ESA Rosetta: NASA instruments on comet spacecraft begin activation countdown

This artist's impression shows the Rosetta orbiter at comet 67P/Churyumov-Gerasimenko. 

Credit: ESA /ATG Medialab

Three NASA science instruments are being prepared for check-out operations aboard the European Space Agency's Rosetta spacecraft, which is set to become the first to orbit a comet and land a probe on its nucleus in November.

Rosetta was reactivated Jan. 20 after a record 957 days in hibernation. U.S. mission managers are scheduled to activate their instruments on the spacecraft in early March and begin science operations with them in August.

The instruments are an ultraviolet imaging spectrograph, a microwave thermometer and a plasma analyzer.

Claudia Alexander

"U.S. scientists are delighted the Rosetta mission gives us a chance to examine a comet in a way we've never seen one before—in orbit around it and as it kicks up in activity," said Claudia Alexander, Rosetta's U.S. project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

"The NASA suite of instruments will provide puzzle pieces the Rosetta science team as a whole will put together with the other pieces to paint a portrait of how a comet works and what it's made of."

Rosetta's objective is to observe the comet 67P/Churyumov-Gerasimenko up close. By examining the full composition of the comet's nucleus, and the ways in which a comet changes, Rosetta will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in seeding Earth with water, and perhaps even life.

The ultraviolet imaging spectrograph, called Alice, will analyze gases in the tail of the comet, as well as the coma, the fuzzy envelope around the nucleus of the comet.

The coma develops as a comet approaches the Sun.

Alice also will measure the rate at which the comet produces water, carbon monoxide and carbon dioxide.

These measurements will provide valuable information about the surface composition of the nucleus.

The instrument also will measure the amount of argon present, an important clue about the temperature of the solar system at the time the comet's nucleus originally formed more than 4.6 billion years ago.

The Microwave Instrument for Rosetta Orbiter (MIRO)will identify chemicals on or near the comet's surface and measure the temperature of the chemicals and the dust and ice jetting out from the comet.

The instrument also will see the gaseous activity in the tail through coma.

The Ion and Electron Sensor is part of a suite of five instruments to analyze the plasma environment of the comet, particularly the coma.

The instrument will measure the charged particles in the Sun's outer atmosphere, or solar wind, as they interact with the gas flowing out from the comet while Rosetta is drawing nearer to the comet's nucleus.

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ESA's billion-star surveyor Gaia counts down to launch

Gaia mapping the stars of the Milky Way. Credit: ESA/ATG medialab; background: ESO/S. Brunier

ESA's billion-star surveyor Gaia will be launched from Europe's spaceport in Kourou on 20 November to begin a five-year mission to map the stars with unprecedented precision.

Gaia's main goal is to create a highly accurate 3D map of our Milky Way Galaxy by repeatedly observing a billion stars to determine their positions in space and their movement through it.

Other measurements will assess the vital physical properties of each star, including temperature, luminosity and composition. The resulting census will allow astronomers to determine the origin and the evolution of our Galaxy.

Gaia will map the stars from an orbit around the Sun, near a location some 1.5 million km beyond Earth's orbit known as the L2 Lagrangian point.

The spacecraft will spin slowly, sweeping its two telescopes across the entire sky and focusing their light simultaneously onto a single digital camera, the largest ever flown in space – it has nearly a billion pixels.

For the last two months Gaia has been rigorously tested in Kourou as part of the launch campaign.

"Getting ready for launch is an extremely busy phase for the mission teams, but it's also extremely exciting and rewarding to see our mission so close to launch," says Giuseppe Sarri, ESA's Gaia project manager.

The Gaia Deployable Sunshield Assembly (DSA) during deployment testing in the S1B integration building at Europe's spaceport in Kourou, French Guiana, on 10 October 2013. 

Credit: ESA–M. Pedoussaut, 2013

Earlier this month the spacecraft's sunshield passed the final deployment test in the cleanroom in Kourou. It has now been stowed in its final configuration ready for the launch.

Shortly after launch, the sunshield will be deployed, forming a 10.5 m-wide 'skirt' around Gaia's base.