Constellation of spacecraft, and broadcasting method using said constellation

Abstract

In general, a constellation of spacecraft is used to broadcast to a particular region with high angles of view in order to reduce blockage or shadowing. A constellation of a plurality of spacecraft is placed in 24-hour orbits having inclination of about 550, eccentricity of about 0.32, semi-major axis of about 42,000 km, longitude of the ascending node of about 43° East, argument of perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East. The preferred number of spacecraft ranges from three to six. In a particular application of Digital Audio Broadcast to Europe in some embodiments, the most populous cities are provided with service from no more than about 10° from vertical, and broadcast takes place when the spacecraft are above at least 35° North latitude. The broadcast power is reduced during those portions of the orbit in which the ground track lies in the Southern hemisphere. ( 146 )

1 . A constellation, comprising: 
 a plurality of spacecraft, each in its own approximately 24-hour orbit, each of said orbits having an inclination in the range from about 50° to about 58° and an eccentricity in the range of about 0.28 to 0.36, and longitude of the ascending node in the range of 33° East to 53° East.    
   
   
       2 . A constellation according to  claim 1 , wherein; 
 each of said orbits has a semi-major axis of about 42,000 km when said inclination is about 55°, longitude of the ascending node of about 43° East, argument of the perigee is about 270°, and longitude of the ground track at maximum latitude of about 7° East.    
   
   
       3 . A constellation according to  claim 1 , wherein the ground track of each of said orbits moves from East to West monotonically above about 30° North latitude.  
   
   
       4 . A constellation, comprising: 
 a plurality of spacecraft, each including a broadcast capability, and each in its own approximately 24-hour orbit, each of said orbits having an inclination of about 55° and an eccentricity of about 0.32, and each of said orbits also having a semi-major axis of about 42,000 km, longitude of the ascending node of about 43° East, argument of the perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East.    
   
   
       5 . A constellation according to  claim 4 , wherein each of said orbits has apogee altitude of about 49,300 km and perigee altitude of about 22,300 km.  
   
   
       6 . A constellation according to  claim 4 , wherein said plurality is three, and the orbits of said spacecraft are selected to bring each of said spacecraft to apogee at time increments of about eight hours.  
   
   
       7 . A constellation according to  claim 4 , wherein said plurality is four, and the orbits of said spacecraft are selected to bring each of said spacecraft to apogee at time increments of about six hours.  
   
   
       8 . A constellation according to  claim 4 , wherein said plurality is five, and the orbits of said spacecraft are selected to bring each of said spacecraft to apogee at time increments of about four hours fifty minutes.  
   
   
       9 . A constellation according to  claim 4 , wherein said plurality is six, and the orbits of said spacecraft are selected to bring each of said spacecraft to apogee at time increments of about four hours.  
   
   
       10 . A constellation, comprising: 
 a plurality of spacecraft, each including a broadcast capability, and each in its own approximately 24-hour orbit, each of said orbits having an inclination of about 55°, apogee altitude of about 49,300 km, and perigee altitude of about 22,300 km, longitude of the ascending node of about 43° East, argument of the perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East.    
   
   
       11 . A constellation according to  claim 10 , wherein each of said orbits has a semi-major axis of about 42,000 km and an eccentricity of about 0.32.  
   
   
       12 . A method for broadcasting to European cities, said method comprising the steps of: 
 placing a plurality of broadcast spacecraft in similar approximately-24-hour orbits, which may be rotated relative to each other, each of said orbits having an inclination of about 55° and an eccentricity of about 0.32, and each of said orbits also having a semi-major axis of about 42,000 km, longitude of the ascending node of about 43° East, argument of the perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East;    broadcasting from each of said spacecraft during those times when the ground track of said spacecraft is above about 30° to 35° latitude, and reducing the broadcast power during other times.    
   
   
       13 . A method according to  claim 12 , wherein said step of reducing the broadcast power includes the step of cessation of broadcast.  
   
   
       14 . A method for broadcasting according to  claim 12 , wherein plural ones of said spacecraft broadcast simultaneously using one of different (a) frequency ranges, (b) time-division multiplex slots, and (c) code-division multiplex codes.  
   
   
       15 . A method for broadcasting according to  claim 12 , wherein said constellation has more than two broadcast spacecraft.  
   
   
       16 . A method for broadcasting according to  claim 14 , wherein said constellation contains three spacecraft, and the orbit of each of said spacecraft is selected to bring a spacecraft to apogee approximately every eight hours.  
   
   
       17 . A method for broadcasting according to  claim 14 , wherein said constellation contains four spacecraft, and the orbit of each of said spacecraft is selected to bring a spacecraft to apogee approximately every six hours.  
   
   
       18 . A method for broadcasting according to  claim 14 , wherein said constellation contains five spacecraft, and the orbit of each of said spacecraft is selected to bring a spacecraft to apogee approximately every four hours fifty minutes.  
   
   
       19 . A method for broadcasting according to  claim 14 , wherein said constellation contains six spacecraft, and the orbit of each of said spacecraft is selected to bring a spacecraft to apogee approximately every four hours.