The James Webb Space Telescope (Webb) is designed to answer outstanding questions about the Universe and to make breakthrough discoveries in all fields of astronomy.
Webb will orbit the second Lagrange point (L2), 1.5 million kilometres from Earth in the direction away from the Sun. There, its sunshield can always block light and heat from both the Sun and Earth from reaching its telescope and instruments. L2 is not a fixed point, but follows Earth around the Sun.
Designed to protect the telescope’s optics from any heat sources that could interfere with its sight, the sunshield is one of Webb’s most critical and complex components. Because Webb is an infrared telescope, its mirrors and sensors need to be kept at extremely cold temperatures to detect faint heat signals from distant objects in the universe.
In space, one side of the sunshield reflects light and background heat from the Sun, Earth and Moon. That side of Webb will reach around 85 degrees Celsius. Meanwhile, the other side of the sunshield always faces deep space, and will have a temperature of around -233 degrees Celsius.
In the month after liftoff, Webb will unfold like a ‘transformer’ in space. After about a month, the observatory will be fully unfolded and it will reach L2. In the following months, the instruments will be turned on and their capabilities tested. After half a year in space, Webb will start its routine science observations.
Learn more about Webb’s unfolding sequence here.
Webb is an international partnership between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).