"Christopher M. Jones" wrote in message
...
"Explorer8939" wrote:
Does Hubble perform observations while in direct sunlight (ie the
period of its orbit when it is not in the Earth's shadow.

Interestingly, future telescopes will be even more in the
Sun than Hubble is currently, as they will go into higher
orbits, Solar orbits, or other locations farther from
Earth (e.g. Earth-Sun Lagrange points). Both the JWST
and the SIRTF will be in direct sunlight essentially all
the time. Both will employ systems to keep the light out
of the optical systems though. In fact, JWST will deploy
a large sunshade that will keep the entire optical
assembly (including the instruments) in permanent shadow.

For a lot of applications being in sunlight all the time is more desirable
than constantly going into and out of the sunlight. A stable thermal
environment (as opposed to the cycling the Hubble does every 90 minutes)
makes for a more stable telescope.

Jason