scholarly journals Cloud Detection Over Sunglint Regions With Observations From the Earth Polychromatic Imaging Camera

2021 ◽  
Vol 2 ◽  
Author(s):  
Yaping Zhou ◽  
Yuekui Yang ◽  
Peng-Wang Zhai ◽  
Meng Gao
Keyword(s):  
False Positive Rate ◽  
Early Morning ◽  
Low Earth Orbit ◽  
Global Ocean ◽  
Earth Orbit ◽  
Cloud Detection ◽  
Band Ratio ◽  
The Earth ◽  
Positive Rate ◽  
Daily Variability

With the ability to observe the entire sunlit side of the Earth, EPIC data have become an important resource for studying cloud daily variability. Inaccurate cloud masking is a great source of uncertainty. One main region that is prone to error in cloud masking is the sunglint area over ocean surfaces. Cloud detection over these regions is challenging for the EPIC instrument because of its limited spectral channels. Clear sky ocean surface reflectance from visible channels over sunglint is much larger than that over the non-glint areas and can exceed reflectance from thin clouds. This paper presents an improved EPIC ocean cloud masking algorithm (Version 3). Over sunglint regions (glint angle ≤25°), the algorithm utilizes EPIC’s oxygen (O2) A-band ratio (764/780 nm) in addition to the 780 nm reflectance observations in masking tests. Outside the sunglint regions, a dynamic reflectance threshold for the Rayleigh corrected 780 nm reflectance is applied. The thresholds are derived as a function of glint angle. When compared with co-located data from the geosynchronous Earth orbit (GEO) and the low Earth orbit (LEO) observations, the consistency of the new ocean cloud mask algorithm has increased by 4∼10% and 4∼6% in the glint center and granule edges respectively. The false positive rate is reduced by 10∼17%. Overall global ocean cloud detection consistency increases by 2%. This algorithm, along with other improvements to the EPIC cloud masks, has been implemented in the EPIC cloud products Version 3. This algorithm will improve the cloud daily variability analysis by removing the artificial peak at local noon time in the glint center latitudes and reducing biases in the early morning and late afternoon cloud fraction over ocean surfaces.

scholarly journals Cloud Detection of SuperView-1 Remote Sensing Images Based on Genetic Reinforcement Learning

2020 ◽  
Vol 12 (19) ◽  
pp. 3190
Author(s):  
Xiaolong Li ◽  
Hong Zheng ◽  
Chuanzhao Han ◽  
Haibo Wang ◽  
Kaihan Dong ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Reinforcement Learning ◽  
False Positive Rate ◽  
Optical Remote Sensing ◽  
Cloud Detection ◽  
Remote Sensing Images ◽  
Threshold Method ◽  
Data Set ◽  
Action Strategy ◽  
Positive Rate

Cloud pixels have massively reduced the utilization of optical remote sensing images, highlighting the importance of cloud detection. According to the current remote sensing literature, methods such as the threshold method, statistical method and deep learning (DL) have been applied in cloud detection tasks. As some cloud areas are translucent, areas blurred by these clouds still retain some ground feature information, which blurs the spectral or spatial characteristics of these areas, leading to difficulty in accurate detection of cloud areas by existing methods. To solve the problem, this study presents a cloud detection method based on genetic reinforcement learning. Firstly, the factors that directly affect the classification of pixels in remote sensing images are analyzed, and the concept of pixel environmental state (PES) is proposed. Then, PES information and the algorithm’s marking action are integrated into the “PES-action” data set. Subsequently, the rule of “reward–penalty” is introduced and the “PES-action” strategy with the highest cumulative return is learned by a genetic algorithm (GA). Clouds can be detected accurately through the learned “PES-action” strategy. By virtue of the strong adaptability of reinforcement learning (RL) to the environment and the global optimization ability of the GA, cloud regions are detected accurately. In the experiment, multi-spectral remote sensing images of SuperView-1 were collected to build the data set, which was finally accurately detected. The overall accuracy (OA) of the proposed method on the test set reached 97.15%, and satisfactory cloud masks were obtained. Compared with the best DL method disclosed and the random forest (RF) method, the proposed method is superior in precision, recall, false positive rate (FPR) and OA for the detection of clouds. This study aims to improve the detection of cloud regions, providing a reference for researchers interested in cloud detection of remote sensing images.

scholarly journals Combustion Synthesis Technology for a Sustainable Settlement Overnight

2018 ◽  
Vol 20 (1) ◽  
pp. 3
Author(s):  
Osamu Odawara
Keyword(s):  
Combustion Synthesis ◽  
Resource Utilization ◽  
High Vacuum ◽  
Thermal Control ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
The Moon ◽  
The Earth

Space technology has been developed for frontier exploration not only in low-earth orbit environment but also beyond the earth orbit to the Moon and Mars, where material resources might be strongly restricted and almost impossible to be resupplied from the earth for distant and long-term missions performance toward “long-stays of humans in space”. For performing such long-term space explorations, none would be enough to develop technologies with resources only from the earth; it should be required to utilize resources on other places with different nature of the earth, i.e., in-situ resource utilization. One of important challenges of lunar in-situ resource utilization is thermal control of spacecraft on lunar surface for long-lunar durations. Such thermal control under “long-term field operation” would be solved by “thermal wadis” studied as a part of sustainable researches on overnight survivals such as lunar-night. The resources such as metal oxides that exist on planets or satellites could be refined, and utilized as a supply of heat energy, where combustion synthesis can stand as a hopeful technology for such requirements. The combustion synthesis technology is mainly characterized with generation of high-temperature, spontaneous propagation of reaction, rapid synthesis and high operability under various influences with centrifugal-force, low-gravity and high vacuum. These concepts, technologies and hardware would be applicable to both the Moon and Mars, and these capabilities might achieve the maximum benefits of in-situ resource utilization with the aid of combustion synthesis applications. The present paper mainly concerns the combustion synthesis technologies for sustainable lunar overnight survivals by focusing on “potential precursor synthesis and formation”, “in-situ resource utilization in extreme environments” and “exergy loss minimization with efficient energy conversion”.

Geomagnetic field mapping

2020 ◽  
Vol 1 (1) ◽  
pp. 22-29
Author(s):  
Jan Jurica
Keyword(s):  
Solar Flares ◽  
Geomagnetic Field ◽  
Cosmic Radiation ◽  
Measured Data ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Magnetic Pole ◽  
The Earth ◽  
North Magnetic Pole ◽  
Time Periods

This work focuses on creating maps of the geomagnetic field and areas of increased cosmic radiation surrounding the Earth. Data were measured by Proba-V satellite at Low-Earth orbit 820 kilometres above the Earth during 2015. The actual measured data were compared with the calculated magnetic values. The created maps serve to a better understanding of the shape of the geomagnetic field and show magnetic equator, north magnetic pole and more. The map confirms that the area of the South Atlantic Anomaly corresponds with the weakest area of the geomagnetic field. Maps of different time periods of 2015 show small changes in the shape of the geomagnetic field during a year. Increased attention was paid to June 2015, when solar flares were passing near the Earth. The observation confirms that solar flares have a significant effect on the shape of the geomagnetic field.

scholarly journals A Micromachined Earth Sensor Based on Measuring the Gravity Gradient Torque

2009 ◽  
Author(s):  
K. Ghose ◽  
H. R. Shea
Keyword(s):  
Proof Mass ◽  
Inertial Sensor ◽  
Low Earth Orbit ◽  
Relative Orientation ◽  
Gravity Gradient ◽  
Earth Orbit ◽  
Optical Access ◽  
The Earth ◽  
Ir Emission

We present the fabrication and testing of a novel MEMS inertial sensor that directly measures the gravity gradient in low Earth orbit in order to sense the relative orientation of a satellite with respect to the Earth. Instead of the current Earth sensing methods that determine the Earth vector by sensing the Earth’s IR emission, we present a much lighter and more compact MEMS-based approach that determine the Earth vector by measuring the Gravity Gradient Torque on an elongated silicon proof mass. Current Earth sensors require optical access on multiple faces of the satellite. This MEMS-based approach does not require optical access.

