+ View the NASA Portal + Center for Near-Earth Object Studies JPL Small-Body Database Browser Search: [ help ]   991 McDonalda (A922 UC) Classification: Main-belt Asteroid          SPK-ID: 2000991 [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] [ show orbit diagram ] Orbital Elements at Epoch 2459200.5 (2020-Dec-17.0) TDB Reference: JPL 42 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1592876067257917 3.1779e-08   a 3.139486505601701 1.3176e-08 au q 2.639405213776487 1.026e-07 au i 2.069502581425571 3.2665e-06 deg node 63.23457491796459 0.00010401 deg peri 254.7511116743975 0.00010457 deg M 274.5863239083757 1.277e-05 deg tp 2459682.571293578226 (2022-Apr-13.07129358) 7.3576e-05 TDB period 2031.825272360327 5.56 1.2791e-05 3.502e-08 d yr n .1771805897373231 1.1154e-09 deg/d Q 3.639567797426915 1.5275e-08 au   Orbit Determination Parameters    # obs. used (total)      3346      data-arc span      31013 days (84.91 yr)      first obs. used      1936-02-20      last obs. used      2021-01-17      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .44168      source      ORB      producer      Otto Matic      solution date      2021-Feb-24 00:51:33   Additional Information  Earth MOID = 1.62515 au   Jupiter MOID = 1.66486 au   T_jup = 3.190  [ show covariance matrix ] [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] Physical Parameter Table Parameter Symbol Value Units Sigma Reference Notes absolute magnitude H 11.26   n/a E2021B10 IRAS observations used: 15 diameter diameter 38.556 km 0.514 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2011ApJ...741...68M)   geometric albedo albedo 0.040   0.005 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2011ApJ...741...68M)   B-V BV 0.660   0.020 EAR-A-5-DDR-UBV-MEAN-VALUES-V1.2 #obs=1; phase=11.11 deg. U-B UB 0.370   0.045 EAR-A-5-DDR-UBV-MEAN-VALUES-V1.2 #obs=1; phase=11.11 deg. Tholen spectral type spec_T C:   n/a EAR-A-5-DDR-TAXONOMY-V4.0 used 2 color indices 991 McDonalda (A922 UC)          Discovered 1922-Oct-24 by Struve, O. at Williams Bay Reference: DISCOVERY.DB Last Updated: 2003-08-29 [ show close-approach data ] Alternate Designations  A922 UC = 1949 PF = 1950 WG = 1953 GT1 = 1975 EE6  [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] 2021-Feb-28 07:27 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin