scholarly journals Orbital Perigee Deviation under Inclination Window for Sun Synchronized Low Earth Orbits

2019 ◽  
Vol 4 (10) ◽  
pp. 127-130
Author(s):  
Shkelzen Cakaj ◽  
Bexhet Kamo
Keyword(s):  
Orbital Plane ◽  
Earth Observation ◽  
Gas Content ◽  
The Sun ◽  
Orbital Inclination ◽  
The Earth ◽  
Low Earth Orbits ◽  
Earth Observation Satellites ◽  
Earth Orbits ◽  
Earth’S Oblateness

Data processing related to the Earth’s changes, gathered from different platforms and sensors implemented worldwide and monitoring the environment and structure represents Earth observation (EO). Environmental monitoring includes changes in Earth’s vegetation, atmospheric gas content, ocean state, melting level in the ice fields, etc. This process is mainly performed by satellites. The Earth observation satellites use Low Earth Orbits (LEO) for their missions. These missions are accomplished mainly based on photo imagery. Thus, the relative Sun’s position related to the observed area, it is very important for the photo imagery, in order the observed area from the satellite to be treated under the same lighting (illumination) conditions. This could be achieved by keeping a constant Sun position related to the orbital plane due to the Earth’s motion around the Sun. This is called Sun synchronization for low Earth orbits, the feature which is applied for satellites dedicated for the Earth observation. Nodal regression is the phenomenon which is utilized for low circular orbits providing to them the Sun synchronization. Nodal regression refers to the shift of the orbit’s line of nodes over time as Earth revolves around the Sun,  caused due to the Earth’s oblateness. Nodal regression depends on orbital altitude and orbital inclination angle. For the in advance defined range of altitudes stems the inclination window for the satellite low Earth orbits to be Sun synchronized. For analytical and simulation purposes, the altitudes from 600km to 1200km are considered. Further for the determined inclination window of the Sun synchronization it is simulated the orbital perigee deviation for the above considered altitudes and the eventual impact on the satellite’s mission.

scholarly journals Earth’s albedo time series reveals low radiative energy input in December 2020

2021 ◽  
Author(s):  
Antti Penttilä ◽  
Karri Muinonen ◽  
Olli Ihalainen ◽  
Elizaveta Uvarova ◽  
Mikko Vuori ◽  
...  
Keyword(s):  
Time Series ◽  
Time Series Data ◽  
Radiative Energy ◽  
Series Data ◽  
Radiation Balance ◽  
The Sun ◽  
The Earth ◽  
Important Input ◽  
Low Earth Orbits ◽  
Earth Orbits

Abstract The Earth’s spherical albedo describes the ratio of light reflected from the Earth to that incident from the Sun, an important input variable for the Earth’s radiation balance. The spherical albedo has been previously estimated from satellites in low-Earth orbits, and from light reflected from the Moon. However, neither of these methods can produce continuous time series of the entire planet. We developed a global method to derive the Earth’s spherical albedo using the images from the Earth Polychromatic Imaging Camera (EPIC) on board NOAA’s Deep Space Climate Observatory (DSCOVR). The satellite is located in the Lagrange 1 point between the Earth and the Sun and observes the complete illuminated part of the Earth at once. The method allows us to provide continuously updated spherical albedo time series data starting from 2015. This time series shows a systematic seasonal variation with the mean annual albedo estimated as 0.295±0.008 and an exceptional albedo maximum in 2020, attributed to unusually abundant cloudiness over the Southern Oceans.

scholarly journals The Inclination Window for Low Earth Sun Synchronized Satellite Orbits

2013 ◽  
Vol 2 (1) ◽  
pp. 15-19
Author(s):  
Shkelzen Cakaj ◽  
Bexhet Kamo ◽  
Krešimir Malarić
Keyword(s):  
Orbital Plane ◽  
Low Earth Orbit ◽  
Satellite Orbits ◽  
Observation Data ◽  
The Sun ◽  
Orbital Inclination ◽  
Continuous Coverage ◽  
Lighting Conditions ◽  
Earth’S Oblateness ◽  
Over Time

