VIKING

About the data.

The hot plasma instrumentation on VIKING, V3, consists of 7 measuring units. These units measure the distribution function of electrons in the energy range 10 eV to 300 keV and of positive ions without mass separation in the energy range 1 eV to 40 keV.
  1. Spectrometers within the 7 measuring units:
    V3-1: ESP1, ESP2, ESP3
    V3-2: ESP4, ESP5
    V3-3: PISP1, PISP2
    V3-4: SECPISP
    V3-5: ICS1, ICS2
    V3-6: ICS3
    V3-7
  2. Availability of VIKING data on the WEB:
    Currently ESP1, ESP5, PISP1/2 and SECPISP are available. The data are displayed through the usage of the SDDAS software. Possibly other sensors will be added to the available data for display on the WEB in the future. Below, the data that are available now are described.
  3. Unit V3-1: ESP1, (View also V3-1 Design principles.)
    The purpose of this unit is to obtain the electron distribution function with a high energy resolution in the energy range 0.1-40keV. Since it is important to cover the loss cone, the unit contains 3 identical electron spectrometers with viewing directions of 70, 90, 110 degrees with respect to the spin axis. (Note: ESP2/3 data are not available on the WEB.) During each spin period measurements were thus performed within 10 degree from the magnetic field. ESP1 was always operated, but for ESP2 and ESP3 time sharing was used so that only one sensor at a time has delivered data to the telemetry; the choice depending on the direction of the magnetic field. This unit was operated in 3 different modes. In mode 0 the cycle time was 0.6 s and measurements were made at 128 approximately logarithmically spaced energy levels with ESP1 and 64 energy levels with ESP2/3. In mode 1 the cycle time was 0.3 s and the number of energy levels were halved to 64 and 32, respectively. The fastest mode is mode 2 with 32 energy levels for ESP1 and 16 energy levels for ESP2/3. In mode 2 the angular interspacing between spectra was only 2.7 degree. See also energy levels for ESP1 data.
  4. ESP1up:
    Sweeps are alternating as up (0.1-40 keV) and down (40-0.1 keV) sweeps. However, it is difficult to synchronize the energy levels for up & down sweeps. On the WEB plots, only ESP1up sweeps are available.
  5. Unit V3-2: ESP5
    The sensor element consists of two microchannel plates, 15 x 60mm, in chevron configuration, followed by eight separate anodes. The energy range for ESP5 is 5 - 148 keV. The major advantage of this system, as compared to the spectrometers in unit V3-1, is that particles at widely different energies are measured simultaneously. The energy levels are very stable, being defined by the fixed locations of the anodes rather than by a swept voltage. See also energy levels for ESP5 data. This unit is only operated in one mode. The total cycle time was 0.075 s.
  6. Unit V3-3: PISP1/2
    Unit V3-3 contains two positive ion spectrometers designed to give the distribution function with a good resolution both in energy and pitch angle. The energy ranges of the spectrometers are different, 0.04-1.2 keV for PISP2 and 1.2-40keV for PISP1. This unit has three different modes similar to those of unit V3-1 but with fewer steps due to a lower sampling frequency. The total cycle times are the same with 0.6s, 0.3s, and 0.15 s for modes 2, 1, and 0 but the corresponding numbers of energy steps are 32, 16 and 8, respectively. Since the two spectrometers cover two different energy ranges this means that spectra of 64, 32, or 16 energy levels are obtained. See also energy levels for PISP1/2 data.
  7. PISP1up:
    Sweeps are alternating as up (1.3-40keV)and down (40-1.3keV) sweeps. However, it is difficult to synchronize the energylevels for up & down sweeps. PISP1up sweep data do also not show any cross talk from PISP2 data and is thus used here on all WEB plots. For PISP2 data up & down sweeps are used for all WEB plots.
  8. SECPISP:
    The name means sectorized positive ion spectrometer. The purpose of the unit is to give the 3-dimensional positive ion distribution. The electrostatical analyzer consists of two toroidal parts giving a total deflection of 180 °. The toroids have been devided into eight sectors, each one with a separate channel electron multiplier. Thus, there are in effect eight individual spectrometers which, however, share one common analyzer. Thanks to this the relative differences in the energies of the particles measured by the different spectrometers are small. The entrance apertures of the eight sectors are evenly distributed on the mantle surface of a half cylinder. The field of view of each one is 6x25°. Narrow beams may escape detection by V3-3, but not so by V3-4. SECPISP is equipped with two separate power supplies, one for the enrgy range 0.45 - 450 eV and one for 10 eV - 12 keV. With the low energy power supply the instrument can be used for measuring the ion drift motion down to a few km/s. Consequently it caan be used for convection studies. This spectrometer was operated in 4 modes. See energy levels for SECPISP data.