Advanced Geosynchronous Studies [AGS]- Weather Imager
Version with 3-axis Scan Mirror and Fixed Position Calibrators
[A] [A1] [B]
An AGS Imager optical design has been developed that is a compact, "all-reflective" system providing geometric (visible, 0.45-0.85 microns) images smaller than 1/3-kilometer pixels in a flat focal surface 1-degree in diameter. Focal plane separation in converging light is achieved using wedged beam splitters that compensate for astigmatism and coma. Diffraction limited performance for the 30-cm diameter telescope is achieve over the short, mid, and long wavelength bands (1.3-13.5 microns). The field-of-view is scanned over the earth using a two-axis scan mirror. The scan procedure compensates for image rotation.
Following the links from the small images above will provide full screen images that were generated from the 3-dimensional AutoCAD-14 model using "photo-realistic" rendering
[A] Isometric view: Transparent solids have been used to show the internal layout. Not all system elements are rendered in all the views so that the concept of the optical design can be more clearly presented. [Hidden Line Drawing]
[B] Side view: Earth is toward top. A sealed dewar is used to cool the mid and long wavelength detectors (red, bottom). The visible and short wavelength are in a hermetically sealed container (yellow) so they can be operated in air. [Line Drawing]
[C] Bottom view: The beam splitter and fold mirror layout for the VIS/SWL bands can be seen most easily in this view.
[D] 2D conceptual layout of ZEMAX Y-fan raytrace of 1-degree
[E] Close-up LWIR/MWIR Vacuum Dewar and SWL/VIS Vacuum Enclosure.
Beam Splitters are wedged to eliminate astigmatism introduced by using them in converging beam. Performance is optimized at 0.55, 2.0, 4.0, and 10.0 microns wavelength. Performance is limited by detector size in VIS band, and diffraction limited in all other bands. In [A-C], the VIS/SWL planes are rotated 90-degrees from these views. Performance has been analyzed using ZEMAX. The enclosure windows and Focal Plane Assembly filters have been included in the analysis. [Optical Performance Summary for 3D layout]