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Last Updated: Friday, 28 May, 2004, 16:25 GMT 17:25 UK
Rosetta probe passes first tests
Comet Linear   Esa
Rosetta detected water molecules in the "atmosphere" around Comet Linear
Europe's comet-chasing spacecraft Rosetta has successfully completed its first scientific task: observation of Comet C/2002 T7, or Comet Linear.

Rosetta took detailed images of the comet and made scientific measurements from a distance of about 95 million km.

It even managed to detect the presence of water molecules in the tenuous atmosphere around Comet Linear.

The 600m probe is on a 7bn-km journey to rendezvous with a different target: Comet 67P/Churyumov-Gerasimenko.

Once in orbit around the 4km-wide ball of ice and dust in 2014, the craft will despatch a small lander called Philae to the surface of Churyumov-Gerasimenko to study its chemistry.

Mission scientists have nearly completed the first phase of commissioning activities on the spacecraft, which included the individual activation of all instruments on board Rosetta and Philae.

The first check-out showed all instruments were functioning well.

Early switch-on

On 30 April, Rosetta took high-resolution images of Comet Linear with its Osiris (Optical, Spectroscopic, and Infrared Remote Imaging System) camera.

Later that day, three more instruments on board Rosetta were activated in parallel to take measurements of the comet.

The four instruments took images and spectra of Comet Linear to study its coma - the cloud of water vapour and carbon dioxide surrounding the comet's nucleus - and tail at different wavelengths, from the ultraviolet to the microwave.

Detailed analysis of the data will require the complete calibration of the instruments, which will be carried out over the next few months.

Parallel activation of the instruments was not planned until later in the year. But the Rosetta team decided this could be done without any risk to progress of the overall testing of the spacecraft.

The first phase of commissioning is due to be completed in the first week of June.

Rosetta will then go into a quiet "cruise mode" until September, when the second phase of commissioning is scheduled to start.




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