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Rationale and Procedures for Development of a NASA Primary Metrology Laboratory for Large Optics



Theodore V. Vorburger, Christopher J. Evans, William T. Estler


Traceable optics metrology is not an expensive overhead. Rather it can improve NASA''s procurement process and eliminate costly Hubble-like mistakes. In deciding if a part meets specification, ISO Standard 14253, Part 1 requires that the vendor must subtract the measurement uncertainty from the tolerance, ensuring that the customer always gets a good part. This procedure is not common in the US optics industry. Indeed, we have heard of optics companies who effectively relax the tolerance by the size of the measurement uncertainty. This practice could lead to the shipment of questionable parts. By contrast, the rigorous approach described by the ISO standard increases the probability of shipping a part that meets or beats specification. Discrepant measurements were taken during the manufacture of the Hubble primary mirror. If those measurements had been accompanied by rigorous uncertainty analyses, it would have been clear that the results disagreed by more than the estimated uncertainties - thus launching an investigation (rather than launching a flawed mirror). It is therefore in NASA''s best interests to develop traceable large optics metrology capabilities and with them the culture of rigorous statement of measurement results with associated uncertainty. This report provides a preliminary road map toward that end.
NIST Interagency/Internal Report (NISTIR) - 6710
Report Number


figure, finish, interferometry, metrology, optics, roughness, standard, surface, traceability


Vorburger, T. , Evans, C. and Estler, W. (2001), Rationale and Procedures for Development of a NASA Primary Metrology Laboratory for Large Optics, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD (Accessed May 22, 2024)


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Created December 31, 2000, Updated October 12, 2021