The James Webb Space Telescope has arrived at its cosmic parking spot a
million miles away, bringing it a step closer to its mission to unravel the
mysteries of the Universe, NASA said Monday.
At around 2:00 pm Eastern Time (1900 GMT), the observatory fired its
thrusters for five minutes to reach the so-called second Lagrange point, or
L2, where it will have access to nearly half the sky at any given moment.
The delicate burn added 3.6 miles per hour (1.6 meters per second) to Webb's
overall speed, just enough to bring it into a "halo" orbit around L2, 1.5
million kilometers from Earth.
"Webb, welcome home!" said NASA Administrator Bill Nelson in a statement.
Webb will begin its science mission by summer, which includes using its high
resolution infrared instruments to peer back in time 13.5 billion years to
the first generation of galaxies that formed after the Big Bang.
At L2, it will stay in line with the Earth as it moves around the Sun,
allowing Webb's sunshield to protect its sensitive equipment from heat and
light.
For the giant parasol to offer effective protection, it needs the Sun, Earth
and Moon to all be in the same direction, with the cold side operating at
-370 degrees Fahrenheit (-225 Celsius).
The thruster firing, known as an orbital burn, was the third such maneuver
since Webb was launched on an Ariane 5 rocket on December 25.
The plan was intentional, because if Webb had gotten too much thrust from
the rocket, it wouldn't be able to turn around to fly back to Earth, as that
would expose its optics to the Sun, overheating and destroying them.
It was therefore decided to slightly underburn the rocket firing and use the
telescope's own thrusters to make up the difference.
The burns went so well that Webb should easily be able to exceed its planned
minimum life of five years, Keith Parrish Webb observatory commissioning
manager told reporters on a call.
"Around 20 years, we think that's probably a good ballpark, but we're trying
to refine that," he said. It's hypothetically possible, but not anticipated,
that a future mission could go there and refuel it.
Webb, which is expected to cost NASA nearly $10 billion, is one of the most
expensive scientific platforms ever built, comparable to the Large Hadron
Collider at CERN, and its predecessor telescope, Hubble.
Halo orbit
But while Hubble orbits the Earth, Webb will orbit in an area of space known
as a Lagrange point, where the gravitational pull from the Sun and Earth
will be balanced by the centrifugal force of the rotating system.
An object at one of these five points, first theorized by Italian French
mathematician Joseph-Louis Lagrange, will remain stable and not fall into
the gravity well of the Sun and Earth, requiring only a little fuel for
adjustments.
Webb won't sit precisely at L2, but rather go around it in a "halo" at a
distance similar to that between the Earth and Moon, completing a cycle
every six months.
This will allow the telescope to remain thermally stable and to generate
power from its solar panels.
Previous missions to L2 include the European Space Agency's Herschel and
Planck observatories, and NASA's Wilkinson Microwave Anisotropy Probe.
Webb's position will also allow continuous communications with Earth via the
Deep Space Network—three large antennas in Australia, Spain and California.
Earlier this month, NASA completed the process of unfolding Webb's massive
golden mirror that will collect infrared signals from the first stars and
galaxies that formed a few hundred million years after the Universe began
expanding.
Visible and ultraviolet light emitted by the very first luminous objects has
been stretched by the Universe's expansion, and arrives today in the form of
infrared, which Webb is equipped to detect with unprecedented clarity.
Its mission also includes the study of distant planets, known as exoplanets,
to determine their origin, evolution and habitability.
Next steps include aligning the telescope's optics and calibrating its
scientific instruments. It is expected to transmit its first images back in
June or July.
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Space & Astrophysics