One thing I always like to add is that ground based telescopes benefit from being able to take huge amounts of data. The Vera Rubin Observatory will have a 3.5 Gigapixel camera. There are proposals to sometimes run it in a mode with 1 second exposures. So we're talking data rates of gigabytes per second. If you have dedicated fiber lines you can deal with ...
To expand on the "space telescopes are expensive" aspect:
Space telescopes cannot be maintained or repaired. This applies not
just to things like optics and
instruments, but also to space-specific equipment like gyroscopes and
thrusters (the James Webb Space Telescope has an estimated lifetime
of $\sim 10$ years, set by the supply of fuel for the ...
Space telescope Astronomy research published in Science and Nature:
Ground-based telescopes (31.1%), spacecrafts (27.0%), space telescopes (22.8%). (ref)
Number of professional telescopes affected: >1050. (ref) representing tens of thousands of academic physicists, cosmologists, astronomers and other scientists.
Number of amateur astronomers affected: 200,...
It's a problem because there are still lots and lots and lots of ground-based telescopes.
Ground-based telescopes are still (by far) the biggest optical telescopes, and the cost of space telescopes is prohibitive for many research projects. It will be a long time before a telescope anywhere close in size to the VLT can be launched.
Most space telescopes are ...
Short answer, yes, the x-ray grazing incidence mirrors set up like this still function like a Cassegrain to minimize off-axis aberration. However, it is still different in that a classical Cassegrain uses a fast positive paraboloid and a slow negative hyperboloid.
The Cassegrain design combines the paraboloid and hyperboloid to minimize off-axis aberrations ...
1/ 90 degrees gives the most precise angle for triangulations on a 2D Cartesian plane. You can try it out by programming 3D mesh and by glancing sideways travelling on a bike or on a satellite: glancing at 90'C, you have the highest measurement of the movement of X relative to Y compared to looking at 45'. If you have binoculars on the bike helmet (i.e. a ...
I did not find anything conclusive on the web, and I am yet waiting to receive feedback from ESA's contact page. In a German speaking IT forum there is something a bit less vague than the FAQ cited in the question:
The reason for the 106.5 degrees is not easy to see. It has to do with the fact that we are (also) doing an astrometric solution on a great ...
More than 20 if the Wikipedia's List of Space Telescopes is accurate. I extracted the active ones, and removed duplicates (to the best of my knowledge):
Swift Gamma Ray Burst Explorer
Insight (Chinese: 慧眼)
The famous Hubble Space Telescope, HST, see hst
Lunar-based ultraviolet ...