This paper provides a preliminary end-to-end mission design for NASA's Sunjammer solar sail mission, which is scheduled for ground test deployment in 2015 with launch at a later date and targets the sub-L 1 region for advanced solar storm warning. The artificial equilibrium points (AEPs) in the sub-L 1 region accessible by the Sunjammer sail as well as solar sail Halo orbits are investigated. Subsequently, the fly-out from an Earth GTO into either a selected sub-L 1 AEP or Halo orbit is optimized for a trade-off between the V to be provided at GTO perigee and the time of flight. In addition, interesting, time-optimal extended mission scenarios are presented to underpin future solar sail mission applications, e.g. transferring to an AEP high above the ecliptic plane for high-latitude Earth observation. All analyses are carried out both for an ideal Sunjammer sail performance as well as for a realistic performance derived from a detailed sail structural analysis. A comparison of the results shows that non-ideal sail properties increase the time of flight of the trajectories by 2.4 -7.9%.
The paper provides a survey of novel mission concepts for continuous, hemispheric polar observation and direct-link polar telecommunications. It is well known that these services cannot be provided by traditional platforms: geostationary satellites do not cover high-latitude regions, while low-and medium-orbit Sun-synchronous spacecraft only cover a narrow swath of the Earth at each passage. Concepts that are proposed in the literature are described, including the pole-sitter concept (in which a spacecraft is stationary above the pole), spacecraft in artificial equilibrium points in the Sun-Earth system and non-Keplerian polar Molniya orbits. Additionally, novel displaced eight-shaped orbits at Lagrangian points are presented. For many of these concepts, a continuous acceleration is required and propulsion systems include solar electric propulsion, solar sail and a hybridisation of the two.Advantages and drawbacks of each mission concept are assessed, and a comparison in terms of high-latitude coverage and distance, spacecraft mass, payload and lifetime is presented. Finally, the paper will describe a number of potential applications enabled by these concepts, focusing on polar Earth observation and telecommunications.
b O 3 = {er, et, e h } is an orthogonal right-handed polar coordinate frame. er points always along the sun-spacecraft line, e h is the orbit plane normal (pointing along the spacecraft's orbital angular momentum vector), and et completes the right-handed coordinate system (er × et = e h). c See e.g. Ref. 3 pp. 38-39. d Note that one cos α results from the projection of the sail area onto er, whereas the other cos α results from the projection of the two SRP force components onto n.
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