Guide to the NASA HORIZONS database

This section describes how to extract the data of celestial bodies from the NASA Horizons web interface in order to use them as input for the program Solarsystem2009. The x,y,z coordinates of the location and the x,y,z components of the velocity are required for the program. The same coordinate system must be used for all celestial bodies that are calculated simultaneously in the Solarsystem2009 program. Proceed as follows:

The value "Vectors" must be set in the first line of the "Ephemeris Type" web interface. To do this, click on [change] and select "Vector Table".

In the third line "Coordinate Origin", the choice of coordinate origin is set. For most applications, it is recommended to set the center of gravity of the solar system. To do this, click on [change] and enter the following: @0 After the entry, the following is displayed: "Solar system Barycenter (SSB) [500@0]".

In the fourth line "Time Span", enter the start time you want for the calculation. Use the English form of the date year month day. The specification of the stop time is not so important, as you will only use the first value for the coordinates.

Now go to the second line "Target Body" and select the desired celestial body. Various selection lists of planets, moons, satellites, etc. are offered for this purpose. However, you can also search directly for the English name. Select the object and then click on the "Generate Ephemeris" button.

Further down the page, various general details about the celestial body now appear under the heading "Object Data Page". This is followed by the "Results" section where you will find the required coordinates and velocity components. To do this, go to the section that looks like this: