Abstract
A compact synthetic aperture radar microsatellite antenna operating in the L-band is presented. To reduce size and weight of the small spaceborne SAR, we utilize a lightweight deployable parabolic mesh reflector and operate at low Earth orbital altitudes. The antenna is a wrap-rib center-fed parabolic reflector with dedicated receiving and transmitting feeds. Antenna requirements are: gain better than 30 dBic, center frequency of 1.275 GHz with bandwidth of 28 MHz and circular polarization with axial ratio better than 3 dB. This work describes the development of a compact Circularly Polarized SAR L-band antenna system and the design considerations suitable for small spacecrafts. Simulation of the parabolic reflector and effects of different structural elements to the main radiation pattern were analyzed, which include ribs, struts, feed blockage, and mesh surface. A research model of the parabolic reflector was constructed, and the reflector surface verification was realized using two different approaches, a laser distance meter along ribs and the other using 3D scanning of the reflector surface. RMS errors wree 1.92 mm and 3.86 mm, respectively, both below required 4.55 mm of surface accuracy. Near-field antenna measurements of the deployable reflector mesh antenna was realized for final antenna validation, presenting good agreement with the simulation results. Future work comprises prototyping and testing of the full polarimetric feed assembly.
Highlights
Lowering orbital altitudes is a clear advantage for small sats, as it directly reduces the minimum antenna area that complies with the pulse repetition frequency (PRF) constraints
This document is organized as follows: Section 2 describes the main considerations for the design of the deployable mesh reflector antenna; Section 3 describes the antenna effective gain estimation; Section 4 presents methods for the verification of reflector surface accuracy and subsequent results achieved; and Section 5 concludes with a summary of the current study and an outlook to future work
This paper describes the design and development status of a compact CP-SatellitesSynthetic Aperture Radar (SAR) system compatible with a 150-kg class satellite
Summary
Synthetic Aperture Radar (SAR) technology has been widely used in Earth observation applications, as it can provide unique information independent of cloud coverage and during night time. Constellations of small satellites carrying scientific or commercial payloads provide fast responses and near real-time ground monitoring [2]. Many such satellites carry small payloads as optical cameras or radio receivers, with spacecraft mass ranging from less than a kilogram to few hundred kilograms. The bulky payloads and high costs result in SAR missions being commonly sponsored by governmental space agencies Up to this date, the number of compact SAR missions with mass of few hundred kilograms are very limited. Aerospace 2018, 5, 128 there is a strong social demand to realize small and affordable SAR satellites for fast responses and all-weather monitoring Such needs are especially important in the Southeast Asian countries, often covered by clouds, which limits observation with optical satellites. SAR data more affordable for the global remote sensing communities in the future
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