Transcript Catania, 11 June 2014 TOU AIV Strategy, Prototyping Activities, Test & Results Maria Bergomi, Jacopo Farinato, Valentina Viotto (INAF - Osservatorio Astronomico di Padova)

Catania, 11 June 2014
TOU AIV Strategy, Prototyping
Activities, Test & Results
Maria Bergomi, Jacopo Farinato, Valentina Viotto
(INAF - Osservatorio Astronomico di Padova)
General strategy for the AIV
during Definition Phase
2 roadmaps have been followed to prove the AIV feasibility of the 32
telescopes:
1.
INDUSTRY
1.
2.
3.
4.
5.
2.
Paper
Paper
Paper
Paper
Paper
study
study
study
study
study
on
on
on
on
on
the
the
the
the
the
aspherical lens feasibility
aspherical lenses procurement feasibility fitting our time schedule
spherical lenses procurement feasibility fitting our time schedule
albemet structures procurement feasibility fitting our time schedule
N-TOUs AIV feasibility fitting our time schedule
RESEARCH INSTITUTES
1.
2.
3.
4.
Identify an AIV concept and procedure, defined in agreement with the industry
Test on a TOU PRE-BreadBoard of the AIV procedure
Test on the TOU BB of the warm/cold system performance, defined and performed
together with the industry
Test on CaF2 blanks (vibration and thermal cycling)
TOU Alignment Concept
Variable Iris
Beam Expander
B/S
Focussing
CCD
Laser
Back Reflected Light
Transmitted Light
Focussing
CCD
Telescope
To align one lens at a time, using Airy and Newton rings both of the back reflected
and of the transmitted light.
In
1.
2.
3.
order to maximize fringes contrast and airy rings visibility:
CCDs mounted on linear stages
light shields can be inserted between each lens
variable diameter iris is used
Catania, June 11th, 2014
INAF OAPD group
TOU Alignment Set-Up: Vertical
Focussing
CCD
Frame connected to the bench,
To allowthe
lenses
insertion
allowing
rotation
for lenses
insertion
from the
the final
top, with
from
the top,
the possibility
to be
alignment
set-up for
the
180º to insert
BBrotated
will beofvertical
the lenses from both sides
(L3 will be the first one)
Transmitted Light
TOU
Variable Iris
Beam Expander
B/S
Laser
Back Reflected Light
Catania, June 11th, 2014
Focussing CCD
INAF OAPD group
TOU Prototyping philosophy
PRE-BREADBOARD:



LENSES: commercial lenses with the closest
curvature as possible of the FM design lenses
BREADBOARD:
MECHANICS: commercial off-the -shelf

LENSES: custom made spherical lenses with a
mechanics
curvature optimizing on-axis performance.
AIM: to test the alignmentSome
procedure
and
glasses
are different from the FM.
learn from the test setup
 refurbishment:
MECHANICS: thermally equivalent to FM.
PROTOTYPE
– BB
•
Airy and Newton rings visibility
Same
interfaces
as FM.
• decenter
LENSES:and
custom
made
lenses
as
per
FM
tilt misalignment sensitivity

AIM:tools
to validate
the alignment procedure at
(with minor manufaturing
adaptation..).
•
tuning of the test setup components, e.g. the
ambient
temperature
 movement
MECHANICS:
thermally
equivalent
to FM. (20°C, 1 atm) and the
range
of the detectors
Same interfaces as FM.achievement of the performances at the
working temperature (-80°C, 0 atm)

AIM: to test the actual proposed alignment
•
test on-axis performance in warm environment
procedure with FM lenses
•
•
•
•
test on-axis performance in cold environment
aspheric lens (L1) manufacturability
to validate warm AIV
test off-axis performance in warm
environment
test FPA integration
Catania, June 11th, 2014
INAF OAPD group
TOU Pre-BreadBoard
Variable Iris
Beam Expander
B/S
Laser
Focussing
CCD #2
Back Reflected Light
Transmitted Light
Focussing
CCD #1
AIV constraint: in the final system, L3 cannot be adjusted in tip-tilt and centering.
First AIV step will be to align the laser beam to L3, which will be the first lens to be
mounted
Because of that, you need to rotate the TOU breadboard accordingly to which lens
you’re aligning, to see its back-reflected spots…
Catania, June 11th, 2014
INAF OAPD group
TOU Pre-BreadBoard
PLATO
SIMULATOR
CCD#2
PLATO
SIMULATOR
CCD#1
CHANNEL A:
L3, L2 and L1
insertion
CHANNEL B:
L4, L5 and L6
insertion
2 channels have
been realized to
simulate TOU 180º
rotation during AIV
CCD#2
INAF OAPD group
CCD#1
Catania, June 11th, 2014
INAF OAPD group
TOU Pre-BreadBoard
Results
 2 back reflected Airy rings systems visible for each lens
BB illuminated from
the TOP
Transmitted spot can always be used as a check
IF the lens is illuminated from its insertion side and only
back-reflections are used:
Fixed CCD
position
▪ Centering
sensitivity
is always below 50μm
(compact
setup
+
▪ Tip-tilt
sensitivity
is always
below 50 arcsec
stability)
To move away
the detectors do not clearly improve the
sensitivity
For the first lens to be inserted (L3), a reference on the CCD
definition
must be Reference
defined
procedure
 Newton rings systems visible for each lens




