Marcus R. Hatch

Wide-Field Correction In Reflective Schmidt Systems By A Nonrotationally Symmetric Element

Wide-field correction is achieved in reflective versions of the Schmidt and Schmidt-Cassegrain systems by the use of a fold mirror serving also as a corrector. The deformation of the corrector surface is divided into two functions one-with and one with-out rotational symmetry. The bulk of the deformation is defined by the rotationally symmetric part while the residual, which is of a much smaller magnitude, is nonrotationally symmetric. This separation of corrective polynomials facilitates fabrication of the elements. The larger rotationally symmetric part can be diamond turned on a two-axis machine under numerical control, whereas the small residual deformation can be hand figured to an overall system null or to a computer-generated holographic reference in an inter-ferometer. Diffraction-limited performance in the infrared region is achievable to an extent determined by tilt angle of the fold mirror and the f-number.

Predicting Performance Of Optical Systems Undergoing Thermal/Mechanical Loadings Using Integrated Thermal/Structural/Optical Numerical Methods

Predicting performance of electro-optical systems that operate while being subjected to thermal/mechanical loadings has been accomplished by integrating computer-based numerical tools. Honeywell has interfaced thermal, structural, and optical computer programs on both CDC 6600 and Honeywell 6080 computers into a Thermal/Structural/ Optical (TSO) evaluation process. The TSO process integrates the separate analyses by automatizing data transfers among the individual technology programs to permit rapid evaluation of optical systems undergoing thermal/mechanical loadings. The design/analysis process involves iterating the following: thermal/ mechanical error budgets, TSO evaluations of electro-optical systems, and comparisons of TSO results with error budget line items. This paper presents how the TSO process has interfaced the individual technology programs, examples of TSO applications to Honeywell electro-optics systems, and test data from systems that have been subjected to thermal/mechanical loadings. The thermal/mechanical loadings include cryogenic loads, steady state acceleration, random vibration, and decaying dynamic loads. The examples show how the process has been effectively used during the design/analysis stages of projects to evaluate alternate design concepts. The resulting process has resulted in a cost-effective methodology for predicting performance of electro-optical systems undergoing theral/mechanical loadings.

Limb Infrared Monitor of the Stratosphere (LIMB) Experiment

This paper describes the goals and performance characteristics of the LIMS radiometer to be flown on the NIMBUS G spacecraft scheduled for launch into a polar orbit in 1978. Radiance measurements are made of gases (03, H2 0, NO2 , HNO3 , and CO2) that are key elements in the nitrogen ozone photochemistry, which is crucial to an understanding of the natural processes controlling the ozone distribution in the atmosphere. The earth limb is scanned and imaged with an optical system designed for compatibility with a two-stage solid-cryogen cooler. Six different bandpass (Hg,Cd)Te detectors are cooled with solid methane to 65 K. The detected outputs are demodulated and low pass filtered before being multiplexed and digitized with a 12-bit A/D converter. The primary LIMS data output is in the form of a highly multiplexed serial digital word at 4 K bps rate. Every LIMS word transmitted from spacecraft to ground control contains data from each radiance channel and pertinent housekeeping functional performance data. Inversion algorithms are used to operate on the CO2 limb radiance profiles which determine the vertical temperature distribution. Along with the measured radiance profiles in the other spectral bands, this inferred temperature profile is used to calculate the vertical distribution of NO2, H2 0, 03 , and HNO3. Profiles are determined with 1 and 2 km resolution over altitudes of 10 km to 80 km.

Integrated Thermal/Structural/Optical Evaluations Of A Spinning Cryogenic Infrared Sensor Undergoing Thermal/Mechanical Distortions

Predictions of optical performance for spinning cryogenic infrared sensors that operate in changing thermal and structural dynamic environments requires performing analyses involving several technologies. Although the individual thermal, structural and optical analyses are not unique, the interfacing of these analyses is unique in the optical industry. This interfacing is an important problem in performing cost-effective system analyses that often require several design/analysis iterations. We have addressed this problem by writing interface codes in order to automate the data transfer among the separate analyses. Several design/analysis iterations were performed using the T/S/O process until the design met optical performance and other requirements across the wide temperature range. The design and trade-off process for the cryogenic spinning sensor (which contains materials with different coefficients of thermal expansion) is discussed. This paper shows how the T/S/O process has been used to design a sensor that is nearly athermal across a wide temperature range.