Hubble Space Telescope mirror under construction at Perkin-Elmer. The construction of the main mirror was begun in 1979 and completed in 1981. However, the polishing ran over budget and behind schedule, producing significant friction with NASA. Due to a miscalibrated null corrector, the primary mirror was also found to have a significant spherical aberration after reaching orbit. A NASA investigation heavily criticized Perkin-Elmer for management failings, disregarding written quality guidelines, and ignoring test data that showed this miscalibration.