Abstract: An Earth monitoring system comprises a satellite constellation (310) and a schedule calculation module (302) located on Earth. The schedule calculation module (302) may be configured to implement a satellite management method receiving a request post-launch for a location to be imaged; recalculating an existing schedule of the satellites to provide an updated schedule that includes imaging the location; and providing the updated schedule for transmission to one or more of the satellites.

Abstract: One or more environmental events on earth are monitored by a method comprising receiving a notification of an environmental event occurring, wherein the notification is derived from first environmental data. An area on Earth corresponding to the notification is identified. A determination is made that the event meets one or more predetermined event criteria and in response to the determination the event is monitored by collecting additional environmental data. Additional environmental data determined to be relevant to the event according to one or more relevance criteria is tagged to the event in a geographically indexed database and used to estimate the severity of the event at locations within the identified area.

Abstract: The present disclosure relates to a method of generating auxiliary data for controlling a satellite travelling in orbit around Earth, the method comprising: receiving tracking data for the satellite; applying an orbit determination algorithm including: estimating an orbit for the satellite based on the tracking data; and predicting, based on the estimated orbit, future ephemerides data of the satellite; generating auxiliary data comprising predicted future ephemerides data; and transmitting the auxiliary data to the satellite for use in the satellite's attitude and orbit control.

Abstract: An assembly jig comprises: a support member providing a support surface; a tool configured to receive one component of a faster pair such that the component is not rotatable relative to the tool; one or more alignment members to locate the tool relative to the support member; wherein the one or more alignment members and the tool are configured such that, when the tool is located by the one or more alignment members on the support member, the tool is still rotatable with respect to the support member about an axis perpendicular to the support surface.

Abstract: A satellite (140) for operation in orbit around the earth comprises an ADCS (131, FIG. 1) configured for mechanically steering the satellite in the azimuth direction to prolong a dwell time (1105), during which a selected target is visible from the satellite, as the satellite orbits over the target. A processor at the ground station may be configured to process raw SAR data from any of the satellites described here. The raw SAR data may be processed in a number of ways to provide image information including but not limited to forming multilook images, compiling video sequences and colour coding images.

Abstract: A method of operating a spacecraft propulsion system comprises injecting electrons into the plasma surrounding the spacecraft prior to creating the stream of ions, and after commencing creation of the ion stream, continuing the injection of electrons in an amount sufficient to maintain the spacecraft at a positive potential. This method may be implemented in a single thruster. In spacecraft with multiple thrusters the same method may be implemented in each thruster. Where the propulsion system comprises a plurality of thrusters, the method may comprise: operating at least one of the thrusters as a drive thruster, and operating at least one of the thrusters as an auxiliary or “reserve” thruster. The electron source of the at least one auxiliary thruster may be operated before creation of the ion stream to inject the electrons into the plasma surrounding the spacecraft.

Abstract: An RF switching circuit for switching RF signals, the RF switching circuit comprises one or more RF switch drivers and one or more RF switches, the RF switch drivers configured to drive the one or more RF switches by supplying power to the one or more RF switches, the RF switch driver comprising an isolated gate driver comprising one or more inputs, one or more outputs, and electrical separation between the input circuitry and the output circuitry of the isolated gate driver, the RF switch driver configured to receive an input signal indicating when the one or more RF switches should be turned on and/or off, and to send in response an appropriate signal at the appropriate voltage to the one or more RF switches to turn them on or off according to the input signal.

Abstract: A method of detecting and suppressing azimuth ambiguities in synthetic aperture radar (SAR) single look complex (SLC) image data (SAR SLC image data) comprising a Doppler spectrum obtained from received SAR signals by applying an amplitude threshold to the Doppler spectrum of received SAR signals to exclude amplitude values above the amplitude threshold resulting from ambiguous energy in the Doppler spectrum, and substituting the excluded amplitude values using a fitting function to generate a modified Doppler spectrum with the ambiguous energy suppressed; and generating azimuth ambiguity suppressed image data using the modified Doppler spectrum.

Abstract: Multiple synthetic aperture radar “SAR” images of a target area on the earth are acquired using a satellite travelling in an orbit above the earth in a single pass of the satellite over the target area. In some methods, the data for each image is acquired from a different angle of incidence with respect to the target area. Then, the variation of quantity of backscattered radiation with respect to angle of incidence is analysed and used to identify matter imaged in a pixel or pixel group. In other methods, the data for each image is acquired from a different angle of incidence with respect to the target area, and the different angles of incidence are determined based on the specular reflection curve for a particular material. Then the quantity of backscattered radiation is analysed to determine whether the particular material is present based on the quantity of backscattered radiation.

Abstract: A method of method of detecting ambiguities in synthetic aperture radar (SAR) image data is performed on SAR data comprising, for each pixel in an image, an amplitude and a phase value. The method comprises: calculating at least one phase derivative value for respective pixels represented by the SAR data with respect to a spatial direction, determining a threshold for the phase derivative value, and determining pixels with phase derivative values above the threshold to be ambiguous. A method of suppressing azimuth ambiguities in synthetic aperture radar “SAR” single look complex image data, is performed on a Doppler spectrum obtained from received SAR signals.

