1. Mirror Box
Albert Yang, Tatiana Roy
Mentor: Lee Wilson

2. Ae105 Final Presentation 2
Mirror Boxes

3. Two Types of Mirror Boxes
• Mirror box contains all
required infrastructure for
telescope mirrors
– Two reference (rigid)
mirrors and two
deformable mirrors in total
– Will focus primarily on the
deformable mirrors
Ae105 Final Presentation 3
Reference Mirrors
Deformable Mirrors

4. Box Subsystems
• Mirrors
– Mirrors subsystem
holds the mirror in
place
• Picomotors
– Piston/tip/tilt the mirror
• Electronics
– House electronics
• Frame
– Hold all mirror box
elements and interface
with CoreSat
Ae105 Final Presentation 4
105.6mm
106mm
90mm

5. CoreSat Interface
• Must match with pre-established Surrey
mechanical and electrical interfaces
Ae105 Final Presentation 5
Cable
Interface
Mechanical
Interfaces
Mechanical
Interfaces
Interface
with Surrey

6. Functional Requirements
• Survive launch loads
• Provide mechanical support for a set of
deformable mirrors, rigid mirrors, and
mirror electronics
• Allow mirror to operate within the required
range of tip, tilt, and piston positions)
Ae105 Final Presentation 6

7. Performance Requirements
• Provide tip/tilt of up to 6.85°
Ae105 Final Presentation 7
Picomotors Tilting the Mirror Plate
Mirror Sub-
assembly
Reference
Plate
θ

8. Mass Budget
• Mass Requirement: <680g per box
Current Best Estimate:
Ae105 Final Presentation 8
Subsystem Current Mass (g) % total Contingency (g) (30%) Total (g)
Mirror* 28 5.5 9 37
Picomotors 263 51.7 79 342
Electronics 38 7.5 12 50
Frame 180 35.4 54 234
Total Mass 509 154 663

9. Addressing Requirements
• Mirror Mounts
– Updated mount design to solve pinching issue
– Tested new mount design
• Damping Columns
– Designed damping columns to interface with
mirror box and mitigate launch loads
– Chose damping material
• Updated mirror box design
Ae105 Final Presentation 9

10. Mirror Mount: Old Design
• Curved mirror is extremely thin. Mirror is
prone to deformation near mounting sites
– Old mounts designed
for flat mirrors
– Curved mirrors need
different mounts
– Changes in shape
will lead to reduced
overall performance
Ae105 Final Presentation 10
Old Design Relied on
Cylindrical Magnets

11. Mirror Mount: New Design
• Designed new mount
– Single point of contact on
each side of the mirror
– Top cage required to retain
magnet
Ae105 Final Presentation 11
Fixed with epoxy
Magnet/Cage minimum clearance
Tangent Line
Sphere Center Line
Old Mounts New Mounts
Tangent Line
Sphere Center Line
Magnet
Ball Bearing
Ball Bearing
Magnet
Ball Bearing

12. Testing Mirror Deformations
• Zernike coefficients were calculated using
SHWS to measure deformations
– Need 2.4m (radius of curvature) path to SHWS
– Independent test also conducted
– Looking for trefoil shape deformation in mirror
Ae105 Final Presentation 12
Flat Mirror
SHWS Beam Splitter
Mirror Fixture

13. Mirror Deformation Testing Setup
Ae105 Final Presentation 13
Laser
Beam
Splitter
Mask Mirror 1
Laser
Laser
Laser
Mirror 2
Laser
Curved
Mirror
Fixture
Laser
SHWS
One-Way Travel Distance: 2.4m
Radius of curvature of mirror

14. Mirror Mount Deformation Results
• Mirror had high Z4 and Z5 values
• Z9 and Z10 are not present in our test
Consequently, mirror mounts do not deform mirror
Ae105 Final Presentation 14
Z1
Z2 Z3
Z4Z5 Z6
Z8Z9 Z10Z7
Zernike Tested Name
4 .7 Defocus
5 2.5 Oblique Astigmatism
9 <.1 Vertical Trefoil
10 <.1 Oblique Trefoil

15. Mirror Mount Characterization
• A test was also performed on a Haso SHWS
by Caltech Post-Doc Steve Bongiorno
– Performed on different mirror, manufactured to
have less errors
– Concluded mirror aberration
was dominated by
astigmatism, and not by
any trefoil shape
Ae105 Final Presentation 15 Low Relative Values

