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:
Spectral Range: 0.5 microns -
Spectral Resolution: adjustable 32 - 150 nm
Wheel & Fabry-Perot
Ground resolution: 10KM - 100KM
24" long x 5" diameter30" dia x 28" high
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