Performance prediction of the TMT secondary mirror support system

Myung K. Cho

doi:10.1117/12.789286

23 July 2008 Performance prediction of the TMT secondary mirror support system

Myung K. Cho

Proceedings Volume 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation; 70181S (2008) https://doi.org/10.1117/12.789286
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

The Ritchey-Chretien (RC) design of the Thirty Meter Telescope (TMT) optics calls for a 3.1 m diameter Secondary Mirror (M2), which is a large meniscus convex hyperboloid. The M2 converts the beam reflected from the f/1 primary mirror into an f/15 beam for the science instruments. The M2 Mirror (M2M) has a mass of approximately two metric tons and the mirror support system will need to maintain the mirror figure at different gravity orientations. Recent changes in the telescope configuration to RC from Aplanatic Gregorian (AG) prescription and reduction of the fully-illuminated field of view to 15 arc minutes required a design change in the M2 mirror figure from a concave radius to a convex radius, with a significant reduction in diameter, which in turn requires re-optimization of the mirror support systems. The optical performance evaluations were made based on the optimized support systems resulting from the change from AG to RC. The M2 optimized support system consists of 60 axial supports, mounted at the mirror back surface, and 24 lateral supports mounted along the outer edge. The predicted print-though errors of the M2M supports are 10nm RMS surface for axial gravity and 2nm RMS surface for lateral gravity. This M2M support system has an active optics capability to accommodate potential mechanical or thermal errors; its performance to correct low-order aberrations has been analyzed. A structure function of the axial gravity support print-through was calculated.

Citation Download Citation

Myung K. Cho "Performance prediction of the TMT secondary mirror support system", Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70181S (23 July 2008); https://doi.org/10.1117/12.789286

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available