+ View the NASA Portal + Center for Near-Earth Object Studies JPL Small-Body Database Browser Search: [ help ]   117P/Helin-Roman-Alu 1 Classification: Jupiter-family Comet          SPK-ID: 1000121 [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] [ show orbit diagram ] alternate orbits: [epoch=2015-Jun-23.0] K222/18 (default) [epoch=2009-Dec-13.0] K143/20 [epoch=1987-Oct-12.0] SAO/1987 Orbital Elements at Epoch 2457196.5 (2015-Jun-23.0) TDB Reference: JPL K222/18 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .2539225524277177 1.1398e-07   a 4.095628972254243 3.3239e-07 au q 3.055656409822535 6.872e-07 au i 8.697456101424551 6.5577e-06 deg node 58.8820665390657 4.4347e-05 deg peri 222.6229481904272 5.4324e-05 deg M 53.88599015936855 2.1675e-05 deg tp 2456743.338815476521 (2014-Mar-26.83881548) 0.00014987 TDB period 3027.466433222615 8.29 0.00036855 1.009e-06 d yr n .118911310146813 1.4476e-08 deg/d Q 5.135601534685951 4.1679e-07 au Additional Model Parameters  Parameter Value Uncertainty (1-sigma)  A1 [EST] 7.094782444158679E-8 1.201E-8 A2 [EST] 1.841175238669423E-8 4.572E-9   Orbit Determination Parameters    # obs. used (total)      2973      data-arc span      3794 days (10.39 yr)      first obs. used      2010-11-03      last obs. used      2021-03-24      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .61763      source      ORB      producer      Davide Farnocchia      solution date      2021-Mar-29 10:01:17   Additional Information  Earth MOID = 2.04678 au   Jupiter MOID = .258717 au   T_jup = 2.967  [ 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 comet total magnitude M1 6.8   0.7 K222/18 2 parameter fit from 967 observations, autocmod 2.9c comet total magnitude slope K1 13.   n/a K222/18 autocmod 2.9c comet nuclear magnitude M2 11.4   0.5 K222/18 from 1839 observations, autocmod 2.9c comet nuclear magnitude slope K2 5.   n/a K222/18 autocmod 2.9c comet nuclear phase coefficient PC 0.03   n/a K222/18 autocmod 2.9c diameter diameter 9 km n/a Scotti,J (1994) BAAS 26:1375   117P/Helin-Roman-Alu 1          Discovered 1989-Oct-02 by Helin, Eleanor, Roman, Brian and Alu, Jeff at Palomar Mountain Observatory, California Reference: comet.dis Last Updated: 2003-08-29 [ show close-approach data ] Alternate Designations  Perihelion  Year (est.)  New-Style  Desig Roman  Numeral  Year/  Letter   1989.4   117P/1989 T2   1987 XXXVII   1989w  [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] 2021-Apr-20 08:36 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin