ESA scientists announced yesterday that their Rosetta space craft has sent back a picture of Comet Tempel-1. The smudgy white dot might be almost indistinguishable from the rest of the stars in the sky, and it would probably be fair to describe it as one of the less impressive pictures from space we have seen in recent years, but the image does at least prove that Rosetta's cameras work.

The comet, for those who are wondering, is the slightly smudgy looking dot in the left hand bottom corner.

Fortunately, Deep Impact itself will be rather closer when its impactor hits the comet, so there should be better quality pictures available from NASA, on the day.

Rosetta will be watching when Deep Impact hits, but the useful information will come from its scientific instruments, rather than its optical cameras. As you can see, the camera is not perfectly aligned to the comet. This has been done so that the science packages have the best possible view of the event.

The craft will be watching in the microwave, infrared and visible parts of the spectrum, looking at the gas composition and temperature, and the dust expelled by the impact.

Rosetta is one of several space-based observatories that will be watching Deep Impact's encounter with Tempel-1. Hubble, Chandra, XMM-Newton, Spitzer and Swift will all be taking a view and reporting back to research teams on Earth. ®

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