Instrument Overview
  ===================
    The University of Iowa experiment comprises seven miniature
    Geiger-Muller tubes in various physical arrangements and with
    various levels of shielding responding to electrons in several
    energy ranges from 70 keV to tens of MeV, and protons in several
    energy ranges from 700 keV to tens of MeV. No one of the individual
    detectors distinguishes uniquely between protons or electrons. A
    full analysis of the relative responses of the entire array of
    detectors will provide separate energy spectra of electrons and
    protons by using laboratory-determined unit response functions and
    an identification matrix. Overall calibrations were provided by
    observations during the outbound pass of Pioneer 10 through the
    magnetosphere of the Earth on 3 March 1972 and during several solar
    energetic particle events, especially those of July and August,
    1972.
 
    Principle Investigator             : J.A. Van Allen
    Build Date                         : 1972-03-03
    Instrument Mass                    : 1.64  kg
    Instrument Height                  : 0.145 m
    Instrument Length                  : 0.171 m
    Instrument Width                   : 0.145 m
    Instrument Manufacturer            : The University of Iowa
    Instrument Serial Number           : 0853-03
 
 
  Scientific Objectives
  =====================
 
    Encounter Objectives
    --------------------
      The investigation objectives for the Pioneer 10 Jupiter encounter
      data are:
 
      1) The study of the intensity of planetary energetic particles as
         a function of position in the magnetosphere. This includes a
         determination of plasma boundaries that determine the structure
         of the planetary magnetosphere.
 
      2) The study of planetary energetic particle dynamics and
         trajectories in order to better understand planetary magnetic
         storms and plasma sources and sinks.
 
      3) The study of low energy electron and proton events to
         understand the magnetospheric propagation and acceleration of
         such particles as a function of position.
 
 
    Cruise Objectives
    -----------------
      The investigation objectives for the various Pioneer 10 cruise
      data (Earth-Jupiter, and Post-Jupiter) are:
 
      1) The study of the intensity of galactic cosmic rays as a
         function of solar activity and as a function of heliocentric
         position. Long-range objectives are to determine the position
         of the modulation boundary of the heliosphere and the intensity
         of the galactic cosmic rays in the interstellar medium beyond
         it.
 
      2) The study of solar energetic particles as a function of
         heliocentric distance and their propagation in the
         interplanetary medium.
 
      3) The study of low energy electron and proton events to
         understand the interplanetary propagation and acceleration of
         such particles as a function of heliocentric distance.
 
 
  Calibration
  ===========
    The electrical power for the spacecraft is provided by four Type
    SNAP 19 radioisotope thermal generators (RTG's) of the Atomic Energy
    Commission. There are also several much weaker radioisotpe heater
    units (RHU's) for spot heating. The heating of these systems is
    provided by a mixture of plutonium isotopes. Gamma and X-rays from
    the decay of some of the isotopes produce a time varying background
    in the singles rates of the GM tubes. These background rates can be
    calculated using the following formulae.
 
      R(A) = 1.085*RR
      R(B) = 0.903*RR
      R(C) = 1.012*RR
      R(D) = 0.309*RR
      R(G) = 0.903*RR
 
        RR = 3.862E-02*f(t) + 2.211E-02*g(t) counts/second
 
    where
 
      f(t) = 23.792*EXP(-0.3623*t) + 12.120*EXP(-0.0094*t)
             - 35.912*EXP(-0.2432*t)
 
      g(t) = EXP(-0.0081*t)
 
    and t is measured in years with t=0 on June 15, 1970.
 
    [Calibration description exerpted from VANALLEN&RANDALL1985.]
 
    Detector G is a thin solid state detector and is insensitive to this
    radiation and hence requires no correction. Detector G also has a
    small Am-241 alpha particle source at the edge of its viewing cone
    to provide an inflight calibration. This source gives a background
    counting rate of 0.06 counts per second.
 
 
    Instrument Temperature
    ----------------------
      The multiple GM detectors rates require no correction as a
      function of temperature. The singles rates of the GM tubes require
      a slight temperature correction. This temperature correction is of
      the form A'=A(T)*X(T) for detectors A, B, C and G, and for
      detector D, the form is D'=D(T)*Y(T), where
 
        X(T)=1.0+0.0003975*(75.0-T)
 
      and
 
        Y(T)=1.0-0.0002175*(75.0-T).
 
      The temperatures in degrees F as a function of time for Pioneer 10
      are given in the following table.
 
