Lawrence Livermore researchers develop novel optics and payloads for small satellites.
Embracing the landscape change in access to space
Over the last five to ten years, there has been an order of magnitude increase in the annual number of objects launched into space. The increase is due to the reduction of launch costs and the rapid growth of small satellite development. Small satellites are loosely defined as satellites with payloads—structure, command and control, communication, power, navigation, and maneuvering systems—weighing less than 1000 kilograms (kg), with many weighing less than 50 kg.
Lawrence Livermore researchers have been active in advancing capabilities for small satellites over the last decade, starting by emphasizing technologies for the smallest satellite form factors and extending to larger payloads. This work emphasizes novel and cost-effective optical systems, drawing on LLNL expertise in optical design and fabrication and close collaborations with commercial partners. Several miniature space telescopes developed by LLNL have been successfully deployed, maturing their technology readiness levels and demonstrating their utility to applications like space traffic management.
Monolithic optics to enable robust, capable, and compact optical systems
Our researchers developed a new method for optical telescopes, targeted explicitly for small satellites, and inspired in part by LLNL’s pioneering optical design work on the mirror for the Vera Rubin Observatory. Unlike classical approaches, where a secondary mirror is held relative to a primary by a metering structure (for example, a tube), our approach consists of a single piece of ultra-high-quality fused silica with primary and secondary surfaces polished on opposite sides of the monolithic glass. The machining ensures perfect alignment between the surfaces, and the lack of metering structure makes the telescope robust to launch vibrational loads.
These optics are diffraction limited, and the design is athermal (when the glass expands or contracts due to changes in temperature, the focus remains constant), minimizing the need for complicated on-orbit focus adjustment mechanisms. Another advantage of the approach is that tighter tolerances permit more extreme optical surfaces in the design, enabling high focal length to physical length ratios while maintaining diffraction-limited performance, again enhancing the capabilities of small satellites.
The current set of monolithic telescopes qualified for flight includes apertures of 2.5 centimeter (cm) (V1), named for its aperture size in inches), 9 cm (V3), and 18.5 cm (V7). Current research includes development of designs that work in the ultraviolet (to wavelengths of 200 nanometers [nm]) or short-wave infrared (to 2.5 micron [µm]), a design that accommodates an optical spectrograph and larger apertures.
Low cost, half-meter-class space telescopes
In contrast to the monolithic optics development, which first aimed to build telescopes for the smallest form-factor satellites, a team of LLNL researchers developed the largest aperture optical telescope capable of a rideshare launch on a secondary payload adapter (ESPA) ring. The resulting telescope, named CODA, is an all-aluminum, 45-cm-aperture Cassegrain telescope that operates in the optical and near infrared from 300 nm to 1.75 µm.
Our work emphasizes a versatile design to easily couple the optic to different instruments (cameras or spectrographs) and to minimize spacecraft-bus-specific design dependencies, with the goal of providing low-cost optics for constellations of small satellites. The manufacturing approach balances cost and performance, resulting in telescopes that perform near but not at the diffraction limit.
Deploying optical telescopes on small satellite platforms
We are actively exploring applications for our telescopes in partnership with government, industry, and academic partners. In collaboration with our partner Terran Orbital (formerly Tyvak Systems), we deployed two GEOstare satellites, the first (called Space Vehicle 1, or SV1) from January to June 2018 and the second (SV2) from May 2021 to present. SV1 had a single monolithic telescope and SV2 has two monolithic telescopes, each coupled to an optical sensor, providing wide- and narrow-field-of-view images for space-domain awareness and terrestrial observations.
We are developing a payload called N415 that has three monolith optical telescopes (V1, V3, and V7 designs) to provide ultra-wide, wide, and narrow fields of view. The N415 system has autofocus mechanisms for on-orbit adjustments if needed. We have also designed and delivered optical payloads on short timelines (less than 100 days), enabling responsive optical space telescopes.
LLNL leads the technical team for Pandora, a NASA Astrophysics Pioneers small satellite mission. The mission will provide simultaneous optical photometry and near-infrared spectroscopy of exoplanets and their host stars to determine stellar photosphere properties and disentangle star and planetary signals in transmission spectroscopy. A CODA telescope is scheduled for launch in 2025 aboard Pandora.
We also developed a prototype telescope that launched to the International Space Station in 2023. The telescope, known as the Stellar Occultation Hypertemporal Imaging Payload (SOHIP), uses LLNL monolithic optics attached to a gimbal assembly to observe and measure atmospheric gravity waves and turbulence.
