NASA has reached a step closer to launch its James Webb Space Telescope (JWST) into orbit as technicians completed assembly of all the 18 primary mirrors on the flagship-class space observatory.

The last hexagonal section was installed on the giant telescope on Wednesday with the help of a robotic arm. John Grunsfeld, NASA associate administrator for the Science Mission Directorate, said in a statement, “Scientists and engineers have been working tirelessly to install these incredible, nearly perfect mirrors that will focus light from previously hidden realms of planetary atmospheres, star forming regions and the very beginnings of the universe”.

With the completion of mirror installation, the JWST team has reached closer to launch the giant telescope that will one day unravel hidden secrets of the universe, Grunsfeld continued.

As per NASA’s plans, the JWST will be launched into orbit in 2018 with an aim to replace currently working the Hubble Space Telescope. The infrared telescope will allow astronomers to study those regions of the universe that are inaccessible for the Hubble. While staying in the orbit, it will make observations related to stars, galaxies, planets and other planetary bodies hovering in the space.

Mirror installation has been completed, but the JWST’s much work in still in progress, said officials working on the telescope’s next steps. A team of technicians, called the Harris, will install the secondary mirror and the aft-optics assembly on the telescope, said Gary Matthews, director of universe exploration at Harris Corp. After that, technician will install the Integrated Science Instrument Module, also known as heart of the JWST, he continued.

Before the launch in 2018, the telescope will have to pass acoustic, vibration and other tests at NASA’s Goddard center, Matthews added.