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Roberto Ragazzoni INAF – Astronomical Observatory of Padova roberto.ragazzoni@inaf.it. Feasibility of the aspheric lens Catania, June 11 2014.
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Roberto Ragazzoni INAF – Astronomical Observatory of Padova roberto.ragazzoni@inaf.it Feasibility of the aspheric lens Catania, 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 Ragazzoni INAF – Astronomical Observatory of Padova roberto.ragazzoni@inaf.it Feasibility of the aspheric lens Catania, June 11 2014 This is still the “old” PLATO 1.0 group 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)
The aspheric issue… From a summarizing slide of June 15, 2011 (3 yers ago…) • 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
The aspheric issue… From a summarizing slide of June 15, 2011 (3 yers ago…) • 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
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 design • None of the above does apply to PLATO! • Several ground based 4m and 8m class instruments (all with aspheric surfaces)
Two of the lens has an aspheric surface surprisingly similar in size and deviation! Postcards sent around…
January 2010 Isabel Escudero Impact of increasing aperture & FOV on Thales optical design for Plato.
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. Thales Science Plato_v10 Plato_v20
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.
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
TOU BreadBoard Back Reflected Light 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, with the possibility to be rotated of 180º to insert the lenses from both sides (L3 will be the first one) B/S Iris2 CCD TOU Dummy Structure Iris1 Rotating points Beam Expander Transmitted Light Laser CCD
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 G18 BK7 CaF2 N-KZFS11 KZFSN5 S-FPL53 CaF2
Design 4 - 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
Design 5 BK7 G18 BK7 S-FPL51 S-FPL53 KZFSN5 N-KZFS11 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 SG • Gluing blank • Curing (th.cycle) • Shipped to PD • Shipped to UniBE • Vibrating • Shipped to CNES • Thermal cycling • Shipped blank to PD • Shipped to SG • Gluing blank • Shipped to PD • Shipped to CNES • Thermal 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 !!!
Summary… • Selex: Ok with industrial plan • Sagem/Reosc: Ok with industrial plan • MediaLario: 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 • SteinbeisTransferZentrum: 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
