Cometary and Intersteller Dust Analyzer
The Cometary and Interstellar Dust Analyzer (CIDA) instrument intercepts dust and performs real-time compositional analysis for transmission back to Earth. The Stardust-NExT 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-NExT 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 instrument, 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.
Comet and Interstellar Dust flux analyzer being tested.
The 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.