On Non-eclipsing Earth Orbits

Non-eclipsing orbits find obvious application for space missions designed to study the Sun. They also offer advantage to spaceborne thermal instruments in many applications, allowing a more stable operational thermal environment by eliminating the thermal effects of orbit-to-orbit eclipse passages. This paper defines four distinct sets of (idealized) earth orbits, which experience no eclipsing. The noneclipsing orbits are all sun-synchronous, and as is typical in discussing sun-synchronous orbits, these non-eclipsing orbits are based on the idealized system of two-body dynamics perturbed only by Earth oblateness (J
2
effects). All four sets of orbits offer the possibility of flying (solar) eclipse-free for lifetimes of several years without propulsive orbit control, and indefinitely with minimal propulsive orbit control.