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Atmospheric drag at orbital altitude is caused by frequent collisions of gas molecules with the satellite. It is the major cause of orbital decay for satellites in low Earth orbit. It results in the reduction in the altitude of a satellite's orbit. For the case of Earth, atmospheric drag resulting in satellite re-entry can be described by the ...
To improve tracking, NORAD employee John Gabbard kept a separate database. Studying the explosions, Gabbard developed a technique for predicting the orbital paths of their products, and Gabbard diagrams (or plots) are now widely used. These studies were used to improve the modeling of orbital evolution and decay. [9]
At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight atmospheric drag, lunar perturbations, Earth's gravity perturbations, solar wind, and solar radiation pressure can gradually bring debris down to lower altitudes (where it decays), but at very high altitudes this may take centuries. [57]
The orbital decay and the speedup of the orbital period was tested to follow the quadrupole formula with a great precision of 0.013% mainly because of the unique characteristics of the system which has two pulsars, is nearby and possesses an inclination close to 90°. [7] [8] [9]
[2] [10] [11] [12] The ratio of observed to predicted rate of orbital decay is calculated to be 0.997 ± 0.002. [12] The total power of the gravitational waves emitted by this system presently is calculated to be 7.35 × 10 24 watts. For comparison, this is 1.9% of the power radiated in light by the Sun.
Spacecraft that re-enter from either orbital decay or controlled entry usually break up at altitudes between 84-72 km due to aerodynamic forces causing the allowable structural loads to be exceeded. The nominal breakup altitude for spacecraft is considered to be 78 km. Larger, sturdier, and denser satellites generally breakup at lower altitudes.
By measuring the rate and timing of orbital shifts, together with the body's drag properties, the relevant atmosphere's parameters could be back-calculated. It was determined that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated, since Earth's upper atmosphere does taper off into space gradually. [11]
The orbital decay (via gravitational radiation) of stellar binaries consisting of these exotic compact objects is believed to take hundreds of millions of years, hence gamma ray bursts produced this way would be expected to be in old (misleadingly called "early type") galaxies. In contrast, long-duration gamma ray bursts, which are believed to ...