[ Main |
News |
Countdown |
Search |
FAQ |
Glossary
]
DDS - Dust Detector Subsystem
DDS
Dust Detector Subsystem
Eberhard Grun, Principal Investigator
Max-Planck-Institute fuer Kernphsik, Heidelberg, Germany
32K
MISSION OBJECTIVES
- Investigate the interaction of the Galilean satellites with their dust environment, i.e.,
the relationship between the satellites' surface properties and dust impact, and to
measure directly particles ejected from the satellites.
- Examine the interaction of dust particles with the ambient plasma and magnetic field.
- Determine the relationship between dust concentrations and the attenuation of trapped
radiation.
- Determine the effects of the Jovian magnetic field on charged dust particle
trajectories.
- Search for rings around Jupiter and measure the influence of Jupiter's gravitational
field on the interplanetary dust population.
SUMMARY
"Dust" is a term used by astronomers to describe small grains of
matter found not only in planetary systems but also in interstellar
space, often mixed in with interstellar clouds of gas. Dust can be a
natural part of the magnetosphere, or it can come from Jupiter, the
satellites, or even from external forces like Comet Shoemaker-Levy 9.
The Dust Detector Subsystem (DDS) will be used to measure the mass,
electric charge, and velocity of incoming particles. The masses of
dust particles that the DDS can detect go from 10?-16 to 10?-7 grams.
The speed of these small particles can be measured over the range of
1 to 70 kilometers per second. The instrument can measure impact
rates from 1Ęparticle per 115 days to 100 particles per second.
These particles will help determine dust origin and dynamics within
the magnetosphere.
The DDS weighs 4.2 kilograms and uses an average of 5.4 watts of
power.
DDS DESCRIPTION
18K
- The DDS is used to determine the impact of individual dust particles and to
measure their
mass, impact velocity, and charge state. To do this, the DDS consists of an impact
ionization detector and an electronics box containing signal conditioning and
spacecraft interface electronics.
- The sensor is composed of a grounded hemisphere target with a grid system for
measurement of a particles charge, an Ion collector, high voltage power supplies, charge sensitive
amplifiers, a channeltron, and pre-amplifiers.
- An identical instrument is on the Ulysses spacecraft. These instruments are
derived
from the HEOS 2 instrument.
DESIGN DETAILS
- The DDS is based on the impact ionization phenomenon, which is extremely good for
detection of small dust particles moving with high speed.
- The DDS can measure from 3x10?-7 to 1x10?2
impacts per second.
- The measurable particle mass range at 40 km/s is 1x10?-19
to 1x10?-13
kg and at 5 km/s
it is 1x10?-16 to 1x10?-10
kg.
- The measurable particle charges are from 1x10?-14
to 1x10?-10 C for negative charges and
from 1x10?14
to 1x10?-12
C for positive charges.
- Particles with impact speeds greater than or equal to 1 km/s are detectable.
- The detector has a sensitive area of 0.1 m?2.
INSTRUMENT PARAMETERS
- Instrument Mass: 4.2 Kg
- Power Consumption:
- Instrument 2.4 W
- Suppl. Heaters 3.0 W
- Microprocessor: 1802 type
- ROM/RAM: 3 Kb/2 Kb
- Fields of View: 140 Degrees
- Elect. Box Size: 28.3 x 10.0 x 10.0 cm
- Sensor: 44.2 cm in diameter
and 30.1 cm long
- Thermal Range:
- Operating (GLL3-210)
- Detectors: -25 to 45 Degrees C
- Non-operating (GLL 3-210)
- Detectors: -25 to 45 Degrees C
- Instrument Modes:
- Off
- POR
- On
- Sci. Col.
- Memory readout
- Set point
Return to
Project
Galileo Homepage
Return to
Galileo's Science Instruments
32K
18K