NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Precise Determination of the Zero-Gravity Surface Figure of a Mirror without Gravity-Sag ModelingThe zero-gravity surface figure of optics used in spaceborne astronomical instruments must be known to high accuracy, but earthbound metrology is typically corrupted by gravity sag. Generally, inference of the zero-gravity surface figure from a measurement made under normal gravity requires finite-element analysis (FEA), and for accurate results the mount forces must be well characterized. We describe how to infer the zero-gravity surface figure very precisely using the alternative classical technique of averaging pairs of measurements made with the direction of gravity reversed. We show that mount forces as well as gravity must be reversed between the two measurements and discuss how the St. Venant principle determines when a reversed mount force may be considered to be applied at the same place in the two orientations. Our approach requires no finite-element modeling and no detailed knowledge of mount forces other than the fact that they reverse and are applied at the same point in each orientation. If mount schemes are suitably chosen, zero-gravity optical surfaces may be inferred much more simply and more accurately than with FEA.
Document ID
20080046998
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
Authors
Bloemhof, Eric E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Lam, Jonathan C.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Feria, V. Alfonso
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Chang, Zensheu
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
October 25, 2007
Publication Information
Publication: Applied Optics
Publisher: Optical Society of America
Volume: 46
Issue: 31
ISSN: 0003-6935
Subject Category
Astronomy
Distribution Limits
Public
Copyright
Other
Keywords
measurements
Gravity
Optical designs
Instrumentations
metrology

Available Downloads

There are no available downloads for this record.
No Preview Available