NASA Technical Reports Server (NTRS) 20140004079: Advanced UVOIR Mirror Technology Development (AMTD) for Very Large Space Telescopes

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by  NASA Technical Reports Server (NTRS)

Long Term Needs Key Technology Development Accomplishments

ASTRO2010 Decadal stated that an advanced AMTD derived, from Science Requirements, En-
•Large-Aperture, Low Areal Density, High Stiff-
large-aperture ultraviolet, optical, near-infrared gineering Specifications for 4 to 8 m monolithic
ness Mirror Substrates: Both (4 to 8 m) mono-
(UVOIR) telescope is required to enable the next space mirrors and is working on segmented pri-
lithic and (8 to 16 m) segmented primary mir-
generation of compelling astrophysics and mary mirror specifications.
rors require larger, thicker, and stiffer sub-
exoplanet science; and, that present technology is
strates.
not mature enough to affordably build and launch Integrated Model Validation: AMTD has devel-

any potential UVOIR mission concept. oped a powerful tool which quickly creates
monolithic or segmented mirror designs; and ana-
AMTD builds on the state of art (SOA) defined •Support System: Large-aperture mirrors require lyzes their static & dynamic mechanical and ther-
by over 30 years of monolithic & segmented large support systems to ensure that they sur- mal performance. These models will be vali-
ground & space-telescope mirror technology to vive launch and deploy on orbit in a stress-free dated by test.
mature six key technologies. and undistorted shape.
Support System: AMTD has expanded its sub-

AMTD is deliberately pursuing multiple design strate design tool to include launch support sys-
paths to provide the science community with op- tems. Pre-Phase-A point designs for candidate
•Mid/High Spatial Frequency Figure Error: Very
tions to enable either large aperture monolithic or primary mirror architectures have been produced.
smooth mirror is critical for producing high-
segmented mirrors with clear engineering metrics
quality point spread function (PSF) for high
traceable to science requirements.
contrast imaging.

•Segment Edges: The quality of segment edges
impacts PSF for high-contrast imaging applica-
tions, contributes to stray light noise, and af-
Free-Free 1st Mode: 4 m dia Internal Stress: 4 m dia with
fects total collecting aperture. 40 cm thick substrate 6 support pads

•Segment to Segment Gap Phasing: Segment
Segment to Segment Gap Phasing: AMTD is in-
phasing is critical for producing high-quality
vestigating the viability of various passive and
temporally-stable PSF.
active dampening and positioning technologies.

•Integrated Model Validation: On-orbit perform-
ance is driven by mechanical & thermal stabil-
ity. Compliance cannot be 100% tested, but
relies on modeling.
Accomplishments (cont.) Accomplishments (cont.) Advanced UVOIR Mirror

Technology Development
Large-Aperture, Low Areal Density, High Stiff- Mid/High Spatial Frequency Figure Error: AMTD
ness Mirror Substrates: AMTD partner Exelis partner Exelis polished the 40 cm mirror to a zero- (AMTD) for Very Large
developed & demonstrated a technique to manu- gravity figure of 5.5 nm rms. MSFC tested 43 cm
facture a 400 mm thick substrate via ‘stacking mirror from 250 to 300K. Its thermal deformation Space Telescopes
and fusing’ three core structural elements to front was insignificant (smaller than 4 nm rms shape
and back faceplates; making a 40 cm ‘cut-out’ of change).
a 4 meter diameter 60 kg/m2 mirror. This new

process offers a lower cost approach for manu-
facturing Phase II Award
large-

diameter
Plan to build subscale 1.3m-1.5m Pathfinder mir-
high-
ror using same processes and techniques developed
stiffness
under Phase I.
mirrors.
Core
Segments
Post-Fusion: 3 Core Post Slump: 2.5 m

Layers & Vent Hole Radius of Curvature Pathfinder mirror

Visible will be stacked
core with pocket
AMTD is a multiyear effort to
Demo mirror
milled face plates
in V-block
like the Phase I develop, demonstrate and mature
mount and
the resulting Demo mirror
multiple ori- critical technologies to TRL-6 by
entation
2018 so that a viable flight mis-
5.5nm rms
surface.
sion can be proposed to the 2020
Decadal.
Science Advisory Team:
Dr. Marc Postman, STScI
Segment Edges: AMTD Partner STScI demon-
Dr. Remi Soummer, STScI
strated a microdot apodization technique to miti-
Dr. Annand Sivramakrishnan, STScI
gate edge diffraction effects for high contrast im-
Dr. Bruce Macintosh, LLNL
Dr. Olivier Guyon, UoA
Systems Engineering Team
Dr. H. Philip Stahl, NASA
Dr. W. Scott Smith, NASA
Dr. Gary Mosier, NASA
Laura Abplanalp, Exelis
William Arnold, DAI/Jacobs
Microdot attenuation is achromatic & linear with density