Crafting an Orbfit 5 Options File

Default vs User Options Files

Orbfit reads its options from multiple setting files on your machine. Let’s call these the default settings and the user settings. The default settings are read first add can be found in the lib/ folder of wherever you compiled Orbfit on your machine. For me these files are found at ~/Orbfit5.0/lib/*.def

$ cd ~/Orbfit5.0/lib/
$ ls *.def
bineph.def fitdeb.def fitobs.def impcor.def orbfit.def propag.def reject.def

Your user settings have a .oop (Orbfit OPtions) extension and are found in your current working directory and these are read after the default settings, over-riding any common options the two file may have, i.e. User settings trump default settings.

Option Sets

There are various sets of options, each written as a keyword followed by a period:

operations. - usage mode options
object1. & object2. - object specific options
output. - orbital element options
ephem. - ephemeris generation options
propag. - orbit propagation options
ident. - orbit identification options (I don’t report on these option in this post)
lsfit. - least squared fitting of orbits options (I don’t report on these option in this post)

Usage Mode Options

Basically you switch these options on and off depending on your use-case. There are 3 modes for each option:

0: off
1: only perform task if needed
2: on

operations.
    .init_orbdet = 0|1|2
    .diffcor = 0|1|2
    .ident = 0|1
    .ephem = 0|1

.init_orbdet: calcualte and initial orbit with Guass' method. Default: 1
.diffcor: perform some differential corrections of the orbital elements with least square fitting Default: 1
.ident: try to identify a single orbit to the observations of both objects. Default: 1
.ephem: generate an ephemeris for the object(s). Default: 0

Objects Options

object1.
    .name = <string>
    .inc_name = <string>
    .obs_fname = <string>
    .obs_dir = <string>
    .inc_files = <string>

.name: the name for the object; can be used in naming of some input and output files. Note you can have several different run-names for the same object. Default: name of run.
.inc_name: object name in orbital elements file. Default: same as .name
.obs_fname: the basename of the observation file (without .obs extension). Default: same as .name
.obs_dir: location of the observation file. Default: ./ i.e. cwd
.inc_files: initial conditions file (orbital elements). Can be in astorb.dat [BA], MPC [MPC-A] or the native orbfit [OEF] format. Note only the first match in the any set of orbital elements files is used. Speed up the search by explicitly stating the format of the input file by appending a format codename. Default: None

Orbital Elements Output Options

output.
    .epoch = <date-time>
    .elements = CAR|EQU|EQP|KEP
output_files.
    .elem = <string>

.epoch: the epoch at which orbital elements are to be calculated. Can be in many formats (I prefer MJD). Example: MJD 50982.94143519 UTC. Default: orbfit will decide.
.elements: the type of orbital elements to output. CAR for cartesian, EQU for equinoctial, EQP for equinoctial for highly inclined orbits, and KEP for keplerian. Default: EQU
output_files.elem: where to write calculated orbital elements to. Default: <name of run>.oel

Ephemeris Generation Options

ephem.
    .objects = 1|2|3 (or any combination)
    .epoch.start = <date-time>
    .epoch.end = <date-time>
    .step = <float>
    .obscode = <string>
    .timescale = UT1|TAI|UTC|TDT
    .fields = <string>

.objects: the ‘list’ of objects which to calculate an ephemeris for. The ‘list’ include 1 and/or 2 relating to objects 1 and 2. You can also use 3 for the result of an identified orbit from both objects (3). Default: 1 2 3
.epoch.start: the start epoch of ephemeris to be calculated. Can be in many formats (I prefer MJD). Example: MJD 50982.94143519 UTC. Default: orbfit will decide.
.epoch.end: the end epoch of ephemeris to be calculated. Can be in many formats (I prefer MJD). Example: MJD 50982.94143519 UTC. Default: orbfit will decide.
.step: the ephemeris step-size in days Default: 1.0
.obscode: observatory code for ephemeris fro topocentric correction. Default: 500, i.e. geocentric
.timescale: the timescale ephemeris is to be reported in. UT1, TAI, UTC or TDT. Default: TDT
.fields: a list of comma-separated keywords, the values of which you want reported in the ephemeris. Options include cal calendar date, mjd, coord (RA and DEC), mag magnitude, delta distance from the Earth, r distance from the Sun, elong Sun elongation angle, phase Sun phase angle, glat galactic latitude, appmot apparent motion and skyerr sky plane error. Default: ‘cal,coord,delta,r,elong,phase,mag’

ephem.appmot.
    .format = <string>
    .units

.format: format of apparent motion ‘rectangular’ (1) or ‘polar’ (2).
.units: velocity units. Angular unit can rad, deg, arcmin or arcsec. Time units can be d, h, min, s. Example arcsec/min.

Orbit Propagation Options

I list only the most important options here. To see the rest of the options take a look at the lib/propag.def file in you local install of Orbfit.

propag.
    .output_des = <boolean>
    .ab_mag= = <boolean>
    .iast = <int>
    .ilun = 0|1
    .imerc = 0|1
    .iplut = 0|1
    .irel  = 0|1
    .filbe = <string>
    .iclap = 0|1
    .iaber = 0|1
    .istat = 0|1
    .npoint= <int>

.output_des: Output in DES format? Default: False - .rwoformat
.ab_mag: report AB mags Default: False
.iast: number of massive asteroids to use Default: 0
.ilun: include moon Default: 0
.iplut: include pluto Default: 0
.imerc: include mercury Default: 1
.irel: account for general relativity Default: 1
.filbe: asteroid ephemerides file Default: CPV
.iclap: include close approach Default: 1
.iaber: account for aberration effects Default: 1
.istat: add topocentric correction Default: 1
.npoint: the minimum number of data points required for a close approach calculations Default: 100

Tags: orbfit • settings

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