16. Launch Survival
• Large vibration loads during launch: Mirror
will vibrate and possibly shatter
Ae105 Final Presentation 16
1.5g lateral
6g vertical
Vertical
Lateral
1.5g lateral
3g vertical
2.5g lateral
3g vertical
From Delta IV
Handbook

17. Damping Columns
• Damping columns attenuate
vibrational energy by physical
contact during launch
– Damping columns are separated
from the mirror after launch
Ae105 Final Presentation 17
Extruded Tip for Damping Material
Set screw in
a tapped hole

18. Damping Material
• Chose Red Silicone foam as damping
material
– Reported CVCM (collected volatile
condensable materials) of <0.005 (lowest
possible)
– Rated for -100F to 400F (required -50F to
50F)
Ae105 Final Presentation 18
Threads Into Reference Plate
Damping Material at Top

19. Updated CAD: Spring Tubes
• Keep mirror plate
connected to reference
plate while still allowing
for normal picomotor
operation
• Springs housed by
tubes connect
reference plate and
mirror plate
Ae105 Final Presentation 19
One end attaches at
bottom of tube
One end attaches at mirror plate

20. Summary of Mirror Box Progress
• Designed new mirror mounts to solve
mirror pinching issue
– Prototyped new mounts and characterized
with SHWS test
– Showed no appreciable deformation
• Designed damping columns and chose
damping material
– Fabricated sample damping column
• Updated CAD to reflect design changes
Ae105 Final Presentation 20

21. Further Work Required
• Finish launch vibration survivability test
– Finish profiling vibration table to make sure it
can reach the frequencies required
• More SHWS tests with different
configurations for the mirror
– Test mirror with current mount vs. no mount
• Design and assemble reference mirror box
Ae105 Final Presentation 21

22. Backup Slides
Ae105 Final Presentation 22

23. Ae105 Final Presentation 23

24. Ae105 Final Presentation 24

25. Picomotors Objectives
• Purpose is to tip and
tilt mirror
• Must achieve angles
of at least 6.84°from
normal
• Must unlatch mirror
and mirror plate from
launch configuration
to normal operation
Ae105 Final Presentation 25
Picomotor actuates up and down

26. Picomotors Challenges
• Normal operation
must be possible
while also securing
the mirror plate
• Movements of
individual
picomotors cannot
interfere with each
other
Ae105 Final Presentation 26
Picomotors Tilting the Mirror Plate

27. Picomotors final design
• Spring system keeps mirror
plate attached to reference
plate without affecting
picomotor performance
• Picomotor heads interface
with mirror plate through a
kinematic mount to avoid
interference between
picomotors (cone, flat, vee)
Ae105 Final Presentation 27

28. Picomotors Concern:
Interference with Frame
• Ensured in CAD that mirror
plate + PCB + mirror +
mirror mounts could tilt
without intersecting frame
• Using a 20% margin on
the maximum tilt, found
that mirror assembly has
~0.2mm clearance at
closest approach
Ae105 Final Presentation 28
Clearance on both sides

29. Frame Objectives
• The frame must house
the device and provide
attachment points for
the various components
• Must provide
mechanical and
electrical interfaces with
Surrey components
• Allow for easy assembly
Ae105 Final Presentation 29
Interfaces with Surrey

30. Frame Challenges
• Should keep mirror
from dropping
during assembly
(assembled upside
down)
• Picomotors must be
able to fully extend
without causing any
interference
Ae105 Final Presentation 30
Previously problematic area

31. Frame Design
• Threaded holes for all sides
and reference plate
• Lip on sides keeps mirror
from dropping during
assembly
• Original height was increased
(without affecting optics
distances) to accommodate
for picomotors max extension
Ae105 Final Presentation 31
Lips for safe assembly

32. Electronics
• 3 PCBs between bottom
and reference plate, plus
one behind mirror
• 3 PCBs stack has some
cropped edges to
accommodate for
picomotors and spring
tubes (does not affect
electronics
Ae105 Final Presentation 32
Ribbon Cable
Electronics Boards

33. Mirror Box Overview
• Mirror box is the system that contains all
required infrastructure for the telescope
mirrors
Ae105 Final Presentation 33
Box Assembly Inside the Box