+ 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 2459000.5 (2020-May-31.0) TDB Reference: JPL 41 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1591403263795445 3.1804e-08   a 3.140136614738984 1.3229e-08 au q 2.640414248993064 1.0267e-07 au i 2.069376442692746 3.2664e-06 deg node 63.23808507304675 0.00010414 deg peri 254.6807200498184 0.00010469 deg M 239.2155760576255 1.2682e-05 deg tp 2459682.414103648413 (2022-Apr-12.91410365) 7.3706e-05 TDB period 2032.456415328438 5.56 1.2844e-05 3.516e-08 d yr n .177125569475902 1.1193e-09 deg/d Q 3.639858980484904 1.5335e-08 au   Orbit Determination Parameters    # obs. used (total)      3331      data-arc span      30844 days (84.45 yr)      first obs. used      1936-02-20      last obs. used      2020-08-01      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .44218      source      ORB      producer      Otto Matic      solution date      2020-Aug-24 22:26:11   Additional Information  Earth MOID = 1.62812 au   Jupiter MOID = 1.66445 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 11.2   n/a MPO473776 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 ] 2020-Oct-31 16:18 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin