As remote sensing measures, satellite imagery has played an essential role in verifying nuclear activities for decades. Starting with the first artificial satellite, Sputnik 1, in 1957, thousands of satellites are currently missioning in space. Since the 2000s, the level of detail in pixels of an image (spatial resolution) has been significantly improving, thereby identifying objects less than one meter, even tens of centimetres. The more things are identifiable, the wider regions become targets for observation. With the increasing number of satellites, computer vision technology is required to explore the applicability of algorithm-based automation. This paper aims to investigate the R&D publications worldwide from the 1990s to the present, which have tried to apply algorithms to verify any clandestine nuclear activities or detect anomalies at the site. The versatile open-source publications, including the IAEA, ESARDA, US-DOE national laboratories, and universities, are extensively reviewed from the perspective of nuclear nonproliferation (or counter-proliferation). Thus, target objects for applications are essentially located in nuclearrelated sites, and the source type of satellite sensors focuses on electro-optical images with high spatial resolution. The research trend over time by groups is discussed with limitations at the time in order to contemplate the role of algorithms in the field and to present recommendations on a way forward.

Satellite-derived sea surface winds (SSWs) and atmospheric motion vectors (AMVs) over the global ocean, particularly including the areas in and around tropical cyclones (TCs), have been provided in a real-time and continuous manner. More and better information is now derived from technologically improved multiple satellite missions and wind retrieving techniques. The status and prospects of key SSW products retrieved from scatterometers, passive microwave radiometers, synthetic aperture radar, and altimeters as well as AMVs derived by tracking features from multiple geostationary satellites are reviewed here. The quality and error characteristics, limitations, and challenges of satellite wind observations described in the literature, which need to be carefully considered to apply the observations for both operational and scientific uses, i.e., assimilation in numerical weather forecasting, are also described. Additionally, ongoing efforts toward merging them, particularly for monitoring three-dimensional TC wind fields in a real-time and continuous manner and for providing global profiles of high-quality wind observations with the new mission are introduced. Future research is recommended to develop plans for providing more and better SSW and AMV products in a real-time and continuous manner from existing and new missions.

The aim of this paper is to describe a strategy to provide improved accuracy of primary navigation parameters to the Indian regional Navigational satellites. The broadcast parameters of the Navic satellites can be classified under two category, one is the validity period of 7200s called long period normal sets and second one is the validity period of 900s called short period contingency sets of primary navigation parameters. The Navic satellite constellation works with minimum number of synchronous satellites to provide the best user solution within India and boundaries. Thus the outage of any one or more satellites will increase the Dilution of Precision (DOP) and degrades the user solution for any sudden anomalous behaviour of the measurements. This anomalous behaviour (called events) arises due to on-board frequency variations, frequent planned Station Keeping (SK) operations because of synchronous orbits, IRNSS system time scale switch-over or the combination of events. In loop back the broadcast parameters accuracy was continuously monitored through Line of Sight (LOS) range error from the observed IRNSS ground reference stations range measurements. In begin conditions the Least square (Lsq) based solutions were accurate and the observed LOS error were as expected. But post the occurrence of any event, the accumulation of batch data starts freshly for least square solution. The obtained Lsq based solution was inaccurate due to lack of data under many circumstances. During the events occurrence to minimize the outage duration of the satellite contingency sets were generated using continuously running Kalman Filter based near real time estimation using one-way measurements. But the filter estimated state may not be optimum at the particular epoch. Hence a strategy of forward and backward approach (FBF) was adopted just before parameter uplink through sequential (KF) for adaptation of real behaviours of the measurements to providing an improved optimal solution.

In the satellite operation phase, a ground station should continuously monitor the status of the satellite and sends out a tasking order, and a satellite should transmit data acquired in the space to the Earth. Therefore, the communication between the satellites and the ground stations is essential. However, a satellite and a ground station located in a specific region on Earth can be connected for a limited time because the satellite is continuously orbiting the Earth, and the communication between satellites and ground stations is only possible on a one-to-one basis. That is, one satellite can not communicate with plural ground stations, and one ground station can communicate with plural satellites concurrently. For such reasons, the efficiency of the communication schedule directly affects the utilization of the satellites. Thus, in this research, considering aforementioned unique situations of spacial communication, the mixed integer programming (MIP) model for the optimal communication planning between multiple satellites and multiple ground stations (MS-MG) is proposed. Furthermore, some numerical experiments are performed to verify and validate the mathematical model. The practical example for them is constructed based on the information of existing satellites and ground stations. The communicable time slots between them were obtained by STK (System Tool Kit), which is a well known professional software for space flight simulation. In the MIP model for the MS-MG problems, the objective function is also considered the minimization of communication cost, and ILOG CPLEX software searches the optimal schedule. Furthermore, it is confirmed that this study can be applied to the location selection of the ground stations.

