This tutorial paper describes the current development in the use of low earth orbiting satellites (LEOS) for global personal communications. The basic architectures and rationales for design choices are discussed. Representative TDMA and CDMA systems are outlined and a summary of the diierences between LEOS communications and terrestrial cellular is presented along with the prospects for CDMA b...

The effects of the general relativistic gravitomagnetic force on the orbits of a couple of counter–orbiting test particles, denoted as + and –, respectively, in the gravitational field of a central rotating mass are investigated. Based on the fact that, for identical orbital configurations, the secular Lense–Thirring rates of the nodes Ω are the same, contrary to the secular rates of the perige...

[1] Observations of high-latitude plasma structure and scintillation are presented from the January 2001 scintillation campaign timeframe. Comparisons are made using the all-sky imager and two beacon-satellite ground receivers located at Sondrestrom, Greenland. The Coherent Ionospheric Doppler Receiver (CIDR) observes 150and 400-MHz signals transmitted from low-Earth-orbiting satellites. The 25...

The recent discovery of two distant satellites of Uranus suggests that there could be similar bodies orbiting Neptune. Previous surveys for distant satellites of Neptune have had relatively bright magnitude limits (B J ' 20:5) and would have missed satellites with magnitudes and colours similar to the 2 recently discovered Uranian satellites (R 20:4 and R 21:9). We have searched for satellites ...

Stephen Hodgart received a Ph.D. degree from the University of Surrey. He has been with the Surrey Space Centre, since its inception and the launch of their first satellite, UoSAT-1 in 1981. He is currently visiting Reader at the University of Surrey. He was responsible for the first practical low-cost active magnetic and passive gravity gradient control attitude system for a low earth orbiting...

NASA has been interested in having Internet connectivity in space for quite some time. This would allow scientists with direct Internet access to data and devices on the satellites. The rotation of Low Earth Orbiting (LEO) satellites around the Earth result in handover of satellites between ground stations. Two types of handover can be observed in space: Link layer and Network layer. Researcher...

We calculate analytically the most relevant nongravitational perturbations on the mean anomaly of LAGEOS type satellites in order to investigate the constraints they pose on the feasibility of the proposed general relativistic gravitomagnetic clock effect. The gravitoelectric contributions to the proper times induced by the perturbations on the Keplerian mean motions of two counter-orbiting sat...

Free space optical communication provides a very important method for the satellites orbiting around the earth to communicate with each other. Inter-satellite optical wireless communication systems (IsOWC) are one of the important applications of FSO/WSO technology that will be expand in space in the near future. These systems provide a high bandwidth, small size, light weight, low power and lo...