+ View the NASA Portal + Center for Near-Earth Object Studies JPL Small-Body Database Browser Search: [ help ]   101 Helena (A868 PA) Classification: Main-belt Asteroid          SPK-ID: 2000101 [ 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 108 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .1407484668946828 4.5077e-08   a 2.582631310611989 7.3254e-09 au q 2.219129913089146 1.1604e-07 au i 10.19754165120801 4.9447e-06 deg node 343.3842111030089 2.2666e-05 deg peri 348.4129868460718 2.722e-05 deg M 255.6489266420588 1.7455e-05 deg tp 2459639.926723273346 (2022-Mar-01.42672327) 7.4316e-05 TDB period 1515.975018635167 4.15 6.4499e-06 1.766e-08 d yr n .2374709316279553 1.0103e-09 deg/d Q 2.946132708134832 8.3565e-09 au   Orbit Determination Parameters    # obs. used (total)      2396      data-arc span      54723 days (149.82 yr)      first obs. used      1871-03-22      last obs. used      2021-01-17      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .42839      source      ORB      producer      Otto Matic      solution date      2021-Feb-24 19:03:15   Additional Information  Earth MOID = 1.20813 au   Jupiter MOID = 2.42375 au   T_jup = 3.388  [ 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 8.23   n/a E2021B10 IRAS observations used: 15 magnitude slope G 0.35   n/a PDS3 (MPC 17257) Fit diameter diameter 65.84 km 1.3 IRAS-A-FPA-3-RDR-IMPS-V6.0 IRAS observations used: 15 rotation period rot_per 23.080 h n/a LCDB (Rev. 2020-October); Warner et al., 2009 Published Reference List: [Lagerkvist, C.-I.; Rickman, H. (1981) Astron. Astrophys. Suppl. Ser. 45, 177-179.] [Harris, A.W.; Young, J.W. (1989) Icarus 81, 314-364.] geometric albedo albedo 0.1898   0.008 IRAS-A-FPA-3-RDR-IMPS-V6.0 IRAS observations used: 15 B-V BV 0.854   0.020 EAR-A-5-DDR-UBV-MEAN-VALUES-V1.2 #obs=12; phase (min.=3.93, mean=10.53, max.=24.72) deg. U-B UB 0.426   0.033 EAR-A-5-DDR-UBV-MEAN-VALUES-V1.2 #obs=12; phase (min.=3.93, mean=10.53, max.=24.72) deg. Tholen spectral type spec_T S   n/a EAR-A-5-DDR-TAXONOMY-V4.0 used 7 color indices; used ground-based radiometric albedo SMASSII spectral type spec_B S   n/a EAR-A-5-DDR-TAXONOMY-V4.0 based on a high-resolution spectrum by Xu et al. (1995) or Bus and Binzel (2002) 101 Helena (A868 PA)          Discovered 1868-Aug-15 by Watson, J. C. at Ann Arbor Reference: DISCOVERY.DB Last Updated: 2003-08-29 [ show close-approach data ] [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] 2021-Feb-27 05:11 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin