Researchers are working against the clock to fix a blurry telescope whose malfunction could undermine a $330-million US space mission to a distant comet.
JPL/NASA
Out of focus: images of the Deep Impact craft's collision with comet Tempel I may be blurred.
The Deep Impact spacecraft is on course for comet Tempel 1, about 160 million kilometres from Earth. The car-sized craft has an 'impactor' that is due to split off and strike the comet on 4 July, while cameras on the main spacecraft capture the collision, enabling researchers to analyse the comet's make-up in unprecedented detail.
But Deep Impact's main instrument — a high-resolution telescope on the fly-by probe — is out of focus, admit project officials at the Jet Propulsion Laboratory (JPL) in Pasadena, California. This will affect the quality of the images captured from the experiment, the officials say.
The JPL project team has been working quietly for more than a month to try to fix the focus problem, which was discovered shortly after the probe was launched in Florida on 12 January. NASA, which is funding the project, acknowledged the problem on 25 March, after an enquiry from Nature.
JPL scientists have organized a special team to study possible remedies. But so far, efforts to correct the focus have failed, JPL officials say.
Project scientists now plan to employ computer imaging techniques that they hope will improve data from Deep Impact. Similar techniques have been successfully employed in the past on other space telescopes, including Hubble, they say.
The problem telescope was built by Ball Aerospace & Technologies of Boulder, Colorado. Ball officials refused requests for an interview.
As the Deep Impact spacecraft approaches Tempel 1, the impactor will separate from the main craft. The impactor itself has an onboard telescope and camera, which will be used for navigation and for capturing images up to the point of collision.
The main spacecraft is due to fly past the comet at a distance of about 700 kilometres. It carries the problematic high-resolution telescope, as well as a back-up medium-resolution instrument, which is due to capture a wider view of the collision. The back-up instrument is functioning properly, officials say.
But even if pictures from the high-resolution telescope cannot be improved, the instruments are expected to provide "the most detailed pictures of a comet ever taken", says Michael A'Hearn, an astronomer from the University of Maryland at College Park who is chief scientist on the project.