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Grain Impact Analyser and Dust Accumulator (GIADA)

NSSDCA ID: 2004-006A-06

Mission Name: Rosetta
Principal Investigator:Dr. Alessandra Rotundi

Description

The Grain Impact Analyser and Dust Accumulator (GIADA) on Rosetta is designed to perform in-situ studies on the dust and small grain environment of a comet. The primary scientific objectives are to study: 1) dust size distribution at the nucleus; 2) the dust to gas ratio; 3) the time evolution of the dust environment as a function of the heliocentric distance ; 4) the dust mass loss rate; and 5) the grain dynamic properties. It will also perform synergistic relations with other instruments onboard Rosetta. GIADA is contained in a box-shaped housing and consists of three modules: GIADA-3, an assembly of 5 micro-balance systems designed to measure dust mass flux; GIADA-2, the main electronics sub-system; and GIADA-1, which consists of a grain detection system and an impact sensor.

The GIADA-1 grain detection system is pointed towards the nucleus with an acceptance angle of about 40 degrees. It consists of two parallel reference planes. The upper plane is designed for optical detection of grains, with four laser diodes forming a light curtain and eight photodiode detectors situated at 90 degrees with respect to the sources to detect any scattered/reflected signal. The bottom plane is a diaphragm with five piezoelectric transducers to detect grain impact and determine the momentum of the grain. The velocity can be determined by time-of-flight between the two planes and the grain mass estimated. The detection size limit is roughly 10 micrometers. The GIADA-2 electronics system and data processing unit are housed at the bottom of the GIADA instrument and control the data acquisition, sub-systems operation, and interface with the spacecraft electronics.

The GIADA-3 microbalance sensors (MBS) are mounted on top of the instrument, one sensor pointing towards the comet and the other four pointing off to the side. They are baffled to allow impacts from grains over an angle of about 40 degrees. Each sensor consists of a resonating sensing crystal and reference crystal. The MBS's are based on the principles of piezoelectric transducers, as dust is deposited on the exposed sensing crystal the mass changes, varying the oscillation frequency. The output signal is proportional to the amount of dust mass deposited on the sensing crystal. The reference crystal is isolated from the dust and maintains a constant mass and output signal for comparison to account for temperation and power source variations. The crystals oscillate with a frequency around 10 MHz. The sensing crytal has a few tenths of a square cm of exposed surface and is displaced in frequency approximately 1 kHz below the reference crystal. Inverse sensitivities better than 10 billionths of a gram per Hz may be possible.

For more information on the instrument, see:

http://adsabs.harvard.edu/abs/2014JAI.....350011D

Alternate Names

  • GIADA
  • Rosetta/GIADA

Funding Agency

  • European Space Agency International

Discipline

  • Planetary Science: Small Bodies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Alessandra RotundiPrincipal InvestigatorUniversita degli Studi di Napolirotundi@uniparthenope.it

Selected References

  • Bussoletti, E., et al., The GIADA experiment for Rosetta mission to comet 46P/Wirtanen: Design and performances, Adv. Space Res., 24, No. 9, 1139-1148, June 1999.
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