Abstract For spacecraft without on-board navigation capability, their ability to fly close to target comets is limited primarily by the comet's ephemeris uncertainty. Factors contributing to cometary ephemeris uncertainties include measurement errors, star catalog errors, and offsets between the comet's center of mass and its observed center of light. The situation is further complicated by nongravitational forces acting upon a comet's nucleus and the paucity of observers currently making astrometric observations of comets. For comet Halley, the nongravitational forces affecting this comet's motion are consistent with the rocket effect of an outgassing water ice nucleus; the nucleus is apparently rotating in a direct sense about a stable spin axis. Accurate comet Halley ephemerides for close spacecraft flybys will require continued efforts to refine the existing nongravitational force model. In addition, the various flyby missions to comet Halley will require a well organized network of astrometric observers. These observers must rapidly reduce their observations in early 1986, thus allowing continuous updates to the comet's ephemeris just prior to the spacecraft flybys in March 1986.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Cometary ephemerides for spacecraft flyby missions


    Contributors:

    Published in:

    Advances in Space Research ; 2 , 12 ; 145-149


    Publication date :

    1983-01-01


    Size :

    5 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




    Outer-planet probe/flyby missions

    Swenson, B. L. / Mascy, A. C. / Murphy, J. P. et al. | NTRS | 1983


    Analysis of planetary flyby missions

    Ragsac, R.V. / Titus, R.R. | Engineering Index Backfile | 1963


    Outer-planet probe/flyby missions

    SWENSON, B. / MASCY, A. / MURPHY, J. et al. | AIAA | 1983