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CDAWeb Served Heliophysics Datasets Beginning with 'H'

HEL1_6SEC_NESSMAG: HEL1_6SEC_NESSMAG - Mariani/Ness (University of Rome, CNR/Istituto Fisica Interplanetario, and NASA/GSFC)
HEL2_6SEC_NESSMAG: HEL2_6SEC_NESSMAG - Mariani/Ness (University of Rome, CNR/Istituto Fisica Interplanetario, and NASA/GSFC)
HELIOS1_40SEC_MAG-PLASMA: Merged 40.5 s magnetic field, plasma data, ephemeris - R. Schwenn, F. M. Neubauer (Max Planck Institute for Solar System Research, University of Cologne)
HELIOS1_COHO1HR_MERGED_MAG_PLASMA: Helios-1 merged hourly magnetic field, plasma, proton fluxes, and ephermis data - N. Ness, F. Neubauer, F. Mariani (magnetic field), H. Rosenbauer, R. Schwenn (plasma) and J. Freeman (all affiliated with ESA or NASA)
HELIOS1_E6_1HOUR_PARTICLE_FLUX: hourly averaged fluxes of e, H and He - H. Kunow (University of Kiel)
HELIOS1_E6_KUNOW_1HOUR_PARTICLE-FLUX: Hourly averaged fluxes of e, H and He from Helios-1/E6(Kunow) - H. Kunow (University of Kiel)
HELIOS2_40SEC_MAG-PLASMA: Merged 40.5 s magnetic field, plasma data, ephemeris - R. Schwenn, F. M. Neubauer (Max Planck Institute for Solar System Research, University of Cologne)
HELIOS2_COHO1HR_MERGED_MAG_PLASMA: Helios-2 merged hourly magnetic field, plasma, proton fluxes, and ephermis data - N. Ness, F. Neubauer, F. Mariani (magnetic field), H. Rosenbauer, R. Schwenn (plasma) and J. Freeman (all affiliated with ESA or NASA)
HELIOS2_E6_1HOUR_PARTICLE_FLUX: hourly averaged fluxes of e, H and He - H. Kunow (University of Kiel)
HELIOS2_E6_KUNOW_1HOUR_PARTICLE-FLUX: Hourly averaged fluxes of e, H and He from Helios-1/E6(Kunow) - H. Kunow (University of Kiel)
HK_H0_MAG: Hawkeye Magnetic Field Instrument - J. Van Allen (University of Iowa)
HK_H0_VLF: Hk Electric and Magnetic Field Radio Frequency Spectrum Analyzer High Time Resolution - D. Gurnett (University of Iowa)

HEL1_6SEC_NESSMAG
Description
This dataset contains high resolution interplanetary magnetic field data in
six-second averages as measured by the Helios 1 tri-axial fluxgate magnetometer
experiment. Magnetic field vector components in nanotelsa [nT] are given in
solar-ecliptic (SE) spacecraft-centered coordinates with one file for each day. 
The magnetic field magnitude and standard deviations of the vector components
are also included. 
 
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HEL2_6SEC_NESSMAG
Description
This dataset contains high resolution interplanetary magnetic field data in
six-second averages as measured by the Helios 1 tri-axial fluxgate magnetometer
experiment. Magnetic field vector components in nanotelsa [nT] are given in
solar-ecliptic (SE) spacecraft-centered coordinates with one file for each day. 
The magnetic field magnitude and standard deviations of the vector components
are also included. 
 
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HELIOS1_40SEC_MAG-PLASMA
Description
General information about initial ascii files: This subdirectory contains daily
files of 40.5 sec Helios magnetic field and plasma data described below.  It
also contains a file of software written by Aaron Roberts,
readhelios40s_dat.pro, for creating alfvenicity graphs.       The Helios mission
consisted of two spacecraft launched into the inner heliosphere, both executing
orbits from 0.3 to 1 AU with roughly a six month orbital period.     Magnetic
field data were recorded at high resolution, with plasma data recorded  at
approximately 40.5 s resolution.  These datasets give the highest resolution 
plasma (proton and helium) moments with the corresponding average magnetic field
 for each plasma measurement.  There are results from two plasma sensors, one of
 which gives the vector velocity.         The coverage is best in the early
years and varies considerably for the rest of the mission.  The files
Helios1_stats and Helios2_stats give the year, day of  year, number of points,
and percentage of possible points for the days included  in the sets.  There is
no coverage for many days, with the main reason being that  the spacecraft pass
behind the Sun with respect to the Earth, thus cutting off  communication.      
       
The overall intervals covered are:  
Helios 1:  1974 day 346 to          
           1985 day 247              
Helios 2:  1976 day 017 to    
           1980 day 068       
The present set of files were produced by R. Schwenn and obtained from J.
Luhmann. They have been reformatted by Aaron Roberts to assure spaces between
the variables,  and in the process the HGI longitude and the RTN versions of the
variables were added for convenience.  Also, spacecraft positions were
interpolated to make them  distinct. The fill value for missing data in the
original files was either -1 or 0;  all these have been changed to 0. The other
entries are directly from the original  files.            
R. Schwenn should be acknowledged for plasma data and F. Neubauer for magnetic
field data.  GSFC/SPDF nssdcftp (or successor) should be acknowledged as the
immediate  source of the data.               
* The RTN components were calculated from the SSE XYZ components using R -> -X,
T -> -Y, and N -> Z.  The Cartesian coordinates for B and the angles for V are
the  original variables in the file, and no correction was made in the
conversion to RTN  for the actual spacecraft position.  Since RTN and SSE are
defined relative to the helioequatorial plane and to the ecliptic plane,
respectively, and since these planes are inclined by 7.25 degrees relative to
each other (heliocentric orbits of Earth,  Helios 1 and Helios 2 are virtually
co-planar), this introduces errors of up to 100% * (1 - cos 7.25) = 1% in the
RTN components.  However, the V and B are consistent with each other and can be
compared directly.                 
(text by Aaron Roberts, with edits by Joe King; October, 2008)  
 
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HELIOS1_COHO1HR_MERGED_MAG_PLASMA (spase://VHO/NumericalData/Helios1/MAGandPLS/PT1H)
Description
The HELIOS-1 spacecraft was one of the pair of deep space probes developed by
the Federal Republic of Germany (FRG) in a cooperative program with NASA.  The
purpose of the mission was to make pioneering measurements of the interplanetary
medium from the vicinity of the Earth's orbit to 0.3 AU. (The planet Mercury is
at 0.4 AU.)
Data coverage for selected parameters for this data set is: interplanetary 
magnetic  field (1974-12-14 - 1981-06-14), solar wind plasma (1974-12-12 -
1980-12-31), and spacecraft trajectory coordinates (1974-12-10 - 1981-06-14).
Magnetic field data were provided by Prof. F. Mariani, Istituto di Fisica G.
Marconi, Rome, Italy; Plasma data - by Dr. R. Schwenn, Max-Planck-Institut fur
Aeronomie, Lindau, Germany.
Time Coverage of merged files: December 10, 1974 - June 14, 1981.
Helios-1 data have been reprocessed to ensure a uniformity of content and
coordinate systems relative to data from other deep-space missions:
All spacecraft trajectory data were transformed to a Heliographic Inertial (HGI)
coordinate system.
Magnetic field components were transformed to RTN system.
Trajectory data, interplanetary magnetic field data, and plasma data were merged
into individual hourly records.
Data gaps were filled with dummy numbers for the missing hours or entire days to
make all files of equal length.  The character Ə' is used to fill all fields
for missing data according to their format, e.g. ' 9999.9' for a field with the
FORTRAN format F7.1. Note that format F7.1 below really means (1X,F6.1),etc.
 
