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The Cassini-Huygens spacecraft was launched in 1997 as an international and collaborative mission to study Saturn and its many moons. After a seven-year cruise, Cassini began orbiting Saturn for a four-year tour. This paper gives an overview of the maneuver operations component of Cassini navigation. Specifically, this paper reviews the orbit control and staffing strategies developed and executed as a result of these maneuver experiences. Examples of maneuver processing and analysis are also shown.

The Cassini-Huygens spacecraft was launched in 1997 on a mission to observe Saturn and its many moons. After a seven-year cruise, it entered a Saturnian orbit for a four-year, prime mission. This paper highlights significant maneuver activities performed during the last year of the prime mission. Specifically, results of 42 recent maneuvers are presented. Many maneuvers have been skipped, saving fuel and flight team effort. The system has performed more accurately than the pre-launch expectations and requirements. This is in large part why the Cassini-Huygens spacecraft has been navigated with tremendous success during the prime mission.

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The maneuver cancellation analysis consists of cost contour plots employed by the Cassini maneuver team. The plots are two-dimensional linear representations of a larger six-dimensional solution to a multimaneuver, multiencounter mission at Saturn. This realization and the use of the tool itself is just one of the many significant engineering achievements that have come from the Cassini project. After inserting the cost contour capability with an enhancement (taking account of asymptote changes), a tool that was originally only used for analysis could be used for operations once the accuracy of the plots was determined to be acceptable for operations. The plots have been used extensively since the enhancement. By using contours plotted in the B plane with B R and B T components, it is possible to view the effects on V for various encounter positions in the B plane. The plot is used in operations to help determine if the approach maneuver (ensuing encounter minus three days) and/or the cleanup maneuver (ensuing encounter plus three days) can be cancelled and is a linear check of an integrated solution. The plots have also been used to bias the targets of encounters to save V. Nomenclature B = B vector or B plane B R = vertical axis of the B plane B T = horizontal axis of the B plane C3 = excess velocity or characteristic energy G x;y = grid point value on the contour plot for an approach maneuver, m=s G x;y;c = grid point value on the contour plot for a cleanup maneuver, m=s i = leg index J x;y = V calculation of a B plane grid point for an approach maneuver, m=s J x;y;c = V calculation of a B plane grid point for a cleanup maneuver, m=s K = K matrix, a maneuver capability matrix M = the B plane mapping R = R vector of the B plane r o = nominal trajectory apoapsis maneuver location S = the incoming asymptote T = T vector of the B plane T n = nth encounter of Titan V1 = the magnitude of the velocity for a cleanup maneuver, m=s V2 = the velocity magnitude for an apoapsis maneuver, m=s B A = asymptote change B plane state vector B RT = grid variation vector B xy = the variations in the B plane with a perturbed trajectory B R y = y component of grid points in the B plane B T x = x component of grid points in the B plane r = difference in the apoapsis maneuver location for a perturbed trajectory V = change in velocity, m=s V REF = change in velocity given in the reference trajectory, m=s