NASA’s telescope needs will stretch the limits of fabrication in terms of precision, areal density, areal cost, and production, particularly in the areas of optical and UV systems. Proof of feasibility projects that could reduce cost and lead time for manufacture of non-rotationally symmetric shapes such as freeforms, large off axis parabolas, or other light-weighted (LW) telescope designs are of great interest. Unfortunately, differences in substrate flexure leave LW quilting errors during generation and polishing steps while tooling moves across supported and unsupported structures of the optic’s LW pocketing. In addition, post subaperture polishing (SAP) can create additional mid-spatial frequency (MSF) errors. Combined, these errors affect the point spread function of the optic and subsequently degrade the overall performance of the entire system. The Pocket Protector strategy aims to prove feasibility of disrupting the current manufacturing state in two areas: First, it will utilize a six-axis robot to smooth MSF errors on optical components at the post generation step, to reduce the amount of SAP required to remove underlying damage. The Pocket Protector will selectively account for differences in substrate flexure due to underlying pockets to prevent quilting during this step. Second, we propose adding the selective force process to the SAP/smoothing cycle for enhanced final results. The project aims to allow quicker turn-around of high precision, LW optics with reduced MSF and quilting errors, beginning their eradication earlier in the manufacturing sequence and applying the strategy to other required steps.
The fabrication techniques that could be scaled up from the feasibility studies of the Pocket Protector strategy could help reduce cost and lead time for many projects impacted by MSF errors, but specifically those utilizing light-weighted backing technology, such as the LUVOIR Ultraviolet Multi Object Spectrograph, or components that may not be viable options for post-polishing light-weighting due to material considerations.
There is a need for improved performance and lead time for LW optics in the field of high energy laser optics, such as fast steering high power lasers. These require minimal print-through or MSF errors in The Pocket Protector, if proven feasible, could be utilized early on in the process for a large number of commercial jobs at Optimax via integration within our freeform manufacturing processes.