Launch Windows for Libration Point Missions
- Paper number
IAC-07-C1.3.08
- Author
Mr. Martin Hechler, European Space Agency/ESOC, Germany
- Year
2007
- Abstract
The three upcoming ESA missions to the collinear libration points in the sun-Earth system, Herschel/Planck, GAIA and possibly Lisa Pathfinder will be launched from French Guiana by different Rockets, namely Ariane 5, Soyuz and VEGA.
Herschel and Planck are launched together in 2008 on Ariane 5. The launcher injects Herschel directly to a free stable manifold transfer to a large amplitude Quasi-Halo orbit at L 2. Departing from the launch orbit conditions fixed for the whole year, Planck performs a three manoeuvre transfer to a Lissajous orbit, free of eclipse and with a sun-spacecraft-Earth angle below 15 ∘ over 2.5 years. The first manoeuvre after two days, sometimes delayed to avoid star mapper blinding by the moon, corrects for the monthly variation in required apogee radius. The daily launch slot is primarily determined by sun aspect angle conditions during ascent, from after fairing separation. The seasonal launch window is determined by the tank limit on Planck and by eclipse conditions.
GAIA is launched by Soyuz/Fregat end 2011 from the new launch pad in Sinnamary. To reach a full year launch window for a 30 days fast transfer to a 15 ∘ Lissajous orbit free of eclipse for 6 years, a launch scenario is preferred with a nearly circular parking orbit at 19 ∘ inclination; optimising the time of the Fregat burn injecting towards L 2, together with the lift off time. A grid of two target conditions per month is prescribed to the launcher to limit the effort of flight program preparation.
A mission option for Lisa Pathfinder is that the VEGA launcher delivers the spacecraft, end 2009, to a low inclination elliptical orbit, with 1624 km apogee height. From there an apogee raising manoeuvre sequence, using spacecraft propulsion, reaches L 1 transfer conditions. Maximising launch mass leads to a fixed argument of perigee, however a waiting strategy during the transfer turns the line of apsides as needed, utilising the J 2 effect. Target orbit selection and launch window calculations include the optimum choice of the medium gain antenna mounting angle on the spacecraft to reach a maximum seasonal launch window opening.
The transfer optimisations minimise propellant usage, covering manoeuvre decomposition; rather than ΔV-modulus, the sum of thruster on times is minimised. A gradient projection method matches forward and backward integrations. Target orbit parameters are optimisation variables, connecting orbit selection with launch window calculation. Orbits at the libration points are generated by a bisection method.
- Abstract document
- Manuscript document
IAC-07-C1.3.08.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.