A Tapestry of Orbits
Satellites as they cross the night sky look like moving stars, which can be accurately tracked by an observer with binoculars as well as by giant radars and large cameras. These observations help to determine the satellite's orbit, which is sensitive to the drag of the upper atmosphere and to any irregularities in the gravity field of the Earth. Analysis of the orbit can be used to evaluate the density of the upper atmosphere and to define the shape of the Earth. Desmond King-Hele was the pioneer of this technique of orbit analysis, and this book tells us how the research began, before the launch of Sputnik in 1957. For thirty years King-Hele and his colleagues at the Royal Aircraft Establishment, Farnborough, developed and applied the technique to reveal much about the Earth and air at a very modest cost. In the 1960s the upper-atmosphere density was thoroughly mapped out for 100 to 2000 km, revealing immense variation of density with solar activity and between day and night. In the 1970s and 1980s a picture of the upper-atmosphere winds emerged, and the profile of the pear-shaped Earth was accurately charted. The number of satellites now orbiting the earth is over 5000. This book is the story of how this inexpensive research of their orbits developed to yield a rich harvest of knowledge about the Earth and its atmosphere, in a scientific narrative that is enlivened with many personal experiences.
15th-order harmonics 15th-order resonance accuracy air density air drag argument of perigee atmospheric rotation rate average CIRA Clive Brookes coefﬁcients coeﬂicients Committee COSPAR D. G. King-Hele D. M. C. Walker decay decrease deﬁned degree density scale height Doreen Walker early Earth eccentricity effects eﬂects equation Erasmus Darwin error evaluated ﬁnal ﬁrst ﬁtted ﬁtting ﬁve GEM T3 geoid Graham Cook gravity ﬁeld harmonics of order Harrie Massey Hewitt camera inﬂuence kinetheodolite King-Hele and D. M. C. latitude lifetime longitude lumped harmonics Merson Navspasur NORAD oblateness Observatory odd zonal harmonics orbit analysis orbit determination orbital period orbital theory order 15 oscillation perigee distance perigee height Planet prediction service published rocket Royal Greenwich Observatory Royal Society satellite observing satellite orbits satellite’s satellites launched scale height scientiﬁc scientists semi-annual variation Skylab solar activity Space Research Space Sci Sputnik upper-atmosphere density visual observers