1.   The Hubble space telescope takes clearer pictures of stars than earthbound telescopes.

2.   ...earthbound telescopes.

3.   They hope an Earthbound telescope will be built just for that purpose.

4.   For more than a decade she has studied Mercury using earthbound telescopes.

5.   In subsequent weeks, the Hubble Space Telescope and several powerful earthbound telescopes also set their sights on the spot.