JPL PLANETARY AND LUNAR EPHEMERIDES
Export Information [December 6, 2005]
E M Standish, JPL INTRODUCTION ------------ The JPL Planetary and Lunar Ephemerides are available to outside users upon request. The package allows an EXPERIENCED user to obtain the RECTANGULAR COORDINATES (x,y,z) of the sun, moon, and nine major planets by means of a simple subroutine written in standard fortran. Note: this package does NOT provide other coordinates, such as right ascension and declination, azimuth and altitude, longitude and latitude, etc. It provides ONLY rectangular positions and velocities with respect to the International Celestial Reference Frame. We suggest for the more casual user, JPL's interactive website and telnet service, "Horizons", which provides a wide variety of astronomical information and which uses the full precision of our ephemerides. See the website, "http://ssd.jpl.nasa.gov/". In fact, for information about many different kinds of ephemerides (interactive, self-contained, high precision, etc.) see the following website: "http://ssd.jpl.nasa.gov/iau-comm4" and click on "Where to obtain ephemerides". For those who truly need the high-precision, basic JPL ephemerides, there are two methods of acquiring the ephemerides: 1) from this site via ftp and 2) via a CRrom from the publisher, Willmann-Bell (see Appendix B). The final goal of the installation process is the successful execution of the main program "TESTEPH.F". This program reads and interpolates planetary and lunar coordinates from a binary direct-access ephemeris file and compares these results against corresponding numbers produced at JPL. "TESTEPH.F" uses the subroutines which are of eventual interest to the user. It is strongly suggested that a potential user first read through this README in its entirety. This will provide an idea of what is involved in both the installation and in the usage of the ephemeris package. This README contains the following sections; Introduction Location of the files What to do (ftp and install) Unix users vs. other users Contents to be retrieved by the user (which files to get via ftp) Brief item description: what each retrieved item is for Available ephemerides (which ones; what years are covered) Ephemeris sizes (how big the files are) References (publications describing the ephemerides) Software description (the subroutines which provide ephemeris information) Software Usage (calling sequences, etc.) Constants on the Ephemeris Files : what ephemeris constants are on the files Assistance (only in case of emergency) Appendix A : The internal format of the ephemeris files Appendix B : CDrom available from Willmann-Bell Appendix C : Corrections to the software on the CDroms Appendix D : Documentation of DE405 and DE406 Appendix E : Versions of the software in various languages (from outside sources) ******************************************************************************* LOCATION -------- The ephemeris package is available over Internet from the anonymous ftp server: ssd.jpl.nasa.gov When connected, "cd /pub/eph/export/" ****************************************************************************** WHAT TO DO ---------- Retrieve the items, listed in the next sections, from the anonymous ftp site. Read the "usrguide", especially the parts about "NRECL" and "KSIZE" [Note: For UNIX-based users, the ephemeris files are available in binary form, ready for immediate installation on the user's computer. For all others, the ephemeris is supplied in ASCII format and must be converted (a one-time only process) into binary format for installation; software is supplied for this conversion. (Sorry, we have tried to export binary files for other types of platforms, but the lack of uniformity from one computer and/or compiler to the next made this too difficult.) However, I have received the following: "I have been able to read the unix binary files with no problem on my Mac, and I suspect that any machine that formats floating point numbers in IEEE-754 (1985) format will be able to read them."] ****************************************************************************** CONTENTS TO BE RETRIEVED BY THE USER ------------------------------------ *** UNIX users: retrieve the following 7 items: /pub/eph/export/usrguide /pub/eph/export/fortran/testeph.f /pub/eph/export/fortran/selcon.f /pub/eph/export/fortran/binmerge.f /pub/eph/export/fortran/binshort.f /pub/eph/export/unix/unxSYYYY.XXX (multiple files) /pub/eph/export/test-data/testpo.XXX where "SYYYY" is the starting year of each particular ephemeris block ("S" is the sign : "p" for + and "m" for -) and "XXX" is the ephemeris number: 200, 403, 405 or 406. See choices below for the different ephemerides. The UNIX binary files come in 50-year blocks (3.8-4.7 Mbytes each, depending upon the ephemeris). Once they are installed on the user's computer, contiguous blocks may be merged together to form a single ephemeris file; this is done using "binmerge.f". *** non-UNIX users: retrieve the following 9 items: /pub/eph/export/usrguide /pub/eph/export/fortran/testeph.f /pub/eph/export/fortran/selcon.f /pub/eph/export/fortran/asc2eph.f /pub/eph/export/fortran/binmerge.f /pub/eph/export/fortran/binshort.f /pub/eph/export/ascii/ascSYYYY.XXX (multiple files) /pub/eph/export/ascii/header.XXX /pub/eph/export/test-data/testpo.XXX where "SYYYY" is the starting year of each particular ephemeris block ("S" is the sign : "p" for + and "m" for -) and "XXX" is the ephemeris number: 200, 403, 405, or 406. See choices below for different ephemerides. The ASCII files come in 20-year blocks (about 3.5 Mbytes each). The blocks are converted into binary blocks on the user's computer, using "asc2eph.f"; then, contiguous binary blocks may be merged together to form a single ephemeris file using "binmerge.f". An alternative method is to add all of the ascii blocks together and then convert that file into the binary ephemeris on the user's computer, using "asc2eph.f". A smaller portion of a binary ephemeris file may be extracted from a larger file using "binshort.f". ****************************************************************************** BRIEF ITEM DESCRIPTION ----------------------- "usrguide" : User's Guide containing instructions for obtaining and using the ephemerides, including the usage of the subroutines and the testing of the software package. "testeph" : Software Package containing a main program which uses the reading and interpolating subroutines. This program compares the results with similar runs made at JPL in order to ensure that the ephemeris is installed and being read correctly. The reading and interpolating subroutines included in "testeph", along with the ephemeris file(s) themselves, are the items which are of eventual interest to the user. "testpo" : Test results computed at JPL; these are input by the program "testeph" and are used for testing the ephemeris installation. There is a different "testpo" for each different ephemeris; they must match or the test will not work correctly. "binmerge" : Program to merge two adjoining binary ephemerides. "binshort" : Program to extract a portion of an ephemeris from a larger file. for UNIX users -------------- "unxSYYYY.XXX" : Binary ephemeris files from JPL Ephemeris DEXXX, covering 50 years, starting in the year SYYYY ("p/m" for "+/-"). The pieces may be used separately, or the 50-year files (300-year files for DE406) may be merged into a single ephemeris file using the program, "binmerge.f". Also, a shorter-span ephemeris may be extracted from a longer one using the program, "binshort.f". for non-UNIX users -------------- "asc2eph.f" : A one-time conversion program which converts the ephemeris from ASCII format into binary form. "ascSYYYY.XXX" : ASCII ephemeris files from JPL Ephemeris DEXXX, each covering 20 years, starting in the year SYYYY ("p/m" for "+/-"). The 20-year blocks may be converted separately into binary ephemeris files using "asc2eph" or they may be combined into a single ASCII file and then converted into a single binary file. Separate binary files may be merged into a single ephemeris file using the program, "binmerge.f". Also, a shorter-span ephemeris may be extracted from a longer one using the program, "binshort.f". "header.XXX" : Header information for ephemeris deXXX, needed by "asc2eph.f". ****************************************************************************** AVAILABLE EPHEMERIDES --------------------- DE200 : (includes nutations but not librations) JED 2305424.5 (1599 DEC 09) to JED 2513360.5 (2169 MAR 31) This ephemeris has been the basis of the Astronomical Almanac since 1984. It is based upon the dynamical equator and equinox of J2000 (see Standish, 1982 and Standish, 1990). DE403 : (includes both nutations and librations) JED 2433264.5 (1949 DEC 14) to JED 2469808.5 (2050 JAN 02) Kept available since it has been a standard for the IERS and has been used by others in the past. DE405 : (includes both nutations and librations) JED 2305424.50 (1599 DEC 09) to JED 2525008.50 (2201 FEB 20) Our latest ephemeris; it is based upon the International Celestial Reference Frame (ICRF). (DE200 is within 0.01 arcseconds of the frame of the ICRF). DE405 was created in May-June 1997. DE406 : the New "JPL Long Ephemeris" (includes neither nutations nor librations) Note: DE406 is available only in unix on the ftp site. JED 0624976.50 (-3001 FEB 04) to 2816912.50 (+3000 MAY 06) This is the same ephemeris as DE405, though the accuracy of the interpolating polynomials has been lessened (interpolation on the 64-day mesh points remains exact, however). For DE406/LE406, the interpolating accuracy is no worse than 25 meters for any planet and no worse than 1 meter for the moon. DE406 requires about 10 megabytes for each 300-year block. ****************************************************************************** EPHEMERIS SIZES (ftp blocks) ---------------------------- de200 de403 de405 de406 UNIX binary (50-year blocks) : 3.8 Mb 4.1 Mb 4.7 Mb UNIX binary (300-year blocks) : 10.0 Mb ASCII (20-year blocks) : 5.2 Mb 6.4 Mb ASCII (25-year blocks) : 6.1 Mb ****************************************************************************** REFERENCES ---------- Newhall, X X, Standish, E.M. and Williams, J.G.: 1983, "DE102: a numerically integrated ephemeris of the Moon and planets spanning forty-four centuries", Astronomy & Astrophysics, vol. 125, pp. 150-167. Standish, E.M.: 1982, "Orientation of the JPL Ephemerides, DE200/LE200, to the Dynamical Equinox of J2000", Astronomy & Astrophysics, vol. 114, pp. 297-302. Standish, E.M.: 1990, "The Observational Basis for JPL's DE200, the planetary ephemeris of the Astronomical Almanac", Astronomy & Astrophysics, vol. 233, pp. 252-271. Standish, E.M., Newhall, X X, Williams, J.G. and Folkner, W.F.: 1995, "JPL Planetary and Lunar Ephemerides, DE403/LE403", JPL IOM 314.10-127. Standish,E.M.: 1998, "JPL Planetary and Lunar Ephemerides, DE405/LE405",JPL IOM 312.F-98-048. [the preceding 2 references are available in PostScript on the following website: http://ssd.jpl.nasa.gov/iau-comm4/relateds.html] ****************************************************************************** SOFTWARE DESCRIPTION -------------------- The software package (apart from the programs used to initially construct the ephemeris, asc2eph, binmerge, and binshort) consists of a main test program which uses the reading and interpolating routines in order to retrieve the ephemeris data and to compare the results against the Test Data. Two of the subroutines called by testeph.f are of primary interest to the user: "PLEPH" and "SELCON". Three others, "CONST", "DPLEPH", and "STATE" may also be useful. PLEPH : Get the state vector (position and velocity) of one body with respect to another at any given time within the interval covered by the ephemeris. SELCON : Retrieve values of user-requested constants on the ephemeris file. CONST : Retrieve values of all of the constants on the ephemeris file. DPLEPH : Same as PLEPH, but with increased precision in the input time. STATE : Read and interpolate the ephemeris file. (Called by PLEPH). ****************************************************************************** SOFTWARE USAGE -------------- C NOTE : Over the years, different versions of PLEPH have had a 5th argument: C sometimes, an error return statement number; sometimes, a logical denoting C whether or not the requested date is covered by the ephemeris. We apologize C for this inconsistency; in this version, we use only the four necessary C arguments and do the testing outside of the subroutine. ** PLEPH ******** subroutine pleph( tdb, npl, nctr, pv) ********** Input ----- tdb [d.p.] : julian ephemeris date npl [int.] : planet number nctr [int.] : center number identifications for "npl" and "nctr" ------------------------------------ 1 = mercury 8 = neptune 2 = venus 9 = pluto 3 = earth 10 = moon 4 = mars 11 = sun 5 = jupiter 12 = solar-system barycenter 6 = saturn 13 = earth-moon barycenter 7 = uranus 14 = nutations in longitude and obliquity 15 = librations (if they exist on the file) (for nutations and librations, nctr=0) Output ------ pv(6) [d.p.] : x,y,z,x-dot,y-dot,z-dot [au, au/day] for nutations, d(psi), d(eps), d(psi)-dot, d(eps)-dot [rads, rads/day] for librations, (Euler angles and rates, w.r.t. the ephemeris reference frame) [rads, rads/day] ** SELCON ******** subroutine selcon ( nams, nmbr, vals) ********** Input ----- nams(nmbr) [char*6] : names for which values are requested (the list of names is given below) nmbr [int.] : the number of names in 'nams' Output ------ vals(nmbr) [d.p.] : values corresponding to the names in 'nams' ** CONST ******** subroutine const(nmv,vlv,sss,nrv) ********** Input (none) ----- Output ------ nmv(nrv) [char*6] : list of nrv names associated with the values in vlv vlv(nrv) [d.p.] : nrv values associated with the names in nmcc sss(3) [d.p.] : sss(1) : starting jed of the ephemeris file sss(2) : ending jed of the ephemeris file sss(3) : number of days covered by each block of Chebychev coefficients nrv [int.] : number of values in nmv and vlv ** STATE ******** subroutine state(jed,list,pv,nut,*) ********** [This subroutine is identical to that provided in the past; it is still provided to give previous users compatibility; it is not recommended for use by first-time users.] ** DPLEPH ******** entry dpleph( tdb2, npl, nctr, pv) ********** This entry is identical to "PLEPH", except that the input time, tdb2, is doubly-dimensioned for increased precision [ double precision tdb2(2) ]. Any combination of tdb2(1)+tdb2(2) which falls within the time span on the file is a permissible epoch. For ease in programming, the user may put the entire date into tdb2(1) and set tdb2(2)=0. However, for maximum interpolation accuracy, set tdb2(1) equal to the most recent midnight at or before interpolation epoch (i.e., xxxxxxx.5d0) and set tdb2(2) equal to the remaining fractional part of the day. As an alternative, it may prove convenient to set tdb2(1) equal to some fixed epoch, such as start of integration, and set tdb2(2) equal to the remainder of the desired epoch. ****************************************************************************** CONSTANTS ON THE EPHEMERIS FILE ------------------------------- The following is a partial list of constants found on the ephemeris file: DENUM Planetary ephemeris number. LENUM Lunar ephemeris number. TDATEF, TDATEB Dates of the Forward and Backward Integrations CLIGHT Speed of light (km/s). AU Number of kilometers per astronomical unit. EMRAT Earth-Moon mass ratio. GMi GM for ith planet [au**3/day**2]. GMB GM for the Earth-Moon Barycenter [au**3/day**2]. GMS Sun (= k**2) [au**3/day**2]. X1, ..., ZD9 Initial conditions for the numerical integration, given at "JDEPOC", with respect to "CENTER". JDEPOC Epoch (JED) of initial conditions, normally JED 2440400.5. CENTER Reference center for the initial conditions. (Sun: 11, Solar System Barycenter: 12) RADi Radius of ith planet [km]. MA0001...MA0324 GM's of asteroid number 0001 ... 