Powerful space telescope

[synonys]

I was reading the latest news of proposed uses of the Ares V launch vehicle. They said that Ares V could launch a 8 meter space telescope. My question is how big of a telescope do you need to resolve(see the details) a planet like earth?

 

[Urwumpe]

I was reading the latest news of proposed uses of the Ares V launch vehicle. They said that Ares V could launch a 8 meter space telescope. My question is how big of a telescope do you need to resolve(see the details) a planet like earth?

What do you mean with details?

The formula for the maximum angular resolution, you can see, is pretty simple and depends on wavelength and aperture.

R = %lambda/D

 

[Zatnikitelman]

Don't forget you can also increase resolution by using smaller observation points at a distance to each other to get an effective diamater roughly equal to the spacing between the two points. That's part of the reason why they want to put large reflecting telescopes on the moon, put one on one side, one on the other and you have a telescope essentially as large at the diameter of the moon! It is limited by the mirrors having to see the object simultaneously so in reality, the spacing would be much closer but still have an effective diameter bigger than anything we have now.