After its launch in 1990, Hubble returns images that do not have the expected sharpness. The investigation goes back to its large mirror: its curvature is incorrect near the edge. Rays that should converge in the same place do not, producing optical aberration.
Bringing the mirror back to a workshop is not the solution. Engineers design optics capable of compensating for this defect. In December 1993, astronauts installed a new camera with its built-in correction, as well as the COSTAR device for several other instruments.
The telescope regains the sought-after optical performance while its main mirror has not been recut. The comparison with glasses is therefore useful, provided you remember that it is a complex set of corrective mirrors. The starting error did not materially disappear: the path of the light was organized to cancel the effect. A successful repair can sometimes be to correct around the defect.
What we know
Optical fault correction; no replacement or repolishing of the main mirror during this mission.
To go to the source
References consulted on September 21, 2026. Linked pages may be in another language.
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