[Spice_announce] New Planetary and Lunar Ephemeris DE418 is available

[Charles H. Acton]

August 11, 2007

JPL's Solar System Dynamics Group has released the DE418 planetary 
and lunar ephemeris. This has been converted to SPICE SPK format as 
for all previous DExxx ephemerides. The conversion does not involve a 
loss of precision.

de418.bsp is available from the NAIF server at this location:

   ftp://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/

The file (kernel) covers the period:

Start: 1899 DEC 04
End:   2051 JAN 21.

The file requires just over 16 Mbytes of disk space.

The file contains ephemerides for the traditional set of SPICE 
ephemeris objects:

NAIF ID         Object Name
-------         --------------------
0               SOLAR SYSTEM BARYCENTER
1               MERCURY BARYCENTER 
2               VENUS BARYCENTER               
3               EARTH BARYCENTER               
4               MARS BARYCENTER                
5               JUPITER BARYCENTER             
6               SATURN BARYCENTER              
7               URANUS BARYCENTER              
8               NEPTUNE BARYCENTER             
9               PLUTO BARYCENTER               
10              SUN                           
199             MERCURY    (equivalent to 1, Mercury 
barycenter)                     
299             VENUS      (equivalent to 2, Venus 
barycenter)                       
301             MOON                         
399             EARTH                        
499             MARS       (equivalent to 4, Mars 
barycenter)                        

This is a binary kernel, made on a PC/Linux box using the IEEE Little 
Endian binary standard. Because all modern SPICE Toolkits contain 
run-time translation for binary SPK files, this binary file may be 
used as is on any machine other than a DEC VAX or DEC Alpha.  If you 
are using a Sun or other Unix box and wish to convert it to native 
binary format--IEEE Big Endian--you can easily do so using the pair 
of Toolkit utilities named "toxfr" and "tobin," run in that order. Or 
you may use the "bingo" utility available only from the NAIF website:

http://naif.jpl.nasa.gov/naif/utilities.html


The authors of de418 have prepared an extensive set of release notes 
about how the file was produced and how it compares to earlier dexxx 
files. As this document has not yet been cleared for public release 
it is not currently available from the NAIF server. However NAIF will 
make it available "next to" the SPK file as soon as clearance is 
obtained.  In the meantime a few words about the file are contained 
in the de418.cmt text file.

Those interested in doing their own statistical comparison of the 
ephemeris data within de418 with the ephemeris data from any earlier 
dexxx file may do so using the (comparatively new) SPICE application 
program named "spkdiff."  This program and its User's Guide may be 
obtained under the Utilities link on the NAIF web pages (see above 
for URL).



Related SPICE Products yet to be Produced
-----------------------------------------
1) This SPK file will replace use of de403.bsp as the source of 
precision lunar orientation information for the lunar Principal Axes 
(PA) frame. In the near future NAIF will use de418 to produce the 
appropriate lunar orientation binary PCK file; it will replace 
moon_pa_de403_1950-2198.bpc.

2) As needed NAIF will also prepare the allied new lunar frames 
kernels (FKs) replacing the existing lunar FKs:

   moon_060721.tf
   moon_assoc_pa.tf
   moon_assoc_me.tf

3) NAIF will prepare a new masses PCK file to replace the existing 
de-403-masses.tpc.


All of the above will be announced using "spice_announce" once the 
items are available.
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