NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Design, Fabrication, Optical Testing, and Performance of Diamond Machined Aspheric Mirrors for Ground-Based Near-IR AstronomyChallenges in fabrication and testing have historically limited the choice of surfaces available for the design of reflective optical instruments. Spherical and conic mirrors are common, but, for future science instruments, more degrees of freedom are necessary to meet challenging performance and packaging requirements. These instruments will be composed of unusual aspheres located far off-axis with large spherical departure, and some designs will require asymmetric surface profiles. In particular, single-surface astigmatism correction in spectrographs necessitates a toroidal surface, which lacks an axis of rotational symmetry. We describe the design, fabrication, optical testing, and performance of three rotationally symmetric, off-axis, aspheric mirrors and one toroidal, off-axis, biconic camera mirror on aluminum substrates for the Infrared Multi-Object Spectrograph (IRMOS) instrument. IRMOS is a facility instrument for the Kitt Peak National Observatory's Mayall Telescope (3.8 m) and an engineering prototype for a possible design of the Next Generation Space Telescope/Multi-Object Spectrograph. The symmetric mirrors range in aperture from 94x86 mm to 286x269 mm and in f-number from 0.9 to 2.4. They are various off-axis, convex and concave, prolate and oblate ellipsoids. The concave biconic mirror has a 94x76 mm aperture, Rx=377 mm, kx=0.0778, Ry=407 mm, and ky=0.1265 and is decentered. by -2 mm in x and 227 mm in y. The mirrors have an aspect ratio of approximately 4:1. The surface error fabrication tolerances are less than 63.3 nm RMS figure error and less than 10 nm RMS microroughness. The mirrors are attached to the instrument bench via a semi-kinematic, integral flexure mount. We describe mirror design, diamond machining, the results of figure testing using computer-generated holograms, and imaging and scattered light modeling and performance.
Document ID
20020061309
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Ohl, Raymond G.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Mink, Ronald
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Chambers, V. John
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Connelly, Joseph A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Mentzell, J. Eric
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Tveekrem, June L.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Howard, Joseph M.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Preuss, Werner
(Bremen Univ. Germany)
Schroeder, Mechthild
(Bremen Univ. Germany)
Sohn, Alex
(North Carolina State Univ. Raleigh, NC United States)
Krebs, Carolyn
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Optics
Meeting Information
Meeting: SPIE Conference
Location: Kona, HI
Country: United States
Start Date: August 21, 2002
End Date: August 30, 2002
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

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