Why is the Hubble telescope at that height?

Answer 1

Because it shall orbit above the atmosphere but still be at an altitude where it can be reached for repairs by astronauts.

Answer 2

The Hubble Space Telescope is placed in low Earth orbit at an altitude of about 547 kilometers (340 miles) to avoid atmospheric distortion that hinders image clarity. This height allows Hubble to capture high-resolution images of distant galaxies, stars, and other celestial bodies without the distortion caused by Earth's atmosphere.