Orbit Visualization Tool User Guide
The Orbit Visualization Tool is a software for visualization of
satellite orbits in the Earth's magnetic field. The program can
display satellite orbits in five coordinate systems
(GEI, GEO, GSM, SMC, GSE), satellite
footprints projected on the Earth's surface and shown in either geographic
(GEO) or geomagnetic (SMC) coordinates. In addition to satellite orbits the
software computes and displays various models of magnetospheric
structures, magnetopause, bow shock and electric potential, geomagnetic
activity, and interplanetary field conditions. The models are time-dependent
through user-editable activity files, which control models structure and
properties. The program can be used to plan operations or interpret measurements
from scientific satellites, to prepare ground-based satellite
coordination, or as educational tool in astronomy and geophysics.
OVT can be installed on any Unix or Windows 95/98/2000/ME/XP/NT. The
graphics used in this program is based on a Visualization Toolkit (VTK),
which uses 3D accelerating hardware if present, but will still work
with a simple 2D graphics card.
The graphics is mouse maneuverable: left mouse button to rotate the
picture, right mouse button to zoom in and out, and SHIFT+left mouse button to
move the focus.
The graphics window shows objects in one of five geocentric Cartesian coordinates described
below. Let us denote the unit vector toward the Sun by S and the unit
vector along the magnetic dipole axis by D (positive northward).
- GEI: Geocentric Equatorial Inertial
- X-axis pointing toward the first point of Aries (the position of Sun at vernal equinox).
- Z-axis points toward geographic north.
- GEO: Geographic
- Z-axis along the geographic north pole.
- X-axis in the equatorial plane at the Greenwich meridian (longitude=0).
- GSM: Geocentric Solar Magnetospheric
- X-axis pointing toward the Sun.
- Y-axis perpendicularto the Earth magnetic dipole and the Sun direction
- SMC: Solar Magnetic Coordinates
The difference between GSM and SMC is rotation around the common Y
axis by the dipole tilt angle.
- GSE: Geocentric Solar Ecliptic.
- X-axis points toward the Sun.
- Z-axis points toward the ecliptic north.
In all coordinates the third axis, not mentioned above, completes the right
handed Cartesian triad (X,Y,Z).
The footprint projections on the Earth are shown at an altitude of 100 km above the average
sphere of 6373.2 km in two
coordinates system: geographic GEO (longitude and latitude), and magnetic SMC
(magnetic local time and magnetic latitude). Field line tracing is done with the selected magnetospheric
model (internal + external). Please note that in SMC
coordinates footprints are shown as MLT
(magnetic local time) and MLAT (magnetic latitude) that are equivalent to dipole geomagnetic coordinates.
The corrected geomagnetic coordinates are not used for display purposes because they
do not represent an orthogonal transformation and therefore cannot be included
in the global coordinate transformation matrices.
- The magnetic field models include standard internal field model IGRF 1950-2000 and
Tsyganenko models of the external magnetospheric field: T87, T89, T96 and T2001.
- The bow shock model is according to Farris et al, GRL, v. 18, p.1821,
1991, and Cairns et al., JGR, v.100, p.47, 1995
- The magnetopause model is according to Shue et al., JGR, v. 103, p. 17691, 1998.
- The electric potential model is according to D. Weimer, GRL, 23,
All these model implementations have user-editable time-dependent parameter data.
The orbital module includes a standard ESOC program for computing position
and velocity of Cluster, Double Star or any other s/c with the orbital parameters
defined in Long Term Orbit File (LTOF).
For orbits defined by TLE (two-line elements) SGP4/SDP4 orbit propagator is used.
OVT distribution contains Cluster, Double Star, Polar, Fast and Astrid-2 satellites.
To add another satellite - download the .tle or .ltof orbit file
and click on the menu Satellites -> Import Satellite...
Latest Cluster orbit files can be downloaded from
orbital elements for civilian satellites used can be obtained from CelesTrak
or NASA ftp.
The information about s/c start and stop time as well as it's approximate
revolution period is availabe in satellite's Info window.
If a spin data file (e.g SatelliteName.spin) is present in the odata directory
under OVT installation directory, it
is used to compute orientation of the spin axis in respect to the
magnetic field, velocity vector, and the sun direction. The .spin files must be
in the format required for CLUSTER project, i.e.
1 P 1994-09-01T00:00:00Z 1994-09-07T12:30:00Z 341.00 77.00
14.ffffff 333.800 776.1 0.0 0.0 0.00 0.00 1994-09-01T01:10:00Z
User interface consists of one visualization window integrated with a tree-like
control panel. Objects in the visualization window are mouse maneuverable:
use left button to rotate the picture and right button to zoom in and
out. To change the focus of the viewing scene one can use the middle button on Unix systems
and Shift + left mouse button.
The picture shows orbit of the Cluster1 satellite in GSM coordinates, current
satellite position at time 2001-03-02T21:00:00Z and the magnetic field line
passing through the satellite at this position. The footprints are shown in GEO
coordinates. The position and size of the labels can be controlled by the user.
||The left-side panel shows list of actors
that can be displayed on the right-hand side scene. Each actor has some
editable properties and can be shown/hidden on the scene. This popup menu is
activated with right-side mouse button, after a selection click with
The bow shock and the magnetopause have editable properties that
control their shape and positions. SWP is the solar wind pressure (nPa)
and IMF stands for Interplanetary Magnetic Field.
||Magnetic field models are controlled by the
window shown in the left. Each model has an associated set of
parameters which can be edited by the user. At present we have four
version of the Tsyganenko models, which can be combined with IGRF or
dipole internal field models.
Tsyganenko 2001: The two IMF-related indices G1 and G2 take into account
the IMF and solar wind conditions during the preceding 1-hour interval; their
exact definition is given in the paper by N.A.Tsyganenko "A new data-based model of the near
magnetosphere magnetic field. 2. Parameterization and fitting to observations".
The paper is available online from anonymous ftp-area www-istp.gsfc.nasa.gov,
The checked MP clipping
means that the terrestrial magnetic field lines are not allowed to go
outside the model MP surface (more than 0.5 Re).
||Each activity data can be edited by the Data Editor.
The data record with the time earlier or equal to the requested time is taken
from the Data Editor.
If the requested time is earlier then the time of the first record - the first record is used.
||Magnetospheric structure represents a shell
of outermost field-lines which are determined from current
magnetic field model. If MP clipping is set,
the field lines are not permitted to extend outside the MP model. If
the MP clipping is off, then the field-lines derived from the
magnetospheric model can extend significantly beyond the MP model. However
in such a case their footprint is very narrow and corresponds to the
topological magnetic cusp (for models T87, T89).
Fieldline thickness can be specified (view the image).
View from -Y
View from Z
On this pictures you can see magnetopause, in a wireframe representation, and a
surface created from two fieldlines, starting form
To visualize data click on the satellite with the right mouse button and choose "Load Data..."
Load Data Wizard will apear.
The data file should contain two columns: 1-st - Time
2-nd - Magnitude
Time can be specified as DATE-TIME pair or in days/hours/minutes/seconds.
In the last case you will be asked by OVT to specify the offset time.
DATE format: YYYY-MM-DD or YYYY/MM/DD or YYYY/DDD
TIME format: hh:mm or hh:mm:ss or hh.hhhh or sssss.ss
Data file example:
# comment - this is a Polar current magnitude data
2001-12-30 12:00:00 4.5
2001-12-30 12:01:00 5.6
||The time setting (left) is self-explanatory.
"<<" and ">>" buttons are used to shift
the start time by the interval.
||Orbit Monitor can be accessed by Sat's
pop-up menu. Orbit Monitor shows the current satellite position, velocity,
distance from the center of the earth, magnetic field conditions, derived from
the magnetic field model, and footprint coordinates. The footprints
are shown for both hemispheres, if exist. In addition, the orbit monitor
shows the estimated radial distance to the current model of the
magnetopause and the angle of the satellite spin axes with respect to the
magnetic field vector, satellite velocity, and the sun direction. The
later data require presence of the spin axis attitude file in the ODATA
directory. The spin attitude file has suffix .spin and must be in the
format required by the CLUSTER project. The .spin files included in the
distribution contain artificial data for demonstration purposes. They
should be removed or replaced by real data.
Dumping of orbit data
Dumper panel is expanded if "Dump >>" is pressed;
"Log" will dump the data specified in the Dumper Settings Window to a selected file.
"Log All" will dump the data for the whole orbit.
"Settings" button pops-up dumper settings window.
Data available for dumping: data from the orbit monitor, Bx, By, Bz, Dipole Tilt angle.
||The picture shows footprint of CLUSTER1
over northern polar regions with time lables.
The tic marks are every 5 minutes.
Footprints can be
shown either in GEO or in SMC coordinates.
||Zooming at the CLUSTER spacecraft shows the
spacecraft trajectories (red, black, green, magenta) and the threading field-lines (green).
The satellite is depicted as a sphere or as cylinders with a small pyramid, depending on the
absence or presence of the spin attitude files. In the later case, the
pyramid shows the actual orientation of the spin axis.
The color convention:
- Cluster 1 - red
- Cluster 2 - black
- Cluster 3 - green
- Cluster 4 - magenta
||The CLUSTER configuration window shows configuration
parameters of the four spacecraft.
XYZ box shows the minimum box size in current coordinates that will
confine all four spacecraft.
Ellipsoid shows three axes of an ellipsoid that will confine
FAC box shows a box in local field-aligned coordinates around the
gravity centre that will confine four spacecraft: dB-along the
field-lines, dA-in the azimuthal (LT) direction, and dR-in the dBxdA,
pseudo-radial direction. The configuration parameters are automatically
saved in file ovt/userdata/clusters.conf.
||The new version has useful control of the viewer position
which can be selected as a top of any of the axes X, Y, Z, or the
direction perpendicular to the orbit. The focal point can be a particular
satellite, center of the Earth, or a given geographic point.
Projection method can be parallel or perspective.
When printing or saving image make sure that
the graphics is not covered by other window. The resolution of the
hard copy corresponds to the resolution of screen objects.
One can export image to a file and print or edit it with another program.
Time advance arrows < and > change time by one step within the
requested interval. Double arrows << and >>
move to the start or end points, respectively.
The Earth can be shown either as continents, or as
The axis XYZ can be hidden/shown and refer to the
current selection of space coordinates.
Frame grid in three space planes can be also shown in the
picture. Frame properties are editable.
Caption text can be included in the graphics window. Font and size of the text
can be changed by the user.
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OVT Team, 2000-2002.