Cometary and Interstellar Dust Analyzer (CIDA)
instrument intercepts dust and performs real-time
compositional analysis for transmission back to
Earth. The Stardust CIDA is the same instrument
design that flew on Giotto and two Vega spacecraft,
where it obtained unusual data on the chemical
composition of individual particulates in Halley's
comet. The instrument is located on the underside
of the Stardust spacecraft.
CIDA is a mass spectrometer, which determines
the size of ions by comparing differences in their
flight times. The instrument operates relatively
simply. When a dust particle hits the target of
the nstrument, an electrostatic grid extracts
ions from it. Depending on the polarity of the
target grid, positive or negative ions can be
extracted from the dust. The extracted ions move
through the instrument, are bounced off a reflector,
then read by a detector. Heavier ions take more
time to travel through the instrument than lighter
ones, so the flight times of the ions are used
to calculate their mass.
instrument consists of an inlet, target, ion extractor,
time-of-flight (TOF) mass spectrometer (MS) and
ion detector. The inlet is baffled to prevent
sunlight from entering and raising the background
noise in the detector. The target was planned
to be a corrugated Ag or other heavy metal material.
It was not necessary to have a moving Ag foil
for the Wild 2 flyby, as was done for the higher
flux at Halley. The target area was increased
to 50 cm2 from the Halley Mission instrument's
5 cm2 target.
During its operation, a light flash, which accompanies
the dust impact on the target, is detected and
used to set the zero for the TOF measurement.
Electrostatic grids extract ions, depending from
the impact microplasma. These ions move down a
bent-tube TOF MS, with an electrostatic reflector
to focus ions of similar energies onto the ion
detector. By measuring their arrival time, the
mass of the ions can be determined. It is expected
that at the 6.1 km/s flyby speed, molecular ions
as well as atomic ions will be important in the
observations. The instrument is sensitive at least
over the range AMU=1 to 150, though sub-micron
sized particles produce observable signals and
compositional profiles too.
use of a recorder mode allow a superior data set
to be collected, than what was possible from the
data-constrained links that were available during
previous PIA flights. Most of this data will be
played back slowly over ensuing days or weeks
after the comet flyby.
The co-investigator in charge of the CIDA is Jochen
Kissel of MPE, the Max-Planck-Institut f. Aeronomie
in Lindau, Finland. The instrument has been developed
and built by von Hoerner & Sulger GmbH in
Schwetzingen, Germany, in close cooperation with
the MPE under contract by the DARA, Deutsche Agentur
f|r Raumfahrtangelegenheiten, Bonn. Software for
the CIDA instrument is being developed by The
Finnish Meterological Institute, Helsinki.
November 26, 2003