中高层大气物理学第一章Atmoshericdrag大气阻力.ppt

LOGO PHYSICS OF THE MIDDLE AND UPPER ATMOSPHERE中高层大气物理学Atmospheric Drag 2011 Atmospheric drag Moving with velocity v with respect to the atmospheric gas CD , ballistic coefficient For a satellite moving in a circular orbit around the Earth Newtonian mechanics Kinetic energy Potential energy Total energy Atmospheric drag (Cont.) The rate of change of energy due to atmospheric drag The rate of change of the orbit radius Change of orbit period Since the variations in r from orbit to orbit is very small, the orbital period T = 2πr/v is a better parameter. Kepler’s third law The period decreases as the density increases. The gain in kinetic energy must be lost by a reduction in potential energy due to the decreasing of orbit radius. The fractional change in the orbital period per period is Early orbit decay records Construct model from orbit data Data for modeling Sputnik, Vanguard, Explorer and Echo series of satellites Supplemented by satellite-borne mass spectrometers, pressure gauges and accelerometers Incoherent backscattering technique, oxygen 630.0 nm line, et al. Model In the improved model of Jacchia 77, N2 and O observed by mass-spectrometers of the OGO 6 and ESRO 4 satellite were included. LOGO