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+<LINK REL="previous" HREF="node90.html"> +<LINK REL="up" HREF="node13.html"> +<LINK REL="next" HREF="node92.html"> +</HEAD> +<BODY > +<BR> <HR> +<A NAME="tex2html1336" HREF="node92.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html1334" HREF="node13.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html1328" HREF="node90.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A> <A HREF="sun67.html#stardoccontents"><IMG ALIGN="BOTTOM" BORDER="0" + SRC="contents_motif.gif"></A> +<BR> +<B> Next:</B> <A NAME="tex2html1337" HREF="node92.html">SLA_EPB - MJD to Besselian Epoch</A> +<BR> +<B>Up:</B> <A NAME="tex2html1335" HREF="node13.html">SUBPROGRAM SPECIFICATIONS</A> +<BR> +<B> Previous:</B> <A NAME="tex2html1329" HREF="node90.html">SLA_EG50 - B1950 to Galactic</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<H2><A NAME="SECTION000478000000000000000">SLA_EL2UE - Conventional to Universal Elements</A> +<A NAME="xref_SLA_EL2UE"> </A><A NAME="SLA_EL2UE"> </A> +</H2> + <DL> +<DT><STRONG>ACTION:</STRONG> +<DD>Transform conventional osculating orbital elements +into ``universal'' form. +<P> <DT><STRONG>CALL:</STRONG> +<DD><TT>CALL sla_EL2UE ( + DATE, JFORM, EPOCH, ORBINC, ANODE, + PERIH, AORQ, E, AORL, DM, + U, JSTAT)</TT> +<P> </DL> +<P> <DL> +<DT><STRONG>GIVEN:</STRONG> +<DD> +<BR> +<TABLE CELLPADDING=3> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>DATE</EM></TD> +<TH ALIGN="LEFT"><B>D</B></TH> +<TD ALIGN="LEFT" NOWRAP>epoch (TT MJD) of osculation (Note 3)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>JFORM</EM></TD> +<TD ALIGN="LEFT"><B>I</B></TD> +<TD ALIGN="LEFT" NOWRAP>choice of element set (1-3; Note 6)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>EPOCH</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>epoch of elements (<I>t<SUB>0</SUB></I> or <I>T</I>, TT MJD)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>ORBINC</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>inclination (<I>i</I>, radians)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>ANODE</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>longitude of the ascending node (<IMG WIDTH="14" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img99.gif" + ALT="$\Omega$">, radians)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>PERIH</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>longitude or argument of perihelion +(<IMG WIDTH="16" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img100.gif" + ALT="$\varpi$"> or <IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img101.gif" + ALT="$\omega$">,</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> radians)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>AORQ</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>mean distance or perihelion distance (<I>a</I> or <I>q</I>, AU)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>E</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>eccentricity (<I>e</I>)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>AORL</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>mean anomaly or longitude +(<I>M</I> or <I>L</I>, radians,</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> JFORM=1,2 only)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>DM</EM></TD> +<TD ALIGN="LEFT"><B>D</B></TD> +<TD ALIGN="LEFT" NOWRAP>daily motion (<I>n</I>, radians, JFORM=1 only)</TD> +</TR> +</TABLE></DL> +<P> <DL> +<DT><STRONG>RETURNED:</STRONG> +<DD> +<BR> +<TABLE CELLPADDING=3> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>U</EM></TD> +<TH ALIGN="LEFT"><B>D(13)</B></TH> +<TD ALIGN="LEFT" NOWRAP>universal orbital elements (Note 1)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(1)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>combined mass (<I>M</I>+<I>m</I>)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(2)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>total energy of the orbit (<IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img24.gif" + ALT="$\alpha$">)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(3)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>reference (osculating) epoch (<I>t<SUB>0</SUB></I>)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(4-6)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>position at reference epoch (<IMG WIDTH="17" HEIGHT="25" ALIGN="MIDDLE" BORDER="0" + SRC="img102.gif" + ALT="${\rm \bf r}_0$">)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(7-9)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>velocity at reference epoch (<IMG WIDTH="19" HEIGHT="25" ALIGN="MIDDLE" BORDER="0" + SRC="img103.gif" + ALT="${\rm \bf v}_0$">)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(10)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>heliocentric distance at reference epoch</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(11)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP><IMG WIDTH="39" HEIGHT="25" ALIGN="MIDDLE" BORDER="0" + SRC="img104.gif" + ALT="${\rm \bf r}_0.