      ----------------------------------------------------------------
      Pioneer 10 Temperatures
      ----------------------------------------------------------------
      YEAR    PERIOD (DOY)    TEMPERATURE
      ----------------------------------------------------------------
      1972     63- 92         76.7-0.507*(DOY-63)
               93-122         61.5-0.437*(DOY-92)
              123-313         48.4-0.0375*(DOY-122)
              314-366         41.2
 
      YEAR     PERIOD (DOY)   TEMPERATURE     PERIOD       TEMPERATURE
      ----------------------------------------------------------------
      1973      1- 40         41.2             41-131         37.1
              132-236         35.9            237-365         39.5
 
      1974      1- 33         39.5             34-365         37.7
 
      1975      1-365         35.8
 
      1976      1- 77         35.8             78             32.3
               79- 80         28.8             81             32.3
               82-170         35.8            171-366         34.03
 
      1977      1-310         34.5            311-365         32.3
 
      1978      1-273         32.3            274-285         25.52
              286-356         32.3            357-365         30.58
 
      1979      1-277         30.58           278-365         28.88
 
      1980      1-332         28.88           333-366         27.20
 
      1981      1-241         27.20           242-365         25.52
 
      1982      1-264         25.52           266-365         23.86
 
      1983      1- 34         23.86            35-300         22.22
              301-365         20.59
 
      1984      1-243         20.59           244-366         18.98
 
      1985      1- 97         18.98            98-326         17.38
              327-365         15.80
 
      1986      1-174         15.80           175-317          9.55
              318-365          8.00
 
      1987      1-204          8.00           205-365          6.43
 
      1988      1- 44          6.43            45-247          4.86
              248-366          3.26
 
      1989      1- 43          3.26            44-246          1.64
              247-270          -.03           271-284         -1.75
              285-365         -3.54
      1990      1-155         -3.54           156-365         -5.33
 
      1991      1- 24         -5.33            25-259         -7.12
              260-365         -8.91
 
 
  Detectors
  =========
    Seven miniature Geiger-Mueller (GM) tubes are used as basic
    detectors. Four of these (A, B, C, and G) are EON Corporation
    end-window type 6213 tubes. The three other tubes (D, E, and F) are
    EON Corporation type 5107 tubes. The seven tubes were placed in a
    variety of physical arrangements.
 
    Tubes A, C, and B are mounted in a single block. The central tube C
    is shielded omnidirectionally. Tubes A and B are similarly shielded
    except for thinner window unidirectional collimators in the +X (s/c
    coordinates) direction. The individual counting rates of the three
    tubes are telemetered separately; also, double coincidences AB and
    triple coincidences ABC with a resolving time of 1 microsecond are
    formed and telemetered.
 
    The second assembly comprises an omnidirectionally shielded
    triangular array of three 5107 tubes. The rate of D and the triple
    coincidence rate of the DEF are telemetered.
 
    The third assembly uses a thin window 6213 (tube G) in a scatter
    geometry with a 90 degree gold-plated elbow as the entrance
    aperture. Detector G looks in the +X direction.
 
    ---------------------------------------------------------------
    University of Iowa Geiger Tube Telescope Energy Ranges and
    Geometric Factors of Pioneer 10 Detectors
    ---------------------------------------------------------------
                               Effective
                                Inverse
                             Omnidirectional             1
                               Geometric               -------
             Effective Energy   Factor                 4*pi*Q
    Detector    Range, MeV    (1/Q),cm**-2   Type    (cm*cm*sr)**-1
    ---------------------------------------------------------------
                             Electrons
 
     G-C          0.0621         23           O          ...
      D           E>31           63           O          ...
     AB           E>21         6910           D          550
     ABC          E>21         6910           D          550
     DEF          E>31         3150           O          ...
 
                               Protons
 
     G-C       2580               8.2         O          ...
      D           E>80           23           O          ...
     AB           E>130        2463           D          196
     ABC          E>130        2463           D          196
     DEF          E>150       11500           O          ...
    _________________________________________________________________
    Type D=Directional  O=Omnidirectional
 
 
  Electronics
  ===========
    The GTT electronics system consists of two basic sections. The first
    is the power converter which regulates and filters the 28 volt, 20
    kHz spacecraft power supply. The on-off command functions through a
    solid state switch by removing power from the driving circuitry.
 
    Output voltages of +7.75, +5.00, -12.00 and +900 are supplied to the
    experiment. The 7.75 and 5.00 volt lines are regulated to 1% and the
    900 volt lines are regulated with VR tubes.
 
    The second section is the signal processor. This is used to
    condition the data from the seven detectors and consists of a
    MOS/TTL/transistor hybrid system containing MOS/TTL logic and
    transistorized discrete component interface circuits. The processor
    is completely redundant with the exception of the interface
    circuits. Upon command to the spacecraft, the signal processor can
    be switched from the main logic system to a stand-by redundant logic
    system. The function of the processor is to sequentially accumulate
    data on a frame basis from the seven detectors. Data are accumulated
    in a 24 bit register and then compressed quasi-logarithmically to 12
    bits for transmission.
 
