scholarly journals Analysis of Precise Orbit Predictions for a Hy-2A Satellite with Three Atmospheric Density Models Based on Dynamic Method

2018 ◽  
Vol 11 (1) ◽  
pp. 40
Author(s):  
Qiaoli Kong ◽  
Fan Gao ◽  
Jinyun Guo ◽  
Litao Han ◽  
Linggang Zhang ◽  
...  
Keyword(s):  
Dynamic Method ◽  
Interpolation Method ◽  
Spherical Surface ◽  
Low Earth Orbit ◽  
Atmospheric Density ◽  
Ground Segment ◽  
Complex Process ◽  
Radial Orbit ◽  
Atmospheric Density Models

HY-2A (Haiyang 2A) is the first altimetry satellite in China, and it was designed to be in a repeated ground track orbit to achieve the mission targets. Maneuvers are necessary to keep the satellite on the designed orbit according to the dynamic precise orbital prediction. Atmospheric density models are essential for predicting the low Earth orbit (LEO) satellites, such as HY-2A. Nevertheless, it is a complex process to determine the optimal atmospheric density model for orbit prediction. In this paper, short-term and long-term orbit predictions based on the dynamic method using three different atmospheric density models are tested. Detailed comparisons and evaluation of the accuracy of the predicted results are performed. Furthermore, to assess the results for the ground tracking of the satellite, the interpolation method especially for a spherical surface is introduced. The results show that among the three models, the Jacchia 1971 model is in the closest agreement with Multi-Mission Ground Segment for Altimetry precise positioning and Orbitography (SSALTO) precise orbits. The root-mean-squares (RMSs) of radial orbit differences between the predicted and precise orbits are 0.016 m, 0.091 m, 0.176 m, 0.573 m, and 1.421 m for predicted 1-h, 12-h, 1-day, 3-day, and 7-day arcs, respectively.

Social Cohesion, Breaks, and Transformations in Italy, 535–600

2018 ◽  
Author(s):  
Walter Pohl
Keyword(s):  
The Political ◽  
Late Antique ◽  
Religious Context ◽  
Ancient Society ◽  
Complex Process ◽  
Term Change ◽  
Two Generations ◽  
Classical Culture

When the Gothic War began in Italy in 535, the country still conserved many features of classical culture and late antique administration. Much of that was lost in the political upheavals of the following decades. Building on Chris Wickham’s work, this contribution sketches an integrated perspective of these changes, attempting to relate the contingency of events to the logic of long-term change, discussing political options in relation to military and economic means, and asking in what ways the erosion of consensus may be understood in a cultural and religious context. What was the role of military entrepreneurs of more or less barbarian or Roman extraction in the distribution or destruction of resources? How did Christianity contribute to the transformation of ancient society? The old model of barbarian invasions can contribute little to understanding this complex process. It is remarkable that for two generations, all political strategies in Italy ultimately failed.

Precision Low Earth Orbit Determination Using Atmospheric Density Calibration

1998 ◽  
Vol 46 (4) ◽  
pp. 395-409 ◽  
Author(s):  
F. A. Marcos ◽  
M. J. Rendra ◽  
J. M. Griffin ◽  
J. N. Bass ◽  
D. R. Larson ◽  
...  
Keyword(s):  
Orbit Determination ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Atmospheric Density

scholarly journals Effects of long-term exposure to the low-earth orbit environment on drag augmentation systems

2021 ◽  
Author(s):  
Zaria Serfontein ◽  
Jennifer Kingston ◽  
Stephen Hobbs ◽  
Susan A. Impey ◽  
Adrianus I. Aria ◽  
...  
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit

scholarly journals Atmospheric Deposition Effects on Agricultural Soil Acidification State — Key Study: Krupanj Municipality

2014 ◽  
Vol 40 (2) ◽  
pp. 137-148 ◽  
Author(s):  
Dragan Čakmak ◽  
Jelena Beloica ◽  
Veljko Perović ◽  
Ratko Kadović ◽  
Vesna Mrvić ◽  
...  
Keyword(s):  
Soil Acidification ◽  
Interpolation Method ◽  
Natural Processes ◽  
Target Loading ◽  
Distance Weighting ◽  
The Status ◽  
Inverse Distance ◽  
Sustainable Productivity

Abstract Acidification, as a form of soil degradation is a process that leads to permanent reduction in the quality of soil as the most important natural resource. The process of soil acidification, which in the first place implies a reduction in soil pH, can be caused by natural processes, but also considerably accelerated by the anthropogenic influence of excessive S and N emissions, uncontrolled deforestation, and intensive agricultural processes. Critical loads, i.e. the upper limit of harmful depositions (primarily of S and N) which will not cause damages to the ecosystem, were determined in Europe under the auspices of the Executive Committee of the CLRTAP in 1980. These values represent the basic indicators of ecosystem stability to the process of acidification. This paper defines the status of acidification for the period up to 2100 in relation to the long term critical and target loading of soil with S and N on the territory of Krupanj municipality by applying the VSD model. The Inverse Distance Weighting (IDW) geostatistic module was used as the interpolation method. Land management, particularly in areas susceptible to acidification, needs to be focused on well-balanced agriculture and use of crops/seedlings to achieve the optimum land use and sustainable productivity for the projected 100-year period.

