   Comments and blank lines may be added freely.  (Anything beginning
   with a space is a comment.)  If a line is uncommented,  it's probably
   controlled via the user interface.

   The default version of this file is stored in 'environ.def'.  Once
   you've run Find_Orb or 'fo' (Find_Orb's non-interactive sibling),  new
   settings are written to 'environ.dat'.  If you decide at some point that
   you'd like to reset to factory defaults,  just delete 'environ.dat'.

   Windows Find_Orb ignores the following 'CONSOLE_OPTS' line.  For the
   console flavor of Find_Orb,  this line gives the default MPC code for
   ephems, which items are shown on-screen, residual display format, and
   whether all,  some,  or only one MPC code(s) are displayed.
CONSOLE_OPTS=500 15 3 1

   The 'settings' give the comet magnitude type used (defaults to 'N', or
   'nuclear');  the format used for orbital elements;  the precision used
   in orbital elements (defaults to five places for angular elements);  the
   ephemeris output options,  in a complicated form;  the maximum residual
   filtered,  in arcseconds (defaults to 2);  and the Gaussian "noise"
   added,  in sigmas,  when running Monte Carlo orbits.
SETTINGS=N,4,5,66560,2.000000,1.000000
DEFAULTS=N4
EPHEM_START=+0
EPHEM_STEPS=100 1
REFERENCE=Find_Orb
EPHEM_LON=W 69.900
EPHEM_LAT=N 44.010
EPHEM_MPC_CODE=1 500

   'filtering' gives the assumed probability that an observation is a blunder
   (defaults to 2%);  the over-observing time span (defaults to one day);  the
   "ceiling" on over-observing (defaults to five observations);  and a number
   which is 1 if "filtering" uses blunder management,  or 0 if we are doing
   traditional rejection based on an observation having residuals greater
   than N sigmas,  with N specified in 'settings' (see above).  By default,
   blunder management is used (see the Find_Orb Web page for a description of
   blunder management and over-observing parameters).
FILTERING=2.000 1.000000 5 1

   Observations sent via e-mail frequently end up with spaces added
   or removed.  Find_Orb will (usually) parse such observations anyway.
   Remove or comment out the following line,  and Find_Orb will switch
   to being "strict" about lines being exactly 80 characters long,  etc.
FIX_OBSERVATIONS=1

   By default,  ephemerides can cover the range -1000 to +3000.  If you want
   to go beyond that,  alter the following line.
TIME_RANGE=-1000,3000

   MPC has requested that NEOCP data not be redistributed.  So in
   pseudo-MPECs,  NEOCP observations are "redacted" (blacked out and the
   data replaced with garbage).  The following observers have kindly given
   permission for their NEOCP observations to be redistributed in
   "unredacted" form.  (Contact me if you're willing to be added to this
   list.)
GREENLIT=033 568 703 G58 G96 H41 H43 H45 I52 I93 J95 V03

   We default to assuming that no object will have an observed arc greater
   than 200 years,  and that if it _is_ longer than that,  it's a mistake.
   This is a pretty good assumption,  though some comets and four asteroids
   do have longer observed arcs than this,  possibly requiring you to
   adjust the following line.
MAX_OBSERVATION_SPAN=200

   For radar stations,  power (in watts), temp in K, gain, altitude limit
   in degrees,  and an arbitrary "radar constant" are needed.  So far,  the
   only radar stations for which I have those data are (251) Arecibo and
   (253) Goldstone.  [Correction:  at least most of these data are provided
   in Table 1 of https://arxiv.org/pdf/1604.01080v1.pdf.  And Table 2 provides
   'relative sensitivities',  based on DSS-14 Goldstone (253) = 1, including
   for bistatic modes.  One could,  and I probably eventually will,  copy the
   (253) line for use with other stations;  compute ephemerides that way;
   replace the power,  temperature,  etc. values with the ones that actually
   apply for that telescope;  then scale up/down the "radar constant" to get
   SNRs that are the appropriate multiple of (253) Goldstone.]
RADAR_251=900000,25,10,70.5,1.5e-11
RADAR_253=430000,17,.94,20,1e-11
   The Parkes radio telescope in Australia lacks an official MPC code.  But it
   has an unofficial MPC code in 'rovers.txt' (q.v.).
RADAR_d43=430000,17,.94,20,7e-14

