View Full Version here: : First Instrument ready for JWST
10-05-2012, 09:20 AM
A European built instrument for the James Webb Space Telescope "JWST" is ready to be shipped to the USA.
Launch date for the JWST is slated for 2018.
10-05-2012, 10:01 AM
Anyone know what the actual angular resolution of the JWT is going to be? The Hubble Space Telescope manages 0.05 arcseconds, or slightly better, even without any fancy computer processing.
10-05-2012, 10:30 AM
:hi:Robert, is this what you require:question:
12-05-2012, 10:38 PM
Thanks very much for that, Ron.
This document is a very useful, if somewhat simplified, description of the instrumentation and optical capabilities. While I knew "most everything" about Hubble when it was launched, these days I have got much too specialized to keep up with JWST.
OK, so the document says the "big space scope" will resolve 68 milliarcseconds when imaging at a wavelength of 2 micrometers. JWST is optimized for near-infrared work, and this does involve a trade-off between resolution and penetrating power through the interstellar dust.
(longer wavelengths.......less extinction of light, but lower angular resolution)
One milliarcsecond is 1/1000 arcsecond, so this equates to an angular resolution of 0.068 arcseconds. Let's say we round this figure to 0.07 arcseconds, just for convenience.
For comparison purposes, the WFC3 imaging camera on the Hubble Space Telescope has 0.04 arcsecond pixels, which I suppose approximates the angular resolving power of the HST.
I note that even when it is used at shorter infrared wavelengths, the JWST has a CCD camera with 0.03 arcsecond pixels....... so, at best, JWST can offer little improvement over the sharpness of Hubble images, despite a price tag that approaches 10 billion dollars (and I don't think we have seen the last of the serial cost overruns that this telescope is notorious for)
And the field-of-view of JWST is very narrow.....no more than 4 arcminutes.
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