Astronomy/space telescopes


Why are Hubble's optics enclosed in a tube with a door, and the upcoming James Webb design is completely open to space? I know Webb is too big to enclose easily, but there must be some advantages/disadvantages/risks involved.


The Hubble's optics are enclosed because its aperture at 2.4 m (7.9 ft.) made it more practical to do so - apart from the fact it followed an original design to that end. The JWST with six hexagonal, optical components - for a total aperture of 6.5 m (21 ft.) would be much more cost intensive to fully enclose apart from which the design doesn't really require it. For example, it features a large solar shield to keep its mirror and four scientific instruments below -220C for maximal operational efficiency.

The chief advantages of the JWST are:

1) The gold plated beryllium mirrors which make it ideal for near infrared observation

2) Its location at the L2 Lagrangian point which will enable it to orbit synchronously with Earth at a relatively constant distance (1.5 million km)

3) The placement defined in (2) will allow for use of just a single sun shield.

The primary disadvantage will be that extra effort will have to be applied to keep it in a "halo orbit" around the L2 Lagrange point. This will demand adequate controls so no "drift" occurs exceeding a 2.0- 4.0 m/s deviation (e.g. from 150 m/s total.)  


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Philip Stahl


I have more than forty years of experience in Astronomy, specifically solar and space physics. My specialties include the physics of solar flares, sunspots, including their effects on Earth and statistics pertaining to sunspot morphology and flare geo-effectiveness.


Astronomy: Worked at university observatory in college, doing astrographic measurements. Developed first ever astronomy curriculum for secondary schools in Caribbean. Gave workshops in astrophysics and astronomical measurements at Harry Bayley Observatory, Barbados. M.Phil. degree in Physics/Solar Physics and more than twenty years as researcher with discovery of SID flares. Developed of first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Develop first ever loop solar flare model using double layers and incorporating cavity resonators.

American Astronomical Society (Solar Physics and Dynamical Astronomy divisions), American Mathematical Society, American Geophysical Union.

Solar Physics (journal), The Journal of the Royal Astronomical Society of Canada, The Proceedings of the Meudon Solar Flare Workshop (1986), The Proceedings of the Caribbean Physics Conference (1985). Books: 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level'. 'Astronomy and Astrophysics: Notes, Problems and Solutions'.

B.A. Astronomy, M. Phil. Physics

Awards and Honors
American Astronomical Society Studentship Award (1984), Barbados Government Award for Solar Research (1980), Barbados Astronomical Society Award for Service as Journal Editor (1977-91)

Past/Present Clients
Caribbean Examinations Council, Barbados Astronomical Society, Trinidad & Tobago Astronomical Society.

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