This guide explains how to design and select optical systems for CubeSats, from optical layout and wavelength considerations to athermalization and vibration control, to help mission engineers balance performance, weight, and cost.”
CubeSats have dramatically increased accessibility to space, offering compact, cost-effective satellite platforms by standardizing the satellite form. These use Canisterized Satellite Dispensers (CSDs) to standardize the interface to the launch vehicle.
These small satellites, typically deployed in 1U, 3U, 6U or 12U configurations, are widely used for Earth observation, scientific experiments, and communications due to their lower launch costs and modular design.
CubeSats and Larger Satellites
CubeSats are constrained by space and weight, necessitating careful balancing of optical design, thermal management, and vibration resistance. They are ideal for missions that prioritize affordability and rapid deployment but must overcome challenges posed by their size and competition for launch slots. For example, a methane-detecting imaging spectrometer was successfully designed to fit in a 6U CubeSat, although it had to be folded to fit within the size constraints. If you are interested in more information on CubeSats, please consult this book or NASA’s CubeSat 101.
6U CubeSat Configuration
In comparison, larger satellites offer greater capacity, enabling the deployment of more sophisticated instruments and higher-resolution imaging systems. While these larger platforms support more complex missions, their high costs and longer development times make them suitable for well-funded projects with broader operational goals and longer schedules.
Optical Considerations for CubeSats
Which type of optical system should be used for your satellite? Optical systems for satellites provide either images or spectral data. Either way, the first group of lenses or mirrors in the system forms an image onto an image sensor or the slit of the spectrometer. If your optical system includes a spectrometer, our imaging spectrometer page can help you decide which type to use. Image sensors are discussed briefly on our wavebands page.
Should the optics used to form the initial image be refracting, reflecting or catadioptric? That is, should the system consist of lenses or mirrors or a combination? One item worth noting is that reflecting and catadioptric systems typically have a mirror that blocks some of the light. This is called obscuration, and it affects the resolution of the optical system. See the MTF page for more details.
A few examples of simple reflecting and refracting optical systems that could be used for systems with a narrow field of view are shown on our telescopes page. More complex lens designs, such as telephoto and Petzval lenses, are frequently used to obtain wider fields of view. The factors described below help determine the best type of optical system for your application.
Field of View
Lenses are capable of providing a much wider field of view (FOV) than mirror-based systems. It is difficult to design a reflective optical system that provides a field of view of more than a few degrees, while lenses can easily reach 180 degrees. The tradeoff is that for a given number of pixels, a wider FOV gives you lower resolution. For more information on this topic, visit our page on ground sampling distance.
Light Collection
Light collection is another important consideration. Will your system receive plenty of light or will it be attempting to acquire a very faint signal? The focal ratio or F/# (pronounced eff-number) of the optical system determines how much light will illuminate each pixel on the image sensor. A fainter signal requires a system with a faster F/#. Here, lenses have a significant advantage over reflecting optics. Lenses as fast as F/0.7 have been used by NASA, which is something reflecting optics cannot match. See the last paragraph on our “Basic Optical Terms” page for a bit more background.
Wavelength Range
If the wavelength range under consideration is more than a factor of two, mirrors are the way to go. The first issue for lenses is achromatization, that is, bringing all wavelengths to a common focus. In addition, the wider the waveband, the more difficult it is to design a high-performance anti-reflection (AR) coating. For visible wavelengths only, it is common to apply a 3- or 4-layer AR coating that reduces reflectivity to < 0.3%, while increasing the range to 400 – 1000nm requires a 10-layer coating that can only reduce the reflectivity to <1%. Mirrors are essentially achromatic by nature.
Ionizing Radiation
Radiation-resistant glasses are of some importance in designing lenses for orbital imaging. The good news is that the first element is the most important one; it absorbs almost all of the ionizing radiation. The other lenses can be made of any material because they are shielded by the first lens or the barrel. For low earth orbit, there is far less radiation than there is for higher orbits, so it’s less of a concern. Schott’s TIE42 provides a lot of good information on radiation-resistant glasses: https://www.schott.com/shop/medias/schott-tie-42-radiation-resistant-optical-glasses-row.pdf
Opto-Mechanical Considerations for CubeSats
Designing imaging systems for LEO requires addressing a host of mechanical, thermal, and environmental challenges to ensure reliable performance in space.
