On 2021-12-23 15:13, Daryl Bahls via Seesat-l wrote: > On a slightly different, but related topic. What would the expected > brightness be shortly after launch at a range of 100,000 to 150,000 km? > > I have a friend who is going to attempt (weather permitting) to > photograph > JWST during that first night pass over the western hemisphere and we > were > wondering what we may, or may not see. Amateur astronomer "Sajith" reports on the comet-ml that he saw it in India shortly after launch as a "comet-like object" From this image of its underside, I think that this is going to be a pretty bright object out at ELS-2 once it's fully deployed. https://twitter.com/TM_Eubanks/status/1474750295238496259/photo/1 The solar panel deployment has been confirmed, the Webb is power positive, and so it's even larger now. https://twitter.com/astrofaisst/status/1474724558938640385/photo/4 Note that these images were taken from the ESC-A upper stage, which will also go out towards the Lagrange point (even if it doesn't stay there). The ESC-A is 5.4 meters diameter; oddly, I can't find a length for it, but it looks to be about 10 meters long. It should also be pretty visible for the next few days. https://www.esa.int/Enabling_Support/Space_Transportation/Launch_vehicles/Ariane_5_ECA2 Regards Marshall > > Daryl > > On Mon, Dec 20, 2021 at 11:12 PM Thierry Legault via Seesat-l < > seesat-l_at_satobs.org> wrote: > >> Thank you Tony, this is interesting. >> >> How can we take into account the fact that the sunshield is made of >> several layers of highly reflective aluminum coated Kapton and >> reflects lights (more or less?) towards the Sun, therefore towards >> the Earth considering the position of the satellite at L2? >> >> https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#/media/File:James_Webb_Space_Telescope_2009_bottom.jpg >> >> I guess that if it were white (like the ISS radiators) it would be >> easier to assess its brightness from surface considerations, in this >> case it seems to me that the situation is closer to Lightsail, more >> unpredictable and highly dependent on the flatness of the shield and >> its precise orientation. Could we expect flares sometimes, visible >> through a telescope? >> Does it make sense to extrapolate from Lightsail characteristics >> (distance and reflective surface)? >> >> Regards >> >> >> >> >> >> >> At 12:21 PM 30/10/2010, Tony Beresford wrote: >> >given the size (300 sq.m) and the average distance of an orbit >> around >> >the L2 Earth Sun point i would say mag 16.5 >> >there are currently 2 European spacecraft at L2, Herschel & Planck >> >There was until recently the US WMAP as well but its mission has >> >finished. >> >All of these objects have been observed by a various >> >observing station who report minor planet positions to >> >the IAU's Minor planet Centre. They are a nuisance as far as the >> >asteroid astronomists >> >are and the MPC are concerned of course. The standard reporting >> form for these >> >objects as privately published by MPC staff has a crude magnitude >> estimate in a >> >variety of pass-bands. An typical magnitude for the Herschel >> telescope >> >is magnitude 20. its somewhat brighter for ESA,s Planck spacecraft >> >being magnitude 17.5 to 18. herschel is an IR telescope of 3.5m >> aperture, >> >while planck is looking at the cosmic background with a slightly >> >smaller aperture. >> > >> >The Minor Planet Centre has a page with a menu offering predictions >> >for the objects mentioned and some others, accesable via the menu >> >selection of 'distant Artificial satellites' on the left hand >> >side of the page at >> <http://www.minorplanetary.org/>http://www.minorplanetary.org >> >further links on that page get you too a list of observations. >> >One is banned from jumping to the page directly.as I tried a some 12 >> hours >> >ago. I guess this is simply a security measure. >> > >> >Tony Beresford >> >> >> _______________________________________________ >> Seesat-l mailing list >> <http://mailman.satobs.org/mailman/listinfo/seesat-l> >> http://mailman.satobs.org/mailman/listinfo/seesat-l >> >> >> >> >> >> >> _______________________________________________ >> Seesat-l mailing list >> http://mailman.satobs.org/mailman/listinfo/seesat-l >> > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Sat Dec 25 2021 - 09:29:21 UTC
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