From fa080de7afc95aa1c19a6e6fc0e0708ced2eadc4 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 8 Jul 2015 20:46:52 -0400 Subject: Initial commit --- math/slalib/doc/pv2ue.hlp | 70 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 math/slalib/doc/pv2ue.hlp (limited to 'math/slalib/doc/pv2ue.hlp') diff --git a/math/slalib/doc/pv2ue.hlp b/math/slalib/doc/pv2ue.hlp new file mode 100644 index 00000000..776f877a --- /dev/null +++ b/math/slalib/doc/pv2ue.hlp @@ -0,0 +1,70 @@ +.help pv2ue Jun99 "Slalib Package" +.nf + + SUBROUTINE slPVUE (PV, DATE, PMASS, U, JSTAT) + + - - - - - - + P V U E + - - - - - - + + Construct a universal element set based on an instantaneous position + and velocity. + + Given: + PV d(6) heliocentric x,y,z,xdot,ydot,zdot of date, + (AU,AU/s; Note 1) + DATE d date (TT Modified Julian Date = JD-2400000.5) + PMASS d mass of the planet (Sun=1; Note 2) + + Returned: + U d(13) universal orbital elements (Note 3) + + (1) combined mass (M+m) + (2) total energy of the orbit (alpha) + (3) reference (osculating) epoch (t0) + (4-6) position at reference epoch (r0) + (7-9) velocity at reference epoch (v0) + (10) heliocentric distance at reference epoch + (11) r0.v0 + (12) date (t) + (13) universal eccentric anomaly (psi) of date, approx + + JSTAT i status: 0 = OK + -1 = illegal PMASS + -2 = too close to Sun + -3 = too slow + + Notes + + 1 The PV 6-vector can be with respect to any chosen inertial frame, + and the resulting universal-element set will be with respect to + the same frame. A common choice will be mean equator and ecliptic + of epoch J2000. + + 2 The mass, PMASS, is important only for the larger planets. For + most purposes (e.g. asteroids) use 0D0. Values less than zero + are illegal. + + 3 The "universal" elements are those which define the orbit for the + purposes of the method of universal variables (see reference). + They consist of the combined mass of the two bodies, an epoch, + and the position and velocity vectors (arbitrary reference frame) + at that epoch. The parameter set used here includes also various + quantities that can, in fact, be derived from the other + information. This approach is taken to avoiding unnecessary + computation and loss of accuracy. The supplementary quantities + are (i) alpha, which is proportional to the total energy of the + orbit, (ii) the heliocentric distance at epoch, (iii) the + outwards component of the velocity at the given epoch, (iv) an + estimate of psi, the "universal eccentric anomaly" at a given + date and (v) that date. + + Reference: Everhart, E. & Pitkin, E.T., Am.J.Phys. 51, 712, 1983. + + P.T.Wallace Starlink 18 March 1999 + + Copyright (C) 1999 Rutherford Appleton Laboratory + Copyright (C) 1995 Association of Universities for Research in Astronomy Inc. + +.fi +.endhelp -- cgit