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HELIOS1_E6_1HOUR_PARTICLE_FLUX
Description
HELIOS-A and -B spacecrafts were the pair of deep space probes developed by the
Federal Republic of Germany (FRG) in a cooperative program with NASA. The
purpose of the mission was to make pioneering measurments of the interplanetary
medium from the vicinity of the earth"s orbit to 0.3 AU. 
The objective of experiment (E6) was to study high-energy, charged, cosmic-ray
particles of solar, planetary, and galactic origin in interplanetary space.
Protons and alpha particles with eneries >1.3 MeV/nucleon, and electrons >0.3
MeV were measured within interplanetary space over the range from 0.3 to 1.0 AU.
The instrument, a particle telescope with 55-deg field of view, consisted of
five semiconductor detectors, one sapphire Cherenkov counter, and one
scintillation counter, all enclosed by an anticoincidence cylinder. The
telescope was calibrated prior to launch using radioactive sources, particle
acceletors, and ground-level muons. It measured protons and alpha particles in
six channels (1.3-3.3, 3.3-13, 13-27, 27-37, 37-45, and >45 MeV/nucleon) and
electrons in five energy channels (0.3-0.8, 0.8-2, 2-3, 3-4, and >4 MeV). For
more detail see pp.253-257 of Raumfahrtforschung, v.19, n. 5, 1975. 
The h-a-cr*.dat and h-b-cr*.dat files contains hourly averaged fluxes of
electrons, protons and alpha particles in the MeV ranges. The files were written
in ASCII-codes. Each record contains 10 hourly averages. The differential fluxes
(particles/sq.m, s, sr, MeV) cover, in several bands, the energy range 0.3-2.0
MeV for electrons, 4.0-51 MeV for protons, and 2.0-48 MeV for alpha particles. 
Also provided are the integral fluxes of alphas above 48 MeV, and protons above
51 MeV. For some of the energy channels, the standard deviations of the averages
are also provided. Each file is preceded by a header record, providing the start
and stop times of the data in the file. 
The acronyms for the rate channels are composed of a letter and an indication of
the energy range in MeV/nucleon for protons and alpha particles respectively.
MeV for electrons. 
The counting rates are given as particles/m^2  sec sr MeV/N, except for the
integral channels P>51 and A>48 which are given as particles/ m^2 sec sr. 
Note: 1. Negative rates (-0.99999E+04) indicate missing or invalid data. 2. The
energy boundaries for the electron channels E 0.2-0.8 and E 0.8-2are only rough
estimates.
 
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HELIOS1_E6_KUNOW_1HOUR_PARTICLE-FLUX
Description
HELIOS-A and -B spacecrafts were the pair of deep space probes developed by the
Federal Republic of Germany (FRG) in a cooperative program with NASA. The
purpose of the mission was to make pioneering measurments of the interplanetary
medium from the vicinity of the earth"s orbit to 0.3 AU. 
The objective of experiment (E6) was to study high-energy, charged, cosmic-ray
particles of solar, planetary, and galactic origin in interplanetary space.
Protons and alpha particles with eneries >1.3 MeV/nucleon, and electrons >0.3
MeV were measured within interplanetary space over the range from 0.3 to 1.0 AU.
The instrument, a particle telescope with 55-deg field of view, consisted of
five semiconductor detectors, one sapphire Cherenkov counter, and one
scintillation counter, all enclosed by an anticoincidence cylinder. The
telescope was calibrated prior to launch using radioactive sources, particle
acceletors, and ground-level muons. It measured protons and alpha particles in
six channels (1.3-3.3, 3.3-13, 13-27, 27-37, 37-45, and >45 MeV/nucleon) and
electrons in five energy channels (0.3-0.8, 0.8-2, 2-3, 3-4, and >4 MeV). For
more detail see pp.253-257 of Raumfahrtforschung, v.19, n. 5, 1975. 
The h-a-cr*.dat and h-b-cr*.dat files contains hourly averaged fluxes of
electrons, protons and alpha particles in the MeV ranges. The files were written
in ASCII-codes. Each record contains 10 hourly averages. The differential fluxes
(particles/sq.m, s, sr, MeV) cover, in several bands, the energy range 0.3-2.0
MeV for electrons, 4.0-51 MeV for protons, and 2.0-48 MeV for alpha particles. 
Also provided are the integral fluxes of alphas above 48 MeV, and protons above
51 MeV. For some of the energy channels, the standard deviations of the averages
are also provided. Each file is preceded by a header record, providing the start
and stop times of the data in the file. 
The acronyms for the rate channels are composed of a letter and an indication of
the energy range in MeV/nucleon for protons and alpha particles respectively.
MeV for electrons. 
Note: 1. Negative rates (-0.99999E+04) indicate missing or invalid data. 2. The
energy boundaries for the electron channels E 0.2-0.8 and E 0.8-2are only rough
estimates.
 
