The Navigation and Mission Design Branch provided mission design and operations planning support to the proposal mission New Worlds Observer (NWO), an exo-planet and general astrophysics mission flying in the vicinity of the Sun-Earth L2 libration point. The two-spacecraft mission consists of a 4-m telescope in a traditional L2 libration point orbit, and a 50-m diameter Starshade spacecraft which flies in formation with the Telescope, at ~80,000 km distance. The Starshade spacecraft will fly between the NWO telescope and the target star when exo-planet observations are being made; it blocks the light from the star in such a way that the telescope can search for planets orbiting the star. The Starshade is the workhorse of the two, changing its orbit approximately every two weeks to get into position for the next exo-planet star target; this is accomplished using a low thrust solar electric propulsion system with approximately 10 km/sec of delta-v capability. The NWO telescope will be performing other astrophysics observations, during this period, only pointing towards the target star when the Starshade is in position. At this time, the Starshade uses a bipropellant propulsion system to maintain its position along this line of sight between the star and telescope to within +/-1 m, maneuvering every 20 minutes during the entire exo-planet observation period.

The NWO mission presents many interesting challenges in the flight dynamics area. During the past year, NMDB has supported two GSFC Integrated Design Center studies, one for the instrument and one for the mission itself. Some of the issues supported for NWO include the redesign of the reference Telescope L2 trajectory, which was nearly coplanar with the ecliptic plane and thus experienced many shadow periods; determining the feasibility of the Starshade Spacecraft trajectory with respect to the two propulsion systems; orbit determination and navigation feasibility, in particular for the constantly maneuvering Starshade; momentum unloading frequency and magnitude for both spacecraft due to non-trivial solar radiation pressure perturbations on these two large-area spacecraft; and mission operations concepts for launch through the 5-year lifetime for the Starshade and the 10-year goal for the Telescope.

Branch members Dave Folta and Karen Richon provided NWO with trajectory analysis, with an initial feasibility analysis of the formation flying concept, which included a high-fidelity example of the Starshade trajectory demonstrating a targeting method for the low thrust retargeting maneuvers. Analysis is being performed by the NMDB to redesign the reference orbit and to refine the Starshade trajectory to demonstrate the feasibility of meeting the science requirements with the current concept in preparation for the Non-Advocacy Review in November 2008 and the submission to the National Science Foundation Decadal review next year.