Orbit Concepts at L2 for Soyuz Launches from Kourou
- Paper number
IAC-05-C1.1.10
- Author
Mr. Martin Hechler, European Space Agency/ESOC, Germany
- Coauthor
Mr. Miguel Bello Mora, DEIMOS Space S.L., Spain
- Coauthor
Mr. Mariano Sánchez-Nogales, DEIMOS Space, Spain
- Coauthor
Mr. Arturo Yañez Otero, GMV S.A., Spain
- Year
2005
- Abstract
The Herschel and Planck spacecraft will be launched together by Ariane 5 ECA from Kourou in 2007 onto the stable manifold of a large amplitude Pseudo-Halo orbit around the L2 libration point in the Sun Earth system. Herschel will remain on that orbit; Planck will perform an amplitude reduction maneuver to reach a Lissajous orbit with a maximum sun-spacecraft-Earth angle of 15 degrees. Different from Ariane, Soyuz will launch first into a low circular parking orbit from which the Fregat upper stage will inject to the transfer. This gives an additional degree of freedom on the choice of the line of apsides of the transfer orbit. Furthermore, because of the limitation of the Fregat tank size, parking orbits at inclinations of up to 30 degrees can be reached from Kourou without mass penalty. The latter property allows selecting the parking orbit near the lunar orbit plane. By means of a lunar gravity assist the stable manifold of small amplitude Lissajous orbits can then be freely reached. There exist a variety of solutions once per month, the stable manifold intersects the moon orbit at two points (after perigee), and the Earth moon transfer can also be constructed in different ways. The phase angle on the target orbit can in addition be prescribed such that the orbit just touches the Earth shadow at the begin of the mission to obtain over 6 years in that orbit without eclipse. From the launch orbit, chosen close to the lunar orbit plane with an apogee below the moon, a phasing sequence can be constructed such that the transfer conditions can be reached for any launch date with 40 m/s for the apogee raising maneuvers, including the gravity losses. A systematic approach has been taken to avoid adverse moon perturbations. This strategy is now proposed for the GAIA mission, a Lissajous orbit with a maximum sun-spacecraft-Earth angle of less than 7 degrees will be reached. Additional gains in spacecraft dry mass are possible when starting at a lower apogee and using more perigee maneuvers performed by the spacecraft. Another interesting case of transfers to orbits around L2 has been studied for the Darwin mission. Darwin consists of 4 spacecraft. One studied option is to launch them in pairs, on two Soyuz launches from Kourou. The launch dates have to be at least 20 days apart, but the spacecraft have to rendezvous in an orbit around L2. It has been shown that without any phasing orbits for a given separation of the launch dates of up to 40 days, a target orbit can be defined in which the two stacks of spacecraft can be brought to the same position. The method developed to systematically search for these pairs of transfers for a given launch delay, first generates a database of direct transfer trajectories for each launch day using the same “fuzzy boundary” bisection method developed in previous studies for Herschel/Planck, scanning over all free parameters (launch hour, argument of perigee, inclination). Two transfer types to the same final conditions can be observed at this step: “long” and “short” transfers. From the data base an initial guess of a pair of trajectories is selected for a given pair of launch dates, by matching time, position and velocity at the XZ-plane crossing in the rotating frame. Using this initial guess a constrained parameter optimization method, shooting forward and backward and matching position and velocity in the middle, will solve the pair of boundary value problems in one go. An almost free rendezvous (1 m/s per stack) comes out, regardless of the launch delay (from 10 to 40 days), with increasing target orbit amplitude for increasing launch delay.
- Abstract document
- Manuscript document
IAC-05-C1.1.10.pdf (🔒 authorized access only).
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