Abstract: A Multi-Band Concentric Helical Antenna (20) operating in a novel conical mode, useful for general and satellite communications is disclosed. A higher frequency helix (24) is placed concentrically inside a lower frequency one (22). In one embodiment, each helix has four helical elements (22a-d, 24a-d). The outer helix is fed at a first frequency (f.sub.1) and the inner helix (24) is fed at a second frequency (f.sub.2). The second frequency (f.sub.2) may be greater than twice the first frequency (f.sub.1). Both helices (22, 24) have the same polarization. The pitch (P.sub.1, P.sub.2), diameter (D.sub.1, D.sub.2), and length (AL.sub.1, AL.sub.2) of the helices are chosen so that said antenna (20) radiates with approximately equal flux at all points in a far-field plane. Alternatively, two inner helices (24, 25) are placed concentrically within an outer helix (22).

Abstract: Methods and apparatus are disclosed which allow many satellites (A1-M, B1-N) in a plurality of Systems (A, B) to use the same radio frequencies (f1-n) so long as there is no interference between radio signals. The methods compute times (t) when satellite radio signals (32, 36) have overlapping reception areas or "footprints" (30, 35) on the Earth's surface (E) whereby a user's reception or transmission of a message would be interfered unless different frequencies (f1-n) are used for the "competing" signals. The methods use a timing algorithm that does not allow two satellites (Ai, Bi) which are "visible" at the same point on the Earth (E) to transmit on the same frequency (fi). In one preferred embodiment, a timing algorithm (48) produces a radio frequency use schedule (49) computed on the Earth from orbital data maintained in an ephemeris (46) of satellite communications systems (A, B) which communicate on frequencies (f1-n) giving rise to interfering radio signals.

Abstract: A satellite communications system is disclosed. One of the embodiments of the present invention includes six to fourteen satellites (12) which operate in a single Equatorial orbit (14). These satellites (12) are capable of providing communications services to locations on the Earth (E) which are within thirty degrees of the Equator (16). Another embodiment of the invention utilizes both the single Equatorial orbit plane (14) in combination with other satellites (12) moving in polar or inclined orbits (60, 63, 210). The embodiment that combines satellites (12) in Equatorial (14), polar (60) and inclined (63, 210) orbits will provide a wide variety of data services to virtually any point on the globe. In the preferred embodiments, the satellites (12) are designed to operate in a circular low Earth orbit at an altitude of from 800 to 1852 kilometers.

Abstract: One of the preferred embodiments of the present invention is a telecommunications system that includes twelve satellites (S) which are equally deployed in four polar low Earth orbits (OR). A preferred embodiment provides a system for transmitting a message between two terminals (G) on the ground through a store-and-forward network. A first satellite (S1/OR1) traveling in a first polar orbit (OR1) receives and stores a message from a sending terminal (GA) on the surface of the Earth (E). As the first satellite (S1/OR1) passes over the North Pole (NP), it transmits the stored message from the sending terminal (GA) down to a relay station (GB) located near the North Pole (NP). The message is stored at this polar relay station (GB) until a second satellite (S1/OR2) moving in a second orbit (OR2) flies within range.