In general, the design concepts of earth-observation satellites are established depending on the purposes of utilization such as commercial imagery business, public services, scientific research. Nowadays, The lightweight satellite structure is considered as an effective method for developing the earth-observation satellite. This paper introduces a design concept of the lightweight satellite structure for the constellation of earth-observation satellites. The modular design of the satellite structure is applied to save manpower and shorten the AIT process, in addition, a propulsion module is adopted to allow a hydrazine propulsion system to be installed on the satellite. The finite element method is used for the structural analysis of the satellite. The axial and lateral frequency requirements of satellite structure were verified by mode analysis. also, the margin of safety of satellite structure parts were satisfied with design requirements. As a result, the structural integrity of the suggested satellite structure is verified by mode analysis and static analysis.

We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.

We show that spacing patterns of planets and satellites in the solar system are formulatable in a single form. It is suggested that a possible explanation for the rule might be the orbital resonance effect, which has existed at an earlier epoch of the solar (planet) system. By extrapolating the formulated spacing patterns beyond the sun-Pluto distance, we find the sun-Planet X distance falls in a range ( 46 ∼ 79 ) A. U..

The origin of five small satellites (1980 S1, 1980 S3, 1980 S26, 1980 S27 and 1980 S28) and F-ring of Saturn which were recently discovered inside the orbit of Mimas, is proposed in terms of the resonant effects by external satellites in the Saturnian primordial extended ring. From the calculations of resonance locations and strengths, the following conclusion could be derived. Assuming that present two objects 1980 S1 and 1980 S3 were originally a single object 1980 S1+S3, 1980 S1+S3 had been formed due to Enceladus' 2/1 resonance and 1980 S26 due to Mimas' 3/2 resonance at first and then 1980 S28. 1980 S27 and F-ring were formed in the next due to 1980 S1+S3's 8/7, 9/8 and 10/9 resonances, respectively.

GLONASS, a satellite navigation system developed in Russia since 1976, is defunct and orbits in an unstable attitude. The satellites in these problems are not managed and there is no precise information, which can increase the risk of collisions with other space objects. In this study, detailed attitude dynamic have to be analyzed through photometry data, which requires spin period and spin axis. The light curve data is obtained by observing through the photometer at the Graz station and the power spectrum is calculated to obtain the cycle of the satellite. The geometric relationship between observer and sun is analyzed for GLONASS-50 satellite. The box-wing model is applied to obtain the phase reflection of the satellite and obtain the Irradiation of the satellite through this information. In Light Curve and Irradiation, the spin axis is calculated for each peak points with the distance square minimum technique. The spin axis of the GLONASS-50 satellite is RA = 116°, Dec = 92°.

The Optical Wide-field patroL-Network (OWL-Net) is a Korean optical space surveillance system used to track and monitor objects in space. In this study, the characteristics of four Initial Orbit Determination (IOD) methods were analyzed using artificial observational data from Low Earth Orbit satellites, and an appropriate IOD method was selected for use as the initial value of Precise Orbit Determination using OWL-Net data. Various simulations were performed according to the properties of observational data, such as noise level and observational time interval, to confirm the characteristics of the IOD methods. The IOD results produced via the OWL-Net observational data were then compared with Two Line Elements data to verify the accuracy of each IOD method. This paper, thus, suggests the best method for IOD, according to the properties of angles-only data, for use even when the ephemeris of a satellite is unknown.

El Niño is the largest fluctuation in the climate system, and it can lead to effects influencing humans all over the world. An El Niño occurs when sea surface temperatures in the central and eastern tropical Pacific Ocean become substantially higher than average. We investigated the change in sea surface temperature in the Pacific Ocean during the El Niño period of 2015 and 2016 using the advanced very-high-resolution radiometer (AVHRR) of NOAA Satellites. We calculated anomalies of the Pacific equatorial sea surface temperature for the normal period of 1981–2010 to identify the variation of the 2015 El Niño and warm water area. Generally, the warm water in the western tropical Pacific Ocean shifts eastward along the equator toward the coast of South America during an El Niño period. However, we identified an additional warm water region in the Niño 1+2 and Peru coastal area. This indicates that there are other factors that increase the sea surface temperature. In the future, we will study the heat coming from the bottom of the sea to understand the origin of the heat transport of the Pacific Ocean.