This paper studies the concept of a new waveguide feeding technique for wideband application of an X-band deployable rectangular parallel-plate slot-array antenna panel network with the vertical polarization for a synthetic aperture radar onboard a 100 kg class microsatellite. The antenna design procedure in high-frequency structure simulator followed by its fabrication and measurement results are explained. Simulations and antenna array measurement results confirmed that the corporate feeding technique achieved wide-beam antenna gain within permissible reflection limit in the desired bandwidth, thereby ensuring wideband operation. The fabricated center antenna panel achieved 35.3 dBi peak gain and 75% peak aperture efficiency, and the four-panel antenna array network achieved 40.8 dBi peak gain and 68% peak aperture efficiency in designed 300 MHz bandwidth. Although there was some mismatch in the measured reflection profile of each panel compared to the simulation results, this discrepancy was subsequently analyzed to be due to the imperfect modeling of the adhesive layer thickness and further analysis revealed that increasing the slot length of all coupling slots in the waveguide feeders by 0.2 mm can nullify this undesired effect.

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.

Within the realm of satellite remote sensing, optimal data acquisition to study natural phenomena under time, resource, and cost constraints is a well-known problem. Furthermore, since the sensors themselves are at remote locations with sparse ground connectivity, the optimal method must use a computationally light forecasting algorithm, which assimilates information from the observations at possibly irregular intervals, in near real time. In this article, we propose and demonstrate the ensemble -guided cyclone track forecasting (EGCTF) method for application in remote tropical cyclone tracking. The algorithm uses ensemble data produced by numerical weather prediction models to guide the forecasting process while assimilating measured cyclone center positions. The algorithm was tested and analyzed with the Global Ensemble Forecasting System (GEFS) data and the National Hurricane Center data for the 2018 year hurricanes within the Atlantic basin. Compared with a baseline method that uses the GEFS-issued mean ensemble track (AEMN) for forecasting and no data assimilation, the proposed algorithm exhibited positive forecast skill for more than 290 test cases over forecast periods spanning 6-48 h. The skill is seen to improve with lengthening forecast periods, with five test cases showing greater than 75% skill for a forecast period of 6 h to 247 test cases for the forecast period of 48 h.