FYST & SOLAT telescopes

FYST & SOLAT

Project Name: FYST & SOLAT telescopes Mirror Support Structures
Client: CPI Vertex Antennentechnik
Partners: CPI Vertex Antennentechnik GmbH
Duration:2017 until 2024

Project summary: The CCAT consortium is developing the Fred Young Submillimetre Telescope (FYST), and Simons Observatory Large Aperture Telescope (SOLAT), both 6-meter aperture telescopes with a surface accuracy of 11 microns, operating at submillimetre to millimetre wavelengths. Together with our client CPI Vertex Antennentechnik GmbH, Airborne designed and built the Mirror Support Structures, using the Automated Laminating Cell (ALC) for automated manufacturing of the CFRP components.

Project Description

The Fred Young Submillimetre Telescope (FYST), and the Simons Observatory Large Aperture Telescope (SOLAT), will be 6-meter aperture telescopes with a surface accuracy of 11 microns, operating at submillimetre to millimetre wavelengths. The FYST will be sited at 5,600 meters elevation on Cerro Chajnantor, and the SOLAT will be just below it at 5,100 meters, in the Atacama desert of northern Chile. The telescopes have an off-axis Crossed Dragone design with a high-throughput wide-field-of-view, a very precise mirror surface and innovative instruments, making them the most powerful of their kind in the world. The FYST is intended to provide insights into the origin and development of our universe since the Big Bang as well as into the formation of stars and galaxies.

The FYST is developed by the CCAT consortium and is named after Fred Young, a Cornell University alumnus who was involved in the project for many years and generously contributed to its funding. The construction phase of both telescopes is expected to lead to them becoming operational in 2025. The telescopes are designed and built by CPI Vertex Antennentechnik GmbH, which contracted Airborne to develop and build the two Mirror Support Structures for the telescope.

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Customer requirements

Design requirements

The FYST is designed with an unprecedented high mirror surface accuracy of just 10.7 micrometre during operation (SOLAT requirements are less stringent). Airborne was required to develop extremely stable, passive Mirror Support Structures that would be virtually unaffected by gravitational forces or changes in ambient temperature. Mounted in a semi-enclosed housing, the mirrors are protected yet exposed to the outside temperatures which can range from -21 to +9 degrees Celsius during observations.

Working process

Airborne developed a hybrid Mirror Support Structure consisting of a thick CFRP sandwich Top Plate with an aluminium honeycomb core, on which the mirror segments are mounted, and a 3D truss structure made from large flat monolithic laminates in the geometry of the trusses and standard C-profiles. An integral part of the structural design was designing the composite material itself to meet the stiffness and low Coefficient of Thermal Expansion (CTE) performance on a laminate and structural level. Airborne designed a hybrid laminate structure using both High-Strength and Ultra High Modulus PITCH carbon fibres. By combining the two, the specific stiffness of the laminate is about five times higher than INVAR 36 (a special low CTE steel alloy), while it’s CTE is just 1/5^th.

Automated production process

Each Mirror Support Structures weights approximately 1,500 kg and consists of 19,000 m² – or 126 km – of UD prepreg tape. The truss skins have a very complex design and many of the components are so large that they are very difficult to manufacture using manual lay-up. Finally, the Ultra High Modulus PITCH carbon fibres are very brittle and therefore difficult to handle. Since there was no automated manufacturing process available in the market capable of manufacturing the complex truss skins, Airborne decided to design a solution internally, which became the Automated Laminating Cell (ALC). The ALC combines Automated Tape Laying (ATL) of the laminate, automatic cutting of the master laminate into the required blanks, and Pick & Place (P&P) of these blanks into the truss geometry.

Design For Manufacturing & Assembly

During the design phase the Design For Manufacturing & Assembly approach was followed. This, in combination with the automated production, enabled Airborne to save thousands of hours of manual labour by employing the ALC. The design was fully optimised by making almost all of the components net-shaped, saving thousands of hours of programming and machining, and resulting in a very low material waste. The design also allowed for the use of relative simple assembly processes, requiring simple standardized tooling concepts. These low cost tools enabled high assembly accuracies for the very large structures by smartly relying on the accuracy of milling machines.

Added value of Airborne

Airborne is an expert in the design and manufacture of high-end complex composite structures, with an extensive experience in the field of scientific telescopes. Additionally, Airborne has extensive experience in automating the manufacturing processes for composite structures, which resulted in the development of ALC manufacturing capability, truly an enabling technology. Together with CPI Vertex Antennentechnik GmbH, Airborne developed and built the Mirror Support Structures for the FYST that are virtually unaffected by gravitational forces or changes in temperature. Designed to operate at submillimetre to millimetre wavelengths, the entire system is passive and has an surface error budget of just 10.7 micrometre during operation. This was never achieved before in this class of telescope. The FYST and SOLAT are expected to be taken into operation in 2025. The novel optical design of the telescopes will deliver a high-throughput, wide-field of view telescope capable of mapping the sky very rapidly and efficiently.