Instrument Information |
|
IDENTIFIER | urn:nasa:pds:context:instrument:ducma.vega1::1.0 |
NAME |
DUST PARTICLE COUNTER AND MASS ANALYZER |
TYPE |
PARTICLE DETECTOR |
DESCRIPTION |
Instrument Overview =================== The detector is a 28 Km thick film of polarised polyvinylidene fluoride (PVDF), covered on each face with a metallic conducting coating. A dust particle impacting the detector will displace a small volume of polarised material in the bulk of the detector, which then results in a fast depolarisation signal whose amplitude is a known function of the particle mass and velocity. Electronic circuits measure the pulse height and ac- cumulate pulse events above four different threshold levels. Since the relative impact velocity is known (i.e. the comet-spacecraft velocity), the mass is determined direct- ly from the known mass/velocity relationship for these detectors. The detector assembly consists of the dust detector (M), and a small anti-coincidence detector (V), mounted perpendicular to the direction of arrival of the dust particles. The purpose of the small detector is to detect very large mechanical shocks on the spacecraft which might trigger the most sensitive level of the dust detector. Further technical details are given in the table below, where the values for the 'differential dust mass ranges' are published in Simpson et al. 'Ducma Measurements of Comet Halley Dust Mass Spectra Bases on Post-Encounter Dust Calibrations', Asteroids, Comets, and Meteors III (1990, Uppsala). This instrument was selected one year before launch and could still be considered at this late stage because it did not require any direct telemetry or telecommand inter- face with the spacecraft. Its inclusion was facilitated because it was allowed to share the data format and telecommands initially allocated to the ING instrument. ----------------------------------------------------- Table. Dust Particle Detector and Mass Analyser characteristics Impact detector 28 micro m**2 PVDF foil Detector area 75cm**2 Maximum count rate 10**5/s Differential dust mass range 1.5x10**-13 to 5.6x10**-11 g, 5.6x10**-11 to 1.6x10**-9 g, 1.6x10**-9 to 4.0x10**-8 g, and greater than 4.0x10**-8 g Integral dust mass range >4.0x10**-8 g Integration time for flux measurements at encounter 2 s ------------------------------------------------------ |
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. Mazets, E.P., et al., Dust in Comet Halley from VEGA Observations, ESA SP-250, 3-10. Perkins, M.A., J.A. Simpson, and A.J. Tuzzolino, A Cometary and Interplanetary Dust Experiment on the VEGA Spacecraft Missions to Halley's Comet, Nuclear Instruments and Methods in Physics Research, A239, 310-323, 1985. Rabinowitz, D.L., A Source Map for Dust Jets Observed in the Coma of Comet P/Halley, Astronomy and Astrophysics, 200, 225-247, 1988. Simpson, J.A., and A.J. Tuzzolino, Polarized Polymer Films as Electronic Pulse Detectors of Cosmic Dust Particles, Nuclear Instruments and Methods in Physics Research, A236, 187-202, 1985. Simpson, J.A., and A.J. Tuzzolino, Cosmic Dust Investigations: Instruments for Measurement of Particle Trajectory, Velocity and Mass, Nuclear Instruments and Methods in Physics Research, A279, 625-639, 1989. Simpson, J.A., R.Z. Sagdeev, A.J. Tuzzolino, M.A. Perkins, L.V. Ksanfomality, D. Rabinowitz, G.A. Lentz, V.V. Afonin, J. Ero, E. Keppler, J. Kosorokov, E. Petrova, L. Szabo, and G. Umlauft, Dust Counter and Mass Analyzer Measurements of Halley's Coma from VEGA Spacecraft, Nature, 321, 278-280, 1986. Simpson, J.A., et al., Halley's Comet Coma Dust Particle Mass Spectra, Flux Distributions, and Jet Structures Derived from Measurements on the VEGA-1 and VEGA-2 Spacecraft, ESA SP-250, 11-16, 1986. Simpson, J.A., D. Rabinowitz, and A.J. Tuzzolino, PVDF Detector Signal Dependence on Mass and Velocity for Penetrating Particles, Nuclear Instruments and Methods in Physics Research, A279, 611-624. Simpson, J.A., et al., DUCMA Measurements of Comet Halley Dust Mass Spectra Based on Post- Encounter Dust Calibrations, Asteroids, Comets, and Meteors III, C.I. Lagerkvist, H. Rickman, B.A. Lindblad, and M. Lindgren (eds.), 435-438, 1990. Vaisberg, O., V. Smirnov, and A. Omelchenko, Spatial Distribution of Low-Mass Dust Particles (m<=10**-10 g) in Comet Halley Coma, ESA SP-250, 17-23, 1986. |