Explorer 34
Explorer 34, was a NASA satellite launched as part of Explorer program. Explorer 34 as launched on 24 May 1967 from Vandenberg Air Force Base, California, with Thor-Delta E1 launch vehicle. Explorer 34 was the fifth satellite launched as part of the Interplanetary Monitoring Platform program, but was known as "IMP-4" because the preceding launch was more specifically part of the "Anchored IMP" sub-program. The spacecraft was put into space between the launches of Explorer 33 in 1966 and Explorer 35 in July 1967, but the next satellite to use Explorer 34's general design was Explorer 41, which flew in 1969.Launch
Explorer 34 was placed into a high-inclination, highly elliptical orbit. The apogee point was located near the ecliptic plane and had an initial local time of about 19:00 hours. The spacecraft was spin-stabilized and had an initial spin period of 2.6-seconds. The spin vector was approximately perpendicular to the ecliptic plane. Like the earlier IMPs, this spacecraft was instrumented to study interplanetary magnetic fields, energetic particles, and plasma.Experiments
Cosmic-Ray Anisotropy
This experiment was designed to study solar particle anisotropy and its variation with time. A telescope, consisting of three aligned detectors -- solid state, plastic scintillator, and Caesium iodide scintillator—and a plastic scintillator anticoincidence shield, were used to measure protons from 0.8 to 7.0 MeV—counts in but not in -- and from 35 to 110 MeV—coincident counts in, measuring dE/dx, and, measuring total energy, but not in. Pulse-height analysis yielded six-point spectra within each of these two energy intervals. Protons from 7 to 55 MeV—counts in and -- were also recorded without spectral information. In addition, a proportional counter provided directional measurements of X-rays with energies above 2 keV and electrons above 70 keV. Counts in each particle-counting mode were obtained in each of eight octants in the ecliptic plane. X-ray counts were obtained in the solar octant. A complete set of count rates and spectral data was obtained every 81.9-seconds.Cosmic-Ray Energy versus Energy Loss
This experiment used a dE/dx vs E telescope with thin and thick Caesium iodide scintillators and an anticoincidence plastic scintillation counter. The telescope axis was parallel to the spacecraft spin axis. Counts of particles penetrating the thin CsI scintillator and stopping in the thick CsI scintillator were accumulated for a 4.48-seconds interval twice every 2.73 minutes. The relative contribution to the count rate of various species and energy spectral information were determined by 1024-channel pulse-height analysis performed simultaneously on the output of both CsI scintillators 16 times every 2.73 minutes. Counts of electrons between 0.3 and 0.9 MeV stopping in the thin scintillator were also obtained once each 2.73 minutes. Except as noted above, the experiment performed well from launch until 3 May 1969.Cosmic-Ray Proton (R versus DE/DX)
The experiment was designed to measure separately the contributions of solar nuclei and of galactic nuclei using a solid-state cosmic ray telescope designed for energy-loss versus range or total energy measurements. The particle energy per nucleon intervals were approximately proportional to Z squared/A. For example, protons had intervals of 0.8 to 9.6 MeV, 9.6 to 18.8 MeV, 29.5 to 94.2 MeV, and 94.2 to 170 MeV and above. The detector viewing angle was perpendicular to the satellite spin axis. A second, smaller, solid-state telescope mounted parallel to the spacecraft spin axis was used to detect electrons in the ranges 80 to 130 keV and 175 to 390 keV. The electron detector was designed to provide information concerning the shape and intensity of the magnetospheric electron spectra. The detector accumulators for each energy interval were telemetered four times every 20.48-seconds. Each accumulation was 4.8-seconds long. The output from three 256-channel nuclear-particle telescope pulse-height analyzers was obtained every 5.12-seconds and was telemetered along with the detector accumulators. The D3 element of the first telescope began to be intermittently noisy 16 November 1967, necessitating a more complex analysis to maintain data usefulness. After September 1968, no useful data above 30 MeV/nucleon were obtained. Otherwise, this telescope functioned until spacecraft reentry. The electron telescope provided useful data for only the first six days after launch.Electrostatic Analyzer
