EXPLANATIONS FOR ASTEROID PROPER ELEMENTS AND FAMILY ASSIGNMENTS SUPPLIED BY J. G. WILLIAMS JPL, 238-332 4800 OAK GROVE DR. PASADENA, CA 91109 DECEMBER 2, 1987 THESE RESULTS ARE NEARLY THE SAME AS GIVEN IN REFERENCE 1 (1979 ASTEROID BOOK). ADDITIONS HAVE BEEN MADE FOR TROJANS, HILDAS, AND OTHER ODD TYPES (279, 887, 944, 1362, AND 1373) SO THAT ASTEROIDS 1 THROUGH 1796 ARE REPRESENTED WITH SOME ENTRY INCLUDING SEMIMAJOR AXIS, THOUGH NOT WITH THE REMAINING PROPER ELEMENTS FOR THE ODD TYPES. SOME PROPER ELEMENTS WERE REVISED, MOST IMPORTANTLY FOR LOST OBJECTS AND THOSE WHICH FORMERLY HAD POOR OSCULATING ELEMENTS. THE NEW ORBITS FOR 330 AND 864 HAVE BEEN ADDED. THE REVISIONS IN FORMERLY POOR ORBITS HAVE LED TO CHANGES IN FAMILY DESIGNATIONS FOR 561, 637, 1037, 1265, 1381, AND 1686. THE ADDITIONS AND REVISIONS IN PROPER ELEMENTS ARE INDICATED WITH A 2 IN THE REFERENCE COLUMN. PROPER ELEMENT FILE THE PROPER ELEMENT FILE CONSISTS OF ENTRIES FOR THE FIRST 1796 ASTEROIDS, ONE LINE PER ASTEROID, WITH THE PARAMETERS SEPARATED BY SPACES. The fields are: PARAMETER DEFINITION NUMBER ASTEROID NUMBER A PROPER SEMIMAJOR AXIS (AU) E PROPER ECCENTRICITY SINI PROPER SINE INCLINATION WBAR PROPER LONGITUDE OF PERIHELION (DEGREES), EQUINOX AND EPOCH OF 1950.0 ANODE PROPER LONGITUDE OF ASCENDING NODE (DEGREES), EQUINOX AND EPOCH OF 1950.0 DWBAR RATE (ARCSEC/YR) OF PROPER LONGITUDE OF PERIHELION DNODE RATE (ARCSEC/YR) OF PROPER LONGITUDE OF NODE RES INDEX INDICATING A RESONANCE OR SPECIAL CASE. VALUES 1-16 IDENTIFY A SECULAR RESONANCE NUMBER. COMMENSURABILITIES ARE INDICATED AS 1:1 FOR TROJANS, 3:2 FOR HILDAS, ETC. W L DENOTES AN ARGUMENT OF PERIHELION LIBRATOR, JXR A JUPITER CROSSER, AND SXR A SATURN CROSSER. A BLANK VALUE INDICATES MORE NORMAL OBJECTS. DMARS CLOSEST COLINEAR DISTANCE OF APPROACH TO MARS (AU). A NEGATIVE VALUE INDICATES A MARS CROSSER. DJUP CLOSEST COLINEAR DISTANCE OF APPROACH TO JUPITER (AU) Q QUALITY CODE RESERVED FOR PALOMAR-LEIDEN ASTEROIDS. VALUES 1, 2, 3, 4, X, 0 ARE IN DECREASING ORDER OF ACCURACY. SEE PALOMAR-LEIDEN SURVEY FOR DETAILS. A BLANK, NOT A ZERO, IS USED FOR NUMBERED ASTEROIDS. FAMILY FAMILY IDENTITY IF A FAMILY MEMBER. REF REFERENCE NUMBER IN BIBLIOGRAPHY BELOW. WARNINGS IF THE FLAG NRES IS NONZERO, THE PROPER ELEMENTS (EXCEPT A), THE RATES, AND THE DISTANCES WILL HAVE DEGRADED ACCURACY. IN SOME CASES THE RESULTS MAY BE ERRONEOUS BUT USUALLY ARE USABLE IF THE VALUES ARE PRESENT. OCCASIONAL FAILURES OF CONVERGENCE DURING THE DMARS AND DJUP CALCULATIONS ARE INDICATED BY BLANKS FOR BOTH PARAMETERS. A TEST FOR A ZERO VALUE OF DJUP WILL ALWAYS DETECT THIS CASE. FOR RESONANCES 5 AND 6, FAILURES OF CONVERGENCE DURING THE CALCULATION OF THE PROPER ELEMENTS WERE SO COMMON THAT THESE PROPER ELEMENTS (EXCEPT A) AND THE CLOSEST APPROACH DISTANCES ARE BLANKED OUT. THE NODE RATE IS INDICATED IN SUCH CASES BUT MAY BE INACCURATE OR ERRONEOUS. THE USER IS WARNED THAT THE PROPER ELEMENT CALCULATIONS WILL HAVE DECREASED ACCURACY NEAR THE SECULAR RESONANCES AND NEAR COMMENSURABILITIES. THE ACCURACIES FOR MARS CROSSERS WILL ALSO BE DECREASED AND THE ACCURACY OF THE CALCULATIONS FOR DEEP EARTH CROSSERS IS VERY POOR. OBJECTS IN THE OUTER PORTION OF THE BELT HAVE DEGRADED ACCURACY FOR DWBAR AND POSSIBLY E. THIS FILE CONTAINS SIX ASTEROIDS LOST AT THE TIME OF THE CALCULATIONS: 473, 719, 724, 878, 1026, AND 1179. A FEW OF THE LOWER QUALITY ORBITS OF REF 1 HAVE NOT BEEN UPDATED, E. G., 452. FAMILIES NUMBERS LESS THAN 100 CORRESPOND TO FAMILIES PREVIOUSLY FOUND (HIRAYAMA, BROUWER, ARNOLD, OR LINDBLAD AND SOUTHWORTH), BUT USUALLY ALTERED HERE. NUMBERS GREATER THAN 100 ARE SIGNIFICANTLY DIFFERENT. IT SHOULD BE APPRECIATED THAT THE QUALITY AND UNIQUENESS OF FAMILY IDENTIFICATIONS VARIES WIDELY SINCE MANY FAMILIES ARE POORLY POPULATED, CROWDED, OR OVERLAPPING WHILE OTHERS ARE ISOLATED OR WELL POPULATED.