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Please use this identifier to cite or link to this item:
http://hdl.handle.net/2014/9765
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| Title: | Toric offset three-reflector antenna for the advanced microwave limb sounder |
| Authors: | Cofield, R.
Cwik, T.
Raouf, N. |
| Issue Date: | 22-Aug-2002 |
| Citation: | Highly innovative space telescope concepts, space telescopes and instruments SPIE astronomical telescopes instrumentation
Waikoloa, HI, USA |
| Abstract: | An advanced Microwave Limb Sounder (MLS), now in concept development for a potential future mission, is a space-borne heterodyne instrument to measure pressure, temperature, and atmospheric constituents from thermal emission between 120 and 2400 GHz. Previous MLS instruments used pencil-beam antennas sized to resolve N 1 vertical scale height. Current atmospheric models need better horizontal resolution than orbit spacing provides. To meet these needs, a new antenna concept combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but extremely astigmatic, with beamwidths 0.13~2.5. Nadir axis symmetry ensures that this Beam AspectRatio (BAR) is invariant over f33' of azimuth. The antenna can feed either an array of receivers or multiplexed low-noise receivers whose FOVs are swept by a small scanning mirror. We describe 3 stages of antenna design: First, using a paraxial-optics method, we choose conic profiles given vertical resolution orbit geometry, then develop the surfaces by nadir axis rotation, matching axisymmetric feeds to the BAR. A ray-trace program validates the design and generates alignment and deformation tolerances. Finally, a physical optics analysis verifies reflector surface currents and radiation patterns. |
| URI: | http://hdl.handle.net/2014/9765 |
| Appears in Collections: | JPL TRS 1992+
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