Hubble – The Next Generation: The James Webb Space Telescope

While NASA is planning their fifth mission to the Hubble Space Telescope (HST) for later this year, its successor, the James Webb Space Telescope (JWST) has already began taking shape.

The telescope is named after James Webb, the NASA Administrator during the Apollo development phase from 1961-1968. Together with characters like Wernher von Braun and George Mueller, James Webb was a major factor for the then successful Apollo program. Webb fought to get the necessary funds to fulfill John F. Kennedy’s mission „to land a man on the Moon and return him safely to the Earth before the decade is out.“

For a deeper insight into this man and the time you can read James E. Webb „Powering Apollo“.

Back to the telescope: Soon after the HST began returning impressive pictures and data it became obvious that large space-based telescopes would play an important role in the future. While the HST is operating in visual wavelength, there are already several other large telescopes in space using other wavelengths.

Hubble’s three cousins of the „Great Observatories“ are Spitzer, operating in the infrared, Chandra, scanning the sky’s X-ray emission and the Compton Gamma Ray Observatory. The European Space Agency (ESA) has its own large X-ray telescope in space, the XMM-Newton.

NASA and ESA have joined forces for the next generation telescope JWST.

The JWST will shift its main focus from the visible wavelengths into the infrared. Nonetheless there will be a lot of breathtaking images. It will be about 22 x 12 x 12 metres in size and will have a mass of some 6.2 tonnes.

The primary mirror will be 6.6 metres in diameter and therefore significantly larger than the 2.4 metres of the HST. The whole spacecraft will be placed in such a way that the mirror and the electronics will be shaded by a giant sun shield.

The launch is planned for June 2013 atop an Ariane 5 ECA rocket from the French spaceport in Kourou. In contrast to the HST which is in Low Earth Orbit (LEO), the James Webb Space Telescope will be stationed an L2, the second Lagrange point.

These points share an interesting property. Something placed at a Lagrange point will stay there or can even orbit around such a point in opposition to a „usual“ spacecraft orbiting a celestial object like Earth, Moon or Sun. Langrange points are defined as locations in space where the gravitational effects of multiple celestial bodies cancel each other out.

The communication and data transfer will run through NASA’s Deep Space Network which will put quite a load on the already stressed DSN.

Unlike the HST, the JWST won’t be serviceable, so there won’t be impressive serivce mission like the ones to the Hubble. The last of these service missions will fly this year as STS-125 with the Space Shuttle Atlantis.

While the JWST as an integrated spacecraft is still in the final development phase, several components like the mirror segments have already been manufactured. The Critical Design Review (CDR) should occur in a few months.

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