Astronauts Restored Hubble’s $1.5 Billion Vision With 5 Spacewalks and Corrective Optics
Updated
Updated · spacedaily.com · Jul 15
Astronauts Restored Hubble’s $1.5 Billion Vision With 5 Spacewalks and Corrective Optics
3 articles · Updated · spacedaily.com · Jul 15
Summary
Five spacewalks over 11 days in December 1993 let shuttle Endeavour’s crew install COSTAR and the new WFPC2 camera, restoring Hubble’s planned optical performance without replacing its 2.4-meter primary mirror.
A 2.2-micrometre error at the mirror’s outer edge had caused spherical aberration, after a misassembled null corrector displaced a lens by about 1.3 millimetres and guided polishing to the wrong shape.
NASA fixed the flaw by adding optics with the opposite error: WFPC2 corrected its own view, while COSTAR used small deployable mirrors to redirect light for three other instruments, replacing the High-Speed Photometer.
Images released on Jan. 13, 1994 showed starlight tightened from a roughly 1-arcsecond halo to about 0.1 arcsecond, confirming the telescope had regained its intended sharpness.
The recovery became a landmark engineering rescue, but investigators found the defect was preventable and reflected failures in testing, oversight and communication before Hubble’s 1990 launch.