The Hubble telescope will be replaced by the James Webb Space Telescope, known as the JWST or Webb telescope, which is slated to launch on March 30, 2021. Learn the difference between the two telescopes and how they measure up to one another.

The LaGrange Point

Webb looks further back in time than Hubble. Hubble has a very close earth orbit, but Webb will be one point 1.5 million kilometers away. This is called the second LaGrange point.

A Lagrange point defines a meeting point between the gravitational forces of two large bodies. In this case, it’s the earth and the sun. It's a special spot where a third body can remain parked for observations.
The Difference in Mirrors

• Webb’s primary mirror is slated to measure 6.5 meters, giving it a much larger collecting area than on any of the space telescopes currently in orbit. In contrast, Hubble's mirror measures just 2.4 meters in diameter and has a collecting area of 4.5 m2.
• The James Webb Telescope has 6.25 times the collecting area. It will be 100 times as powerful as the Hubble Space Telescope.
• Webb has a relatively massive field of view compared to the NICMOS camera aboard the Hubble Space Telescope. Webb will cover about 15 times the area of its predecessor.

What Is the Difference in Orbits?

While the Hubble Telescope turns around the Earth at a height of 570 km. James Webb won't orbit its home planet Earth. Instead, it will remain stationary at the Earth-Sun L2 Lagrange point.

As it remains in place, Webb's solar shield will protect it from the light of the Sun. It will measure distant objects that are red-shifted and out of the visible range of Hubble. 

Is Hubble Still Active?

The Hubble Space Telescope is the only one designed to be maintained by astronauts. It could last until 2030 or beyond. This means it will overlap with the contributions made from the soon to be launched James Webb Telescope.
When Will the James Web Space Telescope Be in Place?

You may be wondering how long it will take for the James Webb Space Telescope to become active after its launch. It should take about one month for the web Space Telescope to reach the second LaGrange point and about six months to begin scientific operation.

How Many Space Telescopes Are There?

NASA's Great Observatories program Has built four orbiting telescopes. This includes The Hubble Space Telescope, the Chandra X-ray Observatory the Hubble Space Telescope, the Spitzer Space Telescope and the Compton Gamma Ray Observatory. Other space telescopes are still in the works.

Hubble Space Telescope and its cousins in the sky have made an extraordinary contribution to astronomy and astrophysics. Scientists continue to improve the tools needed to see further away into other galaxies and to the edges of the universe itself. (For more space info, please click here.)