Last week, Nasa engineers, aiming for new images of the stars, did what every photographer needs to remember to do before taking snapshots – they removed the lens cap. In this case, they sent signals to the wide-field infrared survey explorer (Wise) space telescope to jettison a cover that protected the optical gear during launch and helped to keep it chilled.

Wise will start its infrared survey later this month, and its ‘first light’ images will be released to the public about a month later. The Delta II rocket carrying the telescope into earth orbit had lifted off in mid-December last year. Shortly after the space telescope rea­ched its polar orbit around the Earth, it lined up its solar panels to face the sun.

The mission is planned to undergo a one-month checkout before beginning the most detailed survey yet of the entire sky in infrared light. Hundreds of millions of objects will populate its vast catalogue, including dark asteroids, the closest ‘fai­led’ stars and tremendously en­ergetic galaxies.

The cover of the space telescope served as the top to a Thermos-like bottle, called a cryostat, which chills the heat-sensitive infrared instrument. The instrument consists of a 40-centimetre telescope and four detectors, each with one million pixels. Just as a thermos bottle keeps your coffee warm or your iced tea cold with a thin vacuum layer, a vacuum inside Wise’s cryostat kept the instrument cold while it was on the ground. The cover also prevented any light from reaching the detectors, and protected the chilly interior of the instrument from heat that could have come about from unintentional pointing at earth or the sun during launch. Wise stabilised in its position in surprisingly little time of only three minutes.

With Wise steadily perched, it no longer needs the instrument cover; with space provide an even better vacuum. The Wise team has also verified that the instrument is as cold as pl­anned. The cryostat’s outer sh­ell is slightly below the planned 190 Kelvin (minus 83 degrees Celsius, or minus 117 degrees Fahrenheit), and the coldest of the detectors is less than 8 Kelvin (minus 265 de­grees Celsius). Being an In­frared space telescope the stellar objects that the telescope ob­serves have to be hotter than the sensors on Wise.

“Our detectors are soaking up starlight for the first time,” said William Irace, the mission's project manager at Nasa's Jet Propulsion Laboratory in Pas­adena, California. Scientists and engineers are now busy adjusting the rate of the spacecraft to match the rate of a scanning mirror.

To take still images on the sky as it orbits around earth, Wise would use a scan mirror to counteract its motion. Light fr­om the moving telescope’s primary mirror will be focused onto the scan mirror, which will move in the opposite direction at the same rate. This allows the mission to take ‘freeze-frame’ snapshots of the sky every 11 seconds. That's about 7,500 im­ages a day.

Wise will perform the most detailed infrared survey of the entire sky to date. Its millions of images will expose the dark side of the cosmos — objects such as asteroids, stars and galaxies, that are too cool or dusty to be seen with visible light.

The telescope will survey the sky one-and-a-half times in nine mo­nths, ending its primary mission when the coolant it needs to see infrared light evaporates away.

“It's wonderful to end the year with open Wise eyes,” said Peter Eisenhardt, the mission's project scientist at JPL. "Now we can synch Wise up to our scan mirror and get on with the business of exploring the infrared universe.” Wise is scheduled to begin its survey of the infrared heavens in mid-January.

The writer is doctoral candidate at Carnegie Mellon University, Pittsburgh, PA and also Knowledge Editor of Financial Chronicle