xmmtrack: XMM orbit TRACKing

• SYNOPSIS
  
      xmmtrack
  
• DESCRIPTION
  xmmtrack is an interactive IDL application that visualizes the orbit and attitude data in an ODF in the form of a 3-D animation sequence. The presented scenery includes an astronomically accurate simulation of the Earth-Sun system plus the actual and predicted trajectory of the XMM satellite on its path around the Earth. In more detail, the following graphical elements are present:
  • Earth:
    The central body in the view frame which is illuminated by the Sun on its day side. The Earth's surface shows the main geological features (continents, oceans) and is rotating eastward at a constant rate of 1 per day. The center defines the origin of a Cartesian reference coordinate system whose three orthogonal axes are shown as red, green, and blue lines. They define the directions: respectively.

  • Actual trajectory:
    A thin yellow three dimensional line outlines the actual trajectory of the satellite that this ODF (pointed at via the environment variable SAS_ODF) corresponds to. The end points mark the beginning and the end of the observation.

  • Predicted trajectory:
    A thin red lines marks a complete orbit around the Earth for a specified epoch (see below). Please note: XMM's orbit is highly time variable and the predicted orbit will significantly deviate from the actual trajectory if the reference epochs differ. The predicted orbit is calculated on the bases of interpolated TLE (two-line-element) data from NASA/GSFC's Orbital Information Group.
  • Satellite:
    The satellite is shown as a solid model with a main cylindrical body and rectangular solar panels in its actual attitude. A thin red line signifies the viewing direction, the blue line is the axis and the green line completes the orthogonal right-handed triad. Please note: Under normal circumstances one side of the solar panels is fully illuminated by the Sun at all times. If there is no attitude data available the satellites attitude will be set to RA=Dec=APOS=0 as a result of which the solar panels can become unilluminated.

• GUI CONTROLS:
  The user can interactively change the displayed scenery with a couple of GUI elements:
  • Drawing area:
    The drawing area is sensitive to left-button mouse clicks. Moving the mouse while holding the left button pressed allows to rotate the scenery arbitrarily about all three axes.

  • Animation button group:
    Three buttons labeled Start, Stop, and Reset to start, stop and reset the animation sequence.
  • Satellite Scaling:
    A slider to change the size of the satellite in the displayed frame between 100% and 900%

  • Zoom view:
    A slider to zoom into the view - range is with 1 being the farthest and 10 providing the closest view of the scenery.

  • Animation step:
    A slider to tune the animation step size - range: [100, 5000]s.

  • Time slider:
    The time slider at the bottom allows to advance the scenery to a specific epoch. If the animation is running, push the Stop button, and move the slider to the desired position. To resume the animation from this new point onward simply push the Start button.

  • Predicted orbit:
    By default the predicted orbit is not shown in the scenery. Pushing the button labeled Add will display a full predicted orbit for the displayed reference epoch. The latter is changeable, i.e., the time dependence of the orbit evolution can easily be studied. The predicted orbit is shown with two white reference lines to guide the eye. The short one signifies the position of the perigee. The longer one connects the ascending and descending nodes of the orbit. Those are the points where the orbital plane intersects the equator. Together with the orbit the three main orbital elements are shown in the left panel:
    • orbit inclination
    • R.A. of the ascending node
    • argument of the perigee

• USED SAS COMPONENTS
  
  • oal: inquire orbit/attitude data
  • caloalutils: compute predicted orbit
  • utils: various STime routines