Ed Cannon wrote: > The one > certain thing I've read is that its front end never points > closer than 50 degrees to the Sun even with the aperture door > closed (and maybe something similar with respect to the Moon > and Earth). According to the book "The Hubble Wars" by Eric J. Chaisson (page 72): > ..., no science data of any kind are collected when the > bright limb of the Earth is within 15° of Hubble's field > of view or its dark limb is within 5°. > > Telescope schedulers are also careful to keep Hubble 50° and > 15° clear of the Sun and the full Moon. As noted, in the > event of human or computer error, the telescope can > independently sense these bright objects and automatically > "safe" itself by closing the aperture door... > > With caution, lunar occultations - ... - can be recorded. He then confuses me a little by writing: > Spacecraft motion is also restricted because Hubble > repositions or "slews" very slowly about its own axis - > ... Consequently, when Earth is occulting a given celestial > target, Hubble cannot swing rapidly in the direction of > another object. It is actually more efficient to remain > target toward the original object and to wait half an > orbit for Earth to get out of the way... This sort of implies that the telescope can be left pointing at the Earth without harm. Presumably the aperture door is not closed in these cases (as it is quite a dramatic event to close and open it). Maybe it's only the night side of the Earth that the telescope can be left pointing at. It doesn't sound to me like the Hubble's attitude is sufficiently constrained by these considerations for them to help in predicting flares. Ed Davies. ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
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