Nasa has successfully tested the James Webb space telescope, and is now ready to transport it to Kourou in French Guiana.
Webb is the successor of the aging Hubble space telescope by Nasas. It was built in 1996. It was then called the Next Generation space telescope. It was scheduled to launch in 2007 at a cost of $500m (363m).
Webb is the most complex and comprehensive space science observatory in the world. It includes a mirror measuring 6.5 metres in diameter and a sunshield of tennis court size. These will all be folded into the nose cone of an Ariane 5 rocket by European Space Agency for launch later in the year.
It has been difficult to ensure that the spacecraft will work correctly once it is in orbit. This has caused delays and led to a budget of about $10 billion.
After the final tests have been completed successfully, it is now time to launch the telescope and check if everything works as expected. Webb will take approximately a month to reach its final orbit, which is about 1.5m km (930,000miles) from Earth.