Catania, June 11th, 2014
INAF OAPD group
TOU Pre-BreadBoard
Results
Sensitivity sanity check:
Lens
(insertion order)
Dec. sensitivity
Tilt sensitivity
Dec. tolerance
Tilt tolerance
L1 (3)
±30 m
±18”
±30 m
±108”
L2 (2)
±30 m
±18”
±50 m
±36”
L3 (1)
±30 m
±18”
±30 m
±36”
L4 (4)
±30 m
±18”
±30 m
±36”
L5 (5)
±50 m
±36”
±30 m
±36”
L6 (6)
±30 m
±18”
±70 m
±216”
First rough sensitivity run, to verify the compliance of the setup sensitivities
with a preliminary run of optical tolerances.
Resulting sensitivities are very close to the tightest tolerances for all the
lenses except for L5.
• THIS RESULT IS AN INPUT FOR THE TOLERANCES ANALYSIS
• SENSITIVITIES CAN STILL BE IMPROVED
TOU BreadBoard
Lenses Gluing @ Selex
• Scotch-Weld 2216 B/A glue + primer
used
• Each mount is equipped with small
“shelves”, except for L6
• For L6,whose pads are positioned in the
middle of the lateral faces a dedicated
MGSE is required
• Centering (~1/10mm) and Tilt (<90”) of
the lenses inside their mounts are well
below travel adjustment
• For the FM, rectified mechanical
references might be required to avoid tilt
adjustment on the lenses during the
alignment phase (tolerance: ~30”).
Catania, June 11th, 2014
INAF OAPD group
TOU BreadBoard
Setup
Reference
determination
setup
•
•
Catania, June 11th, 2014
Frame connected to the bench, with the
possibility to be rotated of 180º to insert the
lenses on both sides, always from the top (L3
will be the first one)
MGSE tools for (compatible with FM also):
• Lens insertion: threaded bars
• Lens centering: micrometric actuators +
pre-load system
• Back-reflections isolation: light shields
INAF OAPD group
TOU BreadBoard
Alignment
OBSERVABLES and DEGREES OF FREEDOM:
• Newton rings symmetry : centering
• Back-reflection position with respect to the
reference defined on CCD#1: tip-tilt
L2 - 20µm
• Transmitted spot position on CCD#2: final check
ADDITIONAL SOURCE OF ERROR:
Pixels [6.45um]
• Laser setup long-term (12hs) stability
L1 - 10µm
Pixels [6.45um]
Catania, June 11th, 2014
L1+L2+L3
L1+L2+L3+L4+L5+L6
INAF OAPD group
TOU BreadBoard
Results
Achieved alignment precision, compared with
tolerances:
-
-
Lens
(insertion order)
Dec. precision
Tilt precision
Dec. tolerance
Tilt tolerance
L1* (3)
±18 m
±21”
±30 m
±108”
L2* (2)
±25 m
±18.7”
±50 m
±36”
L3 (1)
±35.3 m
±22.5”
±30 m
±36”
L4 (4)
±21.2 m
±9.6”
±30 m
±36”
L5 (5)
±18 m
±16.3”
±30 m
±36”
L6 (6)
±21.2 m
±31”
±70 m
±216”
Alignment precision: centering and tilt
precisions inside tolerances, but for the
decenter of L3
Time issue: the overall AI took 3 days, and it
may be further improved
Catania, June 11th, 2014
INAF OAPD group
TOU BreadBoard
Lessons learned
SETUP:
- The overall setup could be realized in a more
compact way (smaller source, shorter light
path…) to increase stability
- Variable Iris centering stability turned out to be
poor, so we used it as fixed, skipping backreflections visibility optimization → a higher
precision component could be selected
- A further BS could be inserted before the TOU,
to live-monitor the beam stability
- A more precise laser adjustment tool could be
used to increase the precision of L3 alignment
Catania, June 11th, 2014
GSE: (required modifications – not conceptual)
- Centering MGSE-main structure interferences:
- between centering actuator for L4 and
rotating structure (lower resolution actuator
used)
- between centering pre-load system for L2
and L5 and rotating structure (normal
screw+spring used)
- Lenses insertion MGSE:
- 3 attaching points with threaded bars
require 2 persons to perform the operation
- Interference with BB structure, while
inserting L4
BB MAIN STRUCTURE: (risky and time-consuming
aspects)
- Tip-tilt with shims: “tilt regulating system” would
simplify quite a lot the procedure
- Shims and washers: the screw could be part of
the BB structure, to keep washers in position, it
could then be fixed with nuts
INAF OAPD group
TOU BreadBoard
warm test
Standard interferometric test:
ZYGO
interfer.
F/1.5 transmission
sphere
Reference mirror
(<λ/10rms)
On-axis PSF test
setup:
(monochromatic light)
Folding
mirror
BreadBoard
Test
camera
head
To get familiar
with the COLD
test setups
Test
camera
electronics
Linear
focussing
stage
Collimated
beam
RESULT (far inside expectations):
PtV WFE=1.68 waves (@0.633um)
RMS WFE=0.31 waves
Hartmann test
setup:
results
presented
later
Test
Camera
head
BreadBoard
Hartmann
mask
Focussing
linear
stage
Cold Test Purpose

