Turn a Planet Labs satellite into a (small) "Hubble"?

Question

If we revert a satellite of Planet Labs to look planets of the solar system or deep space, would we obtain a good result? A space telescope (above atmosphere) is automatically better than a ground-telescope, isn't it ?

Answer 1

Interesting question! It is on-topic here but could have also been asked in Astronomy SE as well.

Atmospheric effects on telescope resolution vary greatly from place to place on Earth, but for a (roughly) 4-inch (10 cm) Cassegrain-like reflecting telescope (the Doves are 3U cubesats) on a good night, the resolution is affected roughly the same by the diffraction limit of the optics as it is by the atmosphere, so there is not much to be gained in resolution by putting a 10 cm telescope in orbit.

There might be some niche applications. Using several Doves means you could have continuous coverage of an object, and if you were looking at a near-Earth object you might be able to measure distance using parallax - Doves on two sides of the Earth would see the object slightly offset against the stars being much farther away.

But the Doves have been optimized for short exposures of the bright sunlit Earth, and they may not be able to do long, astronomical exposures where problems of dark current and shot noise have to be carefully managed by optimized astronomical CCD sensors and image processing.

Their attitude control systems may not be able to hold a pointing direction long enough and steady enough for astronomical exposures. You could take many short exposures and overlay them, but if the imager is prone to dark noise then this would not work so well.

A space telescope (above atmosphere) is automatically better than a ground-telescope, isn't it?

A telescope that has been designed and optimized to be a space telescope, especially one with a large aperture certainly can be better in space than on the Earth, but the Doves are optimized to a very different job, so they might not do as well as one would like.

Answer 2

In addition to uhoh's answer:

A space telescope (above atmosphere) is automatically better than a ground-telescope

A space telescope is usually better than a ground-based telescope of the same size, and the difference is bigger for large telescopes.

There are requirements for a telescope that are hard to achieve in space, and maybe a bit easier on Earth:

• accurate pointing (no movement during the observation)
• a stable thermal environment

The PlanetLabs telescopes are built for short, daytime observations so they can mostly skip these requirements.