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Rosetta starts tracking asteroid Steins
4th August 2008
Rosetta started the optical navigation campaign on 4 August 2008, at a distance of about 24 million km from Steins.

Greenhouse Earths
30th July 2008
New research shows that 40 million years ago the Earth was experiencing warmer seas with little or no ice on the planet

The Deep Dark Biosphere
July 26th 2008
Scientists have shown evidence that microbes living deep below the oceans of Earth make up a carbon reserve of about 90 billion tons.

COROT finds exoplanet orbiting Sun-like star
24th July 2008
A team of European scientists working with COROT have discovered an exoplanet orbiting a star slightly more massive than the Sun.

Meteorite Acid Test
July 18th 2008
Evidence of acid rain in 1908 supports the theory that a meteorite impact was responsible for the Tunguska catastrophe.

Cosmic Collisions
July 3rd 2008
Researchers have been using a vast database to show that asteroids are shaped by small impacts over time.

Listening to Planets
July 2nd 2008
Scientists are beginning to understand radio emissions emitted by aurora on Earth. The new study will help future astronomers search for extrasolar planets by listening for the sounds they make.

Looking for Early Earth… on the Moon
June 26th 2008
Material from Earth’s first billion years, including possible evidence of early life, may be preserved in meteorites on the moon.

More SuperEarths Discovered
June 22nd 2008
Astronomers have announced a breakthrough in the field of extra-solar planets. They have identified 45 potential super-Earths,showing that these planets may be present around one out of every three solar-like stars.

We Are Meteorites
June 20th 2008
Molecules important for the origin of life have been positively identified in a meteorite. Scientists have confirmed that raw materials for the first molecules of DNA and RNA have been discovered in the Murchison meteorite.

ExoMars Sweet Spot
June 17th 2008
A device the size of a credit card is being developed to perform multiple laboratory tests on the surface of Mars. The 'lab-on-a-chip' will be included on the European ExoMars rover, and will be used to search for signs of life on the red planet.

Renaming Pluto
June 15th 2008
The International Astronomical Union has defined new rules for naming and categorizing dwarf planets. Those similar to Pluto and with orbits beyond Neptune will now be named 'plutoids'.

Low Frequency Aliens
June 11th 2008
A new type of radio telescope may aid in the search for extraterrestrial intelligent life. The LOFAR telescope could be used to detect signals directed toward Earth, and might even pick up 'leakage radiation' from radio and TV transmitters if they're being used by civilizations around nearby stars.

Low Frequency Aliens
June 11th 2008
A new type of radio telescope may aid in the search for extraterrestrial intelligent life. The LOFAR telescope could be used to detect signals directed toward Earth, and might even pick up 'leakage radiation' from radio and TV transmitters if they're being used by civilizations around nearby stars.

 

 

Rosetta starts tracking asteroid Steins

4th August 2008

Heading toward its first target-asteroid, (2867) Steins, ESA's Rosetta spacecraft has started using its cameras to visually track the asteroid and eventually determine its orbit with more accuracy.

Asteroid (2867) Steins
Credits: ESA

Rosetta started the optical navigation campaign on 4 August 2008, at a distance of about 24 million km from Steins; the campaign will continue until 4 September, when the spacecraft will be approximately 950 000 km from the asteroid.

"The orbit of Steins, with which Rosetta will rendezvous on 5 September, closing to a distance of 800 km, is only known thanks to ground observations, but not yet with the accuracy we would like for the close fly-by," said Gerhard Schwehm, Rosetta Mission Manager based at ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain.

Optical tracking to better understand Steins' orbit

“We will be able to use the first data set for the trajectory correction manoeuvre planned for mid-August.”

The purpose of the tracking campaign is to reduce the error in our knowledge of Steins' orbit from about 100 km to only within 2 km (in the direction perpendicular to the flight direction of the asteroid, called 'cross-track'), so as to allow Rosetta an optimal approach to this celestial body.

Both Rosetta's navigation cameras and the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) imaging system will be used to track Steins.

"For the first three weeks of the campaign, however, only the powerful eyes of OSIRIS will actually be able to spot the asteroid, which will look only like a dot in the sky," said Andrea Accomazzo, Rosetta Spacecraft Operations Manager at ESA's European Space Operations Centre (ESOC), Darmstadt, Germany.

The Rosetta orbiter - spacecraft design Rosetta resembles a large aluminium box whose dimensions are 2.8 x 2.1 x 2.0 metres. The scientific instruments are mounted on the 'top' of the box – the Payload Support Module – while the subsystems are on the 'base' or Bus Support Module.
Credits: ESA/AOES Medialab

"Starting 11 days before closest approach, as the distance with Steins decreases, the two Rosetta navigation cameras will finally be able to see and track the asteroid, too," he added.

For the first three weeks of the campaign, Rosetta will image Steins twice a week and then, starting on 25 August, it will take images daily until 4 September.

The Steins orbital information gathered during the tracking campaign will be used to adjust Rosetta's trajectory for the 5 September fly-by. "We will already be able to use the first data set for the trajectory correction manoeuvre planned for mid-August," said Sylvain Lodiot, from the Rosetta Flight Control Team at ESOC.
 
"As Rosetta's distance from Steins decreases, the precision of the measurements for Steins' orbit will increase even further, allowing us the best possible trajectory corrections later on before closest approach, especially in early September."

OSIRIS to obtain Steins' 'light curves'

Brightness variation of the asteroid measured continuously over one day. The maximum in the light curve is about 23 percent brighter than the minimum.
Credits: Stefano Mottola (DLR), OSIRIS team

Rita Schulz, Rosetta Project Scientist based at ESA's European Space Research and Technology Centre (ESTEC), Noordwijk, the Netherlands, explained that this is the first time in the Rosetta mission that the OSIRIS scientific instrument is being used for tracking purposes.

"But OSIRIS will also take this opportunity to obtain 'light curves' of Steins. Light curves tell us how the asteroid brightness varies with time, providing us with additional preparatory information about the asteroid, such as better knowledge of its shape and rotation characteristics," she said.
 
 
The optical navigation campaign follows a series of active check-outs of Rosetta's scientific instrumentation, which lasted from 5 July to 3 August this year. A mission milestone for Rosetta, these activities also verified the instruments' readiness for the fly-by observations, and allowed on-board software modifications to be implemented for several of them.
 
 
More information
 
Gerhard Schwehm, ESA Rosetta Mission Manager
Email: Gerhard.Schwehm @ esa.int

Rita Schulz, ESA Rosetta Project Scientist
Email: Rita.Schulz@esa.int

Andrea Accomazzo, ESA Rosetta Spacecraft Operations Manager
Email: Andrea.Accomazzo@esa.int

 

 

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