AZoOptics spoke to Paul Townley-Smith about ZYGO's solutions for the space optics industry, the importance of commercialization in space optics, and the future of the industry.
What is ZYGO’s history in space optics, and how did ZYGO’s solutions evolve?
Our design group is composed of leading engineers and designers who have been developing space and commercial optics solutions since the 1980s. Members of the team started out at Perkin Elmer Applied Optics in the early 1980s and were mentored by luminaries such as Juan Rayces, a pioneer in optical design. This group focused on space and defense applications such as star tracking, missile guidance, and optical correlation. In the early 1990s, this group was acquired by Optical Corp of America (OCA), which added a commercial optics focus to the business. In the late 1990s, OCA was acquired by Corning, and the group focused on developing optical telecom devices. This work added fresh perspectives and design approaches for achieving cost-effective yet robust optical devices at scale. These efforts produced market-leading products for Corning, but the optical telecom market crashed in the early 2000s and Corning exited the market. Out of the ashes of the Corning team, around twenty people joined ZYGO to create a team focused on designing and building custom optics. One of the unique attributes of this team is the combined heritage of high-performance space optics and commercial optics applications.
What is ZYGO’s current presence in the industry and what operational devices do you have in space?
There are three main areas where we participate in the space optics business: laser communication, star tracking, and earth imaging. In each of these segments, we design and make a custom optics payload and the customer integrates it into their satellite. A typical satellite in a large communications constellation will have four optical transceivers, two in-plane, and two cross-plane. Each transceiver is composed of a large beam expander optic on the front end with smaller beam management and fiber coupling optics in the back end and we have experience designing all of these optics. For spatial orientation, each satellite typically has two-star trackers, a component of which is a high stability imaging lens that we have designed and developed. ZYGO is also the leading supplier of space-based earth imaging telescopes. Overall we have hundreds of optical devices currently in orbit.
How is ZYGO innovating in the areas of earth imaging, star tracking, and laser communications?
We have a unique blend of commercial and conventional space optics expertise. By employing designs inspired by proven principles from conventional space, the amount of analysis, testing, and qualification can be greatly reduced while maintaining a modest level of risk. By leveraging designs targeted for the commercial optics supply chain, component costs are minimized. With frequent launches and product iterations, new optical designs, structural designs, and material choices can be tested. Each increment provides insight into how to achieve lower cost, higher performance, and higher stability of the optical system.
Could you give our readers an overview of the developments in space optics and the importance of commercialization in this industry?
Most of the history of optics in space has been with expensive, high-performance one-off (or on the basis of a few) projects, such as the Hubble Space Telescope or NRO Geospatial-Intelligence constellation. With the expense involved and only one opportunity to succeed, systems are designed so they can’t fail:
- Engineered with redundancy
- Extensive engineering analysis to validate edges of operating conditions
- Extensive subsystem and prototype qualification
Commercial systems are targeted at the higher quantity and lower-cost applications and are therefore systems with a lower cost of failure. Since the failure of a satellite is not mortal to a program, commercial space can tolerate more risk than conventional one-off programs. Best practices plus learning and discovery replace extensive analysis and qualification testing. Risk is managed through small incremental changes in multiple launches and short-lived satellites of 2-5 years. Instrumentation and self-diagnostic data are used extensively to understand what works and what doesn’t.
How does ZYGO take a commercial approach to produce space optics?
We work closely with the customer’s engineering team to develop specifications that maximize payload performance value with a cost-effective commercial optics supply chain. This includes minimizing the use of exotic materials and using aspherical surfaces sparingly. Wherever possible known design, fabrication, and assembly techniques are employed to limit the risk of failure in orbit. New designs that produce small improvements or rebalancing of tradeoffs are implemented incrementally through frequent launches, to discover what works in orbit versus investing in expensive ground-based simulations and qualification testing.
What are the key challenges faced in Space Optics, for example, the demisability of components?
In a conventional satellite system, the goal is mainly to maximize performance. In commercial space systems, there is a business goal: deliver performance value that significantly exceeds the cost. The challenging requirements of the space environment such as low outgassing, radiation resistance, wide thermal range, magnetic interference limits, and high launch loads restrict the designer’s options for material selection. For large constellations, material selection is particularly limited as the optical components often must be 100% demisable, that is they must burn up during re-entry. A further design challenge is the cost sensitivity to size and weight, which limits the trade space for the designer. Compact designs often give up performance in other dimensions and/or require more sophisticated and expensive components, and high specific stiffness materials that might be used to save weight are typically more expensive. This creates a narrow design window which requires out of the box thinking and innovation to find the best balance of trade-offs.
How do ZYGO’s solutions help to overcome these challenges?
Our fundamental approach is to apply novel twists to classic designs. When looking at an optical design our team looks for ways to maximize the effectiveness of aberration correction of each element, reduce the lens count (particularly aspheric lenses), and employ spherical and aspherical components that are compatible with commercial fabrication techniques suitable for volume production. From the perspective of optomechanical design, simplifying the supporting structures is the main goal, with careful attention paid to how components will interact under thermal expansion to minimize the thermal sensitivity. We minimize the use of exotic materials but make exceptions when we discover high leverage use cases, such as using carbon fiber composites to tune thermal expansion. Fewer, and simpler, lenses and simplified structures naturally lead to a reduction in size, weight, and cost and we have had success in meeting customer requirements while pursuing this approach.
Precision Optics for Defense Applications
What are the key features and benefits of ZYGO’s NewSpace devices?
There are two main areas of concern regarding the performance of space optics, which are surviving launch and performing well in the environment of space. With the benefit of decades of practical experience, ZYGO has proven it can produce robust and highly stable optics that are able to withstand launch loads and maintain high performance in orbit. To overcome the challenge of the dynamic thermal environment typical of low earth orbit, we have designed telescopes that are athermal over a broad temperature range and are tolerant of thermal gradients. To deal with the high vacuum and ionizing radiation environment, we have the depth of expertise to select the right glass, structural materials, and design approach to meet the lifetime goals of the satellite. All of this can be achieved on a commercial cost basis and a schedule that is measured in months, not years.
Where is the space optics industry headed and how is ZYGO positioned for the future?
As constellations get larger, the industry is headed towards increasing scale and increasing performance while lowering costs. Working closely with our customers, we will continue to evolve designs for a lower cost at higher performance levels including increased tolerance to thermal gradients and one hundred percent demisability. Hyperspectral earth imaging telescope systems are of great interest to customers and we are looking at designs to make these systems more compact and higher performance. To meet the demands of large constellations, we are investing in technology to increase capacity and improve throughput in our production facilities. ZYGO has a unique mix of space optics know-how and commercial product development and manufacturing process, which has proven to be exactly what this industry needs right now.
About Paul Townley-Smith
Paul Townley-Smith is currently the Director of Design and Prototyping for ZYGO's Electro-optics Group, which designs and develops custom optical assemblies. He has been developing optical products for over 30 years covering a broad range of applications including space, lithography, AR/VR, telecommunications, medical imaging, laser surgery, machine vision, life sciences, and material processing.
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