   'Settings2' gives five parameters.  The first is 1 if observation weighting
   is used and 0 if it is not.  Next,  the 'faint limit' on ephemerides (by
   default,  ephemerides are not listed if the object is fainter than mag 22).
   The third value defaults to zero;  if it's non-zero,  the positional sigmas
   for observations are shown in the (normally blank) columns 57-65 of MPC
   reports.  The fourth number indicates a central object for orbital
   elements,  if one isn't allowing automatic selection of elements.  By default,
   the central object is 3,  i.e.,  the earth.
      The final number is 1 if FCCT14 astrometric debiasing is applied,  and 0
   if it is not. FCCT14 removes (most of) the star catalog position/proper
   motion biases,  using tables from Farnocchia,  Chesley,  Chamberlin,
   Tholen, _Icarus_ 245 (2015) 94-111,
   http://adsabs.harvard.edu/abs/2015Icar..245...94F  .  See
   https://www.projectpluto.com/bias.htm for more information.
SETTINGS2=1 22.00 0 3 0

   Note the comments in the above paragraph about FCCT14 debiasing.  By
   default,  Find_Orb looks for the 'bias.dat' file to be in the same
   directory as Find_Orb itself.  However,  you can set the file name
   with the following line.
FCCT14_FILE=

   Most JPL filenames can be automatically detected via the list in
   'jpl_eph.txt'.  But if it's in a different folder or an odd name,  you
   can add the path to one of the following,  depending on whether you're
   on Windows or Linux.  (LINUX_JPL_FILENAME is also used for OS/X and *BSD.)
LINUX_JPL_FILENAME=
JPL_FILENAME=

   When Find_Orb loads up a short arc,  it uses "statistical ranging"
   (SR),  and defaults to trying 100 possible orbits at a mix of
   distances and radial velocities to characterize the possible orbits
   for the object.  You can raise or lower that number here.
MAX_SR_ORBITS=100

   By default,  if asteroid perturbers are turned on,  Pallas is included
   if it is within 10 AU of our target object.  This 'asteroid threshhold'
   is scaled by the square root of the perturbing asteroid's mass;  for
   example,  an asteroid with a quarter the mass of Pallas would only
   be included if it were within 5 AU.  This helps to assure that the tiny
   contributions of most of the 300 asteroids do not have to be computed.
   If you think you have a case where they _do_ matter,  increase the
   following setting.  If you think you're unnecessarily including asteroid
   perturbations that cannot possibly matter,  decrease it.
ASTEROID_THRESH=10

   By default,  we consider all 300 asteroids listed in BC-405.  You can
   get a good speed-up by cutting this down,  at the risk of maybe ignoring
   some tiny rock that just happens to pull your target around more than
   you expected.
BC405_ASTEROIDS=300

   By default,  geoocentric elements are referred to the J2000 _equator_.
   Everything else (heliocentric and other non-earth-centric) is referred
   to the J2000 _ecliptic_.  Set the following to be 1 to force all
   elements to be J2000 ecliptic (including geocentric ones),  or 2 to
   force all elements to be J2000 equatorial.  Set it to be 3 to force
   all elements to be body-centric.  Note that for geocentric elements,
   this will result in elements that are slightly different from those you'd
   get by default,  due to precession and nutation since 2000;  the angles
   should be passably close to those seen in TLEs.
ELEMENTS_FRAME=0

   Find_Orb will apply geopotential terms (spherical harmonics) for objects
   close to the earth.  It has a bit of logic to determine how many should
   be computed,  as a function of distance (only J2 for most cases,  but
   many terms as one gets close to the earth).  The following GEO_TERMS
   quantity can be raised to include more terms,  or lowered to get better
   speed for artsats.  However,  through experimentation,  I've found that
   setting it to the default value of 6 gets good results;  increasing it
   doesn't change orbits much,  lowering it causes them to start showing
   errors.
GEO_TERMS=6

   Find_Orb can use either the method of Encke (do a two-body solution relative
   to the 'best fitting' body,  integrating perturbations to that orbit).  By
   default,  it instead uses the method of Cowell (the 'direct' method,  in
   which you just integrate the accelerations from all bodies).  I'm still
   experimenting with both methods.  But you will probably be best off leaving
   this value at zero,  meaning Cowell is used.
ENCKE=1

