Meddelelse
ESO Underskriver kontrakt om polering af E-ELTs tertiærspejl
ESOs Extremely Large Telescope (ELT), som efter planen skal tages i brug i 2024, presser teknologien til det yderste. Det optiske system kommer til at bestå af ikke mindre end fem separate spejle, og hvert af dem udgør deres helt egne tekniske udfordringe
15. februar 2017
Nu har ESO tildelt kontrakten for at polere det tredje spejl i lyset vej igennem teleskopet, det såkaldte M3, til det franske selskab Reosc [1], som er en del af koncernen Safran Electronics & Defense. Firmaet modtager det støbte spejl fra SCHOTT, og det skal designe spejlet og monteringen, polere overfladen og gennemføre alle nødvendige optiske tests før spejlet bliver afleveret[2]. Reosc har også i juli 2016 fået kontrakterne på design, polering af afprøvning af teleskopets sekondærspejl, og på at bygge de deformerbare skal-spejle som kommer til at udgøre E-ELTs fjerde spejl (M4).
M3 bliver et kæmpe konkavt spejl; 3,8 meter i diameter - hvilket er i samme størrelsesorden som hovedspejlene i mange af de nuværende teleskoper i topklasse i Verden. Det bliver en usædvanlig konstruktion, for de fleste nuværende store teleskoper, som for eksempel ESOs Very Large Telescope og NASA/ESA Hubble Space Telescope anvender kun to krumme spejle. I nogen af dem er der også et fladt tredjespejl, som leder lyset hen til et passende focus med instrumenter. M3s krumme flade kommer til at arbejde sammen med primær- og sekundærspejlene om at give en bedre billedkvalitet over et stort synsfelt.
Spejlmaterialet bliver fremstillet af et specielt materiale, som kaldes Zerodur™ fra SCHOTT [3]. Det støbte spejl bliver i Frankrig nedslebet og poleret til en nøjagtighed af overfladen på 15 nanometer.
Noter
[1] Reosc, er en del af Sagem koncernen, som arbejder med højteknologi under navnet Safran. Firmaet er i første række i Verden indenfor design, fremstilling og montering af højtydende optik. Reosc udvikler og fremstiller kvalitetsoptik til satellitter, store teleskoper, højenergilasere og til halvlederindustrien. Firmaet har også bygget de fire 8 m store spejle til ESOs Very Large Telescope, spejlene til Geminiteleskoperne, 11 meter spejlet til Gran Telescopio de Canarias, spejle til det europæiske instrument Nirspec til NASAs James Webb Space Telescope, og spejle til ESAs GAIA astrometrisatellit.
[2] Kontrakten for M2 spejlet blev underskrevet 18. januar 2017.
[3] Zerodur™ blev oprindeligt udviklet til astronomiske teleskoper sent i 1960erne. Materialet har næsten ingen varmeudvidelse, selv ved store temperatursvinginger. Desuden har det stor kemisk modstandsevne, og det kan poleres op til meget høje nøjagtigheder. Det spejlende lag, som fremstilles af aluminium eller sølv, bliver normalt fordampet på den højtpolerede overflade lige før teleskopet bliver taget i brug. Mange kendte teleskoper har fungeret upåklageligt med Zerodurspejle i årtier. Iblandt dem er ESOs Very Large Telescope i Chile.
Links
- Mere information om ELT
- Mere om firmaet Safran Electronics & Defense
- ESOcast 84: The New E-ELT Design Unveiled
- Reosc får kontrakten på adaptive spejle til ELT
- ESO underskriver kontrakt om polering af ELTs Sekundærspejl
Kontakter
Ole J. Knudsen
ESON-Danmark, Stellar Astrophysics Centre, Aarhus Universitet
telefon 8715 5597, mobil 4059 4520, e-mail: eson-denmark@eso.org
Om meddelelsen
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