James Webb Space Telescope of NASA reaches gravitational parking place in solar orbit

On Monday, NASA's James Webb Space Telescope, which will provide the world with an unprecedented look into the early phases of the universe, arrived at its gravitational parking location in orbit around the sun, about 1 million miles from Earth.

Webb arrived in a location of orbital stability between the Earth and the sun known as Lagrange Point Two, or L2, one month after launch, thanks to a final course-correcting manoeuvre by on-board rocket thrusters, according to the space agency's website.

The Hubble Space Telescope, Webb's 30-year-old predecessor, circles the Earth from a distance of 340 miles (547 kilometres), passing in and out of the planet's shadow every 90 minutes.

According to Eric Smith, NASA's Webb programme scientist, the combined gravity of the sun and Earth at L2 will keep the telescope firmly in place, requiring little more rocket energy to keep it from drifting.

The telescope's primary mirror - an array of 18 hexagonal segments of gold-coated beryllium metal spanning 21 feet, 4 inches (6.5 metres) across - has also begun fine-tuning at the mission operations centre, which is significantly larger than Hubble's main mirror.

Webb's size and architecture, which allows it to function mostly in the infrared spectrum, will enable it to see through clouds of gas and dust and observe objects at greater distances, and hence farther back in time, than Hubble or any other telescope.

These characteristics are predicted to usher in a revolution in astronomy, providing the first glimpse of infant galaxies dating back only 100 million years after the Big Bang, the hypothesised flashpoint that set the known universe's expansion in action an estimated 13.8 billion years ago.

Webb's detectors also make it perfect for looking for signs of possibly life-supporting atmospheres around a slew of recently discovered exoplanets - celestial bodies orbiting faraway stars - as well as observing worlds closer to home, such Mars and Saturn's frozen moon Titan.

THE NEXT STEP

Webb will require several more months of preparation before it can make its astronomical premiere. Following Webb's launch on Dec. 25, the 18 segments of its main mirror, which had been folded together to fit within the cargo bay of the rocket that took the telescope to space, were unfurled alongside the rest of the observatory's structural components over a two-week period.

Those portions were recently unfastened from the bolts that held them in place during the launch and slowly moved forward half an inch from their original position, allowing them to be modified into a single, uninterrupted light-collecting surface.

The 18 segments must now be positioned to get the optimum focus of the mirror, which will take three months. Ground teams will begin operating the observatory's spectrograph, camera, and other instruments as the alignment advances. The instruments will then be calibrated for two months, according to Smith.

If all goes according to plan, Webb should be able to start making observations in early summer, with the first photographs serving as proof that the instruments are working properly. However, Webb's most ambitious efforts, including as plans to train its mirror on objects farthest from Earth, will take longer to complete, according to Smith.

NASA, in concert with European and Canadian space agencies, is leading an international effort on the telescope. The main contractor was Northrop Grumman Corp.