0234 [au**3/day**2]. PHASE The phase angle of the moon's rotation. LOVENO The Love Number, k2, for the moon. PHI, THT, PSI Euler angles of the orientation of the lunar mantle. OMEGAX, ... Rotational velocities of the lunar mantle. PHIC,THTC,PSIC Euler angles of the orientation of the lunar core. OMGCX, ... Rotational velocities of the lunar core. ****************************************************************************** ASSISTANCE ---------- If you are really stuck, direct your questions to ********************************************************* * Dr E Myles Standish; JPL 301-150; Pasadena, CA 91109 * * TEL: 818-354-3959 FAX: 818-393-6388 * * Internet: ems@smyles.jpl.nasa.gov [128.149.23.23] * ********************************************************* I shall try to answer your questions when I'm free from my normal obligations. However, I'm not in business to supply ephemerides to the outside world; please realize that I cannot provide customized service to each individual user. Please include your name, address, phone number and e-mail address. =============================================================================== APPENDIX A : The internal format of the ephemeris files On the first record of an export binary file or in the "GROUP 1050 of the ascii "header", there are 3 sets of 13 integers each. (In the binary version, the 13th of each set is stored away from the first 12.) The 13 triplets give information about the location, order and time-coverage of the chebychev polynomials corresponding to the following 13 items: Mercury Venus Earth-Moon barycenter Mars Jupiter Saturn Uranus Neptune Pluto Moon (geocentric) Sun Nutations Librations Word (1,i) is the starting location in each data record of the chebychev coefficients belonging to the ith item. Word (2,i) is the number of chebychev coefficients per component of the ith item, and Word (3,i) is the number of complete sets of coefficients in each data record for the ith item. Data Records ("GROUP 1070") These records contain the actual ephemeris data in the form of chebychev polynomials. The first two double precision words in each data record contain Julian date of earliest data in record. Julian date of latest data in record. The remaining data are chebychev position coefficients for each component of each body on the tape. The chebychev coefficients for the planets represent the solar system barycentric positions of the centers of the planetary systems. There are three cartesian components (x, y, z), for each of the items #1-11; there are two components for the 12th item, nutations : d(psi) and d(epsilon); there are three components for the 13th item, librations : three euler angles. Planetary positions are given in kilometers. DE200 is nominally with respect to the mean equator and equinox of J2000, coinciding with the origin of FK5; DE403 and DE405 are with respect to the Int Cel Ref Frame. The nutations and librations are given in radians. =============================================================================== APPENDIX B : CDrom available from Willmann-Bell The CD's containing DE200 and DE405 (unix and ascii) and also DE406 (unix only) are available from Willmann-Bell. The price is about $25 per disk. Willmann-Bell, Inc. PO Box 35025 Richmond, VA 23235 804-320-7016 804-272-5920 (Fax) http://www.willbell.com/software/jpl.htm There is an order form that calculates all costs to any country in the world on their web page (www.willbell.com). On the home page there is an icon for this. The order form activates security for credit card transactions. If one does not want to order over the web, one can print the order form and fax or mail it to them. I now have a limited supply of the ascii version of DE406. I can lend these to those who need the full extended ephemeris and who can not use the unix version. E M Standish: ems@smyles.jpl.nasa.gov (remember to include postal address) =============================================================================== APPENDIX C : Corrections to the software on the CDroms The enclosed are improvements to the software on the CDroms. (The ftp software on "ssd.jpl.nasa.gov" has been updated.) 