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Roberto RagazzoniINAF – Astronomical Observatory of [email protected]
Feasibility of the aspheric lensCatania, June 11 2014
On behalf and with extensive inputs from the Telescope Group (D. Magrin, D. Piazza, W. Benz, J. Farinato, S. Basso, M. Ghigo, M. Munari, P. Spano’, G. Piotto, M. Barbieri, E. Pace, S. Scuderi, I. Pagano, L. Gambicorti, C. Arcidiacono, R.U.
Claudi, V. Viotto, M. Dima, G. Gentile, R. Canestrari, S. Desidera, S. Benatti)
Roberto RagazzoniINAF – Astronomical Observatory of [email protected]
Feasibility of the aspheric lensCatania, June 11 2014
On behalf and with extensive inputs from the Telescope Group (D. Magrin, D. Piazza, W. Benz, J. Farinato, S. Basso, M. Ghigo, M. Munari, P. Spano’, G. Piotto, M. Barbieri, E. Pace, S. Scuderi, I. Pagano, L. Gambicorti, C. Arcidiacono, R.U.
Claudi, V. Viotto, M. Dima, G. Gentile, R. Canestrari, S. Desidera, S. Benatti)
This is still the “old” PLATO 1.0 group
The aspheric issue…
We have been asphericized by an hard life (thank you Silvio…)
We had two offers from manufacturer for actually making one (in S-FPL51) for test (SESO & Silo)
We have a detailed plan and feasibility by Sagem-Reosc that already manufactured two similar sets for a different space project (and they made similar comments as Zeiss quotation in RUAG report!)
ESA challenged themselves to improve Thales design to achieve performances and found they need two aspherics
Asphere is on a lens with one flat surface MediaLario is testing their manufacturing
abilities on glass S-FPL51
From a summarizing slide of June 15, 2011 (3 yers ago…)
The aspheric issue…
We have been asphericized by an hard life (thank you Silvio…)
We had two offers from manufacturer for actually making one (in S-FPL51) for test (SESO & Silo)
We have a detailed plan and feasibility by Sagem-Reosc that already manufactured two similar sets for a different space project (and they made similar comments as Zeiss quotation in RUAG report!)
ESA challenged themselves to improve Thales design to achieve performances and found they need two aspherics
Asphere is on a lens with one flat surface MediaLario is testing their manufacturing
abilities on glass S-FPL51
From a summarizing slide of June 15, 2011 (3 yers ago…)
The team background
Rosetta Wide Angle Camera design An off-axis tilted FoV design with
aspheric mirrors Emphasys was on detection of faint
gasesous features from comet nuclei Clean PSF: unobstructed pupil,
monochromatic and low scatter designNone of the above does apply to
PLATO!Several ground based 4m and 8m
class instruments (all with aspheric surfaces)
Postcards sent around…
Postcards sent around…
Two of the lens has an aspheric surface
surprisingly similar in size and deviation!
Impact of increasing aperture & FOV on Thales optical design for Plato.
January 2010Isabel Escudero
Purpose of study.
Modify Thales design as follows: Entrance aperture diameter: 15% bigger. FOV: from a circle of 28º diameter to a
square of 28º side length. Image: quality equivalent to that of
Thales design for the whole new FOV (criterion is 90% EEC diameter)
Focal length: same as original Add Fused Silica plate in front Aspherics necessary?
Comparing sizes.10:01:23
plato_thales ME 11-Jan-10
50.00 MM
10:11:01
Science 15-Jan-10
50.00 MM
15:48:36
plato_v10 ME 08-Jan-10
50.00 MM
15:49:37
plato_v20 ME 08-Jan-10
50.00 MM
Thales Science
Plato_v10 Plato_v20
Comparing performance
Design Field object (degrees) Diameter of 90% encircled energy (µm) Plato_Thales Axis/9.6/13.7º/19.6º 34.8 / 42.6 / 58.9 / NA Plato_v10 Axis/9.6/13.7º/19.6º 39.7 / 34.4 / 41.8 / 65.8 Plato_v20 Axis/9.6/13.7º/19.6º 31.9 / 34.0 / 42.8 / 59.6
System EPD (mm) EFL(mm) FOV Thales 83 239.5 28º diameter circle Science 120 247.5 28º diameter circle Plato_v10/Plato_v20 95.45 239.5 28º side square
Design Field Object Incidence Angle at image Distortion (%) Plato_Thales 14º 26.7º 0.7 Plato_v10 19.6º 38.3º 0.7 Plato_v20 19.6º 38º 2.0 Science 14º 31º 2.9
Conclusions: Thales_v10/_v20.
