Hubble’s in-space glasses restore its vision
Hubble launched with a 2.4‑m mirror polished to the wrong shape by about 2.2 micrometres, causing blurred images from spherical aberration. A misassembled null corrector led to the flawed mirror passing testing. During a 1993–1994 servicing mission, astronauts installed corrective optics (including COSTAR and WFPC2) and performed five spacewalks to redirect light to a common focal point, effectively giving the telescope “glasses.” The repair restored near-planned optical performance, though the primary mirror remained imperfect; later instruments replaced COSTAR as technology evolved. The episode underscores the value of serviceable design and rigorous testing in space projects.
