Novel mission concepts for polar coverage: An overview of recent developments and possible future applications

Abstract

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.

Design and Trade-offs of a Pole-Sitter Mission

“…A complete discussion on potential applications enabled by such instrumentation is found in Ref. [2]; suffice to underline that all these instruments are well below the 100 kg mass assumed in the pole-sitter design.…”

Mission analysis and systems design of a near-term and far-term pole-sitter mission

“…In particular, notable examples are those relying on artificial displaced equilibria and non-Keplerian orbits (NKOs) [11,12]. A further comparison of these concepts is provided in Reference [1].…”

“…However, a number of novel potential applications can be enabled, both in the fields of observation and telecommunications. A complete discussion of possible applications is presented in Reference [1].…”

“…However, the Molniya orbit has two intrinsic limitations. The first is the critical inclination of 63.4° or 116.6°, which does not allow for a satisfactory coverage of the polar caps or high-latitude regions [1]. Recent research [2] has therefore considered changing the critical inclination of the Molniya orbit to 90°, using a continuous solar electric propulsion (SEP) system for maintaining the orbit.…”

“…However, in all these mission concepts, the spacecraft does not achieve satisfactory conditions for continuous coverage of the high-latitude regions [1].…”