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Currently, China has 32 Earth observation satellites in orbit. The satellites can provide various data such as optical, multispectral, infrared, and radar. The spatial resolution of China Earth observation satellites ranges from low to medium to high. The satellites possess the capability to observe across multiple spectral bands, under all weather conditions, and at all times. The data of China Earth observation satellites has been widely used in fields such as natural resource detection, environmental monitoring and protection, disaster prevention and reduction, urban planning and mapping, agricultural and forestry surveys, land survey and geological prospecting, and ocean forecasting, achieving huge social benefits. This article introduces the recent progress of Earth observation satellites in China since 2022, especially the satellite operation, data archiving, data distribution and data coverage.

Korea Aerospace Research Institute (KARI) is conducting continuous quality control to provide reliable optical image products to various users. This paper describes KOrea Multi-Purpose SATellites (KOMPSAT-3 and KOMPSAT-3A) characteristics, operation, and image collection mode in order to enhance satellite image application. Also, image product of the satellites and quality management of the image product are described in this paper. The KOMPSAT-3 launched in 2012 and KOMPSAT-3A launched in 2015 collected many imageries around the world and provide them to users through web. Users can search for images through web catalog and order new imaging task. The KOMPSAT images provided under the KARI control is expected to be great help for earth observation and satellite image application enhancement.

The Korea Aerospace Research Institute is conducting continuous quality management to provide reliable Kompsat-5 SAR image products to users. In this paper, the Kompsat-5 satellite operation, data processing, quality management, and data provision were described. The operation and image mode characteristics of the Kompsat-5 satellite from the image point of view were described, and the classification and characteristics of image products provided to users were explained. In addition, image data acquisition, quality index measurement, and its results are described for quality management of SAR images. Finally, it explains how to search for and order Kompsat image product through the ARIRANG system to quickly provide users with image products whose quality has been confirmed through quality management. Kompsat product can be searched and ordered from the ARIRANG Satellite Search and Order System (https://ksatdb.kari.re.kr/arirang/).

ITF-2 is the second CubeSat developed by University of Tsukuba YUI project. It took over ITF-1’s missions (building of a global YUI network, demonstrative experiment of an ultra-small antenna originally developed and a new microcontroller) and its system was designed based on ITF-1. The operation of ITF-2 started right after its release from the Japanese Experiment Module named Kibo attached to the International Space Station on January 16, 2017 and continued until its atmospheric re-entry on January 5, 2019. The Tsukuba ground station conducted more than 1000 operations over one and a half year and acquired considerable data. In addition, we received over 2100 signal reception reports from over 20 countries. In this study, we analyze the data accumulated throughout the operation and evaluate the missions. [ABSTRACT FROM AUTHOR]

In the operation of artificial satellites, it is very important to monitor the health status of the systems and detect any symptoms of anomalies in the housekeeping data as soon as possible. Recently, the data-driven approach to the system monitoring problem, in which statistical machine learning techniques are applied to the large amount of measurement data collected in the past, has attracted considerable attention. In this paper, we propose a new data-driven health monitoring and anomaly detection method for artificial satellites based on probabilistic dimensionality reduction and clustering, taking into consideration the miscellaneous characteristics of the spacecraft housekeeping data. We applied our method to the telemetry data of the small demonstration satellite 4 (SDS-4) of the Japan Aerospace Exploration Agency (JAXA) and evaluated its effectiveness. The results show that the proposed system provides satellite operators with valuable information for understanding the health status of the system and inferring the causes of anomalies. [ABSTRACT FROM PUBLISHER]

Modulation Transfer Function (MTF) of satellite image is an important performance index in satellite image applications. Therefore MTF performance is assessed using satellite image for the ground target during LEOP phase after launch. But the MTF performance assessment using the ground target can be affected by imaging conditions such as cloud and weather. In this paper system requirements and satellite operation for assessing MTF performance of satellite image using stellar sources are proposed. Satellite capability in collecting stellar sources using the satellite which is designed for earth observation and satellite image usefulness for assessing MTF performances were analyzed. The proposed approach will be useful to assess MTF performance of earth observation satellite in lower earth orbit.

We present a large family of knots for which the Rasmussen -invariants of arbitrary satellites do not detect sliceness. This answers a question of Hedden. The proof hinges on work of Kronheimer-Mrowka and Cochran-Harvey-Horn. [ABSTRACT FROM AUTHOR]

Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently, the separation strategies are adopted to safeguard the satellites collocated of leaving the relative distance beyond collision with different sets of orbit parameters. This paper presents the mathematical prototypes which establish the allowable relative distance with uncertainty of orbital determination (OD), as well as the orbital element offset for each pair of collocated satellites, and puts forward algorithms to build such relationship to face the challenge of putting three satellites sharing the same position, the algorithms to allocate the longitude, eccentricity and inclination for each satellite are also given to ascertain that the mathematical prototypes are the guide specification to design collocation strategy for geostationary satellites. [ABSTRACT FROM AUTHOR]

Abstract: The first Korean multi-mission geostationary Earth orbit satellite, Communications, Ocean, and Meteorological Satellite (COMS) was launched by an Ariane 5 launch vehicle in June 26, 2010. The COMS satellite has three payloads including Ka-band communications, Geostationary Ocean Color Imager, and Meteorological Imager. Although the COMS spacecraft bus is based on the Astrium Eurostar 3000 series, it has only one solar array to the south panel because all of the imaging sensors are located on the north panel. In order to maintain the spacecraft attitude with 5 wheels and 7 thrusters, COMS should perform twice a day wheel off-loading thruster firing operations, which affect on the satellite orbit. COMS flight dynamics system provides the general on-station functions such as orbit determination, orbit prediction, event prediction, station-keeping maneuver planning, station-relocation maneuver planning, and fuel accounting. All orbit related functions in flight dynamics system consider the orbital perturbations due to wheel off-loading operations. There are some specific flight dynamics functions to operate the spacecraft bus such as wheel off-loading management, oscillator updating management, and on-station attitude reacquisition management. In this paper, the design and implementation of the COMS flight dynamics system is presented. An object oriented analysis and design methodology is applied to the flight dynamics system design. Programming language C# within Microsoft .NET framework is used for the implementation of COMS flight dynamics system on Windows based personal computer. [Copyright &y& Elsevier]