Dear @osmerj, very interesting your post. It shows us the importance of measurements.
During a measurement many factors must be considered, but from my experience, the following are of great importance and should be monitored at all times: the observer (skill of the person performing the measurement), the measuring instrument (calibrated and with the characteristics corresponding such as: precision and accuracy), work procedures (updated, approved according to international standards with their correct application) and environmental conditions (control of parameters that may influence the measurement such as environmental temperature and relative humidity).
Thanks for sharing your work. Successes!
All those factors are important. In this case, the commission attributed the faults mainly to Perkin-Elmer, NASA discovered that it had not used its best opticians or adequately supervised the process of construction of the mirror. All this because only one lens was out of position 1.3 mm. What delayed such a large project for 3 years. Three years that would have been used for space research, instead of the manufacture of a corrective lens.