AAS 04-136 NEW HORIZONS PLUTO APPROACH NAVIGATION
The navigation of the New Horizons spacecraft during approach to Pluto and its satellite Charon is described. The great distance of the spacecraft from the Earth and Sun presents several new challenges that are identified and described by analytic formula. The two-body dynamics present a particularly interesting problem of satellite orbit determination. A complete covariance analysis is performed describing navigation and science data acquisition accuracies. The results of the covariance analysis are compared with analytic formula to provide insight into the operation of the navigation system.
New Horizons Pluto-Kuiper Belt mission: design and simulation of the Pluto-Charon encounter
Abstract The primary goal of the New Horizons Pluto–Kuiper Belt mission is to explore Pluto by 2020, before Pluto's atmosphere collapses as predicted by scientists, and then explore the Kuiper Belt objects in an extended mission. The baseline mission plans to launch in January 2006, using a Jupiter gravity assist trajectory to reach Pluto. The New Horizons spacecraft will arrive at Pluto as early as 2015, depending on the launch vehicle. For such a mission, whose exploration takes place during a brief flyby period after a long cruise, a thorough planning of the encounter is especially critical to the realization of optimal science observations. A detailed Pluto encounter trajectory design that achieves both solar occultation and Earth occultation by both Pluto and Charon is described in this paper, along with discussions of the design rationale and considerations. Science observations and measurements planned for the Pluto–Charon encounter are simulated and analyzed, and a comprehensive Pluto–Charon encounter process filled with detailed science observation simulations is demonstrated in a 3-D animation.
Orbit determination singularities in the Doppler tracking of a planetary orbiter
The problem of determining the orbit of a spacecraft about another planet (or an asteroid or cometary nucleus) by means of Doppler tracking data is treated. The Doppler shift associated with the relative motion of an orbiting spacecraft and an Earth-based tracking station is derived mathematically and expressed as a powerseries expansion in several small quantities. Partial derivatives of the Doppler shift with respect to the orbital elements and the mass of the attracting body are evaluated analytically, assuming simple two-body motion. Linear dependencies among the partial derivatives indicate unobservable parameters. Eight distinct cases are investigated, according to whether the orbit is elliptical or circular, whether the orbit is viewed face-on or at some other angle, and whether the central-body mass is known a priori or unknown. The full set of singular geometries for the determination of the orbit of a spacecraft about another planet, using Doppler data, is justified mathematically, for the first time. Certain geometries previously hypothesized to be singular are shown to be nonsingular.