Large halo orbits around L1 and L2 are preferred over small orbits for reasons beyond geometry
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Peer-reviewed literature indicates that large halo orbits are preferred under certain conditions due to practical operational factors such as lower station-keeping costs.
Abstract In this study, the choice of a nominal space telescope orbit in the vicinity of the Sun–Venus L 2 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 L 1 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 Δ v . 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.
HERSCHEL/PLANCK (double launch in 2007 on ARIANE) and GAIA (launch in 2010 on SOYUZ/FREGAT) are Astronomy missions in the ESA Scientific Program with different objectives but with quite common requirements of a highly stable thermal environment and sky viewing conditions unobstructed by Earth and sun. A class of orbits near the L2 libration point (outside Earth) in the sun-Earth system has been selected for these projects. Not differentiating in the conventional way between Halo or Lissajous orbits, a family of non-escape orbits around L2 has been classified solely by their property of neither falling towards the Earth nor to the sun within the limits of numerical precision of the initial conditions. The stable manifolds of some of the Lissajous orbits in this family (generally with large amplitudes) touch perigee conditions which can be naturally injected into by a launcher, e.g. a low perigee altitude, and specifically for ARIANE a line of apsides near the equator plane. Thus a ’free’ transfer to some of these orbits which requires no manoeuvres after perigee, except stochastic orbit corrections, exists. Starting from the free transfers to the large amplitude non-escape orbits, transfers to small amplitude (e.g. maximum sun-spacecraft-earth angle below 10◦) have been constructed combining the linear theory for orbits in the restricted circular three body problem with the numerical algorithm. The linear theory defines directions of escape (e-term) and non-escape in the veloc
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