Help for RINGORBS

PURPOSE

"ringorbs" creates an Orbital Elements File containing data for each of the
known planetary ring systems (Jupiter, Saturn, Uranus, and Neptune).  The
file is input to programs NAV and AMOS, which navigate and track features
in the ring plane.

EXECUTION

	ringorbs  OUT=OEF.DAT

where OEF is a 4x110 orbital elements file, in VICAR image format (REAL*8).

ORBITAL ELEMENT FILE FORMAT

The date referred to in the following paragraph is now in the label.
The first element of each record contain the last update to that record
(by NAV or AMOS) in YYYYDDD format.  Initially, this contains the file creation
date.  The date originally was in the format as returned by subroutine OSDATE
(e.g. "WED JAN 22, 1944"). OSDATE has been replaced with DATFMT and the
format is the integer version, not the ASCII version.

The four "lines" of the file contain, in order, the orbital elements for
the rings of Jupiter, Saturn, Uranus, and Neptune.  Each record may be
read directly into a data structure as in the following FORTRAN example:

    COMMON/OE/DATE,PCONST(4),RINGS(7,15)
    REAL*8 DATE,PCONST(4),RINGS(7,15),TMPBUF(110)
    EQUIVALENCE (DATE,TMPBUF),(PCONST,TMPBUF(2)),(RINGS,TMPBUF(6))
    CALL XVREAD(IUNIT,TMPBUF,STATUS)

The first four data items contain the planet orientation constants ALPHAp,
DELTAp, THETA, and ZETAZ.  This is followed by the seven orbital elements for
each ring, SMAA, ECC INCL, OMEGAZ, PIZERO, dOMEGA_dt, and dw_dt.   See the
help file for program NAV for a description of these constants.

The file contains room for a maximum of 15 rings per planet.  The first ring
is always a concentric orbit oriented in the planet's equatorial plane.
The zero-longitude is defined by some standard epoch, as defined below for
each planet.  All orbital elements are set to zero.

The orbital elements for of the nine known rings of Uranus is due to French,
and are store in the following order:

        1 = planet              6 = beta ring
	2 = ring 6		7 = eta ring
	3 = ring 5		8 = gamma ring
	4 = ring 4		9 = delta ring
	5 = alpha ring	       10 = epsilon ring

The zero-longitude for the first ring (planet's equatorial plane) is defined
to be the intersection between Uranus' and Earth's equator (ascending node)
on 10 March 1977.

The orbital elements for Saturn's rings are stored in the following order:

        1 = Planet
        2 = F ring
        3 = Outer edge Encke gap
        4 = Cassini inner edge of outer ring
        5 = Cassini inner edge of 4th outer ring
        6 = Outer B feature
        7 = Maxwell gap outer edge
        8 = Titan gap outer edge
        9 = Keeler gap outer edge
       10 = Inner A ring edge
       11 = Inner B ring edge
       12 = Mid C ring feature
       13 = Inner C ring edge 

The zero-longitude is defined to be the intersection between Saturn's and
Earth's equator (ascending node) at EME 1950.

For Neptune, nine test orbits have been defined (in addition to the standard
first orbit in the planet's equatorial plane).  The first three have
polar orbits and the remainder are equitorial or satillites:

        1 = Planet
	2 =  50000 km (polar)
	3 = 100000 km (polar)
	4 = 150000 km (polar)
        5 =  1989N5 orbit
	6 =  1989N3
	7 =  1989N4
	8 =  1989N2
	9 =  1989N1
       10 =  Triton orbit
       11 =  Nereid orbit

For Neptune, the zero longitude is defined to be the intersection between
Neptune's equatorial plane (at closest approch) and EME1950.  The OMEGAZ
of the polar rings is determined by the asending node of Triton's orbital
plane on Neptune's equatorial plane.

PROGRAM HISTORY

Original Programmer:	Gary Yagi, 22 Jan 1989
Current Cognizant Programmer:  Gary Yagi
Revisions:
 17 Mar 89  GMY  Declare INCL as REAL*8
 12 Jun 89  VRH  Calculate OMEGAZ for Neptune polar rings
 12 Aug 89  VRH  Orbital parameters updated
  8 May 95  AMS  (CRI) Made portable for UNIX
    Feb 97  BTC  Changed RA & DEC for Jupiter from 0,0 to realistic values
 15 Oct 02  VRH  Synchronize NAV and RINGORBS formats, update docs

PARAMETERS: