+ View the NASA Portal + Center for Near-Earth Object Studies JPL Small-Body Database Browser Search: [ help ]   1557 Roehla (1942 AD) Classification: Main-belt Asteroid          SPK-ID: 2001557 [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances ] [ show orbit diagram ] Orbital Elements at Epoch 2459000.5 (2020-May-31.0) TDB Reference: JPL 40 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1047210233226222 4.4508e-08   a 3.011724187083738 1.3134e-08 au q 2.696333348246836 1.3253e-07 au i 10.29871284421751 4.5394e-06 deg node 355.1937532083526 2.031e-05 deg peri 3.616210755519614 2.6755e-05 deg M 116.0298283766081 1.7915e-05 deg tp 2458385.197937104837 (2018-Sep-23.69793710) 9.4519e-05 TDB period 1909.067226431541 5.23 1.2488e-05 3.419e-08 d yr n .1885737678672101 1.2335e-09 deg/d Q 3.327115025920639 1.4509e-08 au   Orbit Determination Parameters    # obs. used (total)      2674      data-arc span      42792 days (117.16 yr)      first obs. used      1903-09-20      last obs. used      2020-11-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .42727      source      ORB      producer      Otto Matic      solution date      2020-Dec-18 02:01:21   Additional Information  Earth MOID = 1.69256 au   Jupiter MOID = 2.11442 au   T_jup = 3.217  [ show covariance matrix ] [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances ] Physical Parameter Table Parameter Symbol Value Units Sigma Reference Notes absolute magnitude H 11.5   n/a MPO452181   diameter diameter 18.766 km 0.279 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2011ApJ...741...68M)   rotation period rot_per 5.67899 h n/a LCDB (Rev. 2020-October); Warner et al., 2009 sidereal period (not synodic); Result based on less than full coverage, so that the period may be wrong by 30 percent or so. Published Reference List: [Durech, J.; Hanus, J.; Oszkiewsicz, D.; Vanco, R. (2016) Astron. Astrophys. 587, A48.] [Hanus, J.; Delbo, M.; Ali-Lagoa, V.; Bolin, B.; et al. (2016) Astron. Astrophys., submitted.] [Hanus, J.; Delbo, M.; Ali-Lagoa, V.; Bolin, B.; et al. (2018) Icarus 299, 84-96.] geometric albedo albedo 0.151   0.037 urn:nasa:pds:neowise_diameters_albedos::2.0[mainbelt] (http://adsabs.harvard.edu/abs/2011ApJ...741...68M)   1557 Roehla (1942 AD)          Discovered 1942-Jan-14 by Reinmuth, K. at Heidelberg Reference: DISCOVERY.DB Last Updated: 2003-08-29 Alternate Designations  1942 AD = 1930 YS = 1950 RF1 = A903 SB  [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances ] 2021-Jan-21 18:13 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin