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We present planning challenges, methods and preliminary results for a new model-based paradigm for earth observing systems in adaptive remote sensing. Our heuristically guided constraint optimization planner produces coordinated plans for multiple satellites, each with multiple instruments (payloads). The satellites are agile, meaning they can quickly maneuver to change viewing angles in response to rapidly changing phenomena. The planner operates in a closed-loop context, updating the plan as it receives regular sensor data and updated predictions. We describe the planner's search space and search procedure, and present preliminary experiment results. Contributions include initial identification of the planner's search space, constraints, heuristics, and performance metrics applied to a soil moisture monitoring scenario using spaceborne radars.

Accepted: 2018-11-14, 資料番号: SA1180363000

Agile attitude maneuvering maximizes the utility of remote sensing satellite constellations. By taking into account a satellite's physical properties and its actuator specifications, we may leverage the full performance potential of the attitude control system to conduct agile remote sensing beyond conventional slew-and-stabilize maneuvers. Employing a constellation of agile satellites, coordinated by an autonomous and responsive scheduler, can significantly increase overall response rate, revisit time and global coverage for the mission. In this paper, we use recent advances in sequential convex programming based trajectory optimization to enable rapid-target acquisition, pointing and tracking capabilities for a scheduler-based constellation. We present two problem formulations. The Minimum-Time Slew Optimal Control Problem determines the minimum time, required energy, and optimal trajectory to slew between any two orientations given nonlinear quaternion kinematics, gyrostat and actuator dynamics, and state/input constraints. By gridding the space of 3D rotations and efficiently solving this problem on the grid, we produce lookup tables or parametric fits off-line that can then be used on-line by a scheduler to compute accurate estimates of minimum-time and maneuver energy for real-time constellation scheduling. The Minimum-Effort Multi-Target Pointing Optimal Control Problem is used on-line by each satellite to produce continuous attitude-state and control-input trajectories that realize a given schedule while minimizing attitude error and control effort. The optimal trajectory may then be achieved by a low-level tracking controller. We demonstrate our approach with an example of a reference satellite in Sun-synchronous orbit passing over globally-distributed, Earth-observation targets., 24 pages, 27 figures

Small spacecraft now have precise attitude control systems available commercially, allowing them to slew in 3 degrees of freedom, and capture images within short notice. When combined with appropriate software, this agility can significantly increase response rate, revisit time and coverage. In prior work, we have demonstrated an algorithmic framework that combines orbital mechanics, attitude control and scheduling optimization to plan the time-varying, full-body orientation of agile, small spacecraft in a constellation. The proposed schedule optimization would run at the ground station autonomously, and the resultant schedules uplinked to the spacecraft for execution. The algorithm is generalizable over small steerable spacecraft, control capability, sensor specs, imaging requirements, and regions of interest. In this article, we modify the algorithm to run onboard small spacecraft, such that the constellation can make time-sensitive decisions to slew and capture images autonomously, without ground control. We have developed a communication module based on Delay/Disruption Tolerant Networking (DTN) for onboard data management and routing among the satellites, which will work in conjunction with the other modules to optimize the schedule of agile communication and steering. We then apply this preliminary framework on representative constellations to simulate targeted measurements of episodic precipitation events and subsequent urban floods. The command and control efficiency of our agile algorithm is compared to non-agile (11.3x improvement) and non-DTN (21% improvement) constellations.

The Earth Observation planning community has access to tools that can propagate orbits and compute coverage of Earth observing imagers with customizable shapes and orientation, model the expected Earth Reflectance at various bands, epochs and directions, generate simplified instrument performance metrics for imagers and radars, and schedule single and multiple spacecraft payload operations. We are working toward integrating existing tools to design a planner that allows commercial small spacecraft to assess the opportunities for cross-calibration of their sensors against current satellite to be calibrated, specifications of the reference instruments, sensor stability, allowable latency between calibration measurements, differences in viewing and solar geometry between calibration measurements, etc. The planner would output cross-calibration opportunities for every reference target pair as a function of flexible user-defined parameters. We use a preliminary version of this planner to inform the design of a constellation of transfer radiometers that can serve as stable, radiometric references for commercial sensors to cross-calibrate with. We propose such a constellation for either vicarious cross-calibration using pre-selected sites, or top of the atmosphere (TOA) cross-calibration globally. Results from the calibration planner applied to a subset of informed architecture designs show that a 4 sat constellation provides multiple calibration opportunities within half a day planning horizon, for Cubesat sensors deployed into a typical rideshare orbits. While such opportunities are available for cross calibration image pairs within 5 deg of solar or view directions, and with-in an hour (for TOA) and less than a day (vicariously), the planner allows us to identify many more by relaxing user-defined restrictions.

