Instrument Information |
|
IDENTIFIER | urn:nasa:pds:context:instrument:gtt.p11::1.0 |
NAME |
GEIGER TUBE TELESCOPE |
TYPE |
PARTICLE DETECTOR |
DESCRIPTION |
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 : 1973-04-06 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 : 0853-04 Scientific Objectives ===================== Encounter Objectives -------------------- The investigation objectives for the Pioneer 11 encounter data (Jupiter, and Saturn) 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 11 cruise data (Earth-Jupiter, Jupiter-Saturn, and Post-Saturn) 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; principally plutonium 238. 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) = 1.137*RR R(B) = 0.905*RR R(C) = 0.958*RR R(D) = 0.254*RR RR = 1.103E - 02*[2*f(t)+0.9*f(t+0.832)] + 5.53E - 03*[3*g(t)+g(t+0.832)] 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 March 15,1971. [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 detector rates and the solid state detector rate 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, and C, and for detector D, the form is D'=D(T)*Y(T), where X(T)=1.0+0.0003694*(75.0-T) and Y(T)=1.0-0.0006514*(75.0-T). The temperatures in degrees F as a function of time for Pioneer 11 are given in the following table. -------------------------------------------------------------- Pioneer 11 Temperatures -------------------------------------------------------------- YEAR PERIOD (DOY) TEMPERATURE PERIOD TEMPERATURE -------------------------------------------------------------- 1973 96 77.8 97 67.0 98 64.8 99 65.8 100 67.0 101-119 69.9 120-125 67.0 126-131 64.8 132-148 58.1 149-153 55.9 154-205 50.1 206-226 46.6 227-272 50.1 273-312 48.4 313-317 43.7 318-365 46.6 1974 1- 28 46.6 29-290 44.7 291-365 42.9 1975 1-101 42.9 102-139 35.8 140-365 42.9 1976 1-167 42.9 168-366 41.1 1977 1- 24 41.1 25-302 39.29 303-365 37.52 1978 1-252 37.52 253-365 35.77 1979 1-149 35.77 150-365 34.03 1980 1-155 34.03 156-172 32.30 173-188 34.03 189-366 32.30 1981 1-216 32.30 217-365 30.58 1982 1-120 30.58 121-365 28.88 1983 1- 48 28.88 49-332 27.20 333-365 25.52 1984 1- 60 25.52 61 23.86 62 22.22 63-184 20.59 185-276 18.98 277-366 17.38 1985 1- 35 17.38 36-116 15.80 117-205 14.22 206-365 12.66 1986 1- 63 11.11 64- 70 9.55 71-139 8.00 140-310 6.43 311-365 4.86 1987 1- 31 4.86 32-189 3.22 190-304 1.63 305-365 -0.03 1988 1- 87 -0.03 88-231 -3.54 232-366 -5.33 1989 1- 7 -5.33 8-150 -7.12 151-292 -8.91 293-365 -10.70 1990 1- 70 -10.70 71-212 -12.49 213-355 -14.28 356-365 -16.07 1991 1-133 -16.07 134-275 -17.86 276-365 -19.65 Detectors ========= Six miniature Geiger-Mueller (GM) tubes are used as basic detectors. Three of these (A, B, and C) are EON Corporation end-window type 6213 tubes. The three other tubes (D, E, and F) are EON Corporation type 5107 tubes. The six tubes were placed in a variety of physical arrangements. The seventh detector (G) is a thin (28 micron thick), single element solid state detector with a physical collimator. This detector was made by Nuclear Diodes, Inc. 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 the collimated solid state detector as input to a charge sensitive amplifier. This signal is delay-line clipped to 180 nanoseconds, amplified and then fed into a fixed level threshold discriminator. This threshold corresponds 0.61 MeV for protons. The output of the discriminator is then fed into an output circuit which shapes the pulse so that it is similar to that from the GM tubes; it is then treated in the same manner. Detector G looks in the +X direction. --------------------------------------------------------------- University of Iowa Geiger Tube Telescope Energy Ranges and Geometric Factors of Pioneer 11 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 A-C 0.04 |
MODEL IDENTIFIER | |
NAIF INSTRUMENT IDENTIFIER |
not applicable |
SERIAL NUMBER |
not applicable |
REFERENCES |
Fimmel, R.O., W. Swindell, E. Burgess, Pioneer Odyssey, NASA SP-396,
Scientific and Technical Information Office, National Aeronautics and
Space Administration, Washington, D.C., 1977. Van Allen, J.A., B.A. Randall, Interplanetary cosmic ray intensity - 1972-1984 and out to 32 AU, J. Geophys. Res., 90, 1399, 1985. Van Allen, J.A., D.N. Baker, B.A. Randall, and D.D. Sentman, The magnetosphere of Jupiter as observed with Pioneer 10, 1, Instrument and principal findings, J. Geophys. Res., 79, 3559, 1974. Van Allen, J.A., B.A. Randall, and M.F. Thomsen, Sources and sinks of energetic electrons and protons in Saturn's magnetosphere, J. Geophys. Res., 85, 5679, 1980. |