Analysis of possible early orbit contingencies and recovery strategies for Herschel/Planck

Paper number

IAC-09.C1.3.9

Author

Dr. Elisabet Canalias, Germany

Coauthor

Mr. Martin Hechler, European Space Agency (ESA), Germany

Year

2009

Abstract

Herschel and Planck, the ESA astronomy cornerstone missions,
 will be launched in April 2009 on Ariane 5.
Herschel, the largest ever infrared telescope, and Planck, to
study the cosmic microwave background radiation,
will be injected together into a nearly parabolic orbit. From there, they
will be manoeuvred
to their operational orbits around the libration point L$_2$ of the
Sun-Earth system: a halo type orbit for Herschel and a small amplitude
 Lissajous orbit for Planck. Essential to nominal orbit insertion is a
correction manoeuvre to be performed
within two days from launch, to correct for the launcher dispersion and other
systematic deviations from the required transfer conditions.


 The present work focuses on preparing recovery strategies in case of
 an under-performance of the launcher or the failure to execute the first correction manoeuvre on time.
It is shown that over a large range of launcher under-performances, it would still be possible to follow the nominal mission design, using the propellant margins.
Similarly, for a nearly nominal launch orbit, a delay of the first orbit correction up to day 20 on Planck is possible. For Herschel, however, the margin is lower and the delay of the first orbit correction would only be feasible up to day
7.

However, the evaluation of how far the nominal scenario could be kept is not the main objective of the paper, but the development of
 other strategies implying substantial changes in the mission design.
For instance, a recovery strategy consists in letting the two spacecraft perform one complete revolution in the initial eccentric orbit, and start manoeuvering
them near the second perigee passage. This procedure appears simple
from a trajectory design point of view, as the same optimization techniques
 used for the original mission design can be applied. However, it is not
straightforward operationally, as the mounting and cycling of the thrusters,
 the constraints on the viewing direction of the star mapper
 with respect to Sun, Earth and Moon during maneuvers,
as well as the necessary attitude changes between the two necessary
thrust arcs around perigee have to be
taken into account. These constraints are different between Herschel and Planck as built.
Furthermore, the propellant margins are not
enough to follow this recovery strategy for all the contingency cases included
in the study.
 Therefore, more complicated designs, taking advantage of moon fly-bys or the Sun-Earth-Moon weak stability boundaries, must also be considered.

Abstract document

IAC-09.C1.3.9.pdf

Manuscript document

IAC-09.C1.3.9.pdf (🔒 authorized access only).

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