{\rm \bf v}_0$"></TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(12)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>date (<I>t</I>)</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="CENTER" NOWRAP COLSPAN=1>(13)</TD> +<TD></TD> +<TD ALIGN="LEFT" NOWRAP>universal eccentric anomaly (<IMG WIDTH="14" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img105.gif" + ALT="$\psi$">) of date, +approx</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"> </TD> +<TD ALIGN="LEFT"> </TD> +<TD ALIGN="LEFT" NOWRAP> </TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM>JSTAT</EM></TD> +<TD ALIGN="LEFT"><B>I</B></TD> +<TD ALIGN="LEFT" NOWRAP>status:</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> 0 = OK</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> -1 = illegal JFORM</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> -2 = illegal E</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> -3 = illegal AORQ</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> -4 = illegal DM</TD> +</TR> +<TR VALIGN="TOP"><TD ALIGN="LEFT"><EM></EM></TD> +<TD ALIGN="LEFT"><B></B></TD> +<TD ALIGN="LEFT" NOWRAP> -5 = numerical error</TD> +</TR> +</TABLE></DL> +<P> <DL> +<DT><STRONG>NOTES:</STRONG> +<DD><DL COMPACT> +<DT>1. +<DD>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) <IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img24.gif" + ALT="$\alpha$">, 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 <IMG WIDTH="14" HEIGHT="27" ALIGN="MIDDLE" BORDER="0" + SRC="img105.gif" + ALT="$\psi$">, the ``universal eccentric anomaly'' at a + given date and (v) that date. + <DT>2. +<DD>The companion routine is sla_UE2PV. This takes the set of numbers + that the present routine outputs and uses them to derive the + object's position and velocity. A single prediction requires one + call to the present routine followed by one call to sla_UE2PV; + for convenience, the two calls are packaged as the routine + sla_PLANEL. Multiple predictions may be made by again calling the + present routine once, but then calling sla_UE2PV multiple times, + which is faster than multiple calls to sla_PLANEL. + <DT>3. +<DD>DATE is the epoch of osculation. It is in the TT timescale + (formerly Ephemeris Time, ET) and is a Modified Julian Date + (JD-2400000.5). + <DT>4. +<DD>The supplied orbital elements are with respect to the J2000 + ecliptic and equinox. The position and velocity parameters + returned in the array U are with respect to the mean equator and + equinox of epoch J2000, and are for the perihelion prior to the + specified epoch. + <DT>5. +<DD>The universal elements returned in the array U are in canonical + units (solar masses, AU and canonical days). + <DT>6. +<DD>Three different element-format options are supported, as + follows. <BR> +<P> +JFORM=1, suitable for the major planets: +<P> <PRE><TT> + EPOCH = epoch of elements <I>t<SUB>0</SUB></I> (TT MJD) + ORBINC = inclination <I>i</I> (radians) + ANODE = longitude of the ascending node <IMG WIDTH="14" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img99.gif" + ALT="$\Omega$"> (radians) + PERIH = longitude of perihelion <IMG WIDTH="16" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img100.gif" + ALT="$\varpi$"> (radians) + AORQ = mean distance <I>a</I> (AU) + E = eccentricity <I>e</I> <IMG WIDTH="83" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img106.gif" + ALT="$( 0 \leq e < 1 )$"> + AORL = mean longitude <I>L</I> (radians) + DM = daily motion <I>n</I> (radians) +</TT></PRE> +<P> +JFORM=2, suitable for minor planets: +<P> <PRE><TT> + EPOCH = epoch of elements <I>t<SUB>0</SUB></I> (TT MJD) + ORBINC = inclination <I>i</I> (radians) + ANODE = longitude of the ascending node <IMG WIDTH="14" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img99.gif" + ALT="$\Omega$"> (radians) + PERIH = argument of perihelion <IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img101.gif" + ALT="$\omega$"> (radians) + AORQ = mean distance <I>a</I> (AU) + E = eccentricity <I>e</I> <IMG WIDTH="83" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img106.gif" + ALT="$( 0 \leq e < 1 )$"> + AORL = mean anomaly <I>M</I> (radians) +</TT></PRE> +<P> +JFORM=3, suitable for comets: +<P> <PRE><TT> + EPOCH = epoch of perihelion <I>T</I> (TT MJD) + ORBINC = inclination <I>i</I> (radians) + ANODE = longitude of the ascending node <IMG WIDTH="14" HEIGHT="13" ALIGN="BOTTOM" BORDER="0" + SRC="img99.gif" + ALT="$\Omega$"> (radians) + PERIH = argument of perihelion <IMG WIDTH="13" HEIGHT="14" ALIGN="BOTTOM" BORDER="0" + SRC="img101.gif" + ALT="$\omega$"> (radians) + AORQ = perihelion distance <I>q</I> (AU) + E = eccentricity <I>e</I> <IMG WIDTH="91" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" + SRC="img107.gif" + ALT="$( 0 \leq e \leq 10 )$"></TT></PRE> + <DT>7. +<DD>Unused elements (DM for JFORM=2, AORL and DM for JFORM=3) are + not accessed. + <DT>8. +<DD>The algorithm was originally adapted from the EPHSLA program of + D.H.P.Jones (private communication, 1996). The method + is based on Stumpff's Universal Variables. + </DL></DL> +<P> <DL> +<DT><STRONG>REFERENCE:</STRONG> +<DD>Everhart, E. & Pitkin, E.T., Am. J. Phys. 51, 712, 1983. +</DL> +<BR> <HR> +<A NAME="tex2html1336" HREF="node92.html"> +<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A> +<A NAME="tex2html1334" HREF="node13.html"> +<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A> +<A NAME="tex2html1328" HREF="node90.html"> +<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A> <A HREF="sun67.html#stardoccontents"><IMG ALIGN="BOTTOM" BORDER="0" + SRC="contents_motif.gif"></A> +<BR> +<B> Next:</B> <A NAME="tex2html1337" HREF="node92.html">SLA_EPB - MJD to Besselian Epoch</A> +<BR> +<B>Up:</B> <A NAME="tex2html1335" HREF="node13.html">SUBPROGRAM SPECIFICATIONS</A> +<BR> +<B> Previous:</B> <A NAME="tex2html1329" HREF="node90.html">SLA_EG50 - B1950 to Galactic</A> +<BR> <HR> <P> +<P><!--End of Navigation Panel--> +<ADDRESS> +<I>SLALIB --- Positional Astronomy Library<BR>Starlink User Note 67<BR>P. T. Wallace<BR>12 October 1999<BR>E-mail:ptw@star.rl.ac.uk</I> +</ADDRESS> +</BODY> +</HTML> |