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Some Earth satellites are to be deployed in equatorial orbit in order to realize their particular objectives. For these satellites, the data transmission between ground stations and satellites has become one of the difficulties when the satellite engineering is to be realized. To make a quantitative assessment, simulations of data transmission are carried out for two typical orbits, of which the altitude are roughly 500km and 550km,and the inclination is 0 deg. Ground stations for data transmission include the such stations as Sanya China, Kourou France, Malindi Kenya. The longitude is 109.3 deg E., and the latitude is 18.3 deg N. for the station of Sanya. The longitude is 40.2 deg E., and the latitude is -3.0 deg S. for the station of Malindi. The longitude is -52.8 deg W., and the latitude is 5.3 deg N. for the station of Kourou. For Sanya, the cutoff angle for data transmission are 10 deg. For both Malindi and Kourou, the cutoff angles for data transmission are 5 deg. Two antenna for data transmission are fixed in the satellite body along +Z axis and –Z axis respectively, and the half beam angle of the boresight is 1 deg. Antenna for data transmission can scan +/-70deg both in X axis and in Y axis. Two cases are considered herein. Case 1 is that data transmission is only allowed when the celestial objects in question are obstructed by the Earth. Case 2 is that data transmission is allowed without considering the celestial objects obstruction by the Earth. For orbit altitude of 500km, 35 times data transmission are available, the average data transmission period is 305 sec,178 minutes are available for data transmission each day in Case 1; For orbit altitude of 550km, 36 times for data transmission are available, the average data transmission period is 322 sec,193 minutes are available for data transmission each day in Case 1. For orbit altitude of 500km, 9.5 times data transmission are available, the average data transmission period is 266 sec,42 minutes are available for data transmission each day in Case 2; For orbit altitude of 550km, 9.9 times for data transmission are available, the average data transmission period is 278 sec,46 minutes are available for data transmission each day in Case 2. The simulations of data transmission will support finalizing the data transmission planning before the satellite engineering project comes true.
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