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Orbits and trajectories
Published in Jonathan Allday, Apollo in Perspective, 2019
Figure 4.7 shows three possible paths around a planet. A satellite placed in an equatorial orbit circles around the planet's equator and will be visible directly overhead by people living at this latitude. A geostationary orbit is an equatorial orbit in which a satellite turns about the Earth in the same time period that the Earth requires to turn about its axis.
Satellite Systems
Published in Jerry D. Gibson, The Communications Handbook, 2018
when an isotropic radiator is used to determine the gain of the antenna. Elevation: The angle at which a satellite is viewed from a site on Earth. Equatorial inclination: The angle that the orbital plane of a satellite makes with the equator. Equatorial orbit: A satellite is in an equatorial orbit when the orbital plane includes the equator. The
Quantum Computing Application for Satellites and Satellite Image Processing
Published in Thiruselvan Subramanian, Archana Dhyani, Adarsh Kumar, Sukhpal Singh Gill, Artificial Intelligence, Machine Learning and Blockchain in Quantum Satellite, Drone and Network, 2023
Ajay Kumar, B.S. Tewari, Kamal Pandey
Newton’s Cannonball thought experiment, which was described in Philosophi Naturalis Principia Mathematica, was the first to introduce the notion of an artificial satellite (1687) (Smith, 2008). Later, Exploring Space Using Jet Propulsion Devices was written in 1903 by Konstantin Tsiolkovsky (1857–1935) and was the first academic book on the use of rocketry to launch spacecraft. Tsiolkovsky was born in Russia and died in 1935. The orbital speed necessary for a minimum orbit was calculated, and he determined that it could be attained by a multi-stage liquid propellant-fuelled rocket with many stages. In 1957, the Soviet Union launched Sputnik 1, the world’s first artificial satellite, as part of the Sputnik programme, with Sergei Korolev acting as the spacecraft’s principal designer. With the help of Sputnik 1, scientists were able to gather information on radio-signal dispersion in the ionosphere; and by analysing its orbital fluctuation, they were able to determine the density of upper atmospheric layers. The unexpected success of Sputnik 1 sparked the Sputnik crisis in the United States, reigniting the Cold War and launching a space race that would last for decades (Burrows, 1999). Satellites could be classified based upon their orbit, altitude, and application, as shown in Figure 5.1. Satellites are classified into three categories based on orbit. Satellite revolving in the sun-synchronous is designed in such a way that it always captures any particular place of earth on fixed local sun time. Most of the remote-sensing/earth-observing satellites are sun-synchronous. Images captured by sun-synchronous orbit satellites are excellent for studying temporal changes. Sun-synchronous orbits are also polar orbits, but all the polar orbits may not be sun-synchronous. Geostationary satellites are those satellites which revolve in the equatorial orbit of the earth and are synchronised in such a way that they remain above a certain fixed area of the earth. All communication and weather satellites are actually geostationary satellites.
Optimal robust control of nonlinear time-delay systems: Maintaining low operating errors during feedback outages
Published in International Journal of Control, 2018
The linearised equation of a satellite on a circular equatorial orbit is represented by the following four dimensional system with two inputs (Jafarov, 2008): Here, the state of the system is , where r(t) and θ(t) represent the polar coordinates of the satellite in the equatorial plane; the constant parameter Ω represents the (constant) underlying angular velocity of the satellite. The input signal u(t) has two components u(t) = (u1(t), u2(t))T, where u1(t) is the radial thrust and u2(t) is the tangential thrust. The time delay τ represents the combination of two factors: the communication delay between the control station on earth and the satellite, and the reaction time of the satellite system.
GNSS-based simulation of spacecraft formation flight: A case study of ionospheric plasma remote sensing
Published in Radiation Effects and Defects in Solids, 2020
A sample simulation scenario of ionospheric plasma observation using GNSS-based satellite formation flying is presented in this study. In the simulation scenario, the ionospheric electron density was simulated using the TIEGCM model on March 17, 2013 at 12:00 pm noon UTC. A three-dimensional EPB was added in the altitude range from 344 km to 431 km with a horizontal center at 8.125° N and 176.875° W. A pair of LEO satellites flying in an equatorial orbit was simulated to fly through this region, where the local time (in this region) is around mid-night with a span of 20 min. The top-down view of the satellite trajectory passing directly below the EPB on a gnomonic projection of the northern hemisphere is shown in Figure 1.