   By default,  the DRAG_SHUTOFF=1 tells Find_Orb not to include the effects
   of atmospheric drag.  Set it to zero if you want objects entering the
   earth's atmosphere to be affected by drag.
DRAG_SHUTOFF=1

   By default,  Find_Orb will look for an orbit covering,  at most,  20
   years (7300 days) of observations.  This is simply for speed reasons,
   and you can toggle additional observations once the object is loaded
   and extend the orbit.   You can adjust the initial parameter here.
AUTO_ARC_LEN=7300

   VECTOR_OPTS gives three values controlling state vector and Cartesian
   coordinate ephemerides.  The first value can be zero (the default) for
   equatorial J2000 vectors,  or one for ecliptic J2000.  (I may add
   mean and/or apparent coordinates at some point,  and perhaps body
   plane coordinates.)  The second value is a multiplier for length.
   Lengths default to being in AU,  with this multiplier being 1.
   Set it to 149597870.7 (the number of kilometers in one AU) to switch
   to kilometers,  or to 23454.7800299146773197201 to switch the distance
   unit to Earth radii (this assumes the equatorial radius of 6378.140 km.)
   The final value gives the time unit:  1=days (default),  24=hours,
   1440=minutes, 86400=seconds.  For example,  VECTOR_OPTS=1,149597870.7,86400
   would get you ecliptic J2000 vectors in kilometers and km/s.
VECTOR_OPTS=0,1,1

   Comet non-gravitational forces in the "standard" Marsden-Sekanina model
   are assumed to be due to sublimating ice.  As described at page 3 of

   http://www.lpi.usra.edu/books/CometsII/7009.pdf

   'Cometary Orbit Determination and Nongravitational Forces',  D. K. Yeomans,
   P. W. Chodas, G. Sitarski, S. Szutowicz, M. Krolikowska, "Comets II",
   this leads to a force whose magnitude is given by a function g(r),  with
   parameters r0, m, n,  and k.  The following line gives those constants for
   non-gravs driven by sublimating water ice.  Sekanina and Kracht have
   proposed different r0, m, n, and k for other sublimation processes.  If
   you want to do that,  change the line below.  (Note that 'alpha' isn't
   given;  it's a normalization quantity to ensure g(1) = 1.  Find_Orb
   will compute it for you.)

COMET_CONSTANTS=2.808,2.15,5.093,4.6142

   Initial orbit determination (IOD) usually takes a couple of seconds.
   For longer arcs,  it might take five or ten seconds.  If it takes more
   than IOD_TIMEOUT seconds (defaults to 20),  we stop looking for a better
   initial orbit and take whatever our best orbit thus far is.  (Such cases
   usually come about because the observations are inconsistent and there
   isn't really a meaningful orbit that fits them.)
IOD_TIMEOUT=20

   Find_Orb defaults to looking for the BC405 ephemeris file (orbital elements
   at 40-day intervals for 300 asteroids used in the BC405 theory;  see
   https://www.projectpluto.com/ast_pert.htm for details) in its configuration
   directory,  then the local directory.  But using the following line,  you
   can move the 'asteroid_ephemeris.txt' file to a different directory,  and/or
   rename it.
# BC405_FILENAME=/home/phred/big/asteroid_ephemeris.txt

   I had a request (https://groups.yahoo.com/neo/groups/find_orb/conversations/messages/35)
   for an option to output planetary state vectors at the epoch of the orbital
   elements to 'elements.txt'.  If you want to do that,  set PLANET_STATES=1.
   By default,  it's blank and planet states are not written out.
PLANET_STATES=

   When looking for precoveries,  one may want to list only images that
   haven't been measured yet,  or only those that have been measured.  (Note
   that the only way Find_Orb knows which images have been measured is by
   looking at the astrometry.  That is to say,  if the astrometry you've used
   to compute the orbit came from an image,  Find_Orb will notice that fact.
   Otherwise,  it'll assume that the image in question hasn't been measured.)
   A value of 1 means "show only measured images";  2="show only unmeasured";
   0 or blank means "show all images".
FIELD_INCLUSION=0

   Set the following COMBINE_ALL parameter to any non-blank value,  and all
   observations in a file will be loaded as if they were of a single object.
   This can be convenient when you're checking a linkage,  for example;  you
   can compute an orbit based on all the observations without having to
   change the designations to all be the same.
COMBINE_ALL=
