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W h i t e**P a p e r s

Knowledge is power. Ignorance a liability.™

About Dream - carbon fiber structures for space, carbon fiber space structures, cyanate ester, space qualified carbon fiber

Click on the graphic to the left to read the Q&A article about Dream's athermal carbon fiber structures. It highlights the reason Dream was founded in 2003, information about carbon fiber, resin, vacuum bagging, durability, CTE, etc.

Click on the graphic to the right to read the Q&A article about Dream's zeroDELTA™ lightweight mirrors. This article discusses numerous aspects regarding lightweight, "ribbed" mirrors; definition of, materials used, benefits, processing, etc.

Optics Related White Papers -

'imaka is a GLAO (Ground Layer AO) project using three zeroDELTA™ mirrors and Dream's carbon fiber mirror mounts; two 400mm mirrors (f1.376 concave and plano) & a 227mm f2.27 concave. The assembly is mounted on a 2.2m telescope, with a 2nd paper here.

Click on the graphic to the left to read the nationally published article about one of Dream's extremely lightweight mirrors. The 16" f1.376 engineered mirror is used for a cutting-edge Adaptive Optics project. The mirror face and features were roughly 3mm, yet Dream was able to process this mirror in-house with very low Mid-Spatial Frequency (MSF) errors, using conventional equipment, tools and materials, further validating Dream's extensive up-front engineering of lightweight mirrors (since 2003) and expertise in processing lightweight mirrors.

Click the graphic to the right to see an article about performance robbing thermals and why they are a centuries-old problem for all mirror materials.

Go here to gain access to videos showing the boundary layer.

Click on the graphic above to read the article about off-axis performance of paraboloidal mirrors.

This article highlights the reason it is impossible for an optician to "polish out" certain errors in paraboloidal mirrors, as well as the reason why correctors are needed for larger fields, faster f-ratios, etc.

Angular Resolution Article: Discusses the real limit set forth by optical physics as it relates to the resolution of mirrors. It also briefly discusses the diffraction-limit, aspect ratio & mirror stiffness, departure from sphere, and the human factor that is ever present in all things optics.

Aspect Ratio & Mirror Stiffness Article: Discusses the realities of the traditional 6:1 aspect ratio as it relates to stiffness with ever larger diameter mirrors, as well as the difficulties of supporting lower stiffness mirrors.

Using NASA LRO Moon Images to Quantify Resolution of a Telescope: A simple method for quantifying the resolution achieved by a astronomical or similar telescope. Watch the effects of atmospheric seeing here. Download 50 & 254 raw images of two different areas of the Moon here & here respectively.

The Realities of Star Testing a Telescope: Discusses the critical fundamentals for more accurate star testing of a telescope system, providing detailed examples illustrating why key fundamentals are so vital.

Optical and/or Optical Testing Articles - not authored by Dream

Inouye Solar Telescope is the world's newest & largest solar telescope. It's a 4m off-axis (no obstruction) Gregorian solar telescope located near the summit of Haleakala in Maui, Hawaii at 10,062 feet. M1 is a f2.0 off-axis paraboloid made of solid Zerodur in a meniscus (contact lens) shape; 4.24m in diameter but only 75mm thick (3.6 tons). IST operates from 380nm to 28µm. First light 530nm wavelength images were taken at 0.0125 arc-sec/pixel and represent the highest resolution solar images taken to date. Angular resolution of 4m aperture at 530nm wavelength is 0.033 arc-sec. Dream is proud to be a small part of this project, delivering a coated & custom plano zeroDELTA™ lightweight mirror with dedicated athermal CF mirror mount & athermal CFSC™ tower, which is a critical fold mirror & assembly within IST's rotating instrument lab below the telescope.

LOng-Range Reconnaissance Imager (LORRI) On New Horizons Spacecraft: The paper discusses the 208mm Clear Aperture (CA) f12.644 Ritchey-Chrétien Cassegrain telescope with 3-lens field flattener. M1 is f1.8216 with -1.012 conic. This instrument was used to take the now famous 2015 images of Pluto, as well as the 2018/2019 images of Kuiper Belt Object (KBO) "Snowman." LORRI operates from 350-850nm waveband, using a 1024x1024 back-thinned CCD detector with 13µm pixels.

Center of curvature test of James Webb Space Telescope (JWST): Discusses center of curvature testing of 18-segment primary mirror of JWST using dynamic interferometry. Each hexagonal primary mirror segment is made from beryllium. This graphic shows a comparison between JWST and HST M1 sizes. JWST is a Three Mirror Anastigmat (TMA) using a f1.2 M1, with a system f-ratio of ~f20.2. Operates from 0.6µm (600nm) to 28.5µm.

Wide-Field InfraRed Survey Telescope (WFIRST): The paper discusses the HST-sized WFIRST space telescope, used from 0.6-2.0µm waveband. WFIRST is also a TMA and also uses a f1.2 M1, with an intermediate focus of f8.

2020 UPDATE: Optical Design of the Roman Space Telescope (RST): Optical design of wide-field instrument, which uses a 300 megapixel camera - 100x larger FOV than HST. It will image from 0.6µm-2µm at roughly 0.15 arc-sec resolution. RST (named after Nancy Gracy Roman) is scheduled to launch in the mid 2020's. The lightweight Primary Mirror (PM) was finished around August of 2020. It's the same diameter as Hubble's PM but roughly 2x faster in f-ratio and 1/4 the mass; 3-piece fused ULE construction. RST is a Three Mirror Anastigmat (TMA), whereas HST was a Ritchey-Chrétien.

Kepler Space Telescope: Kepler is a 0.95m space telescope that uses a f1.2 M1 that is 1.4m in diameter for this Schmidt-type telescope. As of 2018 it uses the largest focal plane array NASA has launched, at 95 million pixels (42 CCDs, 2200x1024 pixels), grabbing ~15° fields over a 430-890nm waveband.

ESO's Extremely Large Telescope (ELT) 4.25m Convex M2: The mounted meniscus M2, 100mm thick, can be seen in a CAD rendering here, figure controlled via 84 axial actuators. M2 is f1.1 with 1800µm of departure from sphere, as well as being freeform. M1 is very close to a paraboloid and is made of 798 hexagonal mirror segments. M1 is f0.932 with a Nasmyth (telescope) focal ratio of f17.48. This paper highlights some of the complexities of finishing & testing some of the optical systems of the ELT, while this paper gives a technical overview of the telescope. Once operational ELT will be the world's largest telescope; 39m.

High-precision optics enable LIGO's new view of the Universe: Discusses some optical aspects of LIGO, arguable the world's most precise interferometer(s), which first detected gravitation waves in 2016. "At the heart of the discovery lies fused silica optics with figure quality and surface smoothness refined to enable measurement of these incredibly small perturbations. LIGO went through extensive testing of First Contact, which is now their optical surface cleaning method of choice.

Subaperture Stitching Interferometry Enhances Advanced Freeform Optics: Discusses the definition of freeform optics, the difficulties of testing them and the differences between Computer-Generated Hologram (CGH) testing them versus using subaperture stitching interferometry.

Removing alignment errors from measurements of spherical, aspheric and freeform optics: Discusses degrees of freedom, degeneracy and the real-world uncertainties of modern optical testing.

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