The 3.5-m all-SiC telescope for HERSCHEL

Toulemont, Y.; Paßvogel, T.; Pilbratt, G. L.; Chambure, Daniel de; Pierot, Dominique; Castel, D.

doi:10.1117/12.551616

Cited by 15 publications

(5 citation statements)

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“…Its 3 mm thick face sheet is stiffened by ribs of up to 100 mm high. The required WFE of this M1 is 3 μm rms for polishing purpose and the 293K-70K cool down allocated contribution is only 2.5 μm rms [12]. It is then of prime importance having a SiC CTE highly homogeneous and isotropic in all 12 segments.…”

Section: A Herschel Primary Mirror Casementioning

confidence: 99%

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

Bougoin

Castel

Levallois

2017

International Conference on Space Optics — ICSO 2012

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Section: A Herschel Primary Mirror Casementioning

confidence: 99%

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

Bougoin

Castel

Levallois

2017

International Conference on Space Optics — ICSO 2012

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“…The LORRI instrument on New Horizons uses an all-SiC, passively athermal 20 cm telescope to produce high-resolution images [20]. The Herschel Telescope employs a 3.5 m diameter mirror that is composed of 12 SiC petals, brazed together and coated with a thin aluminum reflective coating [21]. To obtain higher imaging and thermal-resolution EUV spectroheliograms, at higher cadence, beyond current capabilities, -it is required to build larger aperture (D > 30 cm) multilayer coated optical systems.…”

Section: Sic Opticsmentioning

confidence: 99%

Ultra-smooth finishing of aspheric surfaces using CAST technology

Kong¹,

Young²

2014

Advanced Optical Technologies

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Abstract:Growing applications for astronomical groundbased adaptive systems and air-born telescope systems demand complex optical surface designs combined with ultra-smooth finishing. The use of more sophisticated and accurate optics, especially aspheric ones, allows for shorter optical trains with smaller sizes and a reduced number of components. This in turn reduces fabrication and alignment time and costs. These aspheric components include the following: steep surfaces with large aspheric departures; more complex surface feature designs like stand-alone off-axis-parabola (OAP) and free form optics that combine surface complexity with a requirement for ultra-high smoothness, as well as special optic materials such as lightweight silicon carbide (SiC) for air-born systems. Various fabrication technologies for finishing ultra-smooth aspheric surfaces are progressing to meet these growing and demanding challenges, especially Magnetorheological Finishing (MRF) and ion-milling. These methods have demonstrated some good success as well as a certain level of limitations. Amongst them, computer-controlled asphere surface-finishing technology (CAST), developed by Precision Asphere Inc. (PAI), plays an important role in a cost effective manufacturing environment and has successfully delivered numerous products for the applications mentioned above. One of the most recent successes is the Gemini Planet Imager (GPI), the world's most powerful planet-hunting instrument, with critical aspheric components (seven OAPs and free form optics) made using CAST technology. GPI showed off its first images in a press release on January 7, 2014 . This paper reviews features of today's technologies in handling the ultra-smooth aspheric optics, especially the capabilities of CAST on these challenging products. As examples, three groups of aspheres deployed in astronomical optics systems, both polished and finished using CAST, will be discussed in detail.

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“…Indeed, this characteristic of SiC-mirrors has been demonstrated by the Japanese Akari and ESA's Herschel space infrared telescopes, which were launched in 2006 and 2009, respectively [1,2]. Akari, with a 0.685-m primary mirror, operated successfully at 6 K; and Herschel, with a 3.5-m primary (the largest single mirror ever deployed in space), was cooled with liquid helium.…”

Section: Introductionmentioning

confidence: 93%

Cryo-stability of HB-Cesic optics

Krödel

2011

SPIE Proceedings

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The technical requirements for large future space optics are becoming more and more challenging. This is particularly the case with respect to thermal stability under cryogenic conditions. During the past two years, ECM together with its industrial partners carried out extensive cryo-stability tests of its HBCesic® optical material under a range of conditions.In this paper we report the test configurations and results of two of these tests and qualification campaigns. The first of the tests was carried out with a 600-mm HB-Cesic® mirror that was polished directly without any overcoating. The second of the tests was carried out with an 800-mm HB-Cesic® mirror whose optical surface was coated with a silicon layer prior to polishing. The 600-mm mirror was tested to a cryogenic temperature of 93 K. The 800-mm mirror was tested to a cryogenic temperature of 18 K.

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The 3.5-m all-SiC telescope for HERSCHEL

Cited by 15 publications

References 0 publications

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

Ultra-smooth finishing of aspheric surfaces using CAST technology

Cryo-stability of HB-Cesic optics

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