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 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 Evolution of orbit and clock quality for real-time multi-GNSS solutions

GPS Solutions ◽  
2020 ◽  
Vol 24 (4) ◽  
Author(s):  
Kamil Kazmierski ◽  
Radoslaw Zajdel ◽  
Krzysztof Sośnica
Keyword(s):  
Real Time ◽  
Atomic Clock ◽  
Orbital Plane ◽  
Poor Quality ◽  
Satellite Orbits ◽  
High Quality ◽  
Changes Over Time ◽  
Over Time ◽  
Orbit Characteristics

Abstract High-quality satellite orbits and clocks are necessary for multi-GNSS precise point positioning and timing. In undifferenced GNSS solutions, the quality of orbit and clock products significantly influences the resulting position accuracy; therefore, for precise positioning in real time, the corrections for orbits and clocks are generated and distributed to users. In this research, we assess the quality and the availability of real-time CNES orbits and clocks for GPS, GLONASS, Galileo, and BeiDou-2 separated by satellite blocks and types, as well as the product quality changes over time. We calculate the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Moreover, we employ independent orbit validation based on satellite laser ranging. We found that the most accurate orbits are currently available for GPS. However, Galileo utmost stable atomic clocks compensate for systematic errors in Galileo orbits. As a result, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The GLONASS satellites, despite the high quality of their orbits, are characterized by poor quality of clocks, and together with BeiDou-2 in medium and geosynchronous inclined orbits, are characterized by SISRE of 4–6 cm. BeiDou-2 in geostationary orbits is characterized by large orbital errors and the lowest availability of real-time orbit and clock corrections due to a large number of satellite maneuvers. The quality of GNSS orbit and clock corrections changes over time and depends on satellite type, block, orbit characteristics, onboard atomic clock, and the sun elevation above the orbital plane.

The change in satellite orbital inclination due to a rotating oblate atmosphere with a diurnal variation in density

1983 ◽  
Vol 386 (1790) ◽  
pp. 55-75 ◽  
Keyword(s):  
Orbital Plane ◽  
Atmospheric Model ◽  
Scale Height ◽  
Satellite Orbits ◽  
Orbital Inclination ◽  
Small Eccentricity ◽  
Zonal Winds ◽  
Meridional Winds ◽  
Anomalistic Period ◽  
Density Scale

The effect of the motion of the upper atmosphere on satellite orbits of small eccentricity, e < 0.2, is considered. The atmospheric model allows for oblateness, and has a density profile that approximates to the observed day-to-night variation. The equations governing the changes due to zonal (west to east) and meridional (south to north) winds in the inclination of the orbital plane i during one anomalistic period of the satellite are integrated, with H , the density scale height, assumed to be constant. The resulting expressions for ∆ i w , due to zonal winds, and ∆ i ϕ , due to meridional winds, are given. Compact expressions for ∆ i and the ratio ∆ i /∆ T D , where ∆ T D is the corresponding change in orbital period, are given when H varies linearly with height. An equivalence between the variable- H equation and the constant- H equation is demonstrated for ∆ i w , when the value of H used in the latter is appropriately chosen. It is shown that there is no such equivalence for ∆ i ϕ and ∆ i /∆ T D .

Analysis of the impact of evolution of sun-synchronous orbits in terms of use of spacecraft for remote sensing of the Еarth

2018 ◽  
pp. 3-13
Author(s):  
V. M. Artyushenko ◽  
D. Y. Vinogradov
Keyword(s):  
Orbital Plane ◽  
Time Interval ◽  
The Sun ◽  
Initial Value ◽  
Lighting Conditions ◽  
Intended Purpose ◽  
Synchronous Orbit ◽  
The Impact ◽  
Local Average

The article gives a brief analysis of the influence of disturbing factors on the dynamics of the sun-synchronous orbit. It is shown that the result of the displacement of the local average solar time from the initial value, the usage time of the spacecraft for its intended purpose is greatly reduced. The long term existence of the spacecraft to ensure that minimal changes in the lighting conditions of the route of flight is possible in two ways. The first is due to the periodic adjustments of the inclination of the plane of the sun-synchronous orbit and maintaining medium honeycomb orbit. Second – due to the choice, formation and maintenance of sustainable, sun-synchronous orbit, which provides a maximum time interval of use of the spacecraft for its intended purpose without carrying out the correction of the inclination of the orbital plane. 