Orbit Design and Simulation for Kufasat Nanosatellite

2015 ◽  
Vol 50 (4) ◽  
pp. 157-168 ◽  
Author(s):  
Mohammed Chessab Mahdi
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit ◽  
Analysis Tool ◽  
Solar Panels ◽  
Orbit Design ◽  
Polar Orbit ◽  
Mission Analysis ◽  
The Earth ◽  
General Mission Analysis Tool

Abstract Orbit design for KufaSat Nano-satellites is presented. Polar orbit is selected for the KufaSat mission. The orbit was designed with an Inclination which enables the satellite to see every part of the earth. KufaSat has a payload for imaging purposes which require a large amount of power, so the orbit is determined to be sun synchronous in order to provide the power through solar panels. The KufaSat mission is designed for the low earth orbit. The six initial Keplerian Elements of KufaSat are calculated. The orbit design of KufaSat according to the calculated Keplerian elements has been simulated and analyzed by using MATLAB first and then by using General Mission Analysis Tool.

scholarly journals Hue–saturation–intensity and texture feature-based cloud detection algorithm for unmanned aerial vehicle images

2020 ◽  
Vol 17 (3) ◽  
pp. 172988142090353
Author(s):  
Wang Yi ◽  
Zhang Jing ◽  
Gao Shuang
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Target Identification ◽  
False Positive Rate ◽  
Texture Feature ◽  
Detection Algorithm ◽  
Cloud Detection ◽  
Detection Algorithms ◽  
Saturation Intensity ◽  
Positive Rate ◽  
Aerial Vehicle

There are a large number of cloud-covered areas in most unmanned aerial vehicle images and lead to the loss of information in the image and affect image post procession such as image fusion and target identification. Finding the cloud-occluded area in an image is a key step in image processing. Based on the differences of color and texture characteristics between cloud and ground, a cloud detection algorithm for the unmanned aerial vehicle images is proposed. Simulation results show that the proposed algorithm is better than the classical cloud detection algorithms in accuracy rate, false-positive rate, and kappa coefficient.

The Holographic Solar Photon Thruster (SPT) : A Low-Earth Orbit Solar Sail

Solar Energy ◽  
2003 ◽  
Author(s):  
Gregory L. Matloff
Keyword(s):  
Solar Sail ◽  
Low Earth Orbit ◽  
Back Pressure ◽  
Orbital Energy ◽  
Earth Orbit ◽  
Atmospheric Drag ◽  
Net Radiation ◽  
Solar Sails ◽  
The Earth ◽  
Fixed Orientation

Atmospheric drag limits most solar sails to altitudes>1000 km. A two-sail variant, the Solar-Photon Thruster (SPT) , could be used in Low-Earth Orbit (LEO). An SPT has a fixed-orientation collector sail that focuses light against a smaller, adjustable thruster sail. Maintaining the collector surface parallel to the Earth minimizes SPT drag in LEO. To minimize solar-radiation back pressure towards Earth, the upper collector surface is non-reflective. The reflective lower collector surface directs light reflected and reradiated from the Earth against the thruster. Thruster orientation is adjusted in LEO to increase the orbital energy by the net radiation-pressure. Experiments reveal that holograms are tolerant to solar-wind radiation. SPTs with white-light holographic thrusters are useful in LEO because small thruster rotations produce greatly altered reflectivity. It may be possible to holographically combine SPT collector and thruster.

scholarly journals Cloud detection over snow and ice with oxygen A- and B-band observations from the Earth Polychromatic Imaging Camera (EPIC)

2020 ◽  
Vol 13 (3) ◽  
pp. 1575-1591
Author(s):  
Yaping Zhou ◽  
Yuekui Yang ◽  
Meng Gao ◽  
Peng-Wang Zhai
Keyword(s):  
Detection Rate ◽  
Oxygen Absorption ◽  
Earth Orbit ◽  
Transfer Model ◽  
Cloud Detection ◽  
The Earth ◽  
Imaging Camera ◽  
Ice Surfaces ◽  
Cloud Mask ◽  
Snow And Ice