LEO (Low Earth Orbit) environmental satellites provide continuous coverage of Earth, supplying meteorological and oceanic observation data which are important in aerospace and maritime. The missions of such satellites are mainly based on photo imagery. For photo imagery, it is also important that the area observed from the satellite is treated under the same lighting conditions. This can be achieved by keeping the orbital plane position constant relative to the Sun due to the Earth’s motion around the Sun, defined as orbital Sun synchronization. The line of nodes defines the orientation of the satellite’s orbital plane in space. Nodal regression is defined as the shift of the orbit’s line of nodes over time, as Earth revolves around the Sun. Nodal regression is caused by the Earth’s oblateness. Nodal regression is a very useful feature, especially used to synchronize low Earth circular orbits with the Sun. Nodal regression depends on orbital attitude and orbital inclination angle. This paper provides an inclination window calculation for different attitudes in order to maintain orbital Sun synchronization.

scholarly journals The motion of a geosynchronous satellite

1986 ◽  
Vol 114 ◽  
pp. 293-295
Author(s):  
K. B. Bhatnagar
Keyword(s):  
Angular Velocity ◽  
Solar Radiation ◽  
Radiation Pressure ◽  
Angular Position ◽  
Orbital Plane ◽  
Solar Radiation Pressure ◽  
Orbital Inclination ◽  
Geosynchronous Satellite ◽  
The Earth ◽  
Earth’S Equatorial Ellipticity

The motion of a geosynchronous satellite has been studied under the combined gravitational effects of the oblate Earth (including its equatorial ellipticity), the Sun, the Moon and the solar-radiation pressure. It is observed that the orbital plane rotates with an angular velocity the maximum value of which is 0.058°/yr. and regresses with a period which increases both as the orbital inclination and the altitude increase. The effect of earth's equatorial ellipticity on the regression period is oscillatory whereas that of Solar-radiation pressure is to decrease it.The synchronism is achieved when the angular velocity of the satellite is equal to the difference between the spin-rate of the Earth and the regression rate of the orbital plane. With this angular velocity of the satellite, the ground trace is in the shape of figure eight, though its size and position relative to the Earth change as the time elapses. The major effect of earth's equatorial ellipticity is to produce a change in the relative angular position of the satellite as seen from the Earth. If the satellite is allowed to execute large angle oscillations the mid-point of oscillation would be at the position of the minor axis of the earth's equatorial section. The oscillatory period T has been determined in terms of the amplitude Γ and the tesseral harmonic J2(2). From this result we can determine the value of J2(2) as T and Γ can be observed accurately.

scholarly journals Resonant Orbital Dynamics in LEO Region: Space Debris in Focus

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
J. C. Sampaio ◽  
E. Wnuk ◽  
R. Vilhena de Moraes ◽  
S. S. Fernandes
Keyword(s):  
Collision Avoidance ◽  
Frequency Analysis ◽  
Space Debris ◽  
Semimajor Axis ◽  
Orbital Dynamics ◽  
Accurate Information ◽  
The Earth ◽  
Low Earth Orbits ◽  
Line Elements ◽  
Earth Orbits

The increasing number of objects orbiting the earth justifies the great attention and interest in the observation, spacecraft protection, and collision avoidance. These studies involve different disturbances and resonances in the orbital motions of these objects distributed by the distinct altitudes. In this work, objects in resonant orbital motions are studied in low earth orbits. Using the two-line elements (TLE) of the NORAD, resonant angles and resonant periods associated with real motions are described, providing more accurate information to develop an analytical model that describes a certain resonance. The time behaviors of the semimajor axis, eccentricity, and inclination of some space debris are studied. Possible irregular motions are observed by the frequency analysis and by the presence of different resonant angles describing the orbital dynamics of these objects.

scholarly journals Detailled Study of The Dynamics of Fragments of Comet C/1996 B2 Hyakutake

1999 ◽  
Vol 172 ◽  
pp. 373-374
Author(s):  
E. Desvoivres ◽  
J. Klinger ◽  
A.C. Levasseur-Regourd
Keyword(s):  
Center Of Mass ◽  
Orbital Plane ◽  
Close Approach ◽  
The Sun ◽  
Keplerian Motion ◽  
Cometary Nuclei ◽  
Gravitational Forces ◽  
The Earth ◽  
Common Center ◽  
Loss Of Mass

The fragmentation of cometary nuclei is a frequent phenomenon, but the dynamics of the fragments is not yet well understood. During the close approach of comet C/1996 B2 Hyakutake to the Earth (0.1 AU) on late March 1996, images were taken with the 1 meter telescope of Pic du Midi observatory. Bright condensations were observed near the nucleus on images taken between March, 22,1996 and March, 31, 1996. It was suggested that these features were mini-comæ surrounding fragments receding from the nucleus (Lecacheux et al., 1996). A model was developped for the motion of cometary fragments in the orbital plane of the comet, and the simulations were compared with the observations (Desvoivres et al, 1998).In the model, we consider that the nucleus of the comet and a fragment are under the influence of the gravity of the Sun, of their mutual gravity, and of non-gravitational forces (NGF) due the loss of mass induced by solar heating. From an estimation of those NGF, we compute numerically the trajectories of the fragment and of the nucleus with respect to their common center of mass (CoM). Then, the motion of the center of mass is studied in an heliocentric reference frame using the theory of perturbed keplerian motion.

scholarly journals Potential of Virtual Earth Observation Constellations in Archaeological Research

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4066 ◽  
Author(s):  
Agapiou ◽  
Alexakis ◽  
Hadjimitsis
Keyword(s):  
Satellite Images ◽  
Earth Observation ◽  
Archaeological Research ◽  
Earth System ◽  
Ground Segment ◽  
The Earth ◽  
Integrated Optical ◽  
Earth Observation Satellites ◽  
The Impact ◽  
Research World

Earth observation sensors continually provide datasets with different spectral and spatial characteristics, while a series of pre- and postprocessing techniques are needed for calibration purposes. Nowadays, a variety of satellite images have become accessible to researchers, while big data cloud platforms allow them to deal with an extensive number of datasets. However, there is still difficulty related to these sensors meeting specific needs and challenges such as those of cultural heritage and supporting archaeological research world-wide. The harmonization and synergistic use of different sensors can be used in order to maximize the impact of earth observation sensors and enhance their benefit to the scientific community. In this direction, the Committee on Earth Observation Satellites (CEOS) has proposed the concept of virtual constellations, which is defined as “a coordinated set of space and/or ground segment capabilities from different partners that focuses on observing a particular parameter or set of parameters of the Earth system”. This paper provides an overview of existing and future earth observation sensors, the various levels of interoperability as proposed by Wulder et al., and presents some preliminary results from the Thessalian plain in Greece using integrated optical and radar Sentinel images. The potential for archaeolandscape studies using virtual constellations is discussed here.

Earth observation remote sensing for oil and gas: A new era

2021 ◽  
Vol 40 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Dominique Dubucq ◽  
Leo Turon ◽  
Benoit Blanco ◽  
Hélène Bideaud
Keyword(s):  
Oil And Gas ◽  
Gas Sensing ◽  
Oil And Gas Industry ◽  
Earth Observation ◽  
Gas Industry ◽  
New Era ◽  
Sensing Systems ◽  
The Earth ◽  
Earth Observation Satellites ◽  
New Sensors

In the last seven years, many earth observation satellites from national agencies and commercial providers have been launched, making huge volumes of data freely available to anyone. Open-access software and cloud computing tools also have been developed by the earth observation community. Those, as well as new sensors and vectors such as drone-borne hyperspectral cameras or gas-sensing systems are opening a number of applications for the oil and gas industry in exploration, production, and environmental monitoring.

scholarly journals Managing multiple satellite architectures by spatial grasp technology

2021 ◽  
Vol 1 ◽  
pp. 3-16
Author(s):  
P.S. Sapaty ◽  
Keyword(s):  
Strategic Defense Initiative ◽  
The Earth ◽  
Space Projects ◽  
Strategic Defense ◽  
Low Earth Orbits ◽  
Cruise Missiles ◽  
High Level ◽  
Space Architecture ◽  
And Control ◽  
Earth Orbits

The paper reviews some advanced space projects oriented on many satellites moving around the globe in low Earth orbits, and investigates how to organize their collective operation for solving important world problems, especially those related to global security and defense. It analyzes the application of the developed Spatial Grasp model and Technology (SGT), successfully tested on numerous applications, for simulation and management of multiple satellite architectures. Of particular interest is the latest Space Development Agency Next-Generation Space Architecture that uses a great number of cooperating satellites organized on different layers, which appears to be much more advanced than the known Strategic Defense Initiative project of the eighties. SGT is based on mobile recursive scenarios in a special high-level Spatial Grasp Language (SGL) which can self-navigate and self-match distributed environments while leaving throughout them powerful spatial infrastructures capable of solving any distributed problems. Providing basics of the latest SGT version, the paper describes examples of solutions in it of such problems as distributed tracing and elimination of complexly moving cruise missiles and hypersonic gliders, organization of effective custody layer which will be able to observe not only localized dangerous objects on the Earth but also any distributed terrestrial infrastructures as a whole. It also shows how to introduce a higher virtual layer for satellite constellation which may simplify formulation and solution of many problems in both terrestrial and celestial environments, including advanced command and control of complex national and international operations and campaigns from space.

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