Long-term collision risk prediction for low earth orbit satellite constellations

2000 ◽  
Vol 47 (2-9) ◽  
pp. 707-717 ◽  
Author(s):  
R. Walker ◽  
P.H. Stokes ◽  
J.E. Wilkinson ◽  
G.G. Swinerd
Keyword(s):  
Risk Prediction ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Collision Risk ◽  
Satellite Constellations ◽  
Orbit Satellite ◽  
Low Earth Orbit Satellite

scholarly journals Global change induced trends in ion composition of the troposphere to the lower thermosphere

2008 ◽  
Vol 26 (5) ◽  
pp. 1181-1187 ◽  
Author(s):  
G. Beig
Keyword(s):  
Middle Atmosphere ◽  
Anthropogenic Activities ◽  
Lower Thermosphere ◽  
Cluster Ions ◽  
Atmospheric Density ◽  
Mesosphere And Lower Thermosphere ◽  
Induced Changes ◽  
Positive Ion ◽  
Mlt Region

Abstract. In this paper a brief overview of the changes in atmospheric ion compositions driven by the human-induced changes in related neutral species, and temperature from the troposphere to lower thermosphere has been made. It is found that ionic compositions undergo significant variations. The variations calculated for the double-CO2 scenario are both long-term and permanent in nature. Major neutrals which take part in the lower and middle atmospheric ion chemical schemes and undergo significant changes due to anthropogenic activities are: O, O2, H2O, NO, acetonitrile, pyridinated compounds, acetone and aerosol. The concentration of positive ion/electron density does not change appreciably in the middle atmosphere but indicates a marginal decrease above about 75 km until about 85 km, above which the magnitude of negative trend decreases and becomes negligible at 93 km. Acetonitrile cluster ions in the upper stratosphere are likely to increase, whereas NO+ and NO+(H2O) in the mesosphere and lower thermosphere (MLT) region are expected to decrease for the double CO2 scenario. It is also found that the atmospheric density of pyridinated cluster ions is fast rising in the troposphere.

Effects on Satellite Formation Flying of Tiny Aspherical Gravitation of the Earth

2013 ◽  
Vol 367 ◽  
pp. 270-274
Author(s):  
Guang Yan Xu ◽  
Jian Fu Luo
Keyword(s):  
Formation Flying ◽  
Low Earth Orbit ◽  
High Order ◽  
Formation Flight ◽  
Zonal Harmonic ◽  
Satellite Formation ◽  
Gravitational Perturbations ◽  
The Earth ◽  
Cross Track

J2 perturbation has been widely studied for satellite formations in low earth orbit. However, the effects of some tiny aspherical gravitational perturbations such as high-order zonal harmonic perturbations, sectorial and tesseral harmonic perturbations are not negligible for long term formation flight. In this paper, after eliminating the effects of J2 perturbation which accommodating it, research these tiny perturbations uses numerical analysis and acquires some conclusions. High-order zonal harmonic perturbations may cause divergence in radial, in-track and cross-track direction, while the drift caused by sectorial and tesseral harmonic perturbations is larger than higher-order zonal harmonic perturbations about two magnitudes generally, and drift in cross-track direction is secular.

The turnover of organic carbon and nitrogen in soil

1990 ◽  
Vol 329 (1255) ◽  
pp. 361-368 ◽  
Keyword(s):  
Plant Material ◽  
Field Experiments ◽  
Compartment Model ◽  
Soil Organic Nitrogen ◽  
Carbon And Nitrogen ◽  
First Order ◽  
Complex Process ◽  
Two Compartment Model ◽  
Term Field

Although the decomposition of plant material in soil is an extremely complex process, relatively simple models can give good fits to the decay process. Thus a two-compartment model gives a close representation, over the first few years, of the decay of 14 C-labelled plant material in soil. A model containing a single homogeneous humus compartment decomposing by a first-order process is surprisingly useful for soil organic nitrogen over periods measured in decades. More sophisticated multicompartmental models are now widely used to represent turnover in soil. One of these, the Rothamsted turnover model, is described in detail and shown to give a useful representation of data from the Rothamsted long-term field experiments.

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