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CDA

CDA

Cosmic Dust Analyzer (CDA) on the spacecraft
CDA on the Cassini Spacecraft
Astronomers have long been puzzled by a mysterious faint glow that appears at various times in certain parts of the sky. Eventually, they concluded this was caused by the presence of cosmic dust. Giovanni Cassini was the first astronomer to recognize this dust in interplanetary space, and its presence around the sun, through telescopic observations in the 17th century. Revealing the origins of this cosmic dust, its composition and how it may affect life on Earth has been an ongoing focus of research and exploration ever since.

The Cassini spacecraft continues this research with an instrument capable of detecting the impact of tiny particles -- 1/1,000 of a millimeter wide. To understand their true size and consistency, this cosmic dust can best be visually compared to icy cigar smoke particles. Under certain conditions, the Cosmic Dust Analyzer (CDA) onboard the spacecraft can even detect smaller dust grains called nano-dust. A nano-dust particle is one-millionth of a millimeter in size. Particles this small have as few as one million atoms, and are even smaller than a single influenza virus. Detection of these particles by the Cosmic Dust Analyzer would be equivalent to the detection of a single raindrop falling into the Gulf of Mexico.

Cosmic Dust Analyzer (CDA) instrument
CDA instrument

"We are a factor of 1,000 times more sensitive than an optical instrument and able to see 'dust clouds'," says Dr. Ralf Srama, CDA Principal Investigator of the Max Planck Institute for Nuclear Physics, Heidelberg, Germany. "Therefore we would be able to find one smoke sized particle in a football stadium!"

The CDA is capable of detecting the impact of very tiny particles in the Saturnian system. Saturn's broad, diffuse E ring -- within which several of Saturn's major moons travel in their orbits -- is composed primarily of dust particles that are one-thousandth of a millimeter in size. These particles are tiny, much smaller than the width of a human hair, smaller even than red blood cells, but are easily detectable by the CDA.

Interesting results quickly followed after the instrument was switched "on" early in 1999, five years before the spacecraft reached Saturn.

"First, we detected interplanetary dust particles and measured their composition," Srama says. "Those grains are very rare, and we got just one impact per week."

Cosmic Dust Analyzer (CDA) diagram
CDA Diagram
While in Jupiter's vicinity the instrument detected nano-dust particles traveling through the solar system with speeds of 400 kilometers per second (about 894,800 miles per hour). Continuously released into our solar system by the Jovian system, these particles were "seen" by the instrument as far as 100 million kilometers (62,137,119 miles) away.

It has been predicted that Saturn also releases smaller nano-dust particles traveling at slower speeds. Although more difficult to detect, the cosmic dust analyzer has such outstanding performance and sensitivity that it caught and found these smaller particles at distances of 100 million kilometers (62,137,119 miles) away from Saturn.

"We were even measuring their composition, and we found out that at least some of them are coming from Saturn's main ring (A ring)," Srama says.

For more information read the engineering technical write-up for CDA or visit the science team's Web site: http://www.dsi.uni-stuttgart.de/cosmicdust/.

At a Glance

The Cassini's Cosmic Dust Analyzer has the ability to directly measure the chemical composition of the dust particles impacting the Saturn system. In addition to detecting their speed, size and chemical composition, the instrument can also determine trajectories (orbits). This allows scientists to determine where the dust originated.

The CDA takes measurements when the dust particles impact the collection surface inside the instrument and become vaporized. As a result, a puff of plasma is created, which is extensively measured and analyzed.

This instrument requires very little power and is a passive instrument that allows particles to impact it rather than actively searching for them.

  • Mass (current best estimate) = 16.36 kg
  • Peak Operating Power (current best estimate) = 18.38 W (including articulation)
  • Average Operating Power (current best estimate) = 11.38 W
  • Peak Data Rate (current best estimate) = 0.524 kilobits/s
  • Dimensions (approximate) = 50.7 cm length x 45.0 cm diameter; 81 cm x 67 cm x 45 cm overall