Table of Contents ECSS Model Page
Background information SPENVIS packages
Orbit generator


The SPENVIS orbit generator computes trajectory osculatory orbital elements using a numerical Runge-Kutta integration method. The independent variable is the eccentric anomaly. Osculatory elements are computed at constant equidistant eccentric anomaly steps. Orbits around three planets are currenly available: The selection of the planet is done by a small tool available in the coordinate generator package.

Once a trajectory has been generated, it can be used by different models. This means that, in the context of a given project, it is not necessary to generate coordinates for each model separately.

Warning: The SPENVIS orbit generator (i.e. SAPRE) only provides the user with the best guess for a particular orbit. SAPRE should not be used for a real mission planning.

Finally, note that the Modified Julian Date (MJD) used in SPENVIS is defined as the number of days from 1st January 1950 00:00 UT.


The orbit generator produces the files listed in the table below. A description of the format of the files can be brought up by clicking on their description in the table.

The report file spenvis_sap.html contains the input parameters and summary tables, including details of eclipses and crossings of the bow shock and magnetopause.

The geodetic coordinates on the orbit are stored in the orbit file spenvis_sao.txt. The attitude file spenvis_att.txt contains, for each point, the rotation matrix describing the satellite attitude relative to the local geocentric spherical coordinate system, the velocity vector of the satellite and the Sun direction in satellite coordinates.

Output files generated by the orbit generator
File name Description
spenvis_sap.html Report file
spenvis_sao.txt Time and spatial coordinates
spenvis_att.txt Spacecraft attitude vectors
spenvis_orb_upl Uploaded trajectory file

To generate plots, select the plot type(s), options and graphics format, and click the or button. The current page will be updated with the newly generated plot files.

The button calls up the output page for consecutive runs of multiple models. This button only appears when the orbit generator has been included in the combined model run selection. This feature is available for advanced users only.

Last update: Mon, 12 Mar 2018