Athermalization
Athermalization is important to maintain optical performance across wide temperature ranges. Your optical system will be assembled and tested by humans in a laboratory, so it must work at room temperature as well as at the operating temperature range in space. A good optical engineering firm, like ours, will include athermalization as well as ability to refocus for atmospheric pressure as part of the design process.
Temperature changes cause expansion or contraction of materials, which can defocus the image, misalign lenses or damage components. Athermal designs help counteract these effects, generally by using materials with different coefficients of thermal expansion (CTE) to counteract each other. This can maintain the focus and alignment of the optical system across a wide temperature range. Typically, the athermalization process will be split into a survivability range and an operating range of temperatures. The survival temperature needs to include the bakeout temperature as well as the temperatures experienced during flight.
With reflecting and catadioptric systems, athermalization is simple: just use a low-expansion mirror substrate and make the structure of carbon-fiber epoxy. The challenge is much greater for lenses. Although it is possible to design a lens that is insensitive to temperature, it’s far more difficult. Special glass types are required to compensate for the thermal expansion of the structure, whether it is nearly zero or large, as it is for aluminum.
Vibration Analysis
Vibration analysis is essential, as the intense vibrations during launch can damage the satellite either through fatigue, or excessive loading. Careful engineering and process control is required to ensure that optical elements are securely mounted, so that they maintain alignment despite the forces they experience during launch and deployment. Vibration loading is determined by the launch provider as well as the bus provider and integrator. The effects of the loading cascade down each step of the structure so any changes to the structure can affect the load requirements.
Outgassing
Outgassing is another critical factor in space applications. Many materials, when exposed to high vacuum such as space, release gases that can contaminate nearby sensitive optical surfaces or sensors. To prevent this, only materials with low outgassing properties are used, and the system typically undergoes a vacuum bake-out process to remove volatile substances before launch. Care must be taken with adhesives, coatings, and paints, which are often prone to outgassing. Additionally, other payloads sharing the same launch vehicle may have stringent outgassing requirements that must be adhered to.
Air Evacuation
Unlike other optical systems, which are often sealed to prevent dust entry, space-based systems must allow air to escape as they are depressurized. This is particularly important during the launch phase, as sealed compartments could build up pressure and cause damage. For this reason, pathways for air evacuation are designed into an optical system. These pathways necessitate cleanliness in the manufacturing process, as the introduction of dust particles into the optical system could impair performance.
Thermodynamics
Thermodynamic considerations are critical, as heat generated by components such as image sensors must be effectively dissipated. In the vacuum of space, where convection is not available as a heat transfer mechanism thermal radiation is the primary method of cooling, and engineers must collaborate with spacecraft designers to ensure that heat is radiated away from critical systems. This can add another layer to the athermalization challenge as it can cause thermal gradients which could either warp components or cause them to differentially expand. Optical components, such as mirrors and baffles, require coatings with carefully chosen emissivity and absorptivity properties to balance heat dissipation.
Size & Weight
Weight and stiffness considerations are also vital. CubeSats face tight weight restrictions at 2kg/unit which gives more leeway than previous standards but still tends to constrain the design. Reducing weight is a challenge without compromising the stiffness needed to maintain optical alignment. Lightweight materials must be selected carefully to meet both static and dynamic structural needs, ensuring that the system remains intact and aligned during its mission.
Size can also be a challenge as larger optics are desirable to collect as much light as possible, increasing the ground resolution of the lens. This limits the space for the structure of the lens as well as the rest of the systems in the spacecraft and careful communication is needed between the teams involved to avoid mechanical interference.
Material Selection
Material selection plays a pivotal role in mechanical design. Low outgassing materials are preferred to avoid contamination, and components are designed to burn up upon reentry, reducing the risk of space debris. Aluminum burns up far more easily than steel or titanium, so it is preferred. Metals like tin, cadmium, and zinc, which can form harmful whiskers or sublimate in space, are generally avoided.
TL;DR — CubeSat Optical System Highlights
- CubeSat optics must balance field of view, focal ratio, and wavelength range within strict volume and mass limits.
- Athermalization and vibration control are critical for stable imaging performance in orbit.
- Use low-outgassing materials and radiation-resistant coatings to maintain optical quality over mission life.
- Close coordination between optical, mechanical, and thermal engineers prevents interference and ensures alignment stability.
For more information on planning and designing optical systems for CubeSats, visit our CubeSat Optical System Development page.
Ready to plan your CubeSat optical system? Contact our engineering team to discuss your mission requirements.