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15.5.484 readorbits

readorbits [, file, /list, /replace]

Reads orbital data from file file for use with the astron routine. The file name defaults to $LUXDIR/orbits. If /list is specified, then object ID numbers and comments included in the file are displayed on screen. If /replace is specified, then the new orbital data replaces previously read orbital data, if any. By default, the new orbital data is merged with the previously read data, if any.

The data must conform to the following description, or else garbage results and/or errors may result.

Lines with an equal sign (=) at the very beginning are comment lines. The first data line of the file must contain the number of objects for which data is included in the file. A comment (initiated by an equal sign) may follow.

For each object, the first line of the corresponding data segment consists of the object ID number (which should be distinct from those of the major objects listed for objects in routine astron, i.e., not between 0 and 8, inclusive), followed by the number of data lines for this object, followed by the absolute magnitude, followed by an optional specification of the equinox to which the following data is referred, followed by an optional data format indicator for the data lines, followed by an optional comment (initiated by an equal sign).

If the equinox specification is absent, then J2000.0 is assumed. If it is present, then it must consist of either a scalar, which is taken to indicate a JDE (Julian Date/TDT) specification, or one letter out of j, j, b, b, followed by a (floating-point) year specification, or one letter out of d, d. If the letter is d or d, then the equinox of the date is assumed. If the letter is j or j, then the unit of the following year is Julian. If the letter is b or b, then the unit is pseudo-Besselian: Besselian years are taken to be 365.2421988 days long, and b1950.0 corresponds to JDE 2433282.4235.

The data format indicator must be one letter out of a, a, q, q, or absent. If the data format indicator is a or a or absent, then each data line for the current object must contain the following information in the listed order, with all distances in AU and all angles in degrees: the JDE for which the data is valid (the epoch), the semimajor axis, the eccentricity, the inclination, the longitude of the ascending node, the argument of the perihelion, and the mean anomaly at the epoch.

If the data format indicator is q or q, then the data format is the same as that for a, except that the perihelion distance is substituted for the semimajor axis, and the JDE of the (last) perihelion transit is substituted for the mean anomaly.

The data segments for all objects in the file must be sorted in ascending order of their ID numbers. The data lines for each object must be sorted in ascending order of their JDE.

See also: astron

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