Abstract: A method of operating a synthetic aperture radar “SAR” to acquire image data, comprises steering the SAR beam in azimuth with respect to the direction of travel during a first time period to acquire image data for a first area on Earth to be imaged; steering the SAR beam in azimuth during one or more additional time periods to acquire image data for one or more additional areas on Earth to be imaged; and steering the SAR beam in azimuth in a rearward direction with respect to the direction of travel, during a time period including the first and one or more additional time periods, to reduce the speed of travel of the beam with respect to Earth.

Abstract: A computer-implemented method of classifying objects in an image, the method comprising: receiving image data associated with the image; receiving incidence angle data, wherein the incidence angle data is indicative of an incidence angle from which the image data is collected by a detector; and using a machine learning model to classify one or more objects within the image as belonging to one of one or more categories, wherein classifying the one or more objects within the image is based on: the incidence angle data, and respective values of one or more parameters of the image data.

Abstract: A method of operating a synthetic aperture radar “SAR” to acquire SAR echo data for the formation of an image, comprises calculating a nadir ambiguity index for the nadir of the platform; determining a frequency sweep direction sequence for successive pulses of a waveform to be transmitted by the SAR based on the nadir ambiguity index; obtaining a relative phase sequence for the successive pulses of the waveform; and encoding the waveform with the determined frequency sweep direction sequence and the relative phase sequence.

Abstract: A computer-implemented method for identifying one or more changes across a plurality of images, the method comprising: receiving, at a convolutional neural network, CNN, encoder, CNN input data comprising data associated with each pixel of each of the plurality of images; propagating the CNN input data through the CNN encoder to generate a plurality of feature maps, wherein each feature map comprises a feature classification of each pixel of a respective image of the plurality of images according to a feature classification scheme, wherein the feature classification scheme comprises a plurality of classifications and is generated by the CNN encoder based on training data; receiving, at a ConvLSTM network, ConvLSTM input data comprising the plurality of feature maps generated by the CNN encoder; and propagating the ConvLSTM input data through the ConvLSTM network to generate a change map, wherein the change map comprises change data indicative of one or more changes across the plurality of images.

Abstract: An assembly jig comprises: a support member providing a support surface; a tool configured to receive one component of a faster pair such that the component is not rotatable relative to the tool; one or more alignment members to locate the tool relative to the support member; wherein the one or more alignment members and the tool are configured such that, when the tool is located by the one or more alignment members on the support member, the tool is still rotatable with respect to the support member about an axis perpendicular to the support surface.

Abstract: The present disclosure relates to a method of generating auxiliary data for controlling a satellite travelling in orbit around Earth, the method comprising: receiving tracking data for the satellite; applying an orbit determination algorithm including: estimating an orbit for the satellite based on the tracking data; and predicting, based on the estimated orbit, future ephemerides data of the satellite; generating auxiliary data comprising predicted future ephemerides data; and transmitting the auxiliary data to the satellite for use in the satellite's attitude and orbit control.

Abstract: A method of method of detecting ambiguities in synthetic aperture radar (SAR) image data is performed on SAR data comprising, for each pixel in an image, an amplitude and a phase value. The method comprises: calculating at least one phase derivative value for respective pixels represented by the SAR data with respect to a spatial direction, determining a threshold for the phase derivative value, and determining pixels with phase derivative values above the threshold to be ambiguous. A method of suppressing azimuth ambiguities in synthetic aperture radar “SAR” single look complex image data, is performed on a Doppler spectrum obtained from received SAR signals.

Abstract: A method of operating a Synthetic Aperture Radar ‘SAR’ to acquire image data of a swath comprising one or more subswath(s) is provided, wherein the SAR is carried on a platform moving along a flight direction and a radiated beam is directed towards the swath, the method comprising: electronically steering the beam in azimuth direction along one subswath for each burst; and mechanically steering the beam in a direction opposite to the flight direction during each burst. The method allows to obtain an improved swath to resolution ratio.

Abstract: A method of providing Earth observation data comprises: acquiring Earth observation echo data on a first satellite in a low Earth orbit, determining a time required to downlink predetermined data to a ground station on Earth from the first satellite at the current position of the first satellite. If the time required exceeds a predetermined threshold, the predetermined data may be transmitted to another satellite in orbit above Earth using space-to-space radio communication. Alternatively, the first satellite may receive data relating to the current position of another satellite in orbit above Earth, determine a time required to the predetermined data to a ground station via the other satellite at the current position of the at least one other satellite, and if the determined time for the other satellite is less than the time determined for the first satellite, transmit the predetermined data to the other satellite in orbit above Earth using space-to-space radio communication.

Abstract: An RF switching circuit for switching RF signals, the RF switching circuit comprises one or more RF switch drivers and one or more RF switches, the RF switch drivers configured to drive the one or more RF switches by supplying power to the one or more RF switches, the RF switch driver comprising an isolated gate driver comprising one or more inputs, one or more outputs, and electrical separation between the input circuitry and the output circuitry of the isolated gate driver, the RF switch driver configured to receive an input signal indicating when the one or more RF switches should be turned on and/or off, and to send in response an appropriate signal at the appropriate voltage to the one or more RF switches to turn them on or off according to the input signal.