Download Ronald`s presentation

Large Deployed and
Assembled Space
Telescopes
November 14, 2007
Ronald S Polidan
Chief Architect, Civil Systems Division
Charles F Lillie, Gary Segal, Dean Dailey
Northrop Grumman Space Technology
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Agenda
 Expectations
 Deployable Observatories
 Very Large Observatories
 Technology Needs
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Astrophysics Beyond 2020 – Expectations
 JWST will have launched in 2013, fulfilled its 5 year prime
mission and be on its way to its 10-year lifetime goal
 New “infrastructure” elements and technologies are changing
the architectural approaches to big space telescopes
 Bigger launch vehicles: EELV Heavy and Ares V
 Advanced optics technology (ultra-light weight mirrors, replication, improved
wavefront sensing and control technologies, …)
 Advanced deployment and assembly (robotic or crewed) technologies
 Linearly extrapolating from the past:
 Hubble (1990): 2.4 m aperture, 11,110 kg total mass, $4.1 B (FY06, A-D)
 JWST (2013): 6.5 m aperture, 6,200 kg total mass, $3.5 B (FY06, A-D)
 For a similar cost we should expect to produce a ~20 m telescope,
launching in the mid-2020s
 Assuming anything faster than linear technology development produces
25 meter or larger filled aperture telescopes
20-m or Larger Filled Aperture Telescopes Should be Expected in the 2020’s
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Current State of the Art: JWST
Solar Arrays
HGA
Sunshield
Tower Ext.
SMSS Deployment
Secondary
Deployment
PM Deployment
Cool Down
Fixed Width Aft Membrane
Momentum Trim
Flap
Core
Area
Fixed Fwd and Aft
Spreader Bars
Aft UPS Bipod Launch
Lock Attachment
Points
Fixed Side
Spreader Bars
Momentum
Trim Flap
Note: S/C Solar Array
and Radiator Shades
Shown in Stowed
Positions for Clarity
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Telescopic
Side
Booms
Unitized Pallet Structures
(UPS)
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Simplest Approach: Scaling Up JWST
 Scaling up JWST to large EELV and Ares V
launch vehicles


Lowest cost option: a JWST “rebuild” with no
new technology development
Use identical cord fold deployment &
sunshield architecture and technology
 The bottom line for several reasons but
mostly having to do with vertical height in
the faring (a high center of gravity, load
paths and acoustic loads are additional
complications) limits you to