Two aspheric surfaces are required for larger EP & FOV.
If FOV = 28º diameter circle, one aspheric surface is enough.
Fused silica plate becomes a lens: curvatures and aspheric are needed.
Note values of distortion (=> calibration and post-processing for field superposition).
Note large angles of edge field object at image plane: relevant for radiometry.
Conclusion by ESA…
Do we need aspheres…?
Yes… Accordingly to ESA (upgrading of THALES design)
at least two; With our own design (actually all the “last”
versions) just one.
Feasibility strategy
ESA never questioned feasibility of one TOU
ESA often being concern about “mass” (well, sort of…) production
Construction is one of the issues..We focus on demonstrating a fast
procedure (less than one week) in the warm…
Aggressive plan to demonstrate we can handle CaF optical elements
Frame connected to the bench, allowing the rotation for lenses insertion from the top and their alignment similarly to what would happen with the final structure, withthe possibility to be rotated of 180º to insertthe lenses from both sides(L3 will be the first one)
TOU BreadBoard
Rotating points
TOU Dummy Structure
Laser
Beam Expander
Iris1
B/S
Back Reflected Light
Transmitted Light
CC
D
CCD
Iris2
Alternative designs
A design with an aspheric CaF (because SESO claimed that with some manufacturing process that would be easier/cheaper/faster)
A design CaF-free (in case we fail space qualification of CaF lens)
A design taking into account the common directives of manufacturer
Design 4
BK7 G18CaF2
CaF2N-KZFS11 S-FPL53 KZFSN5
BK7
Design 4 - EE
90%EE<30×30 arcsec2 ~ 2×2 pixels2
90%EE<37.5×37.5 arcsec2 ~ 2.5×2.5 pixels2
90%EE<45×45 arcsec2 ~ 3×3 pixels2
2×2 pixels2
Design 5
BK7 G18S-FPL51
N-KZFS11S-FPL53 KZFSN5
BK7
S-FPL51
Design 5 - EE
2×2 pixels2
90%EE<30×30 arcsec2 ~ 2×2 pixels2
90%EE<37.5×37.5 arcsec2 ~ 2.5×2.5 pixels2
90%EE<45×45 arcsec2 ~ 3×3 pixels2
Baseline - EE
90%EE<30×30 arcsec2 ~ 2×2 pixels2
90%EE<37.5×37.5 arcsec2 ~ 2.5×2.5 pixels2
90%EE<45×45 arcsec2 ~ 3×3 pixels2
The CaF issue…
Already flown… One company (SESO) would prefer as
asphere Baseline design has CaF in the spherical,
smallest and more protected position (L3) We have in our hand a produced L3
identical to the flight one (assuming baseline)
We have two blanks similar in size, glued to the same holder and cured in two different ways now in CNES and UniBern for thermal and vibration tests…
We have an acceptable, although not brilliant, B plan CaF-less
Foreseen Activities (CaF2):
Shipped blank to PD
Shipped to SGGluing blankCuring (th.cycle)Shipped to PDShipped to UniBEVibratingShipped to CNESThermal cycling
Shipped blank to PD
Shipped to SGGluing blankShipped to PDShipped to CNESThermal cycling
Survived!
Survived!
Remember that L3 in the BB
is made in CaF2 as well!
Foreseen Activities (BB):
Mounting lenses on mounts (gluing) Aligning within tolerances Testing the “warm” optical quality
interferometrically Measuring the “warm” PSF directly Measuring the “warm” PSF via Hartmann Measuring the “cold” PSF directly Measuring the “cold” PSF via Hartmann Validation or lessons learned of the
alignment process
DONE !!!
One aspheric done on purpose…
Various studies issued…
Various studies issued…
Production plans…
Production plans…
Production plans…
Summary…Selex: Ok with industrial planSagem/Reosc: Ok with industrial planMediaLario: Interested, feasibility Ok, now joining
Selex?Seso: Ok but would prefer CaF2 (technology driven)RUAG: Market analysis…
Zeiss: doable, delivery time non critical
Asphericon: doable at the limit (delivery time) of their abilities
Steinbeis TransferZentrum: identified several technologies
Leica: doable, but reccomending harder material Fisba: they do not have capabilities (in spite of…)
PrazisionOptik: they do not make aspheres
SwissOptics: they think are doable but exceed the size they handle
What is next…?
Regain informal contact with all industries (some already made on their own… Sagem & MediaLario)
Select one or two for an updated formal adjourned contact
Place the accent on the serial and industrial production
Take –very fastly- a final choice as the overall baseline based on existing informations