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+.help pertel Jun99 "Slalib Package"
+.nf
+
+      SUBROUTINE slPRTL (JFORM, DATE0, DATE1,
+     :                 EPOCH0, ORBI0, ANODE0, PERIH0, AORQ0, E0, AM0,
+     :                 EPOCH1, ORBI1, ANODE1, PERIH1, AORQ1, E1, AM1,
+     :                       JSTAT)
+
+     - - - - - - -
+      P R T L
+     - - - - - - -
+
+  Update the osculating orbital elements of an asteroid or comet by
+  applying planetary perturbations.
+
+  Given (format and dates):
+     JFORM   i    choice of element set (2 or 3; Note 1)
+     DATE0   d    date of osculation (TT MJD) for the given elements
+     DATE1   d    date of osculation (TT MJD) for the updated elements
+
+  Given (the unperturbed elements):
+     EPOCH0  d    epoch (TT MJD) of the given element set (Note 2)
+     ORBI0   d    inclination (radians)
+     ANODE0  d    longitude of the ascending node (radians)
+     PERIH0  d    argument of perihelion (radians)
+     AORQ0   d    mean distance or perihelion distance (AU)
+     E0      d    eccentricity
+     AM0     d    mean anomaly (radians, JFORM=2 only)
+
+  Returned (the updated elements):
+     EPOCH1  d    epoch (TT MJD) of the updated element set (Note 2)
+     ORBI1   d    inclination (radians)
+     ANODE1  d    longitude of the ascending node (radians)
+     PERIH1  d    argument of perihelion (radians)
+     AORQ1   d    mean distance or perihelion distance (AU)
+     E1      d    eccentricity
+     AM1     d    mean anomaly (radians, JFORM=2 only)
+
+  Returned (status flag):
+     JSTAT   i    status: +102 = warning, distant epoch
+                          +101 = warning, large timespan ( > 100 years)
+                      +1 to +8 = coincident with major planet (Note 6)
+                             0 = OK
+                            -1 = illegal JFORM
+                            -2 = illegal E0
+                            -3 = illegal AORQ0
+                            -4 = internal error
+                            -5 = numerical error
+
+  Notes:
+
+  1  Two different element-format options are available:
+
+     Option JFORM=2, suitable for minor planets:
+
+     EPOCH   = epoch of elements (TT MJD)
+     ORBI    = inclination i (radians)
+     ANODE   = longitude of the ascending node, big omega (radians)
+     PERIH   = argument of perihelion, little omega (radians)
+     AORQ    = mean distance, a (AU)
+     E       = eccentricity, e
+     AM      = mean anomaly M (radians)
+
+     Option JFORM=3, suitable for comets:
+
+     EPOCH   = epoch of perihelion (TT MJD)
+     ORBI    = inclination i (radians)
+     ANODE   = longitude of the ascending node, big omega (radians)
+     PERIH   = argument of perihelion, little omega (radians)
+     AORQ    = perihelion distance, q (AU)
+     E       = eccentricity, e
+
+  2  DATE0, DATE1, EPOCH0 and EPOCH1 are all instants of time in
+     the TT timescale (formerly Ephemeris Time, ET), expressed
+     as Modified Julian Dates (JD-2400000.5).
+
+     DATE0 is the instant at which the given (i.e. unperturbed)
+     osculating elements are correct.
+
+     DATE1 is the specified instant at which the updated osculating
+     elements are correct.
+
+     EPOCH0 and EPOCH1 will be the same as DATE0 and DATE1
+     (respectively) for the JFORM=2 case, normally used for minor
+     planets.  For the JFORM=3 case, the two epochs will refer to
+     perihelion passage and so will not, in general, be the same as
+     DATE0 and/or DATE1 though they may be similar to one another.
+
+  3  The elements are with respect to the J2000 ecliptic and equinox.
+
+  4  Unused elements (AM0 and AM1 for JFORM=3) are not accessed.
+
+  5  See the slPRTE routine for details of the algorithm used.
+
+  6  This routine is not intended to be used for major planets, which
+     is why JFORM=1 is not available and why there is no opportunity
+     to specify either the longitude of perihelion or the daily
+     motion.  However, if JFORM=2 elements are somehow obtained for a
+     major planet and supplied to the routine, sensible results will,
+     in fact, be produced.  This happens because the slPRTE routine
+     that is called to perform the calculations checks the separation
+     between the body and each of the planets and interprets a
+     suspiciously small value (0.001 AU) as an attempt to apply it to
+     the planet concerned.  If this condition is detected, the
+     contribution from that planet is ignored, and the status is set to
+     the planet number (Mercury=1,...,Neptune=8) as a warning.
+
+  Reference:
+
+     Sterne, Theodore E., "An Introduction to Celestial Mechanics",
+     Interscience Publishers Inc., 1960.  Section 6.7, p199.
+
+  Called:  slELUE, slPRTE, slUEEL
+
+  P.T.Wallace   Starlink   14 March 1999
+
+  Copyright (C) 1999 Rutherford Appleton Laboratory
+  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
+
+.fi
+.endhelp