1. OPTI 521 Presentation By Tianquan Su

2. Background MissionLaunch WorkFail

3. Failure Further analysis and computer simulation of the WF/PC images indicated that 0.5-waverms wavefront spherical aberration at 547nm, which could not be eliminated by adjustment.

4. Where is the problem? Only spherical aberration, no coma: -- probably the primary mirror

5. About the primary mirror The primary mirror is an aspherical mirror with 2.4m diameter. It should have 0.04 wave rms wavefront error at 632.8 nm.

6. Why it was misshaped -- wrong testing Three measures used in the testing of the primary mirror: o Refractive Null Corrector (RvNC) -- whose data showed the mirror flaw that match with the telescope error o Reflective Null Corrector (RNC) -- whose data showed the mirror has no flaw o Inverse Null Corrector (test the RvNC by stimulate the mirror) -- whose data also showed aberration Funny thing is the manufacturer, Perkin-Elmer Corporation (P-E), trusted the only black sheep of the three

7. What is RNC? RvNC (refractive null corrector) RNC (reflective mull corrector) RNC structure

8. Testing Chamber

9. What’s wrong with it?

10. What’s wrong with RNC The metering rod (with the field cap on)

11. The initiator of evil Top view of the field cap

12. Lesson learned -- don’t but your eggs in one basket!

13. Thank you!