-0.080 1.13x10^-1
PL03 Z❯=1 45 0.080-0.137 1.13x10^-1
PL04 Z❯=1 45 0.137-0.215 1.13x10^-1
PL05 Z❯=1 45 0.215-0.540 1.13x10^-1
PL06 Z❯=1 45 0.54-0.99 1.13x10^-1
PL07 Z❯=1 45 0.99-2.14 1.13x10^-1
PL08 Z❯=1 45 2.14-3.5 1.13x10^-1
39 Z❯=2 60 0.035-0.069** 9.7x10^-2
38 Z❯=6 60 0.069-0.20** 9.7x10^-2
32 Z=1 60 0.33-0.61 2.6x10^-3
1 Z=1 60 0.52-1.45 4.4x10^-1
33 Z=2 60 0.23-0.48 9.7x10^-2
Electron Channels
E[beta]01 45 0.022-0.035 6x10^-3
E[beta]02 45 0.035-0.061 6x10^-3
E[beta]03 45 0.061-0.112 6x10^-3
E[beta]04 45 0.112-0.183 3.9x10^-3
E[beta]05 45 0.183-0.5 2x10^-3
E[gamma]06 45 ❯0.252 8.1x10^-3***
E[gamma]07 45 ❯0.480 3.5x10^-3***
E[gamma]08 45 ❯0.853 1.7x10^-4***
E[gamma]09 45 ❯1.20
----------------------------------------------------------
Note: this table shows only a subset (the most commonly
used) of the channels available.
* For Z❯=1 channels, passband is given for protons only.
** Indicates oxygen passband.
*** [epsilon]G for the difference between adjacent integral
channels.
Electronics
===========
Timed accumulations of particle counts satisfying various
analog pulse-height discrimination levels. Timed accumulations
of particle counts satisfying simultaneous analog pulse-height
discriminations for multiple detectors. Pulse-height analog-to-
digital conversions from multiple, simultaneous detectors for
direct telemetry.
'LECP' Detector Operational Modes
=================================
FAR ENCOUNTER
-------------
Data Path Type : UNK
Instrument Power Consumption : 4.725000
Used in the vicinity of planetary encounters. High intensity
detectors turned off (A, B, DELTA, DELTA PRIME). (Affected
channels are documented in detailed level catalog.) Bit Rate
allocated 1/3 for Particle Multiple Parameters (PMP) data, also
called Pulse Height Analysis data, and 2/3 for Rate data
(counts/second). Full composition discrimination capabilities
enabled (in both Rate and PMP forms). Angular scanning is
typically 6.4 minutes per 360 degree scan but is often changed.
Experiment Bit Rate is 600 bits per second. Electrons measured
up to 0.5 MEV. minimum sample time is 0.4 sec.
FAR ENCOUNTER STOW
------------------
Data Path Type : UNK
Instrument Power Consumption : 4.725000
This mode includes the Full Far Encounter Mode configuration
with the exception that the angular scanning is halted so that
the detectors are fixed looking into a non-standard direction.
This direction is such that the detectors peek around a sun
screen (which covers the sector 8 position of the scan plane)
having the effect of protecting the low energy ion and
electron detectors by reducing their geometric factors. For
the one application of this mode the geometric factor was
reduced by a factor of 26 for the low energy ions (Alpha
detector) and by an as yet uncalibrated factor for the
electrons (Beta and Gamma detectors).
NEAR ENCOUNTER
--------------
Data Path Type : UNK
Instrument Power Consumption : 4.525000
Sometimes used at the closest-in positions during a planetary
encounter. The high intensity detectors are turned on (A, B,
DELTA, DELTA PRIME). (Affected channels are documented in the
detailed level catalog.) Particle Multiple Parameter (PMP)
composition discrimination capabilities are turned off
(including the rate channels derived from the multiple para-
meter information). All data appears in rate (counts/second)
form. Angular scanning is typically 6.4 minutes per 360
degrees scan but is often changed. Scanning cyclics driven by
the spacecraft computer are included. Experiment Bit Rate is
600 bits per second. Electrons are measured up to greater than
10 MEV. Minimum sample time is 0.4 sec.
URANUS SCAN CYCLIC
------------------
Data Path Type : UNK
Instrument Power Consumption : 4.725000
Data accumulated as with the Far Encounter Mode. Angular
scanning controlled by spacecraft. Two quick full angular
scans are obtained using 6 second scanning and lasting for 96
seconds total. In between these scan periods the sensors are
held fixed looking in sector 7. The scan periods occur every
12 minutes.
Instrument Mounting
===================
LECP Instrument is mounted on the science boom about half way
between the boom's spacecraft anchor point and imaging scan
platform. The mounting is such that the 360 degree scan plane
of the LECP scanning head (not to be confused with the
scanning of the imaging instruments) is coplanar with the
spacecraft's roll axis. Also, on the Canopus star lock the
LECP scan plane is about 30 degrees rotated away from the
ecliptic plane. A line passing between sectors 1 and 8, and
between sectors 4 and 5, is parallel to the spacecraft roll
axis. Sectors 1 and 8 point in the general direction or earth,
and with the Canopus lock, sector 3 points generally in the
retrograde direction (referring to the direction with respect
to the directions of motion of the orbiting planets) and about
30 degrees north of the ecliptic."
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OBJECT = INSTRUMENT_REFERENCE_INFO
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OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "KHURANAETAL1986"
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OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "KRIMIGIS1981"
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REFERENCE_KEY_ID = "KRIMIGISETAL1977"
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OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "KRIMIGISETAL1981"
END_OBJECT = INSTRUMENT_REFERENCE_INFO
OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "MAUKETAL1990"
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OBJECT = INSTRUMENT_REFERENCE_INFO
REFERENCE_KEY_ID = "MAUKETAL1991"
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END_OBJECT = INSTRUMENT
END
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