This section contains nine interactive tools which allow you to feed in some numerical sets of data and obtain the output. They are fundamental yet essential mathematical models, such as coordinate transformations and conversions between orbital elements and rectangular Cartesian coordinates. Each program was originally written in FORTRAN and converted to Perl in order to get it working on the Web.
Fill in the following boxes and hit the button "Compute" to obtain the results.
The Julian Date (JD) is the number of mean solar days (and fraction of a day) elapsed since the epoch noon on January 1st, 4713 B.C. Since the astronomical day was defined to count from noon rather than midnight, the Julian Date is always different from UT by 0.5. For example, 1970, 7, 12, 0 (midnight) (UT) = 2440779.5 (JD) .
The folowing program converts the civilian date expressed by the year,
month, day, and the time (hour, minute, and second) in Universal Time (UT)
into the Julian Date (JD). Also, it provides the day of week for that date.
(Note: This program is only valid for an epoch between March 1900 and Febrary
2100.)
Year: Month: Day: Hour: Minute: Second:
This program transforms a given vector from earth centered, earth fixed coordinates to a topocentric geographic coordinate system. The earth fixed system's Xaxis is in the direction of the Greenwich Meridian, the Zaxis north, and the Yaxis completing a righthanded system. The geographic system's Xaxis points south, the Yaxis east, and the Zaxis zenith.
Latitude of Local Coordinate Site (in degrees): Longitude of Local Coordinate Site (in degrees): Xcomponent of Vector in Earth Centered, Earth Fixed Coordinates: Ycomponent of Vector in Earth Centered, Earth Fixed Coordinates: Zcomponent of Vector in Earth Centered, Earth Fixed Coordinates:
This program transforms a given vector from M50 equatorial coordinates to earth centered, earth fixed coordinates. The earth fixed system's Xaxis is in the direction of the Greenwich Meridian, the Zaxis north, and the Yaxis completing a righthanded system.
Hour Angle of the Vernal Equinox (in degrees): Xcomponent of Vector in M50 Equatorial Coordinates: Ycomponent of Vector in M50 Equatorial Coordinates: Zcomponent of Vector in M50 Equatorial Coordinates:
This program transforms a given vector from earth centered, earth fixed coordinates to M50 equatorial coordinates. The earth fixed system's Xaxis is in the direction of the Greenwich Meridian, the Zaxis north, and the Yaxis completing a righthanded system.
Hour Angle of the Vernal Equinox (in degrees): Xcomponent of Vector in Earth Centered, Earth Fixed Coordinates: Ycomponent of Vector in Earth Centered, Earth Fixed Coordinates: Zcomponent of Vector in Earth Centered, Earth Fixed Coordinates:
This program converts from earth centered nonrotating coordinates to right ascension, declination, and radial distance from the origin of the inertial coordinate system. The earth centered nonrotating coordinate system has Xaxis pointing toward the vernal equinox, Zaxis pointing toward either the Celestial or Geographic north pole, and Yaxis completing the right handed coordinate system.
Xcomponent of Vector in Earth Centered nonrotating Coordinates: Ycomponent of Vector in Earth Centered nonrotating Coordinates: Zcomponent of Vector in Earth Centered nonrotating Coordinates:
This program converts from right ascension, declination, and radial distance into earth centered nonrotating coordinates. The right ascension is measured positive from the Xaxis toward the Yaxis in the XY plane. The declination is measured positive from the XY plane up to the inertial vector.
Right Ascension (in degrees): Declination (in degrees): Magnitude of Inertial Vector:
This program calculates the position and velocity vectors in the orbit fixed PQW coordinate system given the orbital elements.
SemiMajor Axis: Eccentricity: Gravitational Parameter: Current Time since Chosen Epoch, T0: Time of Previous Periapsis Passage since Chosen Epoch, T0:
This program calculates the position and velocity vectors in the earth centered nonrotating coordinate system given the orbital elements.
SemiMajor Axis: Eccentricity: Inclination (in degrees): Longitude of the Ascending node (in degrees): Argument of Periapsis (in degrees): Gravitational Parameter: Current Time since Chosen Epoch, T0: Time of Previous Periapsis Passage since Chosen Epoch, T0:
This program converts the position and velocity vectors from the orbit centered coordinate system, PQW, to the inertially fixed coordinate system, XYZ.
Longitude of the Ascending node (in degrees): Argument of Periapsis (in degrees): Inclination (in degrees): Xcomponent of Position Vector in PQW Coordinates: Ycomponent of Position Vector in PQW Coordinates: Zcomponent of Position Vector in PQW Coordinates: Xcomponent of Velocity Vector in PQW Coordinates: Ycomponent of Velocity Vector in PQW Coordinates: Zcomponent of Velocity Vector in PQW Coordinates:
This page is created by Masaharu Suzuki The University of Texas at Austin
Last Modified: Wed Feb 11, 1999
