Spacewatch

The International Space Station has been making conspicuous transits across our night sky for almost a month, but its spell of visibility ends over the coming week as its orbit shifts westwards into the evening twilight. Our best remaining chance to glimpse it occurs at about 22:00 BST tonight when it reaches 73° high in the SSW as seen from London on its way from the W to the ESE. From Manchester, with the twilight even more obtrusive, it peaks at 49° on that pass.

Barring a late change to its flight schedule, the shuttle Atlantis is due to land on Friday afternoon, UK time, to conclude its servicing mission to the Hubble Space Telescope. Meantime, another of Nasa's so-called Great Observatories, Spitzer, has reached the end of its main mission. Launched in 2003 to work at infrared wavelengths, it used liquid helium coolant to keep its instruments operating at peak efficiency. Sadly, the final dregs of helium evaporated last Friday, so Spitzer has been forced to begin a "warm mission", with reduced sensitivity. Last week's good news is that the Kepler spacecraft has begun its search for Earth-like planets by staring continuously at an expanse of sky between Vega and Deneb, the bright stars that mark the two most northerly corners of our Summer Triangle. The week also saw Europe's successful launch of the Herschel and Planck observatories towards their vantage point 1.5 million km beyond the Earth's orbit.