M4L4: The James Webb Telescope
Scheduled
to launch in 2018, the James Webb Space Telescope (JWST) is the Hubble Space
Telescope’s successor. It’s being launched on an Ariane 5 rocket, provided by
the European Space Agency (ESA). Because of its massive size, the James Webb
will unfold in space.
The
Webb will be nearly 1 million miles from Earth. To be exact, it’ll be 940,000
miles (about 1.5 million kilometers) from Earth. It will be sent to the L2 –
the second Lagrangian point in the Earth/sun system.
The
Webb Telescope’s science instruments will operate at temperatures near absolute
zero, the theoretical temperature at which all molecular and atomic motion
ceases. The sunshield subsystem separates the observatory into a warm
sun-facing side and a cold anti-sun side
The
Webb Telescope’s 18 mirrors are coated in a thin layer of 24-karat gold. Gold
reflects red light better than other materials, making the mirror 98 percent
reflective, rather than the 85 percent achieved by ordinary mirrors. This will
help the Webb telescope to selectively read only the infrared light.
Comparison with Hubble
space telescope
- Hubble was
launched by Discovery Space Shuttle. JWT will launched by Arianne 5
rocket.
- Hubble Space Telescope
orbits the earth roughly every 95 minutes at the height of 547 km. In
contrast, the JWT will be positioned at 1.5 million km at L2 point
- Hubble can be
services by the astronauts. JWT cannot be serviced by Astronauts since it
is located too much far from the Earth.
- The primary mirror
of Hubble is a single glass mirror, 2.4 meters in diameter. In case of
JWT, the primary mirror has 18 segments made up of Beryllium and is about
6.5 meter in diameter.
- Mirror mass of
Hubble is 828 kg while that of JWT is 276 kg only.
- Hubble is supposed
to serve for atleast 25 years, from the date it was launched. JWT will
work only for 5-10 years
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