OMNIDIRECTIONAL PLASMA SENSOR VDP

Welcome to VDP home page.

J. Safrankova, Z. Nemechek, M. Simerski, L. Prech

Faculty of Mathematics and Phisics of Charles University, Prague, Czech Republic

G. Zastenker, A.Fedorov, O. Vaisberg, A.Leybov

Space Research Institute, Academy of Sciences of Russia, Moscow, Russia

Yu. Sharko, T. Romasenko

Design bureau AALAM, Bishkek, Kirgizstan

Description

 The VDP instrument was designed for determination of integral flux vector or integral energetic spectrum at the range 0.2 - 2.4 keV of ions or electrons of magnetospheric plasma. The instrument includes 6 identical Faraday caps, located by following ways:
Cap #1 is directed toward the Sun. It's main axis lies along axis of spacecraft rotation (+X).
Cap #6 has antisunward direction (-X).
Caps #2 - #5 are directed along +Y, +Z, -Y, -Z axes respectively. These axes rotate with spacecraft.

The figure shows cross-section of one Faraday cup.

Positive grid (C2) and negative grid (C3) is used to select ions or elecrons measurement. In case of constant voltage, sensor supplies the total flux of ions plus flux of electrons above 2400 eV energy, or total flux of electrons plus flux of ions above 2400 eV energy. To get ion or electron spectra the voltage of C2 or C3 is changed step by step over 16 steps in range 0 - 2400 V. Cup #1 does not have negative grid and supplies the ion flux plus electron flux with energy more then 170eV.

The maximum of data rate is 16 sample per second. In case of spectra measuring one step is held during one second and full spectrum takes 16s.

The output range of direct current amplifier is -6.0 - + 6.0 V. The flux can be calculated by : 


                   P = 0.43E+9 1/cm*cm*s/V

The minimal digitased flux is 6.0E+5 1/cm*cm*s
and the maximum flux is 2.6E+9 1/cm*cm*s.

Operation and Measurements

VDP instrument works since August 14, 1995. Two Faraday caps #4 and #6 have problems and are not developed now.

Following pictures demonstrates instrument perfomance:

The example of magnetopause crossing on October 9.
Click picture to get big one.

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