Meddelelse
Forbedret spejl til adaptiv optik er leveret
Nyt tyndskals-spejl til VLT har bemærkelsesværdig optisk kvalitet
4. februar 2014
I december 2011 leverede det franske firma Safran-Reosc deres første Zerodur tyndskals-spejl til ESO (ann12015). Firmaet har nu overgået dette ved at levere deres andet skalspejl [1] med endnu højere kvalitet end det første. Begge spejle er kun 2 millimeter tykke, men 1,12 meter i diameter og vil være afgørende for opgraderingen af enhedsteleskop nummer 4 på ESOs Very Large Telescope (VLT) til et fuldt adaptivt system [2]. Et tyndskals-spejl deformeres flere tusinde gange pr. sekund for at modvirke effekten af turbulens i Jordens atmosfære. Resultatet er et langt skarpere billede, der giver astronomerne mulighed for at undersøge universet i langt større detalje end hidtil.
Det nye skalspejl er forbedret på mange måder. Dets overflade er lavet fem gange mere nøjagtig end det gamle spejl og blot meget små kræfter er nødvendige for at korrigere overfladens form – halvt så store som for det første skalspejl. Det er meget vigtigt, da det sikrer rigeligt med kræfter til at korrigere forringelsen i billedkvalitet, der opstår pga. turbulens i atmosfæren. Skalspejlets tykkelse er blevet tre gange mere ensartet og spejlets finish er også blevet forbedret på begge sider.
Det er brug for et ekstra spejl, da disse systemer uundgåeligt er meget skrøbelige. Hvis det første skalspejl skulle gå i stykker, ville det gøre et af VLT-enhedsteleskoperne ubrugeligt i årevis, mens en erstatning blev fabrikeret. Det nye spejl er en forsikring imod en sådan usandsynlig, men katastrofal begivenhed.
Det nye spejl var tænkt som reserve, men da det har vist sig at være langt bedre end det første spejl, vil det i sidste ende blive taget i brug, mens det første spejl bliver holdt i reserve.
Leverandørerne af det komplete deformerbare sekundærspejl-system, som støtter den tynde skal, Microgate og ADS International (Italien), har udviklet mange nye procedurer, håndteringsredskaber og transportkasser for at sikre det skrøbelige spejl på hver del af rejsen. Paradoksalt nok er det sikreste sted for skalspejlet, når det er blevet monteret på teleskopet og holdes på plads af magnetfelterne fra 1170 svingspoler.
Den succesfulde afslutning af dette projekt viser, at Safran-Reosc mestrer denne teknik og det er meget positivt for E-ELT teleskop-projektet. Anvendelsen af disse processer viser, at denne teknologi kan udvikles bruges til de meget store deformerbare spejle, der er tænkt til E-ELT. De skal have den samme tykkelse som de nuværende spejle, men en meget større diameter på 2,5 meter.
Noter
[1] Dette andet tyndskals-spejl vil blive færdiggjort med særlige overladebelægninger og 1170 magneter, der limes fast på dets konkave bagside. Når spejlet er installeret som en del af sekundærspejl-systemet vil magneterne styres af svingspoler, der ved aktivering danner et magnetfelt, som trækker i de permanente magneter og derved ændrer skalspejlets form.
[2] Med installationen af det nye spejl bliver alle adaptive korrektioner udført af teleskopets sekundærspejl og alle teleskopets instrumenter vil få gavn af en voldsomt forøget billedkvalitet. I tidligere systemer blev korrektionerne udført i de individuelle instrumenter.
Kontakter
Elise Vernet
Adaptive Optics System Department
ESO, Germany
Tel: +49 89 3200 6322
Email: evernet@eso.org
Pierre Yves Madec
Adaptive Optics Facility System engineer
Adaptive Optics System Department
ESO, Germany
Tel: +49 89 3200 6524
Email: pmadec@eso.org
Robin Arsenault
Adaptive Optics Facility Project Manager
Project Management Department
ESO, Germany
Tel: +49 89 3200 6524
Email: rarsenau@eso.org
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Om meddelelsen
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