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HELIOS2_40SEC_MAG-PLASMA
Description
General information about initial ascii files: This subdirectory contains daily
files of 40.5 sec Helios magnetic field and plasma data described below.  It
also contains a file of software written by Aaron Roberts,
readhelios40s_dat.pro, for creating alfvenicity graphs.       The Helios mission
consisted of two spacecraft launched into the inner heliosphere, both executing
orbits from 0.3 to 1 AU with roughly a six month orbital period.     Magnetic
field data were recorded at high resolution, with plasma data recorded  at
approximately 40.5 s resolution.  These datasets give the highest resolution 
plasma (proton and helium) moments with the corresponding average magnetic field
 for each plasma measurement.  There are results from two plasma sensors, one of
 which gives the vector velocity.         The coverage is best in the early
years and varies considerably for the rest of the mission.  The files
Helios1_stats and Helios2_stats give the year, day of  year, number of points,
and percentage of possible points for the days included  in the sets.  There is
no coverage for many days, with the main reason being that  the spacecraft pass
behind the Sun with respect to the Earth, thus cutting off  communication.      
       
The overall intervals covered are:  
Helios 1:  1974 day 346 to          
           1985 day 247              
Helios 2:  1976 day 017 to    
           1980 day 068       
The present set of files were produced by R. Schwenn and obtained from J.
Luhmann. They have been reformatted by Aaron Roberts to assure spaces between
the variables,  and in the process the HGI longitude and the RTN versions of the
variables were added for convenience.  Also, spacecraft positions were
interpolated to make them  distinct. The fill value for missing data in the
original files was either -1 or 0;  all these have been changed to 0. The other
entries are directly from the original  files.            
R. Schwenn should be acknowledged for plasma data and F. Neubauer for magnetic
field data.  GSFC/SPDF nssdcftp (or successor) should be acknowledged as the
immediate  source of the data.               
* The RTN components were calculated from the SSE XYZ components using R -> -X,
T -> -Y, and N -> Z.  The Cartesian coordinates for B and the angles for V are
the  original variables in the file, and no correction was made in the
conversion to RTN  for the actual spacecraft position.  Since RTN and SSE are
defined relative to the helioequatorial plane and to the ecliptic plane,
respectively, and since these planes are inclined by 7.25 degrees relative to
each other (heliocentric orbits of Earth,  Helios 1 and Helios 2 are virtually
co-planar), this introduces errors of up to 100% * (1 - cos 7.25) = 1% in the
RTN components.  However, the V and B are consistent with each other and can be
compared directly.                 
(text by Aaron Roberts, with edits by Joe King; October, 2008)  
 
