The Roman Space Telescope has the same size mirror as Hubble, but it will survey the sky up to 1,000 times faster — not because it sees deeper, but because it sees wider: each Roman image captures a patch of sky at least 100 times larger, making Hubble’s method look like counting a crowd one face at a time.

The Roman Space Telescope has the same size mirror as Hubble, but it will survey the sky up to 1,000 times faster — not because it sees deeper, but because it sees wider: each Roman image captures a patch of sky at least 100 times larger, making Hubble’s method look like counting a crowd one face at a time.

The Roman Space Telescope is easy to describe badly. Say that it has the same size mirror as Hubble and people may expect a replacement. Say that it will survey the sky up to 1,000 times faster and people may imagine a telescope that simply sees deeper or has a more powerful eye. Neither picture quite gets it right. Roman’s advantage is not that it turns Hubble into a small instrument. Hubble remains one of the most precise observatories ever bu…