Instrument Overview
    ===================
 
      The prime objective of the energetic-particle
      analyzer is to measure the energy and flux of the
      cometary ions that might be accelerated by, for
      example, solar-wind magnetic fields.  Two similar
      telescopes provide information about the angular
      distribution of the ion flux.  The first telescope,
      T1 is viewing at 55 deg to the east of the Sun;and
      the T2 telescope, looks at 90 deg to the east of
      the Sun, both in the ecliptic plane and
      approximately opposite to the spacecraft velocity
      vector.  Each telescope consists of two silicon
      detectors, A (8 mm in diameter and 0.1 mm thick)
      and B (16 mm in diameter and 1 mm thick), and an
      anti-coincidence scintillation shield.  Electrons
      with energies of less than 0.2 MeV are deflected
      away from the entrance aperture by a magnet.  The
      low-energy (30-640 keV) ions trigger a signal in
      detector A only.  More energetic particles are
      detected in both A and B, and it is possible to
      distinguish between electrons, protons and heavier
      nuclei by comparing the amplitudes of the signals
      delivered by the two detectors.  The characteristic
      parameters of these two telescopes are given in the
      table below.
 
 
 
 Table. Energetic-Particle Analyzer characteristics
 Ion energy range (detector A)
 Resolution                           20 heV-640 keV
 -  range  20-160 keV                 10 keV
 -  range 160-400 keV                 20 keV
 -  range 400-640 keV                 40 keV
 Energy ranges (detectors A and B)
 -  electrons                         0.5-0.75 MeV
 -  protons                           3.2-13 MeV
 -  ions (Z >= 2)                     3.2-13 MeV/nucleon
 Integral flux of protons and nuclei  Energy >/= 13 MeV/nucleon
 Geometrical factor                   0.2 cm**2 sr
 Field of view                        25deg half cone
 Time resolution                      4 s (encounter);
                                      10 or 20 min (cruise)
 
 
      The scientific objective was to study the high
      energy (from about 50 keV to 700 keV) ion
      environment of comet Halley.  Ions (probably mostly
      water group) were successfully observed (for
      details, see Somogyi et al.  Nature 321, 285, 1986;
      Gribov B.E.  et al., Astronomy and Astrophysics
      187, 293 1987; Kecskemety K.  et al., J. Geophys.
      Res.  94, 185, 1989; Somogyi A.J.  et al., in:
      'Comet Halley - Investigations, Results,
      Interpretations', Ellis Horwood Limited,
      Chichester, England, Vol. 1, 203, 1990; and
      Kecskemety K. and T.E. Cravens, J. Geophys.
      Res. 97, 2891, 1992.)
 
 Calibrations: electronic calibrations were performed
 only, the results were used to determine the relative
 width of the ion energy channels and from this to obtain
 the real values of the energy limits of the channels
 starting from the nominal values.
 
 The instrument was mounted to point in a fixed direction
 relative to the spacecraft.
 
 Principal investigator: Prof. A.J. Somogyi.
 
 Coinvestigators:
 G. Erdos, J. Ero Jr., M. Farago, T.I. Gombosi,
 K. Kecskemety, A. Kondor, T. Kovacs Jr., Gy. Kozma,
 L. Lohonyai, R. Redl, J. Szabo, L. Szabo, K. Szego,
 I. Szentpetery, A. Szepesvary, I. T.-Szucs,
 M. Tatrallyay, A. Varga, J. Windberg,
 A. Zarandy (Central Research Institute for Physics,
 Budapest, Hungary);
 R.Redl (Technical University, Budapest, Hungary);
 T.E. Cravens (Space Physics Research Laboratory,
 University of Michigan, Ann Arbor, USA);
 A. Dyachkov, I.N. Klimenko, A.P. Remizov, M.I. Verigin,
 G.A. Vladimirova (Space Research Institute, Moscow, USSR);
 E. Keppler, A.K. Richter (Max-Planck-Institute
 fur Aeronomie, Katlenburg-Lindau, FRG);
 Yu.I. Logachev, V.G. Stolpovskii (Moscow State
 University, Moscow, USSR)
 R. Marsden, K.-P. Wenzel (Space Science Dept., ESA,
 ESTEC, Noordwijk, The Netherlands).
 
 Instrument Section/ Modes of Operation
 
 TUNDE-M consists of two particle telescopes: T1 is viewing
 at 55 deg to the east of the Sun, T2 looks at 90 deg to
 the east of the Sun, both in the ecliptic plane. The
 telescopes consist of two circular surface barrier
 semiconductor detectors with an Al layer of
 15x10**-6 g/cm**2 coated on the front detector (A)
 and an anticoincidence scintillation detector MCP.
 Low energy electrons (below about 160 keV) were
 deflected with a magnet.
 Field of view (half cone): 25 deg.
 Geometric factor: 0.25 cm**2 sr.
 Particles stopping in the thin front detector were
 not identified (they are referred as ion channels),
 those reaching the thick detector were identified
 via the dE/E method.
 
 T1 was working all along the mission, T2 was rendered
 inoperative before the Halley encounter.
 
 Modes of operation: Trassa-1 and Trassa-2
 (cruise phase) and BRL (fast telemetry, started at
 04:17:03 UT, March 6, 1986, ended at 08:24:53 UT,
 same day). Data were gathered in 66 channels, some
 referred as ions, others as identified particles,
 both between preset energy limits (given at the
 data set description).
 
 Data rate: 1 frame of 66 real numbers in every
 4 s (BRL mode). The measurement was continuous,
 with an integration time of 4 s.
 
 Other technical details can be found in:
 Somogyi A.J. et al., in: Proc. of Int. Conf. on
 Cometary Exploration, Budapest 1982
 (ed. T.I. Gombosi), Vol. 3, p351, 1983
 
 and
 
 Somogyi A.J. et al., in: 'Field, particle and
 wave experiments on cometary missions'
 (eds. K. Schwingenschuh and W. Riedler),
 Austrian Academy of Sciences, Proc. of
 International Workshop, Graz, Austria 1985,
 p237, 1986.
 
 Details concerning scientific result were published in:
 Somogyi et al. Nature 321, 285, 1986;
 
 Gribov B.E. et al., Astronomy and Astrophysics 187,
 293 1987;
 
 Kecskemety K. et al., J. Geophys. Res. 94, 185, 1989;
 
 Somogyi A.J. et al., in: 'Comet Halley - Investigations,
 Results, Interpretations', Ellis Horwood Limited,
 Chichester, England, Vol. 1, 203, 1990;
 
 Kecskemety K. and T.E. Cravens, J. Geophys. Res.
 97, 2891, 1992.