Course element

the course elements describe the middle course of an astronomical object. The movement is treated with the three keplerschen laws.

table of contents 1 the six course elements 1,1 the large shaft section A 1,2 the numeric eccentricity ε 1,3 the inclination (flight path angle) i 1,4 thatTo argument of the knot (knot length) Ω 1,5 the argument of the Periapsis ω 1,6 the Periapsiszeit T 2 an additional course element 2,1 the course period P 2,2 the middle daily movement μ 3 see also 4 Web on the left of

the six course elements

a Keplerbahn troublefree for definition6 course elements are necessary. In the Zweikörperproblem (without orbit/trajectory disturbances by third bodies and not gravitative influences these 6 course elements are sufficient.

Orbit/trajectory disturbances cause a slow change of the 6 course elements, so that these only oskulierende elements are, i.e.: the Keplerellipse only during a short period match the contour. Some disturbancescan be considered by indication of temporal changes of the course elements.

the large shaft section A

you is indicated generally either in km or in AE.

Example Earth's orbit:
large shaft section = 149.597 millions km
= 1 AE

the numeric eccentricity ε

you also e one names. From it Periapsisdistanz

= A result * (1 - ε) and

Apoapsisdistanz = A * (1 + ε).

Also the eccentricity angle can be indicated φ.

sin φ = ε

the inclination (flight path angle) i

The inclination is the angle of the course level to the reference level.

the argument of the knot (knot length) Ω

the argument of the knot is the angle of the Koordinatennullpunkt of the reference level to the ascending knot.

Example:
The knot length of the course of a planet is the ekliptikale lengththe ascending knot (that is the angle from the Frühlingspunkt to the ascending knot). The knot length of a satellite is the Rektaszension (along ground equator) concerning the Frühlingspunkts.

the argument of the Periapsis ω

the argument of the Periapsis is the angle of the ascending knotto the Periapsis. In the solar system it is usually the argument of the Perihels. For the moon or earth satellite it is the argument of the perigee.

Also the length of the Periapsis can be indicated π.

π = Ω + ω

as broken angles; ofthose first in the reference level, which second in the course level is measured.

It is an useful simplification, if the flight path angle is small, for example the Perihellänge of a planet.

the Periapsiszeit T

the Periapsiszeit is time of the Periapsisdurchgangs or the epoch E plus position.

an additional course element

is often indicated still the course period or the middle daily movement as seventh course element, itself however from the large shaft section and that the 3. Kepler law results in.

the course period P

the course periodis the siderische scan time. For the earth it is measured in tropical years.

the middle daily movement μ

for the middle daily movement applies:

μ = to 360 * 60 * 60 "/ P _days

see also

• satellite orbit element -to special course data for earth satellite
• orbit

Web on the left of

• Minor planet center (English)
• cent ral office for Astronomical Telegrams (English)