Check that the optical quality obtained
through the alignment performed in warm
conditions is maintained also in conditions
similar to the observing one (-80°C)
Catania, June 11th, 2014
INAF OAPD group
The Cryo-Vacuum Camera and
some tools
Catania, June 11th, 2014
INAF OAPD group
The Optical Setup
Catania, June 11th, 2014
INAF OAPD group
Inside the Cryo environment…
Camera Holder
Prototype Holder
Catania, June 11th, 2014
INAF OAPD group
Inserting the Prototype…
Catania, June 11th, 2014
INAF OAPD group
The Prototype in the Chamber
Catania, June 11th, 2014
INAF OAPD group
First Test: PSF on axis in cold
Performed by the Research Institutes + Industry
Climate Chamber (T~-80º)
Input optical window
Collimated Beam (D=300mm)
Test Camera remotely
adjustable in focus
Advantages:
- Parallel beam in input
- No other Optical Parts inside
the chamber
- Only 1 motorized axis in cold
Interferometer + BE
Average of 10 frames
PSF (FWHM~ 1.37 TOU Pixels)
90% of EE in spec
BUT
Strongly affected by data
reduction parameters,
mostly due to the high
background light
2nd test: Hartmann in cold
Performed by the Research Institutes + Industry
Climate Chamber
T~-80º
Hartmann Mask (76 apertures)
Collimated Beam
P1
Interferometer + BE
Input optical window
P1
P2
+2mm
P2
CCD (movable
in focus)
Advantages:
- Parallel beam in input
- No other Optical Parts inside
the chamber
- Only 1 motorized axis in cold
If the relative position of P1 and P2 is known with a high accuracy (linear stage with
encoder), we can verify the optical quality in terms of Encircled Energy on the focal
plane, even without reaching it with the CCD!
Hartmann Test: the Procedure
• 3 sets of 100 images at three TDS locations along the optical axis, each one
separated by 1mm, moving the camera with the linear stage
• for each set, the mean of the 100 images has been computed, to minimize the
contribution of bad pixels and electronic noise, obtaining three processed frames
• The centroids of the 76 spots, for each frame, have been computed as the center of
mass of the light distribution of each spot
• The centroids of the two frames taken
at a distance of 2mm, have been used
to compute the parameters of the lines
representative of the 76 beams. Such
parameters allow to reconstruct the
“rays” distribution at any focal distance
• The 3rd set have been used to compute
the indetermination of the
measurements (0.8 pixels in cold)
• The EE has been measured on the
extrapolated positions of the 76 rays,
in correspondence of the focal plane
Catania, June 11th, 2014
INAF OAPD group
Focus extrapolated minimizing the
RMS radius of the 76 centroids
Catania, June 11th, 2014
INAF OAPD group
EE Comparison warm vs cold
WARM measured: 5.8 ±0.8 pixels (expected 2.8 pixels)
COLD measured: 4.1 ± 0.5 pixels (expected 2.0 pixels)
Catania, June 11th, 2014
INAF OAPD group
EE computed in the Hartmann
extrapolated Focus with finer data
reduction (some outlayers removed)
Catania, June 11th, 2014
INAF OAPD group
Bread-Board Test Conclusions
The alignment procedure (using L3 as reference and the Newton rings of the
various optical elements on both sides) has been validated, even if it has been
revised from on-field experience, including, when needed, interferences between
surfaces of different lenses rather than the two surfaces of the same lens, to
achieve the required precision.
 The typical timescale of the alignment procedure has been demonstrated to be of
the order of two to three days, and it can be improved by implementing a few
changes on the GSE and with experience.
 There is margin for improvement in the area of getting independent and redundant
information about the amount of decenter and tilt of the lenses.
 Warm quality very good in term of WF but inconsistent with Hartmann computed
EE, which is a factor 2 worse than expected (finer data reduction never performed
in warm)
 Cold quality in term of EE Hartmann computed is a factor 2 worse than expected
(but finer data reduction improves the EE of a factor 2)
 The retrieved enclosed energies show that the system maintains the alignment in
the transition from warm to cold conditions and, moreover, that the performance
improves in the cold of an amount comparable to the expected ones
No major risks, issues to be clarified
Catania, June 11th, 2014
INAF OAPD group