~ 8 meter aperture for the largest EELV
~ 12 meter aperture for an Ares V
 For truly large telescopes, we need
something more advanced than a
cord fold approach
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Shift to a Family of Deployment Options
Recent analysis driven by the proliferation of diverse missions requiring
both large and smaller telescopes have shown that the choice of deployment
approach will depend on:
• Launch constraints
– Total mass
– Launch environment
• Required telescope agility
– Fixed targets or
– Imaging while tracking
• Applicable and available
mirror technology
– Need smaller, stiffer
segments
– Availability of larger,
ultra-light segments
• Acceptable cost and risk
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Manufacturing, Launch & Deployment Risk
and Cost
• Size of the primary mirror
required for the mission
Relative Risk & Cost vs Primary Diameter
Hubble
Spitzer
JWST
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2
FanFold
Chord-Fold
Monolith
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4
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Stacked Hex
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Primary Mirror Diameter (m)
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Telescope Deployment Architecture Approach
Should be Optimized for Cost and Mission Needs
Chord-Fold Deployment
Depending on
manufacturability
of segments
2m - 18 Segment PM, 2m Fairing
Depending on
segment size &
Mission Rqmts
2m - 7 Segment PM, 2m Fairing
Fan-Fold Deployment
3m - 7 Segment PM, 3m Fairing
Robotic Deployment
Scalable to Very
Large
Diameters
3m - 10 Segment PM, 2m Fairing
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4m - 10 Segment PM, 2m Fairing
3m - 7 Segment PM, 2m fairing
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Scaling to Very Large Apertures
One of our long term goals has been the development
of an efficient deployment approach that would scale
to very large telescopes
1m Segments
3m SMD Primary
2m Segments
6m Primary
3m Segments
8.5m Primary
Scaling in Segment Size
3.5m Segments
10.5m Primary
2m Segments
10m Primary
Hybrid Mirror
3.5m Segments
24.5m Primary
Scaling in Number of Rings
●●●
SMD (3m)
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6m UV/Vis/IR
SAFIR (10m)
28m UV/Vis/IR
Advantages of Stacked Hex Deployment
 Scalability to very larger telescopes  Minimal additional structure required for launch
 Most efficient packaging
 Tripod secondary support contributes to PM
 No outboard mechanisms allowing
stiffness
minimal shroud diameter
 Heritage concept with hardware implementation
experience
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SAFIR Observatory Concept
Far infrared wavelength
detection requires
~ 4 deg K cooling
10 meter, 7 hex
segment deployment
scheme
New telescope payload
JWST bus
subsystem re-use
• Positioning boom
• Deploys and positions scope
• Thermally decouples scope
from sunshield
• Very low frequency, highly
damped jitter isolation
• Maintains balance between
mass and pressure centers
over large F.O.R.
Stowed in EELV 5 m heavy
(Restraint shell removed for clarity)
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Lower frequency telescope attachments provide
greater observatory flexibility and performance!
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Stack Deployment Animation
• Application of
NGST High
Accuracy
Reflector
Deployment
System (1990)
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Thermal And Dynamic Isolation Boom
• Thermal and dynamic isolation boom concept with fine
pointing
• Produces ~3 Pi steradian instantaneous field
of regard
• Allows for improved momentum
management by control of CP/CG
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Advanced Sunshield Approaches
• The level of thermal stability being demanded by
future big telescope missions preclude the use of
simple sunshields
• Need to look toward multi-layer or
possibly active sunshields
• These too will need to be deployed
Flat
Conical
“Sugar Scoop”
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Scaling to Very Large Apertures
 Long standing analysis and design
confirms that deployment of stacked,
Hex segments provides the most
efficient approach to scaling to large
telescope apertures
 Two basic approaches to scaling segmented telescopes:
Scale the number of deployed rings
Issues
• Deployment of large
number of segments
• Largest number of
rigid body actuators
• Highest weight ratio
• Highest number of
segment prescriptions
Issues
• Highest risk of
Scale the size of the segments
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manufacturability of
very large segments
• Requires largest faring
diameter
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Structurally Connected Interferometer – 40 m
Stowed four segment
deployable truss structure
Lightweight honeycomb sunshield
containment shell structure (outer shell and
inner shell)
3.5 M monolithic
primary reflectors
with deployable
secondary reflectors
40 M
17 M
Deployed optical
bench truss with
aux spar support
(low frequency
isolation from
bus)
Spacecraft bus
Sunshield provides 60
deg operating cone
Stowed
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Deployed
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30-m spherical primary mirror telescope
Secondary (f/d = 1.79)
30 meter spherical
primary mirror
Spherical corrector assembly
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30 m Assembled Spherical Telescope concept
Bus and
telescope
rendezvous and
dock here
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30 M Spherical Telescope Observatory Concept
 Five EELV heavy launches
 Total lift capability ~ 40,000 Kg’s
 Observatory SWAG ~ 27,000 Kg’s
 Weight margin ~ 48%
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On-orbit Servicing
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Courtesy of Jack Frassanito & Associates
and Dr. Harley Thronson
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Key Technologies Enabling
Next Generation Space Telescopes
 Rapid, low cost fabrication of ultra-light
weight primary mirror segments
Nonolaminate
on Mandrel
 Eliminates time consuming grinding and polishing
 Several approaches including vapor deposition of
nanolaminates bonded to actuated substrates
 Active figure control of primary mirror
segments
 High precision actuators
 Surface parallel actuation eliminates need for stiff
reaction structure (SMD)
 High speed wavefront sensing and control
 High density figure control enables very light weight
mirror segments
Image Plane & WFS&C Sensor
Model
Sensor
Scene
Tracker Focal
Plane
Fine Figure &
Phase Sensor
Imaging FPA
(4096 X 4096
8mm pixels)
Beam Footprint
at FPA Plane
 High speed, active while imaging WFS&C allows for rapid
slew and settle and earth imaging
 Highly-packageable & scalable
deployment techniques
 Deployment architecture should take advantage of light
weight mirrors
 Active control for light weight structural
elements to supply good stability
 Reduces weight required for vibration and thermal control
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Conclusions
 Space telescopes with 20-meter and larger
apertures are within affordable reach by the
mid-2020’s
 To achieve this we need to initiate a technology
development plan that thoroughly explores the
trade options and identifies and matures the
enabling technology
 We need the sustained technology development
funding to mature the technology
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