development of 1kW high power X-band SAR installed on small satellite for on-demand observation

Paper number

IAC-18,C3,4,6,x45958

Author

Dr. Koji Tanaka, Japan, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency

Coauthor

Prof. Hirobumi Saito, Japan, Japan Aerospace Exploration Agency (JAXA)

Coauthor

Mr. Hiromi Watanabe, Japan, Keio University

Coauthor

Dr. Koichi Ijichi, Japan, Japan Space Systems

Coauthor

Dr. Keiichi Hirako, Japan, Keio University

Coauthor

Prof. Seiko Shirasaka, Japan, Keio University

Year

2018

Abstract

We are developing a X-band synthetic aperture radar (SAR) system that can be used for observations both night and day or whatever the wether  installed on a small satellite. We propose an on-demand observation system for  the disaster. In this paper, we describe a development of the engineering model (EM) and the prototype model (PM) of the high power system of this X-band SAR.
  Ground resolutions of the X-band SAR with a single polarization are 1m at 350 km altitude and 3-10m at 600km altitude. A satellite is supposed to be 130kg in mass and the size is 0.7m x 0.7m x 0.7m on a rocket. A size of the deployed antenna is 4.9m x 0.7m. All electronics instruments are installed in a satellite body.  
  The high power system for this SRA system consists of 1kW pulsed amplifier that includes a power combiner with a waveguide resonator, a front-end and a filter. This amplifier adopted the state of art high power GaN HEMT devices. A chirped transmitting signal with frequencies of 9.5-9.8 GHz, with the duty of 25 %, and with pulse repetition of 3-7kHz are amplified. The peak output power of 1kW from the amplifier is required for 5 minutes while the base plate temperature increases from 5 ℃ to 60 ℃. One structural panel made by aluminum plate was allocated to this high power amplifier. Target mass of this amplifier is around 8kg.
  We designed and manufactured 200 W amplifier modules as an EM adopting the GaN HEMT devices and a novel six input ports power combiner with the waveguide resonator. The output of 1 kW was generated by combining 6 outputs of the amplifier modules. We intend to cut costs by utilizing the commercial-off-the-shelf components. Also, one of the most significant problems was the thermal design of such high power components for the small satellite. We decided the operating temperature of the GaN HEMT device by failure rate prediction, and designed the amplifier modules and the structure panel in order to keep temperature below the operating temperature by heat storage capacity of the aluminum alloy structural panel. We measured the electrical performances under several temperature conditions and evaluated environmental resistance by the thermal vacuum test, the impact and vibration test and the radiation test. Also, we evaluated a tolerance against a discharge from the view point of the  on-demand purposes.

Abstract document

IAC-18,C3,4,6,x45958.brief.pdf

Manuscript document

IAC-18,C3,4,6,x45958.pdf (🔒 authorized access only).

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