Why does the James Webb telescope have to fly 1.5 million km?

NASA's James Webb Space Telescope will outperform its famous predecessor, the Hubble telescope, in many ways, including position in space.

The $10 billion James Webb telescope is significantly larger, more complex, and more powerful than the Hubble space telescope, which has been studying the universe from Earth's orbit for more than three decades. The new observatory successfully launched at 19:20 pm on December 25, Hanoi time will fly further to the Larange 2 (L2) point between the Earth and the Sun, 1.5 million km from our planet.

Simulation of James Webb telescopes in orbit.

Larange points are gravitationally stable points where spacecraft can "stop", maintaining relative position without consuming much fuel. But Webb glasses don't just operate at the L2 point to save propellant.

Webb is optimized for observing the universe in infrared (IR) light, a long wavelength that humans can perceive as heat. In contrast, Hubble observes mainly in the visible and ultraviolet wavelengths.

To capture the weakest IR signal, Webb's scientific instruments must be in extremely cold conditions. Therefore, the observatory is equipped with a 5-layer heat shield the size of a tennis court when fully spread. But the heat shield does not provide the necessary protection if Webb is not facing the Sun.

"The special thing about this orbit is that the telescope is aligned with the Earth when moving around the Sun," a NASA representative explained about the L2 point. That allows the large heat shield to protect the telescope from the light and heat of the Sun, Earth, and Moon."

"If all goes to plan, Webb's equipment will operate at - 225 degrees Celsius. Meanwhile, the heat on the hot side where the solar cells, communication antennas and other equipment of Webb will suffer will suffer. temperature of 88 degrees Celsius. The temperature difference between the hot and cold sides of the telescope is huge. You can almost boil water on the hot side and freeze nitrogen on the cold side," NASA said.

The distance to the L2 point represents another important difference between Hubble and Webb. The older Hubble telescope was designed to be repaired and upgraded by astronauts during spacewalks between 1993 and 2009.

The first of these missions is particularly important because it helps repair Error in Hubble's primary mirror caused the first series of images to be blurred. But the distance of 1.5 million km is too great to send astronauts, so the Webb telescope with its 6.5 m-wide primary mirror, nearly three times larger than the Hubble telescope's mirror, will operate on its own at the L2 point.

Once launched, Webb will take about 30 days to reach its destination. Webb will orbit the point L2 and initiate a manifold observational shift. The telescope will study some of the first stars and galaxies in the universe, understand the atmospheres of exoplanets that could harbor signs of life, among other missions. Webb is not the first spacecraft to operate at point L2. NASA's Wilkinson Microwave Anisotropy Probe operated there from 2001 to 2010, similar to the European Space Agency's (ESA) Herschel Space Telescope (2009-2013) and the Planck probe. (year 2009 - 2013).

There are a total of 5 Lagrange points between the Earth and the Sun. Point L3 is in line with L1 and L2, but on the other side of the Sun. L4 and L5 lie 60 degrees in front of and behind the Earth.