Calcium fluoride
lens & blanks tests
L3 Calcium fluoride lens
•
L2*
L3
L4
L5
BUT…BRITTLE
• Difficult to machine SOLVED
• Susceptible to mechanical and thermal shocks
(launch environment) SCARCITY OF
INFORMATION
STOP
120m
m
357 mm
•
L1*
•
Excellent transmission & low dispersion over a wide
wavelength range (from UV (0.13 μm) to mid IR (9
μm)
One single lens to reduce chromatism mass
reduction
Naturally resistant to high radiation
L
6
Fernandez-Rodriguez F et al. “Analysis of optical properties behavior of
Clearceram, fused silica and CaF2 glasses exposed to simulated space
conditions”, Proc. ICSO (2010)  20 mm * 5 mm polished blanks
tested for thermal cycling and UV radiation
187 mm
Blanks tests
Korth-Kristalle GmbH
Non-polished parallel-plane disks
120 mm diameter; 26 mm thickness
Rough surfaces + the presence of edges:
even more fragile than final lenses (edges
are crack propagators)
@SELEX Galileo: same glue and process planned for flight model, but connection
points chosen to maximize the thermal contact between the barrel and the facilities:
Blank#1: cured with an oven at 50°C
Blank#2: at room temperature
To simulate space conditions
• Vibration tests
@Uni Bern
• Thermal cycles
@CNES
Vibration tests @Uni Bern
2 tri-axial accelerometers used to perform tests
• on the lens to measure response
• closed-loop monitoring
Runs:
Mainly due to
• Resonance search
settling in the
• Sine
tests assembly
interface
• Random
No evidence of changed mechanical properties and no visual signs of
damage or deterioration but…
Cf. Test_509_PLATO_dummy_lens_mount_report.pdf
Vibration tests @Uni Bern
Confirmation of brittleness of material
Test Engineer: Michael Gerber
Test Manager: Daniele Piazza
Copy Distribution: Daniele Piazza
Karsten Seiferlin
Piers Christiansen
Thermo-vacuum tests @CNES
Polarized light visual
inspection: some scores and 3
weak areas (unknown when
they occurred)
Cf. PLATO-CAMTOLE-RP-154-CNES.pdf
Homogenous environment
Thermo-vacuum tests @CNES
Thermal cycling
45°C
45°C
20°C
20°C
-100°C
13 thermo-couples
-100°C
No visual changes after
the thermal tests even in
the weak areas
L3 TOU breadboard @SELEX
L3 as for flight model (23 mm thickness, 116 mm diameter)
mounted on a specific flexible quasi-isostatic mount.
Tested inside TOU Breadboard:
• Thermal cycling (20°C, -80°C)
• TOU Optical test in working conditions (-80°C, 0 atm)
Visual inspection revealed no damage
CaF2 conclusions
CaF2 intensively tested in simulated space launch and working conditions:
• Blanks: thermo-vacuum + vibrations
• L3 lens inside TOU: thermo-vacuum
• Blanks + lens inside TOU: trip from Padova to Firenze in Roberto’s car
(40°C external temperature)
Both uneventfully succeeded to mechanical and thermal shocks: no
deterioration or damage were reported due to the test but…
… some weak areas were spotted on one blank before CNES tests
(vibration test of a polished blank with rounded edges or of L3 could be
foreseen in next phase? Polished blanks are in fact more resistant than the
blanks)
No major risks identified, a few issues to be clarified.
Catania, June 11th, 2014
INAF OAPD group
Conclusions





AIV procedure validated and very fast (3 days that may easily go down to 2
days); a few GSE tools may be improved
The retrieved enclosed energies show that the system maintains the alignment
in the transition from warm to cold conditions and, moreover, that the
performance improves in the cold of an amount comparable to the expected
ones (this was the main goal of the performed activity). Issues to be clarified
on the obtained performance (warm and cold conditions) in terms of EE
The CaF2 lens behaved uneventfully during the whole operations. This fact,
coupled with the positive results coming from the vibration (RD17) and thermal
cycling tests (CNES, report in prep.) confirms the choice of this material for this
(close to) pupil lens. Issues to be clarified concerning the weak areas found on
the blanks, but not related to the vibration and thermal cycling test
The mount of L6 has to be revised with the aim of increasing the gluing points
and to assess positional stiffness and thermal compliance with the relative
displacement of the edges of the lens
No major risks, issues to be clarified (and this was the purpose of this exercise)
Catania, June 11th, 2014
INAF OAPD group