PLATO Telescope Optical Units Meeting in Bern March 12 th 2010.
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Transcript of PLATO Telescope Optical Units Meeting in Bern March 12 th 2010.
![Page 1: PLATO Telescope Optical Units Meeting in Bern March 12 th 2010.](https://reader035.fdocuments.us/reader035/viewer/2022072010/56649dc95503460f94abf18c/html5/thumbnails/1.jpg)
PLATO Telescope Optical Units
Meeting in BernMarch 12th 2010
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(proposed) Agenda
• 9:15 Welcome & scope of the meeting (Ragazzoni)• 9:25 Optical design status (Magrin)• 9:55 Radhard glass affaire (Ragazzoni)• 10:15 Mechanical design status (Piazza)• 10:45 Coffee break (careful in Swiss you get 2 coffes..)
• 11:00 AIV and prototype activity (Farinato)• 11:30 Discussion on prototyping (All)• 12:15 Setting up of next steps (Catala +All)
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Scope of the meeting
• By 22nd of March we are supposed to deliver to ESA a nominal design and a plan for prototyping
• Consolidating (or defining policy to achieve such a goal) the nominal design
• Protoyping activity is “to be assessed if necessary” accordingly to the ESA document (Nov 12th 2009)
• Furthermore in view of talks with industry we should start to establish how TOUs will be splitted among the Alps…
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Rad Hard glasses business
• From beginning we setup an internal catalog of radhard glasses
• BaF2 was among them and was selected as front lens
• BaF2 was (properly) criticized and dropped after the Yellow Book released
• Instead S-FPL-51 by Ohara was choosen for front lesn
• Other lenses assumed being shielded by 3mm Alluminum
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Rad Hard glasses business
• Thaless design used the same glass as front lens
• Prophetical words extracted from ESA doc. SRE-PA/2009.081 (Nov. 12 2009):
• “…radiation hardness.. may generate surprise in the detailed design phase.”
• Analysis of the L2 environment with a simplified model of the tubes commenced several weeks ago…
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Rad Hard glasses business
• …but (detailed) outcome only yesterday (sigh…).
• Radation dose in L2 is 3.5 krad/yr inside the tube and 55 krad/yr for the front lens
• Inside lenses: only one lens significantly affected (dropping transparency to 60%@500nm and 82%@650nm in 3 years)
• Outside lens: dramatic deterioration to, 8%@500nm and 75%@700nm...!!!
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Rad Hard glasses business
• The inside lens can be easily substitude by its rad-hard counterpart
• The front lens glass is to be replaced but this requires careful re-optimization
• We are confident this can be done in a week time span, but this requires here we define policy on how to choose rather than taking a final decision.
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Other issues raised by the ESA document…???
• Main concern is on CCD (optomechanics is 2nd place) and assumes prototyping is being done in the coming year.
• Criticism of taking Thaless as starting ref. already largely discussed in ESA
• Pointing stability (but this is to be taken into account by the bus industrial studies)
• Suggestion of the aspheric being a pure conical is a good one but unfortunatley unfeasible (but we take as action to consider designing a null-lens in our study)
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Other issues raised by the ESA document…???
• Further to rad hardness “thermal performances and stability at low temperature not properly taken into account” so we take the action to discuss this item with our Milan collegues.
• “Studying optical methods of assembling optics in barrel segments” is already in place
• It is missing a “full verification at P/L system level” criticism that we have to take seriously in the coming time