1) In "testeph.f" on both CDroms, line 95 should now be INTEGER LINE/0/ 2) In "testeph.f" on both CDroms, the statement at line 142 was DEL=DABS(R(NCOORD)-XI)/(DABS(R(NCOORD))+DABS(XI)) it should be replaced by: DEL=DABS(R(NCOORD)-XI) if(ntarg .eq. 15 .and. ncoord .eq. 3) * del=del/(0.23d0*(et-2451545.d0)) 3) In "testeph.f" on both CDroms, the statement that was at line 446 should now be IF(FIRST) CALL STATE(0.D0,0,0,0.D0) 4) In "asc2eph.f" on both CDroms, the statement near line 190 was READ (*,'(2I6,3000(/3D26.18))',IOSTAT =IN) . NRW, NCOEFF, (DB(K),K=1,NCOEFF) it should replaced by: 1 READ(*,'(2i6)')NRW,NCOEFF if(NRW .EQ. 0) GO TO 1 READ (*,'(3D26.18)',IOSTAT =IN) (DB(K),K=1,NCOEFF) 5) In "asc2eph.f" ***>> on the DE406 ascii CDrom only <<*** : "3D26.18" in line 268 should be replaced by "3D23.15" 6) In "asc2eph.f" on both CDroms, the 4th from last line was READ (*, '(A)') BLANK it should now be: IF(HEADER .NE. 'GROUP 1070') READ (*, '(A)') BLANK 7) In "testeph.f", line 910 reads T(1)=((PJD(1)-(DBLE(NR-3)*SS(3)+SS(1)))+PJD(4))/SS(3) It should be replaced by the following 3 lines: tmp1 = DBLE(NR-3)*SS(3) + SS(1) tmp2 = PJD(1) - tmp1 T(1) = (tmp2 + PJD(4))/SS(3) =============================================================================== APPENDIX D : Documentation of DE405 and DE406 DE405 Documentation is available from the anonymous ftp site, "ssd.jpl.nasa.gov", in the directory, "/pub/eph/export/DE405/", The memo is in two forms: 1) in a single complete PostScript file, "de405iom.ps", or in 2) LaTeX file, "de405iom.tex" with the accompanying figures, "de405fig1.ps", ... "de405fig8.ps". The situation is similar for DE403. =============================================================================== Appendix E : Versions of the software in various languages (from outside sources) There are a number of contributed versions of the reading routines in various languages; there are also ephemeris toolkits, binary file conversions, etc. These are simply listed here; I have not tested them. All responsibility for these software packages resides with their authors, and all questions pertaining to their use must be directed to the authors themselves. However, I would appreciate hearing of any problems with them. E M Standish (ems@smyles.jpl.nasa.gov) C-Versions ---------- From Paul Hardy : http://www.ephemeris.com/software.html The ephemeris.com Software Library, designed to read, write, and interpolate NASA's JPL ephemeris files (DE200, DE405, DE406, etc.) is now available online at http://www.ephemeris.com/software.html The software includes standalone programs to read and write ASCII and binary ephemeris files, interpolate positions, and verify calculations with pre-computed data from JPL. The accuracy should match the accuracy of JPL's software. The software is written in C, and should work on any Unix machine. It will probably run on any other computer that has the Gnu C compiler. This software is designed to directly read the binary and ASCII ephemeris files on JPL's ephemeris CD (available from http://www.willbell.com), regardless of the machine's byte ordering. ----------------- From Kourosh Arfa-Kaboodvand, Technical University of Darmstadt: (Kourosh@ipgs.ipg.verm.tu-darmstadt.de) /pub/ephem/export/C-versions/kourosh From David Hoffman, Johnson Space Center (david.a.hoffman1@jsc.nasa.gov): /pub/ephem/export/C-versions/hoffman ----------------- From Dr. Piotr Dybczynski, Astronomical Observatory, Poznan, Poland (dybol@phys.amu.edu.pl) /ftp.astro.amu.edu.pl, IP: 150.254.66.60 FITS-version ------------ From Arnold Rots of Harvard-Smithsonian Astrophysical Observatory (arots@head-cfa.harvard.edu) ftp://heasarc.gsfc.nasa.gov/xte/calib_data/clock/bary Python version -------------- From Ray Buvel rbuvel@wi.rr.com Matlab-Based JPL Solar System Ephemeris Toolbox ----------------------------------------------- From Brian Sauser, formerly at the Kennedy Space Center http://www.openchannelfoundation.org/projects/Matlab-Based_Solar_System_Ephe UNIX - LINUX Binary Format Conversion ------------------------------------- From Thierry Pauwels, Royal Observatory of Belgium: Thierry.Pauwels@oma.be ===============================================================================