Using TLE data to determine satellite orbits

1. Satellite orbit

Satellites and celestial Bodies in the sky under the action of various gravity in a certain orbit rotation, but the actual orbit is very complex, the general project also can not achieve so precise demand (in fact, accurate satellite parameter data can not be casually disclosed), so the first order approximation of the Kepler elliptical orbit can be. To determine an Kepler elliptical orbit requires some basic elements, and there are many combinations of elements , but there are simple conversion relationships between groups of different forms. Commonly used is the six elements of Kepler, which have obvious geometrical meanings.

1. Track half-length axis, half the length of the elliptical axis. For the circle, that is, the radius, in addition, according to Kepler's third law, the half-length axis and the operating cycle have a definite conversion relationship.

2. Orbital eccentricity, the ratio of the distance between the two focal points of the ellipse to the long axis. The eccentricity is 0 o'clock the orbit is a circle, the eccentricity is the ellipse between the 0~1, the larger the ellipse is, the higher the eccentricity equals the 1 o'clock the orbital is the parabola; the eccentricity is more than the 1 o'clock track is a hyperbola. The half-length axis of the parabola is infinite, and the hyperbolic half-length axis is less than 0.

3. Orbital inclination, this is the angle between the orbital plane and the equatorial plane of the earth, with the angle between the polar direction of the North Pole and the normal direction of the orbital plane, the value of the orbital inclination from 0°~180°. For geosynchronous geostationary satellites over the equator, the dip is 0.

4. Ascending intersection of the Red meridian: It is an angular amount. The orbital plane has two intersections with the Earth's equator, and the orbits of the satellites from the southern hemisphere through the equator to the northern hemisphere are called ascending segments, and the point crossing the equator is the ascending intersection. Conversely, the operating arc of a satellite from the northern hemisphere to the southern hemisphere is called the descending segment, and the intersection on the corresponding equator is the descending intersection. In the Earth's orbit around the sun, the point at which the sun crosses the equator from the southern hemisphere to the northern hemisphere is called the vernal equinox. The angle of the spring equinox and the ascending intersection of the center of the Earth is the red meridian of ascending intersection, and the counter-clockwise from vernal equinox to ascending intersection point. The orbital inclination and the ascending intersection of the Red meridian determine the azimuth of the orbital plane in space.

5. Perigee amplitude angle: This is the angle of the perigee and ascending intersection to the center of the Earth. While the front determines the position of the orbital plane in space, the orbit itself can be rotated in the orbital plane.

6. Perigee time, it is the satellite through the near location of the moment, in years, months, days, hours, minutes, seconds, is the time of the movement of the point, the satellite location changes in time need an initial value.

1 and 2 of these two elements determine the shape of the track, whether it is an ellipse or a circle, and how large the ellipse is. The two quantities of 3 and 4 determine the position of the satellite orbital plane in space, but in which position the orbit in the orbital plane is uncertain. 5 This value combines the orbital shape and the orbital plane to determine the position of the track in the orbital plane. 6 determines the position of the satellite at some point in time, so that a complete orbit is determined.

2. TLE (two-line Element) data

The United States in 2000 years to track around 7500 of artificial objects, including satellites and rocket debris, online release near the thousands of satellite orbit, using two lines of element orbital report, covering the meteorological satellites, marine satellites, Earth resources satellites, educational satellites and other applications of the satellite. There are few satellite orbital parameters predicted by the two-line element orbital report, and the accuracy is not tbus high, called the coarse track root number, but the accuracy is sufficient for the average small and medium earth station.

The specific contents of the TLE data are described in detail in reference 2 and are not discussed.

Reference documents:

1. Orbital elements (http://baike.baidu.com/link?url=87mNHh7IDMNN7v1wjDWk-BN5r8MjjFuUK7vbKN_ 1jxawoct1jpwp75ukdp0zvx9niudhxbul_oadwsgua-bo0k)

2. The concept and calculation method of TLE data and satellite orbits (http://www.shenkong.net/Explore/1207/TLESJHWXGDDGNHJSFF09081535.htm)

3. Tbus,agros and Tle Rail (http://blog.sina.com.cn/s/blog_764f855d0100rgw1.html)

4, [Science]tle satellite orbital parameters detailed, and perigee calculation (http://lt.cjdby.net/thread-332217-1-1.html)

Using TLE data to determine satellite orbits