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HELIOS2_COHO1HR_MERGED_MAG_PLASMA (spase://VHO/NumericalData/Helios2/MAGandPLS/PT1H)
Description
The HELIOS-1 spacecraft was one of the pair of deep space probes developed by
the Federal Republic of Germany (FRG) in a cooperative program with NASA.  The
purpose of the mission was to make pioneering measurements of the interplanetary
medium from the vicinity of the Earth's orbit to 0.3 AU. (The planet Mercury is
at 0.4 AU.)
Data coverage for selected parameters for this data set is: interplanetary 
magnetic  field (1976-01-18 - 1980-03-04), solar wind plasma (1976-01-18 -
1980-03-04), and spacecraft trajectory coordinates (1976-01-18 - 1980-03-04).
Magnetic field data were provided by Prof. F. Mariani, Istituto di Fisica G.
Marconi, Rome, Italy; Plasma data - by Dr. R. Schwenn, Max-Planck-Institut fur
Aeronomie, Lindau, Germany.
Time Coverage of merged files: January 1, 1976 - March 4, 1980.
Helios-2 data have been reprocessed to ensure a uniformity of content and
coordinate systems relative to data from other deep-space missions:
All spacecraft trajectory data were transformed to a Heliographic Inertial (HGI)
coordinate system.
Magnetic field components were transformed to RTN system.
Trajectory data, interplanetary magnetic field data, and plasma data were merged
into individual hourly records.
Data gaps were filled with dummy numbers for the missing hours or entire days to
make all files of equal length.  The character Ə' is used to fill all fields
for missing data according to their format, e.g. ' 9999.9' for a field with the
FORTRAN format F7.1. Note that format F7.1 below really means (1X,F6.1),etc.
 
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HELIOS2_E6_1HOUR_PARTICLE_FLUX
Description
HELIOS-A and -B spacecrafts were the pair of deep space probes developed by the
Federal Republic of Germany (FRG) in a cooperative program with NASA. The
purpose of the mission was to make pioneering measurments of the interplanetary
medium from the vicinity of the earth"s orbit to 0.3 AU. 
The objective of experiment (E6) was to study high-energy, charged, cosmic-ray
particles of solar, planetary, and galactic origin in interplanetary space.
Protons and alpha particles with eneries >1.3 MeV/nucleon, and electrons >0.3
MeV were measured within interplanetary space over the range from 0.3 to 1.0 AU.
The instrument, a particle telescope with 55-deg field of view, consisted of
five semiconductor detectors, one sapphire Cherenkov counter, and one
scintillation counter, all enclosed by an anticoincidence cylinder. The
telescope was calibrated prior to launch using radioactive sources, particle
acceletors, and ground-level muons. It measured protons and alpha particles in
six channels (1.3-3.3, 3.3-13, 13-27, 27-37, 37-45, and >45 MeV/nucleon) and
electrons in five energy channels (0.3-0.8, 0.8-2, 2-3, 3-4, and >4 MeV). For
more detail see pp.253-257 of Raumfahrtforschung, v.19, n. 5, 1975. 
The h-a-cr*.dat and h-b-cr*.dat files contains hourly averaged fluxes of
electrons, protons and alpha particles in the MeV ranges. The files were written
in ASCII-codes. Each record contains 10 hourly averages. The differential fluxes
(particles/sq.m, s, sr, MeV) cover, in several bands, the energy range 0.3-2.0
MeV for electrons, 4.0-51 MeV for protons, and 2.0-48 MeV for alpha particles. 
Also provided are the integral fluxes of alphas above 48 MeV, and protons above
51 MeV. For some of the energy channels, the standard deviations of the averages
are also provided. Each file is preceded by a header record, providing the start
and stop times of the data in the file. 
The acronyms for the rate channels are composed of a letter and an indication of
the energy range in MeV/nucleon for protons and alpha particles respectively.
MeV for electrons. 
The counting rates are given as particles/m^2  sec sr MeV/N, except for the
integral channels P>51 and A>48 which are given as particles/ m^2 sec sr. 
Note: 1. Negative rates (-0.99999E+04) indicate missing or invalid data. 2. The
energy boundaries for the electron channels E 0.2-0.8 and E 0.8-2are only rough
estimates.
 
