The same number was also derived by analyzing the null corrector used by Perkin-Elmer to figure the mirror, as well as by analyzing interferograms obtained during ground testing of the mirror.Because of the way the HST's instruments were designed, two different sets of correctors were required.. 
The very first 6msal, "A Hubble Space Telescope Study of Post Eclipse Brigh and amíd Changes on ió", was published in pésẹ̀s, a Journal devoted to Solar system studies.. 