Inprentus Delivers Highly Curved, Concave Diffraction Gratings for NASA Solar Science Mission

Inprentus, a global leader in advanced manufacturing of blazed diffraction gratings, has delivered the first set of spherical, highly concave diffraction gratings for a NASA-sponsored solar science mission — a significant technical achievement and a major milestone in the company's contract with NASA.

The gratings, delivered in early August, are the first of two sets Inprentus will produce for the ESIS-II (EUV Snapshot Imaging Spectrograph II) Mission under a Small Business Innovation Research (SBIR) Phase III contract with NASA, as highlighted here.

The delivery also marks a technical milestone for the company: these gratings were ruled on seven highly concave spherical substrates of a specialized triangular shape. The ESIS-II gratings are formed on spherical surfaces curved to match the inside of a six-foot-diameter ball. Producing them required the contact lithography tool to follow the curved contours of the substrate precisely to form grooves with variable line spacing.

"Inprentus’ flexible manufacturing platform allows the tool to follow any arbitrary path, perfect for creating freeform gratings. The technical team rose to the significant challenge required to make these concave gratings. The high degree of curvature required writing custom path scripts for the tool to follow," said Cody Jensen, Chief Technology Officer of Inprentus. "Our technology is based on a programmable, digital ruling architecture with 8 axes of control. We have now added a 9th axis of control, which makes the platform even more robust for following curved contours," added Nick Toombs, Senior Development Engineer. 

Each grating consists of thousands of grooves precisely placed within the custom-shaped optically polished area of the substrate. The grooves are formed using Inprentus’ dynamic contact mode lithography technique, which ensures that light collected by the ESIS-II optics forms sharp images to enable precise scientific measurements. The same process “blazes” the groove shape so the grating diffracts a specific type of light — in this case, extreme ultraviolet (EUV) — with maximum efficiency.

This first set of gratings will be used for ground testing of the ESIS-II optical system. The flight-ready set that follows will enable the instrument to capture simultaneous video at multiple EUV wavelengths, revealing how the Sun’s hot gases move during solar storms. That data is expected to improve space weather forecasting for both satellites and crewed space missions alike. The flight gratings are scheduled to be delivered later this year.