 
  Mounting
  ========
    The Z-axis of the instrument is parallel to the axis of rotation of
    the spacecraft. The +X axis points outward into free space from the
    rim of the instrument compartment of the spacecraft. The
    magnetometer and a portion of the magnetometer boom subtend a
    trivial fraction of the fields of view of the collimators of A, B,
    and G; otherwise, there is no physical obstruction within the fields
    of view.
 
    The rotational axis (+Z) of the spacecraft is pointed continuously
    at the earth within an error of less than one degree and therefore
    lies approximately in the ecliptic plane. The spin period and
    sampling period are asynchronous; thus angular distributions of
    particle intensities as a function of roll angle in the equatorial
    plane of the spacecraft are assembled as a software operation by
    using attitude data supplied by the Ames Research Center. In our
    analysis the roll angle is measured from the ascending node of the
    spacecraft's equator on the ecliptic to the +X axis of the
    instrument at the midtime of the sample.
 
 
  Operational Considerations
  ==========================
    The instrument uses 12 bits in each 192-bit main science frame of
    the spacecraft's telemetry format. Quasilogarithmic data compression
    is used to maintain 1% accuracy at all possible counting rates. All
    outputs are digital. A complete cycle of the GTT data comprises
    eleven main science frames as follows: sync word, G, A, B, G, AB,
    ABC, C, D, ABC, and DEF.
 
    Counts from each detector channel are accumulated for a period of
    time in seconds equal to 192/b, where b is the telemetry rate in
    bits per second for the entire spacecraft (b=16, 32, 64, 128, 512,
    1024, or 2048, as selected by ground command).
 
 
  Operational Modes
  =================
    INSTRUMENT MODE ID                : ON
    GAIN MODE ID                      : N/A
    DATA PATH TYPE                    : REALTIME
    INSTRUMENT POWER CONSUMPTION      : 1.6    ???????
 
    The GTT experiment utilizes two commands. A power ON/OFF command and
    a function command for Main/Standby processor selection.
    [VANALLENETAL1980]
 
 
    Section ID: 'GEIGER TUBES A, B, C, & D'
    ---------------------------------------
      Scan Mode ID                     : N/A
      Data Rate                        : 16-2048
      Sample Bits                      : 24
      Total FOVS                       : 1
 
      Fields of view
        FOV Shape Name                 : Cone
        Horizontal Pixel FOV           : N/A
        Vertical Pixel FOV             : N/A
        Horizontal FOV                 : 30
        Vertical FOV                   : 30
 
      Parameters
        Instrument Parameter Name      : Particle Count Rate
        Minimum Instrument Parameter   : 0.1
        Maximum Instrument Parameter   : 2.0E04
        Noise Level                    : 0.4
        Instrument Parameter Unit      : counts/second
        Sampling Parameter Name        : TIME
        Minimum Sampling Parameter     : N/A
        Maximum Sampling Parameter     : N/A
        Sampling Parameter Interval    : 115.5
        Sampling Parameter Resolution  : 0.75   ????????
        Sampling Parameter Unit        : second
 
      Detector ID                      : Geiger Tube G
      Electronics ID                   : GTT
      Filter Number                    : N/A
      Telescope ID                     : N/A
 
 
    Section ID: 'GTT'
    -----------------
      Scan Mode ID                     : N/A
      Data Rate                        : 16-2048
      Sample Bits                      : 24
      Total FOVS                       : 1
 
      Fields of view
        FOV Shape Name                 : Cone
        Horizontal Pixel FOV           : N/A
        Vertical Pixel FOV             : N/A
        Horizontal FOV                 : 40
        Vertical FOV                   : 40
        FOVS                           : 1
 
      Parameters
        Instrument Parameter Name      : Particle Count Rate
        Minimum Instrument Parameter   : 0.1
        Maximum Instrument Parameter   : 2.E04
        Noise Level                    : .06
        Instrument Parameter Unit      : counts/sec
        Sampling Parameter Name        : TIME
        Minimum Sampling Parameter     : N/A
        Maximum Sampling Parameter     : N/A
        Sampling Parameter Interval    : 115.5
        Sampling Parameter Resolution  : .75   ???????
        Sampling Parameter Unit        : second
 
  ['Detectors', 'Electronics', 'Mounting', and 'Operational
  Considerations' descriptions exerpted from VANALLENETAL1974.]