Accepted: 2018-03-25, 資料番号: SA1180069000

We proposed a new architecture of antenna, transmitter and receiver feeding configuration for small synthetic aperture radar (SAR) that is compatible with 100kg class satellite. Promising applications are constellations of earth observations together with optical sensors, and responsive, disaster monitoring missions. The SAR antenna is a deployable, passive, honeycomb panel antenna with slot array that can be stowed compactly. RF (radio frequency) instruments are in a satellite body and RF signal is fed to a deployable antenna through non-contacting choke flanges at deployable hinges. This paper describes its development strategy and the present development status of the small spaceborne SAR based on this architecture.

In this paper, we discuss the design scheme of a waveguide feeder for a wideband rectangular parallel plate slot-array antenna for a high resolution synthetic aperture radar sensor on-board a 100kg micro-satellite, scheduled to be launched in 2020. We analyze the performance of the edge-feed system with two waveguide feeders for each antenna panel. HFSS simulation results show that the edge-feed system reduces the undesired Poynting vector tilt in the parallel plate and achieves good antenna gain and efficiency with larger bandwidth, thereby giving it an edge over the conventional end-feed system However, the two-feeder antenna system increases the weight and active reflection and due to asymmetric design, phase opposition is difficult to achieve, thereby leading to structural complexity.

This paper investigated the possibility of using an $X$ -band traveling-wave antenna for application in synthetic aperture radar (SAR) on a small-satellite platform. A rectangular slotted parallel-plate antenna panel capable of radiating dual polarization over the same physical aperture was selected for this purpose. The design procedure, which provides for an optimal antenna pattern in a SAR application, is described. A meta-heuristic multiobjective optimization algorithm was applied to synthesize an appropriate far-field pattern, which enhances the quality of the SAR image. Subsequently, the optimization results were used to build a more realistic model of the antenna panel in electromagnetic simulation software. An antenna panel was fabricated, and its electrical characteristics were measured. The fabricated prototype weighed 1310 g and measurements showed nearly 50% aperture efficiency for both circular polarizations [34.6-dBic right-hand circular polarized (RHCP), 34.5-dBic left-hand circular polarized (LHCP), and peak gain at 9.65 GHz], with low side-lobes. A beam shift of 2.1° was observed between the RHCP and LHCP beams at the design center frequency and was later analyzed to be the result of an error in the modeling of the adhesive layer.

資料番号: SA1170214000

学位の種別: 課程博士, 審査委員会委員 : （主査）東京大学教授 齋藤 宏文, 東京大学教授 橋本 樹明, 東京大学教授 保立 和夫, 東京電機大学教授 小林 岳彦, 東京工業大学教授 廣川 二郎

We are developing a small synthetic aperture radar (SAR) that is compatible with 100kg class satellite. A constellation of such small SAR satellites is promising for shot revisit time of earth observations. The SAR antenna is a deployable honeycomb panel antenna with slot array, that can be stowed compactly. RF instruments are on a satellite structure and RF signal is fed to a deployable antenna through a non-contact choke flange at a hinge. This small SAR project for a responsive observation mission is funded for 2015 - 2018 by Japanese government.

第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 16th Space Science Symposium (January 6-7, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000046195, レポート番号: P-196

第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 16th Space Science Symposium (January 6-7, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000046194, レポート番号: P-195

A compact microwave power combiner for combining output from six solid-state power amplifiers is studied. The combiner consists of 6 standard microstrip line inputs from high power amplifier, resonant cylindrical cavity and one standard rectangular waveguide output. The effect of input power amplifier failure is also studied and simulation results are described. Insertion loss of less than 0.3 dB over 200 MHz bandwidth in X-Band is simulated.

第15回宇宙科学シンポジウム (2015年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 15th Space Science Symposium (January 6-7, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000034282, レポート番号: P-283

第15回宇宙科学シンポジウム (2015年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 15th Space Science Symposium (January 6-7, 2015. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000034280, レポート番号: P-281

Hodoyoshi III and IV series of small satellites are scheduled to be launched at the end of year 2013. These sun-synchronous, Low Earth Orbit (LEO) satellites will perform remote sensing operations carrying with them powerful optical sensors. The huge volumes of payload data gathered from the sensors needs to be relayed to the ground station for processing and interpretation. This requires a powerful wireless transmitter with large bandwidth meeting to the power, size specifations of small satellites (< 50kg class).The purpose of this thesis is the simulation of a proposed X Band Radio Frequency (RF) Transmitter design and exploration of means to improve the design. The simulation was carried out in LabView and Matlab environment. One of the ways in which the design could be improved is found to be to perform linearisation of the power amplifier in the RF Transmitter path. The transfer characteristics of different power amplifiers wereexperimentally tabulated. Different digital linearization techniques were researched upon. The experimental data was further used in the simulations to test their effectiveness.Towards the end of the thesis two innovative, original models of digital linearization were proposed. The simulation results of one of the models showed very promising results. An hardware-in-loop test implementation of the transmitter is proposed, and is underway at the moment of submission of the thesis report. Validerat; 20121008 (anonymous)