Sharpest whole-planet picture of Jupiter obtained

Munich, Oct 3 : New image-correction technique in an instrument on the ESO's (European Southern Observatory's) Very Large Telescope (VLT) has delivered the sharpest whole-planet ground-based picture ever of Jupiter.

The series of 265 snapshots obtained with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype instrument mounted on ESO's VLT reveal changes in Jupiter's smog-like haze, probably in response to a planet-wide upheaval more than a year ago.

Being able to correct wide field images for atmospheric distortions has been the dream of scientists and engineers for decades.

The new images of Jupiter prove the value of the advanced technology used by MAD, which uses two or more guide stars instead of one as references to remove the blur caused by atmospheric turbulence over a field of view thirty times larger than existing techniques.

"This type of adaptive optics has a big advantage for looking at large objects, such as planets, star clusters or nebulae," said lead researcher Franck Marchis, from UC Berkeley and the SETI Institute inountain View, California, USA.

"While regular adaptive optics provides excellent correction in a small field of view, MAD provides good correction over a larger area of sky. And in fact, were it not for MAD, we would not have been able to perform these amazing observations," he added.

MAD allowed the researchers to observe Jupiter for almost two hours on 16 and 17 August 2008, a record duration, according to the observing team.

Using MAD, ESO astronomer Paola Amico, MAD project manager Enrico Marchetti and Sebastien Tordo from the MAD team tracked two of Jupiter's largest moons, Europa and Io - one on each side of the planet - to provide a good correction across the full disc of the planet.

"It was the most challenging observation we performed with MAD, because we had to track with high accuracy two moons moving at different speeds, while simultaneously chasing Jupiter," said Marchetti.

With this unique series of images, the team found a major alteration in the brightness of the equatorial haze, which lies in a 16,000-kilometer (10,000-mile) wide belt over Jupiter's equator.

More sunlight reflecting off upper atmospheric haze means that the amount of haze has increased, or that it has moved up to higher altitudes.

"The brightest portion had shifted south by more than 6,000 kilometers (nearly 4,000 miles)," explained team member Mike Wong.

"The change we see in the haze could be related to big changes in cloud patterns associated with last year's planet-wide upheaval, but we need to look at more data to narrow down precisely when the changes occurred," declared Wong.

ANI