Cryogenic Optical Performance of a Lightweighted Mirror Assembly for Future Space Astronomical Telescopes: Correlating Optical Test Results and Thermal Optical Model

A 43cm diameter stacked core mirror demonstrator was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two CNC pocket milled face sheets. The 93% lightweighted Corning ULE mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model

Measuring Subjective Outcomes: Rethinking Reliability and Validity

Reliability and validity are criteria used to assess metric adequacy and are typically quantified by correlation coefficients. Reliability is described as the extent to which repeated measurements yield consistent results. Validity is described as the extent to which a measure actually measures what it purports to measure. These conceptualizations are less useful when applied to measures of subjective outcomes because they do not convey other influences that “drive” correlation coefficients. Consistency is a manifestation of a reliable instrument but does not ensure that an instrument is reliable. Establishing the validity of an instrument is a complex process that is heavily dependent on an investigator's hypothesis. Hence, validity coefficients may be more a reflection of hypothesis adequacy than of the extent to which instruments measure what they purport to measure. Appreciating how coefficients are influenced will better enable clinicians to assess the adequacy of subjective outcome measures