Heritage of ZERODURÃÂ® glass ceramic for space applications

2014

Extreme Lightweight ZERODUR ® Mirrors (ELZM) have been developed expressly to provide architects of spaceborne missions a new, cost-effective, option for implementation of medium and large Optical Telescope Assemblies (OTAs, up to 4+ meters in diameter). ZERODUR ® is a traditional material in space with over a 30 year heritage. We will discuss the attributes of the material and fabrication methods to aggressively reduce weight to an extent now routinely available. Recent and emerging independent measurements of material properties will confirm the utility of this approach for new generations of OTAs. Data on dimensional stability over a broad practical temperature range will be referenced, as will recent mechanical strength data. Other data confirming suitability for use in space will be referenced. We will discuss how this data can be used for the architecture of a ELZM based cost-effective spaceborne OTA.

Section: Recent and Emerging Zerodur® Materials Characterizationmentioning

confidence: 96%

“…SCHOTT has produced a mirror substrate material, ZERODUR ® , with excellent attributes demonstrated by 35 years spaceborne use in OTAs [2]. ZERODUR ® has been selected for use in over 30 spaceborne missions, including two NASA Great Observatories.…”

Section: Introduction: the Problemmentioning

confidence: 99%

Extreme lightweight ZERODUR mirrors (ELZM): supporting characteristics for spaceborne applications

Hull

2014

“…The heritage of ZERODUR ® mirrors in spaceborne optical telescope assemblies (OTAs) has been examined in a recent paper [7]. In some cases these heritage mirrors have not been lightweighted, an example being the 300mm diameter Hubble secondary mirror.…”

Section: Characteristics Of Zerodur ® Lightweight Mirror Blanksmentioning

confidence: 99%

Lightweight ZERODUR mirror blanks: recent advances supporting faster, cheaper, and better spaceborne optical telescope assemblies

Hull

2014

While there is no single material solution ideal for all missions, recent advances by SCHOTT in fabricating lightweight mirror blanks makes ZERODUR ® a highly viable solution for many spaceborne telescopes. ZERODUR ® is a well-characterized very low-expansion material. Monolithic mirrors are made without bonding or fusing out of highly homogeneous and isotropic blanks currently available in sizes up to 4m plus. We will summarize results recently given in a series of papers on the characteristics of these lightweight mirror blanks in sizes from 0.3m up, and describe the method of blank fabrication, with its compatibility to contemporary optical fabrication techniques that control of all optical spatial frequencies. ZERODUR ® has a 35 year heritage in space on numerous missions, including the secondary mirror of Hubble, and all the Chandra mirrors. With the lightweighting we will discuss, ZERODUR ® is now a high performing, affordable and rapidly produced mirror substrate suitable for lightweight imaging telescopes.

“…Two NASA Great Observatories have selected ZERODUR®; the secondary mirror of the Hubble Space Telescope, and all the Wolter mirrors in Chandra. Over thirty other missions have used ZERODUR®, and now this material is available with a degree of lightweighting appropriate to most sensor systems [3]. This method of making mirror blanks is optimized for cost, schedule and low risk.…”

Section: Introduction; the Problemmentioning

confidence: 99%

Lightweight ZERODUR: a cost-effective thermally stable approach to both large and small spaceborne telescopes

Hull¹,

2014

ZERODUR®, known as the "gold standard" material for systems which require dimensional stability in the presence of gradients and transients, is now available lightweighted to the 85% to 90% level for use in high performance spaceborne telescopes and sensor systems. This establishes a design option that may have cost, testability, performance and risk advantages for an entire sensor system payload. The technical approach to making these primary mirrors is the same, whether the aperture is <0.3m to <4.0m. Since each mirror blank is made from a single monolithic billet of near zero-expansion, isotropic and homogeneous ZERODUR® material, the resulting mirror is very stable over a wide range of scenes and orbits, with minimal to no need for ancillary thermal stability and wavefront sensing and control systems. Telescopes using ZERODUR® and low expansion metering structures can accommodate thermal design challenges of both non-thermal (UV, VIS, LLLTV, NIR, SWIR and mm) and thermal (MWIR, LWIR) imaging systems, and deliver optimal performance. This lightweight mirror technology is discussed, with actual examples by SCHOTT of 0.3m and 1.2m mirrors presented. Lightweight ZERODUR® mirrors offer superior optical performance, attractive cost and aggressive lead times, and are available to present and future spaceborne sensor trades.