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HELIOS2_E6_KUNOW_1HOUR_PARTICLE-FLUX
Description
HELIOS-A and -B spacecrafts were the pair of deep space probes developed by the
Federal Republic of Germany (FRG) in a cooperative program with NASA. The
purpose of the mission was to make pioneering measurments of the interplanetary
medium from the vicinity of the earth"s orbit to 0.3 AU. 
The objective of experiment (E6) was to study high-energy, charged, cosmic-ray
particles of solar, planetary, and galactic origin in interplanetary space.
Protons and alpha particles with eneries >1.3 MeV/nucleon, and electrons >0.3
MeV were measured within interplanetary space over the range from 0.3 to 1.0 AU.
The instrument, a particle telescope with 55-deg field of view, consisted of
five semiconductor detectors, one sapphire Cherenkov counter, and one
scintillation counter, all enclosed by an anticoincidence cylinder. The
telescope was calibrated prior to launch using radioactive sources, particle
acceletors, and ground-level muons. It measured protons and alpha particles in
six channels (1.3-3.3, 3.3-13, 13-27, 27-37, 37-45, and >45 MeV/nucleon) and
electrons in five energy channels (0.3-0.8, 0.8-2, 2-3, 3-4, and >4 MeV). For
more detail see pp.253-257 of Raumfahrtforschung, v.19, n. 5, 1975. 
The h-a-cr*.dat and h-b-cr*.dat files contains hourly averaged fluxes of
electrons, protons and alpha particles in the MeV ranges. The files were written
in ASCII-codes. Each record contains 10 hourly averages. The differential fluxes
(particles/sq.m, s, sr, MeV) cover, in several bands, the energy range 0.3-2.0
MeV for electrons, 4.0-51 MeV for protons, and 2.0-48 MeV for alpha particles. 
Also provided are the integral fluxes of alphas above 48 MeV, and protons above
51 MeV. For some of the energy channels, the standard deviations of the averages
are also provided. Each file is preceded by a header record, providing the start
and stop times of the data in the file. 
The acronyms for the rate channels are composed of a letter and an indication of
the energy range in MeV/nucleon for protons and alpha particles respectively.
MeV for electrons. 
Note: 1. Negative rates (-0.99999E+04) indicate missing or invalid data. 2. The
energy boundaries for the electron channels E 0.2-0.8 and E 0.8-2are only rough
estimates.
 
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HK_H0_MAG
Description
Gurnett, D. A., and L. A. Frank, A region of intense plasma wave turbulences on
auroral field lines, JGR, 82, 1031, 1977
Farrell, W. M., and J. A. Van Allen, Observations of the Earth"s  polar cleft at
large radial distances with Hawkeye 1 magnetometer, JGR, 95, 20945, 1990
Modification History
Created by S. Chen on 2-5-97
Modified by R. Kessel on 13 June 2000
 
