As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended missions through September 2017. Cassini is a three-axis stabilized spacecraft. It uses reaction wheels to achieve high level of spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes in-flight estimates of reaction wheel bearing drag torque and made them available to the mission operations team. These telemetry data are being trended for the purpose of monitoring the long-term health of the reaction wheel bearings. Anomalous drag torque signatures observed over the past 15 years are described in this paper. One of these anomalous drag conditions is bearing cage instability that appeared (and disappeared) spontaneously and unpredictably. Cage instability is an uncontrolled vibratory motion of the bearing cage that can produce high-impact forces internal to the bearing that will cause intermittent and erratic torque transients. Characteristics of the observed cage instabilities and other drag torque "spikes" are described in this paper. In day-to-day operations, the reaction wheels' rates must be neither too high nor too low. To protect against operating the wheels in any undesirable conditions (such as prolonged low spin rate operations), a ground software tool named Reaction Wheel Bias Optimization Tool (RBOT) was developed for the management of the wheels. Disciplined and long-term use of this ground software has led to significant reduction in the daily consumption rate of the wheels' low spin rate dwell time. Flight experience on the use of this ground software tool as well as other lessons learned on the management of Cassini reaction wheels is given in this paper.


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    Titel :

    Inflight Performance of Cassini Reaction Wheel Bearing Drag in 1997-2013


    Beteiligte:
    Lee, Allan Y. (Autor:in) / Wang, Eric K. (Autor:in)

    Kongress:

    AIAA Atmospheric Flight Mechanics Conference ; 2013 ; Boston, MA, United States
    AIAA InfoTech@Aerospace 2013 Conference ; 2013 ; Boston, MA, United States
    AIAA Guidance, Navigation, and Control Conference ; 2013 ; Boston, MA, United States
    AIAA Modeling and Simulation Technologies Conference ; 2013 ; Boston, MA, United States


    Erscheinungsdatum :

    2013-08-19


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Keine Angabe


    Sprache :

    Englisch





    Inflight Performance of Cassini Reaction Wheel Bearing Drag in 1997-2013 (AIAA 2013-4631)

    Lee, A.Y. / Wang, E.K. / American Institute of Aeronautics and Astronautics | British Library Conference Proceedings | 2013


    Cassini Reaction Wheel Bearing Drag Performance 1997-2013

    Lee, Allan Y. / Wang, Eric / Lee, Cliff et al. | NTRS | 2013