Designing Optics for Lunar Rovers, Satellites and Other Space-Based Applications

The year 2024 will be full of new satellite manufacturing, launches and operations, with major players like Amazon expected to start full-scale deployment of Project Kuiper and strong demand for low Earth orbit (LEO) satellites driving development and launches from the likes of SpaceX and Telesat among others. This is a trend that is expected to continue over the long term as well. In the 2023 edition of Northern Sky Research’s (NSR) Satellite Manufacturing & Launch Markets report, the satellite market research firm forecasts over 32,500 missions to be ordered and launched over the next decade.

Many of those new and existing satellite development projects require specialized instruments that can survive and operate over long periods of time in space, where radiation resistance is crucial. One type of component that is in major demand especially for earth and weather observation satellites is radiation resistant optics. Resolve Optics, a U.K.-based specialized lens and optical design manufacturer, has been responding to that demand, as they have been supplying lenses and optical systems for space applications over the last two decades. In just one such example, the company is currently developing an optimized wide waveband lens for a multispectral microscope to be used on a new solar powered lunar rover known — Lunar Vertex — being developed by Intuitive Machines, due for delivery and launch in 2024.

A computer generated concept image of Intuitive Machines Noca-C lander for the IM-3 mission taking four NASA investigations to Reiner Gamma. Due for delivery and launch in 2024, Resolve Optics received an order to supply an optimized wide waveband lens for a multi-spectral microscope required for a Moon exploration mission. (Image: Intuitive Machines)

Photonics & Imaging Technology recently caught up with Rob Watkinson, the head of purchasing and customer support for Resolve Optics, to discuss how they overcome the challenges of developing optics for lunar rovers, satellites and other spaceborne applications. Check out our Q&A with Watkinson about overcoming the challenges of designing radiation resistant optics and lenses below.

Photonics & Imaging Technology: Can you provide some background information on what type of optical systems, components or technologies Resolve Optics has primarily been designing and manufacturing for use or operation on satellites?

Rob Watkinson: Our customers include international space agencies and a growing number of commercial satellite and space vehicle manufacturers. Over the years we have supplied space ready optics for monitoring the outside of spacecraft looking for signs of damage caused by space debris or micro meteorites. For inspection tasks, where the optical system is required to view a specific area to aid operation. As part of a vision systems used to guide and dock payload craft visiting platforms such as used on the International Space Station. And, to enhance remote sensing from satellites. In this application our powerful, high-resolution lenses enable the Earth to be viewed from space providing valuable data on weather patterns and the impact of climate change.

P&IT: Are there any new or in-service satellites that Resolve Optics has developed optical components for? What new or unique applications are those components or systems currently providing or enabling and for what type of end users?

Watkinson: One project we can talk about is our cooperation with video streaming specialists, including one Didcot, U.K.-based company, Sen, to supply radiation hard lenses for their satellite-based Ultra-High Definition (UHD) video cameras. To make technology work in space is not straight forward, with both mechanical and environmental challenges, such as extreme temperature changes and radiation that can damage electronics and hardware. Space is also very mass sensitive because each gram costs money to launch. As a consequence, Sen decided they needed a specialist provider who could custom design and manufacture cameras to meet both the unique constraints of spaceflight hardware and the environmental challenges of operating in space for several years.

Commercially available camera lenses were not suitable for this application because the glass would increasingly suffer from radiation ‘browning’ – meaning that image quality would gradually deteriorate over the life of the satellite. Sen chose Resolve Optics to assist with this project because of its expertise in custom designing low mass, high performance lenses using radiation resistant glass that could meet the harsh demands of the space environment. Sen launched its first set of UHD video cameras incorporating Resolve Optics lenses into space in 2019 and successfully demonstrated the excellent performance of its video streaming platform. The next step in Sen’s plan is to launch its own satellite constellation so that it has full control over its live data stream.

P&IT: What are some of the key materials that you have found to help enable radiation resistance?

Watkinson: When designing a lens or optical system for use in a spaceborne application a key concern when it comes to radiation resistance is the type of optical glass you use. Standard glass will turn brown when exposed to radiation. So as previously mentioned, when radiation resistance is required, we will typically go for cerium doped non-browning glasses. These glasses will resist the browning effect for significantly longer than standard glass. This means our radiation resistant lenses have operating lifetimes of years even by subject the constant stream of cosmic radiation encountered in space. By comparison, a lens constructed from standard glasses would turn grey and lose all transmission in a matter of just a few weeks.

P&IT: Is the company researching the use of any new materials or glass types that can improve radiation resistance in lenses or optical instruments used on satellites?

In-house vibration and shock testing of satellite optical modules, such as those pictured here, is one of the satellite optics development and design activities occurring at the Resolve Optics facility on a regular basis. (Image: Resolve Optics)

Watkinson: We are constantly on the lookout for new non-browning glass types that can offer more flexibility within our optical designs. A great example of this was our development of lenses able to produce clear sharp images free of the strong yellow tint that has traditionally been a limiting issue when using radiation tolerant lenses for use on color sensors. The specialist doped glass used in these lenses can withstand long-term exposure to radiation up to an accumulative dose of one hundred million RAD and temperatures up to 85 °C without loss of transmission.

However increased radiation resistance is not really a driving factor in space optics. The non-browning glasses we use are all rated to 108 rad which is generally well in excess of any other components in the system. For example, your camera sensor would fail long before the lens.

P&IT: What approach do you take to designing ruggedized lenses or optical systems that can survive the severe shock and vibration that they’ll be subject to during launch? What type of designs can face challenges in the launch phase and what are some of the design aspects that can lead to malfunction or damage?

Watkinson: To minimize the effects of vibration and shock it is good design practice to keep your optical components small and light. Less mass minimizes the effect vibration and shock will have. To stop components in your optical system from moving requires that all parts are retained as tightly as possible and that retaining rings cannot work loose. This can be done by staking the retaining rings so that they cannot come loose. However, if your required optical components are heavier then it may be preferential to bond all the elements in position. Consequently, the mechanical design of space ready optics must consider the mass of the elements and determine what method of retaining is required.

Also, importantly, the effects of vibration and shock must be considered across the operating temperature range of space launch to ensure optical components cannot become loose due to temperature cycling. To ensure all ruggedized lenses and optical systems produced can withstand the launch vibration and shock profile provided by the customer, Resolve Optics has invested in in-house testing equipment. All lenses we supply for spaceborne applications are designed to meet vibration specifications and qualified on our vibration test center before being shipped.

An image of space ready lens designed for small satellites, developed by Resolve Optics. (Image: Resolve Optics)

P&IT: When you look back at 2023, were there any specific types of lenses, optical components, modules, or other products that you saw increased demand or interest in from satellite developers and manufacturers?

Watkinson: Over the last 12 months we have had a significant increase in demand for satellite lenses that operate in specific bandwidths. This creates a challenge to ensure that maximum transmission and focus is maintained. Increasingly satellite developers and manufacturers are also asking us to create optical systems that can hold focus over a wide temperature range.

P&IT: Are there any specific space applications where you expect to see increased demand for or interest in during 2024?

Watkinson: If the trends of 2023 rollover into 2024 – then many of the enquiries, we receive will continue to be for LEO satellite applications. In addition, we also expect to receive further requests to design lenses and optical systems for orbiting space platforms, lunar rovers and satellites operating in other orbits.

This article was written by Woodrow Bellamy III, Senior Editor, Photonics & Imaging Technology.