Instrument Information |
|
IDENTIFIER | urn:nasa:pds:context:instrument:sakig.sow::1.0 |
NAME |
SOLAR-WIND INSTRUMENT |
TYPE |
PARTICLE DETECTOR |
DESCRIPTION |
Instrument Overview =================== The Solar-Wind Instrument on MS-T5 employs a Faraday cup to measure the bulk velocity, density and temperature of solar-wind ions. This conventional cup, mounted flush with the outer skin of the spacecraft, consists of four grids and\ an ion collector. The front grid G(1), is connected to the satellite skin. A square-wave voltage is applied to the modulator grid G(2), alternating at 400 Hz between 0 and V volt. This produces a pulsating current by repelling and transmitting those incoming particles whose energy is between 0 and a maximum voltage V of 1.5 kV, which can be selected from the ground. The voltage will be fixed for most of the mission, although the instrument has several operating modes, such as automatic voltage change for every spin, automatic fine voltage sweep between two voltages, etc. The third grid is grounded to block any leakage of modulating voltage from G(2) to the collector. The fourth grid is negatively biased at - 100 V to suppress photo-electrons from the collector. The sensor is not sensitive to the solar-wind stream beyond an angle of attack of +/- 60deg. The table below summarizes the sensor's characteristics. Both DC and AC collector currents are detected. The former (ion current and secondary-electron current), which vary during each satellite spin, are used to check the angular characteristic of the Faraday cup itself and to monitor the photo-electron contribution to the collector current. The modulated ion current measured between 2x10**-12 A and 10**-8 A is sampled at 128 points between - 90deg and +90deg with respect to the solar-wind direction, i.e. every 180deg/128=1.4deg the collector Current is sampled as a function of the spin angle. The bulk velocity and ion density are calculated from the point where the slope of the collector-current versus spin angle function becomes a maximum. ______________________________________________ Table: Characteristics of MS-T5 Solar-Wind Instrument Transmission of the grids G(1) G(2), G(4) : 90% G(3) : 77% Overall : 70% Distance between grids 4 mm Collector diameter 90 mm Maximum voltage to be applied to G(2) 1.5 kV +/- 40 V Collector impedance 10 M Ohms (with 20 pF) collector-ground stray capacity ______________________________________________ |
MODEL IDENTIFIER | |
NAIF INSTRUMENT IDENTIFIER |
not applicable |
SERIAL NUMBER |
not applicable |
REFERENCES |
Reinhard, R and B. Battrick (eds), 'Space Missions to Halley's Comet', European
Space Agency ESA SP-1066, ESA Pub Div, Moordwijk, Netherlands, 1986. 'Encounters with Comet Halley, The first results', Nature, Volume 321, No. 6067, 15 May 1986. |