On the design of a space telescope orbit around the Sun–Venus [formula omitted] point

Abstract

In this study, the choice of a nominal space telescope orbit in the vicinity of the Sun–Venus L2 libration point is discussed from the viewpoint of illumination conditions and station-keeping costs. Such a location for the space telescope is especially appealing for the observation of potentially hazardous asteroids approaching the Earth from the daytime side of the sky. In contrast to the case of a telescope placed near the Sun–Earth L1 point, a significantly longer warning time can be achieved. Moreover, a Lissajous-type quasi-periodic orbit can be selected so that a predefined percentage of the orbit is shadowed. When a nominal orbit is allowed to be permanently sunlit, a large halo orbit is preferred due to the lower station-keeping cost. For two sets of unstable halo and Lissajous orbits, the station-keeping cost is evaluated by conducting Monte Carlo simulations in the ephemeris model of motion. Two modifications of the target point station-keeping technique are examined: the X-axis control and the 3-axis control. The simulation scenario includes orbit insertion and navigation errors, impulse execution errors, and constraints on the minimum imparted Δv. Dependence of the station-keeping cost on orbit insertion and navigation errors is analyzed. Some of the large halo orbits appear to be linearly stable. The corresponding central manifold location in the phase space is determined, which makes a simple targeting strategy possible.