# US 11,442,161 B2 · Satellite borne synthetic aperture radar > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,442,161 B2 - Document ID: US11442161B2 - Status: Granted - Kind: B2 - Application number: 16/577,670 - Filed: 2019-09-20 - Published: 2021-03-25 - Granted: 2022-09-13 - Earliest claimed: 2019-09-20 - Assignees: Embraer S.A. - Applicants: Embraer S.A. - Inventors: João Roberto Moreira Neto; Janio Kono - Web page: https://patentgrep.com/patent/US11442161B2 ## CPC - G01S 13/90: using synthetic aperture techniques {, e.g. synthetic aperture radar [SAR] techniques} - B64G 1/2227: {Inflating} - B64G 1/66: Arrangements or adaptations of apparatus or instruments, not otherwise provided for - G01S 7/03: Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver - H01Q 1/081: {Inflatable antennas} - H01Q 1/288: {Satellite antennas} - H01Q 15/20: Collapsible reflectors - H01Q 19/19: comprising one main concave reflecting surface associated with an auxiliary reflecting surface - B64G 1/44: using radiation, e.g. deployable solar arrays - G01S 2013/0263: {Passive array antenna} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - B64G: COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract The example non-limiting technology herein provides a Synthetic Aperture Radar (SAR) solution on board a micro-satellite that provides global revisit within 1 month; a cost below US$ 10 million; and satellite mass lower than 100 kg. One solution uses an inflatable Cassegrain type antenna with a phased beam steering array in the 1.2 GHz band. ## Claims ### Claim 1 A satellite borne Synthetic Aperture Radar (SAR) for surveying the earth's surface, comprising: a geometrically-adjustable Cassegrain type antenna with aperture size in a range between 15 to 30 meters, comprising an inflatable balloon with a controlled pressure during orbit providing, during orbit, adjustable antenna geometry and characteristics for radar wavelengths larger than millimeters, the geometrically-adjustable Cassegrain type antenna comprising a two-dimensional active antenna array enabling electronic beam steering in elevation and azimuth directions with in-orbit adjustable electronic beam steering range, the Cassegrain type antenna comprising a sub-reflector that is centralized or offset for defining an illumination pattern on earth's surface with in-orbit adjustable geometry; and a Power, Attitude and Orbit Control Subsystem comprising a pressure control of geometrically-adjustable Cassegrain antenna reflectors, a telemetry infrastructure and a real-time data down link enabling the satellite to be controlled by a satellite control center and to download acquired radar data to a ground station. ### Claim 2 (depends on 1) The satellite borne SAR as claimed in claim 1, wherein the gain and beamwidth of the illumination beam of the geometrically adjustable inflatable Cassegrain type antenna can be modified in orbit by changing the shape of the main and secondary reflectors, wherein independent pressure control of first and second cavities are used to control the shapes of the main and secondary cavities to modify the antenna characteristics. ### Claim 3 (depends on 1) The satellite borne Synthetic Aperture Radar as claimed in claim 1, wherein the geometrically adjustable inflatable Cassegrain type antenna has a large diameter enabling a transmission power lower than 100 watts, a total radar power consumption less than 100 W, and a total satellite weight less than 100 kilograms. ### Claim 4 (depends on 1) The satellite borne Synthetic Aperture Radar as claimed in claim 1, wherein the geometrically adjustable inflatable Cassegrain type antenna is configured so that the illumination beam of the Cassegrain type antenna is electronically steerable on the earth's surface, so that an imaging swath width in the range up to several hundreds of kilometers can be reached by an orbit of around 500 km, achieving a global revisit time of 1 month with 10 meter resolution, wherein localization of the imaging swath of the earth's surface can vary beyond elevation and azimuth steering deflection limits by geometrically adjusting the geometry of the main and sub-reflectors of the inflatable Cassegrain antenna by respective pressure controls. ### Claim 5 (depends on 4) The satellite borne Synthetic Aperture Radar as claimed in claim 4, wherein Global revisit time of one week is achieved by a constellation of 2 satellites with a resolution of 30 meters. ### Claim 6 (depends on 4) The satellite borne Synthetic Aperture Radar as claimed in claim 4, wherein Global revisit time lower than one week and/or resolutions better than 10 m can be reached by a satellite constellation of more than 2 satellites. ### Claim 7 (depends on 1) The satellite borne Synthetic Aperture Radar (SAR) of claim 1 wherein the pressure control modifies the illumination beam gain and/or beamwidth provided by the geometrically-adjustable Cassegrain antenna reflectors. ### Claim 8 (depends on 1) The satellite borne Synthetic Aperture Radar (SAR) of claim 1 wherein the pressure control provides a controllable amount of inflation that defines the geometry of the two-dimensional active antenna array and thereby focusses the RF radiation beam pattern of the array. ### Claim 9 An orbital platform comprising: a housing; a SAR radar system comprising an inflatable geometrically adjustable Cassegrain antenna mounted to the housing, the antenna comprising a two-dimensional steerable active antenna array, a sub-reflector and a main reflector, the antenna array emitting microwave pulses that the sub-reflector reflects to the main reflector and the main reflector reflects to the target; and solar panels mounted to the housing; wherein the solar panels provide sufficient energy to enable substantially continuous operation of the SAR radar system. ### Claim 10 (depends on 9) The orbital platform of claim 9 wherein the SAR radar system consumes less than 100 watts. ### Claim 11 (depends on 9) The orbital platform of claim 9 wherein the orbital platform has a total mass of less than 100 kg. ### Claim 12 (depends on 9) The orbital platform of claim 9 wherein the SAR radar system achieves a global revisit time of 1 month with 10 meter resolution; one week when operating in a constellation of two satellites with a resolution of 30 meters; and less than one week and/or resolution better than 10 meters when operating in a constellation of more than two satellites. ### Claim 13 An orbital platform comprising: a housing; a SAR radar system comprising an inflatable Cassegrain antenna mounted to the housing, the antenna comprising a two-dimensional steerable active antenna array, a sub-reflector and a reflector, the antenna array emitting microwave pulses that the sub-reflector reflects to the reflector and the reflector reflects to the target; and solar panels mounted to the housing; wherein the solar panels provide sufficient energy to enable substantially continuous operation of the SAR radar system, wherein the gain and beamwidth of the illumination beam of the inflatable Cassegrain type antenna can be modified in orbit by changing the shape of the main and secondary reflectors, wherein independent pressure control of first and second the cavities are used to control the shapes of the main and secondary cavities to modify the antenna characteristics.