Hudson Research Inc design and builds telescopes and other optical instruments for various customer applications. In our role as systems architect and integrator for the G-301 Space Shuttle mission G-301 Space Shuttle mission, we needed to design an infra-red (IR) telescope that would meet the size weight and optical requirements of the Hyperspectral Imaging Spectroscope instrument. The specifications for the telescope were: 

Focal Length                200mm to 2000mm
Zoom Ratio                   10:1
Spectral Range:          0.5 microns - 25 microns
Spectral Resolution:  adjustable 32 - 150 nm
Spectral Filter:             Selectable Filter Wheel & Fabry-Perot
Ground resolution:    10KM - 100KM
Dimensions                   24" long x 5" diameter30" dia x 28" high
Weight                            150 lbs

A review of the literature showed that no conventional design would meet the total requirements. A design was evolved which, after nine generations of design and simulatuion yielded an instrument that met the specifications. The core of the instrument was modeled after a successful radio telescope design which was modified to include the two-stage spectral filter system and was folded to meet the physical constraints. The design is an all-reflective nested set of parabolas which essentially reduces the entrance aperture to a 40mm diameter beam. This is then folded, passed through the spectral filter system, and then folded again and brought to ficus on the photocathode plane of the QFE imaging sensor. The core telescope produces a collimated output beam which is folded by a plane mirror (first folding mirror) then passed throught the spectral filter assembly, and finally brought to ficus by the second folding mirror, an off-axis parabola. Within the spectral filter the beam can be routed throught either the filter wheel, the Fabry-Perot interferometric filter, both or neither. This allows for all possible combinations of filtration including full bandwidth imaging (0.5 microns - 25 microns). Zoom is achieved by a small movement of the secondary mirror. The optics are gold-coated first surface high precision mirrors. The gold coating was chosen to match the spectral bandpass of the entrance window of the imaging sensor. Critical interelement dimensions are maintained by the use of an Invar support structure. The telescope has a full-length thermal baffle to shield it from thermal sources within the GAS canister. A schematic diagram of the system is shown below. CONTACT US  for further Information

Figure 1   Schematic Diagram of the G-301 Telescope & Spectral Filter