Abstract. Satellite cloud detection over snow and ice has been difficult for passive remote sensing instruments due to the lack of contrast between clouds and cold/bright surfaces; cloud mask algorithms often heavily rely on shortwave infrared (IR) channels over such surfaces. The Earth Polychromatic Imaging Camera (EPIC) on board the Deep Space Climate Observatory (DSCOVR) does not have infrared channels, which makes cloud detection over snow and ice surfaces even more challenging. This study investigates the methodology of applying EPIC's two oxygen absorption band pair ratios in the A band (764, 780 nm) and B band (688, 680 nm) for cloud detection over the snow and ice surfaces. We develop a novel elevation and zenith-angle-dependent threshold scheme based on radiative transfer model simulations that achieves significant improvements over the existing algorithm. When compared against a composite cloud mask based on geosynchronous Earth orbit (GEO) and low Earth orbit (LEO) sensors, the positive detection rate over snow and ice surfaces increased from around 36 % to 65 % while the false detection rate dropped from 50 % to 10 % for observations of January 2016 and 2017. The improvement in July is less substantial due to relatively better performance in the current algorithm. The new algorithm is applicable for all snow and ice surfaces including Antarctic, sea ice, high-latitude snow, and high-altitude glacier regions. This method is less reliable when clouds are optically thin or below 3 km because the sensitivity is low in oxygen band ratios for these cases.

scholarly journals Cloud Products from the Earth Polychromatic Imaging Camera (EPIC): Algorithms and Initial Evaluaiton

2018 ◽  
Author(s):  
Yuekui Yang ◽  
Kerry Meyer ◽  
Galina Wind ◽  
Yaping Zhou ◽  
Alexander Marshak ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Single Channel ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Effective Pressure ◽  
Threshold Method ◽  
Science Data ◽  
The Earth ◽  
Cloud Optical Thickness ◽  
Cloud Mask

Abstract. This paper presents the physical basis of the EPIC cloud product algorithms and an initial evaluation of their performance. Since June 2015, EPIC has been providing observations of the sunlit side of the Earth with its 10 spectral channels ranging from the UV to the near-IR. A suite of algorithms has been developed to generate the standard EPIC Level 2 Cloud Products that include cloud mask, cloud effective pressure/height, cloud optical thickness, etc. The EPIC cloud mask adopts the threshold method and utilizes multichannel observations and ratios as tests. Cloud effective pressure/height is derived with observations from the O2 A-band (780 nm and 764 nm), and B-band (680 nm and 688 nm) pairs. The EPIC cloud optical thickness retrieval adopts a single channel approach where the 780 nm and 680 nm channels are used for retrievals over ocean and over land, respectively. Comparison with co-located cloud retrievals from geosynchronous earth orbit (GEO) and low earth orbit (LEO) satellites shows that the EPIC cloud product algorithms are performing well and are consistent with theoretical expectations. These products are publicly available at the Atmospheric Science Data Center at the NASA Langley Research Center for climate studies and for generating other geophysical products that require cloud properties as input.

GPS Receiver Demonstration on a Galileo Test Bed Satellite

2007 ◽  
Vol 60 (3) ◽  
pp. 349-362 ◽  
Author(s):  
Takuji Ebinuma ◽  
Martin Unwin
Keyword(s):  
Low Earth Orbit ◽  
The Other ◽  
Earth Orbit ◽  
Gps Receiver ◽  
Test Bed ◽  
Gps Receivers ◽  
Preliminary Results ◽  
The Earth ◽  
Gps Satellites ◽  
Leo Satellite

GPS receivers have been used successfully on low Earth orbit (LEO) satellite missions for several years. The use of a GPS receiver at altitudes higher than LEO, however, is non-trivial as the receiver will be outside the main lobe of the GPS broadcast signals, and it will have to track signals from GPS satellites transmitting from the other side of the Earth. This paper will review the special hardware and software adaptations required for GPS receiver operations on a medium Earth orbit or geostationary satellite, along with preliminary results from simulations and an in-orbit experiment.

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