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EVANS ENGINEERING

Dennis Charles Evans; Independent Consultant

EVANS Optical, System, Design, & Software ENGINEERING

General Services Provided By Evans Engineering

Space Flight Instrument Systems Engineering: from conceptualization to operation and data analysis and interpretation. Specialties include optical instrument design (vacuum ultraviolet, visible, through long wavelength infrared). Design for control of stray light is an engineering specialty. Photometric analysis and calibration of flight instruments is another area of expertise.

Satellite Instrument Systems Engineering

Services & Equipment. or Current Tasks

Short Resume or Long Resume or Publications or Experience

This site is under construction.

The full Evans Engineering active site is at: http://www.erols.com/ee/

Satellite Instrument Systems Engineering

• Performance Specification and Definition
• Design and Analysis
• Modeling and Simulation
• Integration, Testing, and Calibration
• Article: What is Systems Engineering (Netscape html file, 22kBy)
  • University of Arizona Systems Engineering Department (article with slide show)
• Article: Systems Engineering Lessons Learned (40kBy)
• Article: The "Unwritten Laws" of Systems Engineering , (17kBy)
  • related to the basic 3 laws which are:
    1. Everything interacts with everything else;
    2. Everything goes somewhere; and
    3. There is no such thing as a free lunch.
• Swales Aerospace, Inc. Mechanical, Thermal, Optical, & Systems Engineering

Optical Design Applications

• Design and Analysis of Ultraviolet, Visible, and Infrared Instruments
• Ray Tracing
  • RAY TRACE LANGUAGE(RTL); ACCOS; ASAP; CODE-V; ZEMAX; et al.
  • Wave Front Analysis; Polarization Analysis
• 3D Modeling
  • AutoCAD
  • AutoVision
  • .DXF, .IGS, ...
• Stray Light Control - Design and Analysis - BRDF (Bi-directional Reflectance Distribution Function)
  • Stray Light Analysis (link to Breault Research Organization)
  • SORIC BRDF Database (link to Stellar Optics Research International Corporation)

Other Applications Available

• AutoCAD 12, 13, 14; 2001i; AutoVision
  • Specializing in 3D modeling and Perspective Images
• APL; BASIC; FORTH
• MS-Office and MS-Project

General Science Support

• Astronomy
• Cosmology
• Geophysics
• Aerospace Engineering
• Project Management
• Consulting

Examples of Projects Supported by

EVANS Optical, System, Design, & Software ENGINEERING

Advanced Geosynchronous Studies [AGS]- Weather Imager

Version with 2-axis Scan Mirror and Deployable Calibrators

Version with 3-axis Scan Mirror and Fixed Position Calibrators

AGeoS Imager - 2D and 3D Optical Layouts

[1][2]

[Left, 1] A 3D perspective view from a detector inside a small telescope showing numerous internal reflections which interfered with the performance of the device.

[Right, 2] A 3D perspective view looking into a Cassegrainian telescope showing reflections of the light source which was contributing to calibration errors and performance misunderstandings.

[3][4]

[Left, 3] An RTL ray trace of a 10 arc-minute square field imaged onto a 256 square array infrared detector. The ray path of a dual paraboloid set has been folded in order to fit into a 30 degree sector of a 10 inch long cylinder.

[Right, 4] A perspective view from the entrance lens of a star tracker looking toward the sky. The green object is the back side of a sunshade on the payload instrument which is illuminated by the full earth. With this object visible to the tracker, the tracker could not meet performance specifications. The tracker stray light baffle was moved 1/2 inch and redesigned so the instrument sunshade could no longer be seen from the star tracker lens.

[5][6]

[5] A perspective view from the entrance baffle vane of an infrared telescope. Note the convergence of the interior vanes to the right side of the image. When the vane edges were moved away from a uniform cone by a few millimeters, the stray light in the instrument was reduced about 2 orders-of-magnitude. This shows the power of 3D modeling and image rendering connected with APART/PADE and other analytical tools.

[6] A rendered view of the same telescope as in [5], with the primary and secondary mirrors made reflective. The detector can be seen, as desired, but some edges that should not be illuminated can also be seen. Additional baffle vanes inside the throat of the central conical baffle were recommended.

[7]

[7] The image quality of the optics in an instrument such as the GOES-8 and -9 (Geostationary Observational Environmental Satellite) has as much influence on performance as the detector aperture size. For this model of GOES, the perfect 26 microradian aperture is represented by a square, 59 units on an edge. The image that best matches the result of having a star drift across the aperture is the one with a normal distribution and a half width of 20 units.