An electrostatic analyzer and an E-cross-B velocity selector normal to the spacecraft spin axis were used to separately determine proton and alpha particle spectra in the solar wind. For each species, measurements in the energy per charge range 310 to 5100 eV were made at 14 points logarithmically equispaced in energy. During individual spacecraft rotations, counts were obtained in each of sixteen 22.5° sectors for a given species and energy. The sum of these counts, the sum of the squares of these counts, and the sector number of maximum counting were telemetered to Earth. After successive 61.44-seconds spectral determinations for protons and alpha particles, 15 consecutive readings for protons at 1408 eV were obtained. A period of 3.07 minutes separated two spectra of the same species. The instrument operated normally until 30 January 1968. At that time, it was turned off as spacecraft apogee had moved into the magnetotail. Later, attempts to reactivate the sensor failed.Ion Chamber
The instrumentation for this experiment consisted of a, Neher-type ionization chamber and two Lionel type 205 HT Geiger–Müller tubes. The ion chamber responded omnidirectionally to electrons above 0.7 MeV and protons above 12 MeV. Both GM tubes were mounted parallel to the spacecraft spin axis. GM tube A detected electrons above 45 keV that were scattered from a gold foil. The acceptance cone for these electrons had a 70° full-angle and an axis of symmetry that was 20° off the spacecraft spin axis. GM tube B responded to electrons and protons above 22 and 300 keV, respectively, in an acceptance cone of 70° full-angle centered at the spin direction. Both GM tubes responded omnidirectionally to electrons and protons of energies above 2.5 and 50 MeV, respectively. Pulses from the ion chamber and counts from each GM tube were accumulated for 9.92-seconds and read out every 10.24-seconds. The time between the first two ion chamber pulses in an accumulation period was also telemetered. This experiment performed normally from launch through 8 September 1967, when GM tube A failed. On 5 November 1967, GM tube B failed and the experiment was terminated.Low-Energy Proton and Alpha Detector
This experiment used a dE/dx versus E telescope with one thin and two thick surface-barrier, solid-state detectors and an anticoincidence plastic scintillator counter. The two thick detectors acted together as one detector. The telescope axis was perpendicular to the spacecraft spin axis. Counts of particles penetrating the thin detector and stopping in a thick detector were accumulated for two 4.48-seconds intervals every 2.73 minutes. The relative contributions to the count rate of protons and alpha particles with energies between 4.2 and 19.1 MeV/nucleon and energy spectral information were determined by 1024-channel pulse-height analysis, which was performed simultaneously on the output of the solid-state detectors eight times every 2.73 minutes. Protons stopping in the thin detector were measured by passing the output signal through an eight-level energy threshold discriminator. The eight corresponding proton energies ran from 1.1 to about 4 MeV. Data from any one level were transmitted once every 2.73 minutes. The anticoincidence scintillator failed in March 1968. This resulted in somewhat higher background count rates, which rendered isotopic separation more difficult. Except as already noted, the experiment performed well from launch until 3 May 1969.Low-Energy Proton and Electron Differential Energy Analyzer (LEPEDEA)
This experiment was designed to separately measure low-energy electron and proton intensities inside the magnetosphere and in the interplanetary region. The instrumentation system consisted of a cylindrical electrostatic analyzer and a Bendix continuous channel multiplier array, and, in addition, an Anton 213 Geiger–Müller tube designed to survey the intensities of electrons with energies >40 keV in the outer magnetosphere. The electrostatic analyzer was capable of measuring the angular distributions and differential energy spectra of proton and electron intensities, separately, within 15 contiguous energy intervals. The analyzer accumulators were read out four times every 20.48-seconds. Each accumulation was about 480 ms long. A complete scan of the spectrum for four directions in a plane perpendicular to the spacecraft spin axis required 307.2-seconds for each energy interval. The detector responses for four approximately 60° segments of the angular distribution were slaved to the spacecraft telemetry system. The viewing direction of the segments was calculated from the spacecraft optical aspect information. The instruments performed normally from launch until the satellite decayed on 3 May 1969.Low-Energy Solid-State Telescope
A four-element solid-state telescope with an acceptance cone half-angle of 20° was mounted normal to the spacecraft spin axis. During each 2.73-minutes interval, 9.82-seconds accumulations were obtained in each of 16 distinct counting modes. These modes involved protons in five energy intervals covering 0.6 to 18 MeV, alpha particles in four intervals covering 1.7 to 80 MeV, and electrons, deuterons, tritons, and Helium-3 nuclei in the intervals 0.3 to 3, 5 to 20, 5.5 to 25, and 11 to 72 MeV, respectively. Onboard calibration checks were performed every 6 hours. The experiment performed normally from launch to the spacecraft reentry date, 3 May 1969.