Tuesday, November 8, 2011

Loading Orbital Elements in Distant Suns

Loading orbital elements into astronomy programs can be challenging at times. I have an older one, Distant Suns, that works quite well but is in need of an update. The HORIZONS ephemeris provides the osculating orbital elements for an object. This provides enough information to specify the orbit if the definitions are known. The process of loading the elements for 2005 yu55 into Distant Suns is shown below and the program shows the its location at the time of closest approach to the Earth. The time shown at the bottom of the image is UT.

click for clearer view

The HORIZONS User Manual gives the following definitions for the elements,

Not all of these elements are needed to specify an orbit. For example the ascending node can be used instead of the longitude of perihelion since the latter is just the sum of the ascending node and the argument of perihelion. Another drop down menu would have been more useful. This method was used for the choice between periapsis and the semi-major axis which specify the size of the orbit.

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