Copyright ©1993 - 1999 by Howard R. Cole.  All Rights Reserved.



Data File Formats

Rendezvous is capable of using several different coordinate systems in its calculations.   The file formats for each of these systems is described below:

Two Line Element Format (tle)

o Files with .tle extension are NORAD two line element sets. The following excerpt describing the format is taken from a posting by T.S. Kelso to the Usenet "sci.space.new" newsgroup:
Data for each satellite consists of three lines in the following format:

AAAAAAAAAAA
1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN

Line 1 is an eleven-character name.

Lines 2 and 3 are the standard Two-Line Orbital Element Set Format identical
to that used by NORAD and NASA.  The format description is:

Line 1
Column     Description
01-01     Line Number of Element Data
03-07     Satellite Number
10-11     International Designator (Last two digits of launch year)
12-14     International Designator (Launch number of the year)
15-17     International Designator (Piece of launch)
19-20     Epoch Year (Last two digits of year)
21-32     Epoch (Julian Day and fractional portion of the day)

34-43 First Time Derivative of the Mean Motion or Ballistic Coefficient (Depending on ephemeris type)
45-52     Second Time Derivative of Mean Motion (decimal point assumed; blank if N/A)
54-61 BSTAR drag term if GP4 general perturbation theory was used. Otherwise, radiation pressure coefficient.  (Decimal point assumed)
63-63     Ephemeris type
65-68     Element number
69-69     Check Sum (Modulo 10) (Letters, blanks, periods, plus signs = 0; minus signs = 1)

Line 2
Column     Description

01-01 Line Number of Element Data
03-07 Satellite Number
09-16 Inclination [Degrees]
18-25 Right Ascension of the Ascending Node [Degrees]
27-33 Eccentricity (decimal point assumed)
35-42 Argument of Perigee [Degrees]
44-51 Mean Anomaly [Degrees]
53-63 Mean Motion [Revs per day]
64-68 Revolution number at epoch [Revs]
69-69 Check Sum (Modulo 10)

All other columns are blank or fixed.

Example:

NOAA 6
1 11416U          86 50.28438588 0.00000140           67960-4 0  5293
2 11416  98.5105  69.3305 0012788  63.2828 296.9658 14.24899292346978



Earth Centered Rotating Format (ecr)

o Files with an ecr extension are Earth Centered Rotating state vectors.  A sample file would look like this:

7 11 1991
18 40 0.0
SAT 1
0.0  2000000.0 35.083 -106.65 6900.0 0.0 0.0
SAT 2
0.0  2000000.0 42.129 -120.72 6840.0 0.0 -5.38

The first two lines contain the date and time of the epoch in free format (any number of white space characters can separate the fields).

The third and fourth line and subsequent pairs of lines contain the name for the state (this is the name that will appear in the browser), and the state itself with these fields in free format:

SatName
timeOffset   altitude  latitude  longitude    speed  ascent_angle  course

The timeOffset value is the number of seconds from the epoch date at which the state is valid.

The next three numbers indicate the position of the satellite as altitude, latitude, and longitude.  The altitude is measured in meters, and the latitude and longitude are measured in decimal degrees.

The next three numbers indicate the velocity of the satellite as the speed, the ascent angle, and the course measured from true north.  The speed is given in meters/second, and the ascent and course angles are given in decimal degrees.


Earth Centered Inertial Format (eci)

o   Files with an eci extension are Earth Centered Inertial J2000 state vectors. The first two lines are the date and time of the epoch and have the same format as the .ecr files.

Each additional entry consists of two lines, the name of the satellite and its state vector.   These entries have this format:

SatName
timeOffset  x y z  vx  vy  vz

Again, the timeOffset is the number of seconds from the epoch date at which the state is valid.

The next three numbers (x y z) indicate the position of the satellite as cartesian components in the ECI J2000 coordinate system given in units of meters.

The next three numbers (vx vy vz) indicate the velocity of the satellite as cartesian components in the ECI J2000 coordinate system given in units of meters/second.


Element Set Format (element)



Heliocentric Ecliptic (hce)