Toric offset three-reflector antenna for an advanced microwave limb sounder

Richard E. Cofield; Thomas A. Cwik; Nasrat A. Raouf

doi:10.1117/12.460463

18 December 2002 Toric offset three-reflector antenna for an advanced microwave limb sounder

Richard E. Cofield, Thomas A. Cwik, Nasrat A. Raouf

Proceedings Volume 4849, Highly Innovative Space Telescope Concepts; (2002) https://doi.org/10.1117/12.460463
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

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 ~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 Aspect Ratio (BAR) is invariant over ±33 degrees 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.

Citation Download Citation

Richard E. Cofield, Thomas A. Cwik, and Nasrat A. Raouf "Toric offset three-reflector antenna for an advanced microwave limb sounder", Proc. SPIE 4849, Highly Innovative Space Telescope Concepts, (18 December 2002); https://doi.org/10.1117/12.460463

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available