Small X/L Band SAR Satellites for Mega Constellation at vLEO/LEO

Paper number

IAC-24,B4,7,8,x82817

Author

Prof. Hirobumi Saito, Nihon University, Japan

Coauthor

Mr. Mitsuteru Kaneoka, CSP Japan, Inc., Japan

Coauthor

Mr. Kazuyuki Nakamura, Japan

Coauthor

Prof. Yasuyuki Miyazaki, Nihon University, Japan

Year

2024

Abstract

We have developed small X band SAR (synthetic Aperture Radar) satellites of 1-m ground resolution with a novel deployable slot array antenna. This antenna is cost-effective since it is passive and plain antenna. Three of the small SAR satellites have been already launched since 2021 by a start-up company in Japan. The satellite body is in size of 0.4m x 0.7m x 0.7m and the deployed SAR antenna is in size of 5m x 0.7m. 

We can make easily a disk-shaped satellite body with 1m diameter x 0.2m height and attach this deployable slot array antenna to the disk body. This quasi-two-dimensional SAR satellite configuration, SAR DiskSat is suitable for stacking in a rocket faring for mega-constellation launching. Another advantage of the SAR-DiskSat is the possibility of vLEO (very low Earth orbit) operation. A thin edge cross-section makes atmospheric drag small. A small electrical propulsion for CubeSats can compensate the atmospheric drag of the SAR DiskSat at 350-400km altitude. At such vLEO there is an advantage of short-range SAR operation in terms of signal-to-noise ratio. This advantage of RF power makes it easier to improve its ground resolution. The final goal of this SAR-DiskSat would be a mega constellation of 0.25-m ground resolution in VLEO. This slot array antenna is equipped with feed waveguides and can be embedded a delay line in the antenna segment.  It is possible to widen the SAR swath with a technique of elevation frequency scan at expense of a ground resolution.

L band wave can penetrate below the top of forest, while X band SAR are suitable for monitoring of urban areas. L band SAR monitoring becomes more important for carbon credit markets. A simple scaling on signal-to-noise ratio of SAR image indicates that L band SAR requires larger antenna area or average RF power than X band. Our SAR DiskSats utilize deployable panel antennas, which are not suitable for significant increase on antenna area unlike deployable parabola antennas. However, L band SAR observations from vLEO can compensate its disadvantage. It is shown that L band DiskSat with a similar size to X band becomes feasible at vLEO. Our SAR antenna type, deployable slot array panel-antennas can only enjoy the advantage of vLEO unlike other types. Our presentation will describe the feasibility of L band SAR DiskSat.

Abstract document

IAC-24,B4,7,8,x82817.brief.pdf

Manuscript document

IAC-24,B4,7,8,x82817.pdf (🔒 authorized access only).

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