+ View the NASA Portal + Center for Near-Earth Object Studies JPL Small-Body Database Browser Search: [ help ]   121P/Shoemaker-Holt 2 Classification: Jupiter-family Comet          SPK-ID: 1000141 [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] [ show orbit diagram ] Orbital Elements at Epoch 2453237.5 (2004-Aug-20.0) TDB Reference: JPL 42 (heliocentric ecliptic J2000)  Element Value Uncertainty (1-sigma)   Units  e .3384566137765764 1.1932e-07   a 4.002945176938433 9.0147e-08 au q 2.648121907218573 4.7587e-07 au i 17.71778365749723 1.0729e-05 deg node 99.66992336183945 2.5236e-05 deg peri 6.229876733146102 1.7828e-05 deg M 358.4351874021517 1.453e-05 deg tp 2453250.215332557404 (2004-Sep-01.71533256) 0.00011822 TDB period 2925.283019167699 8.01 9.8817e-05 2.705e-07 d yr n .1230650154672648 4.1572e-09 deg/d Q 5.357768446658294 1.2066e-07 au   Orbit Determination Parameters    # obs. used (total)      595      data-arc span      11549 days (31.62 yr)      first obs. used      1989-03-04      last obs. used      2020-10-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      0      norm. resid. RMS      .65062      source      ORB      producer      Otto Matic      solution date      2020-Oct-18 17:46:45   Additional Information  Earth MOID = 1.6647 au   Jupiter MOID = .114586 au   T_jup = 2.872  [ 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 5.6   1. 42 2 parameter fit from 278 observations, autocmod 2.8 comet total magnitude slope K1 20.25   n/a 42 autocmod 2.8 comet nuclear magnitude M2 12.5   0.5 42 from 134 observations, autocmod 2.8 comet nuclear magnitude slope K2 5.   n/a 42 autocmod 2.8 comet nuclear phase coefficient PC 0.03   n/a 42 autocmod 2.8 diameter diameter 3.24 km n/a Lamy,P.L.,Toth,I.,Fernandez,Y.R.,Weaver,H.A. (2004) Comets II, pp. 223-264   121P/Shoemaker-Holt 2          Discovered 1989-Mar-09 by Shoemaker, Carolyn & Eugene, & Holt, Henry at Palomar Mountain Observatory, California discovered on plate/photo taken on discovery date Reference: comet.dis Last Updated: 2003-08-29 [ show close-approach data ] Alternate Designations  Perihelion  Year (est.)  New-Style  Desig Roman  Numeral  Year/  Letter   1996.7   121P/1995 Q3         1988.7   121P/1989 E2   1988 XI   1989j  [ Ephemeris | Orbit Diagram | Orbital Elements | Mission Design | Physical Parameters | Discovery Circumstances | Close-Approach Data ] 2021-Mar-05 11:47 UT (server date/time)   Site Manager:   Ryan S. Park Webmaster:   Alan B. Chamberlin