Could future COP talks help to de-junk near-earth space?

Soundings ◽  
2021 ◽  
Vol 78 (78) ◽  
pp. 81-85
Author(s):  
Susmita Mohanty
Keyword(s):  
Space Debris ◽  
Outer Space ◽  
Low Earth Orbit ◽  
Observation Data ◽  
Earth Space ◽  
Near Earth Space ◽  
Earth Environment ◽  
Outer Space Treaty ◽  
Earth Observation Data ◽  
Earth’S Climate

Space debris has reached alarming proportions and is growing at a frightening pace, because of the expanding number of satellites circulating in Low Earth Orbit (LEO), designed to increase global Internet coverage and provide earth observation data. LEO satellites are now being launched in mega-constellations, including by Elon Musk's company SpaceX. It is time to completely overhaul the 1967 Outer Space Treaty, which was not designed to deal with current problems. The COP forum should therefore include the near-earth environment within its concept of the earth's climate, enabling the UN to acknowledge, as a collective, the growing menace of human-made debris in near-earth space, and, in partnership with the UN-Outer Space Affairs Office (UN-OOSA), call for a new declaration on LEO.

scholarly journals GIST-PM-Asia v1: development of a numerical system to improve particulate matter forecasts in South Korea using geostationary satellite-retrieved aerosol optical data over Northeast Asia

2016 ◽  
Vol 9 (1) ◽  
pp. 17-39 ◽  
Author(s):  
S. Lee ◽  
C. H. Song ◽  
R. S. Park ◽  
M. E. Park ◽  
K. M. Han ◽  
...  
Keyword(s):  
Particulate Matter ◽  
South Korea ◽  
Northeast Asia ◽  
Initial Distribution ◽  
Low Earth Orbit ◽  
Optical Data ◽  
Future Research ◽  
Observation Data ◽  
Forecast System ◽  
Short Term

Abstract. To improve short-term particulate matter (PM) forecasts in South Korea, the initial distribution of PM composition, particularly over the upwind regions, is primarily important. To prepare the initial PM composition, the aerosol optical depth (AOD) data retrieved from a geostationary equatorial orbit (GEO) satellite sensor, GOCI (Geostationary Ocean Color Imager) which covers a part of Northeast Asia (113–146° E; 25–47° N), were used. Although GOCI can provide a higher number of AOD data in a semicontinuous manner than low Earth orbit (LEO) satellite sensors, it still has a serious limitation in that the AOD data are not available at cloud pixels and over high-reflectance areas, such as desert and snow-covered regions. To overcome this limitation, a spatiotemporal-kriging (STK) method was used to better prepare the initial AOD distributions that were converted into the PM composition over Northeast Asia. One of the largest advantages in using the STK method in this study is that more observed AOD data can be used to prepare the best initial AOD fields compared with other methods that use single frame of observation data around the time of initialization. It is demonstrated in this study that the short-term PM forecast system developed with the application of the STK method can greatly improve PM10 predictions in the Seoul metropolitan area (SMA) when evaluated with ground-based observations. For example, errors and biases of PM10 predictions decreased by  ∼  60 and  ∼  70 %, respectively, during the first 6 h of short-term PM forecasting, compared with those without the initial PM composition. In addition, the influences of several factors on the performances of the short-term PM forecast were explored in this study. The influences of the choices of the control variables on the PM chemical composition were also investigated with the composition data measured via PILS-IC (particle-into-liquid sampler coupled with ion chromatography) and low air-volume sample instruments at a site near Seoul. To improve the overall performances of the short-term PM forecast system, several future research directions were also discussed and suggested.

scholarly journals ON THE EFFECTS OF SOLAR RADIATION PRESSURE ON THE DEVIATION OF ASTEROIDS

2021 ◽  
Vol 57 (2) ◽  
pp. 279-295
Author(s):  
L. O. Marchi ◽  
D. M. Sanchez ◽  
F. C. F. Venditti ◽  
A. F. B. A. Prado ◽  
A. K. Misra
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
Scientific Research ◽  
Orbital Plane ◽  
Solar Radiation Pressure ◽  
The Sun ◽  
Mass Ratio ◽  
High Area ◽  
Planetary Defense

In this work, we study the effects of solar radiation pressure (SRP) on the problem of changing the orbit of an asteroid to support planetary defense, scientific research, or exploitation of materials. This alternative considers a tethered reflective balloon (or a set of reflective balloons) attached to the asteroid, with a high area-to-mass ratio, to use the SRP to deflect a potentially hazardous asteroid (PHA) or to approximate the target asteroid to Earth. The tether is assumed to be inextensible and massless, and the motion is described only in the orbital plane of the asteroid around the Sun. The model is then used to study the effects that the tether length, the reflectivity coefficient, and the area-to-mass ratio have on the deviation of the trajectory of the asteroid.

scholarly journals Study the Effect of Solar Radiation Pressure at Several Satellite Orbits

2013 ◽  
Vol 10 (4) ◽  
pp. 1253-1261 ◽  
Author(s):  
Baghdad Science Journal
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
Jacobian Matrix ◽  
Solar Radiation Pressure ◽  
Equation Of Motion ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Satellite Orbits ◽  
Orbit Satellite ◽  
Low Earth Orbit Satellite

The effects of solar radiation pressure at several satellite (near Earth orbit satellite, low Earth orbit satellite, medium Earth orbit satellite and high Earth orbit satellite ) have been investigated. Computer simulation of the equation of motion with perturbations using step-by-step integration (Cowell's method) designed by matlab a 7.4 where using Jacobian matrix method to increase the accuracy of result.

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 Clouds, cores, and stars in the nearest molecular complexes

1991 ◽  
Vol 147 ◽  
pp. 221-228
Author(s):  
P. C. Myers
Keyword(s):  
Column Density ◽  
Velocity Dispersion ◽  
Molecular Complexes ◽  
Star Cluster ◽  
The Sun ◽  
Core Size ◽  
Core Mass ◽  
The Core ◽  
Internal Motions ◽  
Over Time

The properties and structure of six molecular complexes within 500 pc of the Sun are described and compared. They are generally organized into elongated filaments which appear connected to less elongated, more massive clouds. Their prominent star clusters tend to be located in the massive clouds rather than in the filaments. The complexes have similar structure, but big differences in scale, from a few pc to some 30 pc. They show a pattern of regional virial equilibrium, where the massive, centrally located clouds are close to virial equilibrium, while the less massive filaments and other small clouds have too little mass to bind their observed internal motions. Complexes can be ranked according to increasing size, mass, core mass, and the mass and number of the associated stars: they range from Lupus to Taurus to Ophiuchus to Perseus to Orion B to Orion A. The cores in nearby complexes tend to have maps which are elongated, rather than round. The core size, velocity dispersion, and column density of most cores are consistent with virial equilibrium. Cores in Orion tend to exceed cores in Taurus in their line width, size, temperature, mass, and in the mass of the associated star, if any. Stars in Orion tend to be more numerous and more massive than in Taurus, while those in Taurus tend to be more numerous and more massive than in Lupus. The mass of a core tends to increase with the mass of the cloud where it is found, with the mass of the star cluster with which it is associated, and with its proximity to a star cluster. These properties suggest that complexes and their constituent cores and clusters develop together over time, perhaps according to the depth of the gravitational well of the complex.

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