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HK_H0_VLF
Description
BUILD_DATE:                     1974-01-01
INSTRUMENT_MASS:         0.23 (LESS BOOMS) kg
INSTRUMENT_HEIGHT:       0.058 mt
INSTRUMENT_LENGTH:       0.140 mt
INSTRUMENT_WIDTH:         0.140 mt
INSTRUMENT_MANUFACTURER_NAME:   UNIV IOWA
INSTRUMENT_SERIAL_NUMBER:     VLF-05
                         Electric Antenna
The electric antenna on HAWKEYE consisted of two extendible beryllium copper
elements 0.025 inch in diameter which could be extended to a maximum tip-to-tip
length of 42.7 m. Except for the outermost 6.1 m of each element, which had a
conducting surface, the antenna was coated with Pyre-ML to electrically insulate
the antenna from the surrounding plasma. The insulating coating was required to
insulate the antenna from the perturbing effects of the plasma sheath
surrounding the spacecraft body. At high altitudes, the thickness of the plasma
sheath surrounding  the spacecraft body was quit large, on the order of 9 m.
Since the conducting portion of the antenna must extend beyond the plasma
sheath, it was necessary that the antenna be rather long, at least 30 m.
tip-to-tip. The antenna mechanism used on HAWKEYE was the Dual-Tee extendible
antenna manufactured by Fairchild Industries. The antenna length was 42.49
meters after final deployment until the last orbit, when an attempt was made to
retract the antenna to reduce the spacecraft drag.
                   Magnetic Antenna
 The magnetic antenna for this experiment consisted of a search coil with a high
permeability core mounted on a boom approximately 1.5 m. from the centerline of
the spacecraft body. The boom was a three element telescoping device developed
at the University of Iowa. The boom supporting the flux gate magnetometer on the
opposite side of the spacecraft was the same type. Both booms were extended
simultaneously by an electric motor.
           The search coil core was .305 m. long and was wound with
approximately 20,000 turns of copper wire. The axis of the search coil was
parallel to the spin axis of the spacecraft. A preamplifier was located with the
sensor to provide low-impedance signals to the main electronics package in the
spacecraft body. The frequency range of the search coil antenna was from 1.0 Hz
to 10.0 kHz.
                         Electronics
 The potential difference between the electric antenna elements was amplified by
a high input impedance differential amplifier to provide a 0 to 5 volt analog
voltage, V-Diff, to the spacecraft encoder. As the spacecraft rotated the
potential difference between the antenna elements  varied sinusoidally at the
spacecraft rotation rate, with an amplitude proportional to the electric field
strength and a phase determined by the direction of the electric field. The
frequency response of the differential amplifier was 0.05 Hz to 10 Hz and
included the entire range of spin rates expected as the antenna was deployed.
The V-Diff signal was sampled 6 times each frame by the encoder. The gain of the
differential amplifier could be controlled by command to provide dynamic ranges
of +/-0.5 and +/-8.0 volts for the antenna potential difference measurements.
           Signals from the electric antenna in the frequency range from 10 kHz
to 200 kHz were analyzed by the narrow band step frequency receiver. The primary
purpose of this receiver was to provide very good frequency resolution in the
neighborhood of the electron plasma frequency and upper hybrid resonance
frequency. The step frequency receiver consisted of 8 narrow band filters (+/-5%
band-width) which were sequentially switched into a log compressor. The  log
compressor provided a 0 to 5 volt analog voltage, SFR, to the spacecraft
encoder. The switch (S4) position was controlled by clock lines from the
spacecraft encoder and was stepped through 8 frequencies, 13.3, 17.8, 23.7,
31.1, 42.2, 56.2, 100, and 178 kHz, at a rate of four frequencies per telemetry
frame (5.76 seconds). The log compressor provided a 0 to 5 volt analog voltage,
SFR, to the spacecraft encoder which was proportional to the logarithm of the
signal strength over a dynamic range of 100 db.
           The 8-channel spectrum analyzer  provided relatively coarse frequency
spectrum measurements of both electric and magnetic fields over a broad
frequency range of 1.0 Hz to 10.0 kHz. The primary purpose of the 8-channel
spectrum analyzer was to provide field strength measurements to complement the
high-resolution frequency-time spectra from the wide-band receiver.
           Switches S1 and S2 were controlled by clock lines from the spacecraft
encoder and commutate the filter outputs to two log compressors which provided
field strength measurements SA-1 and SA-2 (0 to 5 volts) to the spacecraft
encoder. These outputs were sampled twice per telemetry frame. Switch S3, which
was controlled by a clock line, commutates the electric and magnetic field
signals to the 8-channel spectrum analyzer.
          Approximately every 5 minutes the impedance of the electric antenna
