After a 30-day journey, NASA's James Webb Space Telescope (JWST) has reached its destination at the Lagrange 2 (L2) point about one million miles (1.5 million km) from Earth. At 2:00 pm EST, it fired its main engines for 297 seconds to alter its velocity by 3.6 miles per hour (1.6 m/s) and send it into its new orbit.
The final course correction for the long-delayed US$10 billion space telescope comes at the end of a month-long suspenseful process of deploying the spacecraft, which was folded up like a giant piece of origami so it would fit into the nose cone for its launch on December 25, 2021, from ESA's Centre Spatial Guyanais in French Guiana.
During the passage to L2, the JWST deployed its solar array and communications antenna, spread out and tensioned its tennis court-sized sun shield, and raised and unfolded its 6.5 m (24 ft) wide primary mirror. The latter is made of a matrix of 18 gold-plated beryllium hexagons controlled by hundreds of actuators that mission control used to ensure correct calibration as temperature dropped to below -223.2 °C (-369.7 °F).
Today's engine burn was calculated to be as short as possible to conserve propellant. By doing this, the onboard thrusters used to keep the JWST on station and pointing in the right direction can keep operating for over 10 years.
Unlike most spacecraft, the JWST isn't orbiting the Earth, Sun, or some other celestial body. Instead, it revolves around L2, which is one of five points in the neighborhood of Earth where the gravitational forces of the Sun and the Earth balance one another out, creating a semi-stable point in space where a satellite can go into what is called halo orbit, which is a special three-dimensional orbit.
By going into this orbit, the Webb sits at a point with the Sun and Earth behind it as the craft faces toward interstellar space. This allows the sun shield to always protect the telescope from radiation that would interfere with the instruments and keep the telescope at cryogenic temperatures. The telescope can then peer deep into the infrared band of the electromagnetic spectrum where it can look so far into space that it can see light coming from the very early eras of the universe as well as study the formation and evolution of galaxies.
One other advantage of being in such an orbit is it allows the JWST to maintain constant contact with mission control through NASA's Deep Space Network of Earth-based communications and tracking antennas.
Though the Webb is now on station, it is still far from ready to go to work. Over the next six months, NASA engineers will go through the complex commissioning process as well as further aligning the telescope's optics to within a nanometer of specifications.
The video below shows the JWST reaching its destination at L2.
Source: NASA
