1、ITU-R RECMN*S- SERIES 95 YB55212 0527835 Ob3 - RW. ITU-R S.1064-1 109 RECOMMENDATION ITU-R S. 1064- 1 * POINTING ACCURACY AS A DESIGN OBJECTIVE FOR EARTHWARD ANTENNAS (Question ITU-R 215/4) ON BOARD GEOSTATIONARY SATELLITES IN THE FIXED-SATELLITE SERVICE ( 1994- 1995) The ITU Radiocommunication Asse
2、mbly, considering that antenna-beam pointing errors produce both a loss in orbit utilization and a change in antenna gain in the that antenna-beam pointing errors obstruct efficient use of the radio frequency in multiple beams; that antenna-beam pointing errors are particularly significant for small
3、 coverages; that utilization of the beacon tracking technique is very beneficial for small coverages; that progress in the development on on-board sensors and control systems will result in improvements in that determining beam pointing accuracy is a function of a complex technicaVeconomic trade-off
4、 that the Radio Regulations (RR) contain geostationary-satellite pointing accuracy requirements in that geostationary satellites are in operation with complex beam patterns and it is very difficult to apply that the pointing accuracy during station keeping and stabilization phases (0.2% of the time
5、on average) is a) desired direction; b) c) d) e) pointing accuracy; 0 g) RR No. 2628 and RR No. 2629; h) those FU to these patterns; j) inevitably worse than in a normal mode, recommends that as a design objective the pointing direction of maximum radiation of any earthward beam of antennas on 1 geo
6、stationary satellites shall be capable of being maintained within: - - whichever is greater. 5% of the half-power beamwidth relative to nominal pointing direction; or 0.2“ relative to the nominal pointing direction, This recommends applies only to beamwidths of less than 5“ and beams with complex pa
7、tterns. that, in the event that the beam is not rotationally symmetrical about the axis of maximum radiation, the that the following Notes will be considered as part of this Recommendation. 2 tolerance in any plane containing this axis shall be related to the half power beamwidth in that plane; 3 NO
8、TE 1 - The pointing accuracy consists of four different factors: - constantterm, - seasonal or long term, - dailyterm, - shortterm. * This Recommendation should be brought to the attention of Radiocommunication Study Groups 7.8, 10 and 11. ITU-R RECMN*S. SERIES 95 4855232 0527816 TTT 110 Rec. -R S.1
9、064-1 There are two methods to calculate the pointing error due to each of the above factors: - - linear sum method. Provisionally, the sub-total error of each class should be estimated by the RSS method and the total pointing errors should be the sum of the subtotals of each class. The method of co
10、mbining the above error sources is subject to further study. NOTE 2 - The application of this Recommendation to antennas of geosynchronous satellites with slightly inclined orbits is subject to further study. NOTE 3 -The definitions of beamwidth and reference pointing direction for different types o
11、f antennas need further study. Provisionally, in the case that the pointing direction of maximum radiation is difficult to specify, the direction to the centroid of the footprint of the antenna beam should be applied as the reference pointing direction. NOTE 4 -The footprint (of an antenna beam on a
12、 specified surface) is defined as follows: An area bounded by a contour on a specified surface formed by the intersection of the surface and that portion of the beam of an antenna above a specified minimum gain level, the orientation of the beam with respect to the surface being specified. NOTE 5 -
13、The method of calculating the centroid needs further study. NOTE 6 - During station keeping manoeuvres and stabilization phases the pointing accuracies shall be capable of being maintained within: - - whichever is greater. root sum square (RSS) method, and 7% of the half-power beamwidth relative to nominal pointing direction; or 0.3“ relative to the nominal pointing direction,