was determined at a frequency of 17 Hz by driving a small AC current into the
antennas and measuring the resultant voltage on the antennas with the 8-channel
spectrum analyzer. The 17 Hz oscillator was gated on for 1 frame out of every 64
frames by a clock line.
           Immediately following the impedance measurement the pulser circuit
produced a 10 volt pulse with a duration of 20 micro- seconds. This pulse was to
stimulate local plasma resonances, such as plasma oscillation, from which the
electron density could be determined. A pulse of +10 volts was applied to one
antenna element and a -10 volt pulse was applied to the opposite antenna
element. The pulser was switched on by command. The pulser was on when the
experiment was in VLF45 mode and off when the experiment was in the VLF10 mode.
The pulser voltage was coupled to the antenna through a 220 pf capacitor which
would have allowed some meaningful data to be obtained from the experiment even
if the pulser output were to short to ground. The pulse was applied at the end
of the impedance measurement frame.
 The potential difference between the electric antenna elements was amplified by
a high input impedance differential amplifier to provide a 0 to 5 volt analog
voltage, V-Diff, to the spacecraft encoder. As the spacecraft rotated the
potential difference between the antenna elements  varied sinusoidally at the
spacecraft rotation rate, with an amplitude proportional to the electric field
strength and a phase determined by the direction of the electric field. The
frequency response of the differential amplifier was 0.05 Hz to 10 Hz and
included the entire range of spin rates expected as the antenna was deployed.
The V-Diff signal was sampled 6 times each frame by the encoder. The gain of the
differential amplifier could be controlled by command to provide dynamic ranges
of +/-0.5 and +/-8.0 volts for the antenna potential difference measurements.
           Signals from the electric antenna in the frequency range from 10 kHz
to 200 kHz were analyzed by the narrow band step frequency receiver. The primary
purpose of this receiver was to provide very good frequency resolution in the
neighborhood of the electron plasma frequency and upper hybrid resonance
frequency. The step frequency receiver consisted of 8 narrow band filters (+/-5%
band-width) which were sequentially switched into a log compressor. The  log
compressor provided a 0 to 5 volt analog voltage, SFR, to the spacecraft
encoder. The switch (S4) position was controlled by clock lines from the
spacecraft encoder and was stepped through 8 frequencies, 13.3, 17.8, 23.7,
31.1, 42.2, 56.2, 100, and 178 kHz, at a rate of four frequencies per telemetry
frame (5.76 seconds). The log compressor provided a 0 to 5 volt analog voltage,
SFR, to the spacecraft encoder which was proportional to the logarithm of the
signal strength over a dynamic range of 100 db.
           The 8-channel spectrum analyzer  provided relatively coarse frequency
spectrum measurements of both electric and magnetic fields over a broad
frequency range of 1.0 Hz to 10.0 kHz. The primary purpose of the 8-channel
spectrum analyzer was to provide field strength measurements to complement the
high-resolution frequency-time spectra from the wide-band receiver.
           Switches S1 and S2 were controlled by clock lines from the spacecraft
encoder and commutate the filter outputs to two log compressors which provided
field strength measurements SA-1 and SA-2 (0 to 5 volts) to the spacecraft
encoder. These outputs were sampled twice per telemetry frame. Switch S3, which
was controlled by a clock line, commutates the electric and magnetic field
signals to the 8-channel spectrum analyzer.
          Approximately every 5 minutes the impedance of the electric antenna
was determined at a frequency of 17 Hz by driving a small AC current into the
antennas and measuring the resultant voltage on the antennas with the 8-channel
spectrum analyzer. The 17 Hz oscillator was gated on for 1 frame out of every 64
frames by a clock line.
           Immediately following the impedance measurement the pulser circuit
produced a 10 volt pulse with a duration of 20 micro- seconds. This pulse was to
stimulate local plasma resonances, such as plasma oscillation, from which the
electron density could be determined. A pulse of +10 volts was applied to one
antenna element and a -10 volt pulse was applied to the opposite antenna
element. The pulser was switched on by command. The pulser was on when the
experiment was in VLF45 mode and off when the experiment was in the VLF10 mode.
The pulser voltage was coupled to the antenna through a 220 pf capacitor which
would have allowed some meaningful data to be obtained from the experiment even
if the pulser output were to short to ground. The pulse was applied at the end
of the impedance measurement frame.
Modification History
CDF created Jan 1999 by Mona Kessel
modified Aug 1999 by Mona Kessel, Carolyn Ng
modified Oct 1999 by Mona Kessel
modified Nov 1999 by Mona Kessel, final for archiving
 
Dataset in CDAWeb
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