Column format string

Reading a text file without a predefined format can be done using a column format string. It is assumed that the text file contains one Cartesian orbit state vector per row with field separated with spaces, like the following example:

Mod. Julian Epoch       X (km)          Y (km)           Z (km)     VX (km/s)    VY (km/s)  VZ (km/s)

9250.0000000000         443.2628        6762.4130        -0.0008    1.4272     -0.1034      7.6136

9250.0001157407         457.5052        6760.9366        76.1335    1.4212     -0.1919      7.6131

9250.0002314815         471.6863        6758.5758       152.2581    1.4149     -0.2803      7.6116

9250.0003472222         485.8031        6755.3313       228.3631    1.4084     -0.3686      7.6092

..

The column format string is semi-colon separated string with three fields as follows

<OSV> ; <FRAME> ; <UNITS>

The fields are

OSV: a colon-separated string identifying the time, position and velocity fields.

• The Time field can be identified as

  • UTC: Time in UTC like for example 2023-09-20T08:47:22.000

  • TT: Time in Terrestrial Time, as defined here.

  • TT2000: Time in Terrestrial time referred to year 2000 (1/1/2000 00:00:00)

  • JD: Julian Day, as defined here

  • MJD2000: Modified Julian Day referred to year 2000 (1/1/2000 00:00:00)

• The Position fields are X, Y Z

• The Velocity fields are VX,VY,VZ

• Columns with no meaning that may exist in the file in-between the relevant OSV fields must be identified with a different string, e.g. DUMMY, or underscore, or any other character.

FRAME: It identifies the reference frame, with two options:

• ECI: Earth Centred Inertial coordinates

• ECF: Earth Centred Fixed coordinates

UNITS: To identify the distance units for the Position and Velocity fields, with two options

• KM: Kilometres

• M: Meters

The example above should require the following format string

MJD200,X,Y,Z,VX,VY,VZ;ECF;KM

 

The following text file should require the string UTC,X,Y,Z,VX,VY,VZ;ECI;KM

2023-09-20T08:47:22.000     2502.796836   -2065.949451    6279.834337   -6.368470287    2.258320994    3.273958949

2023-09-20T08:50:22.000     1317.983870   -1624.412807    6751.273865   -6.756114197    2.632721741    1.948404842

2023-09-20T08:53:22.000       85.330937   -1123.916655    6977.027538   -6.898449638    2.911457733    0.552388342

...