TITLE:
     Simulation of Formation Flight Near L2 for the TPF Mission

AUTHORS:
G. Gomez
Departament de Matemātica Aplicada i Anālisi
Universitat de Barcelona, 08007 Barcelona, Spain
e-mail: gerard@maia.ub.es

M.W. Lo 
Navigation and Mission Design
Jet Propulsion Laboratory, California Institute of Technology
M/S 301-140L Pasadena, California 91109, USA
e-mail: mwl@hari.jpl.nasa.gov

J. Masdemont 
Departament de Matemātica Aplicada I
ETSEIB
Universitat Politčcnica de Catalunya
Diagonal 647, 08028 Barcelona, Spain
e-mail: josep@barquins.upc.es

K. Museth
Computer Science Graphic Group
California Institute of Technology
Pasadena, California, USA
e-mail: kmu@gg.caltech.edu

ABSTRACT:
The TPF Mission (Terrestrial Planet Finder) is one of the center pieces
of the NASA Origins Program. The goal of TPF is to identify terrestrial
planets around stars nearby the Solar System. For this purpose, a
space-based infrared interferometer with a baseline of approximately 100
m is required. To achieve such a large baseline, a distributed system of
five spacecraft flying in formation is an efficient approach. Since the
TPF instruments needs a cold and stable environment, near Earth orbits
are unsuitable. Two potential orbits have been identified: a SIRTF-like
heliocentric orbit; a libration orbit near the L2 Lagrange point. In this
paper, we focus on the second case: an orbit near the L2 Lagrange point.
The formation flight problem near the Lagrange points is of great
interest. Our work in the study of the feasibility of formation flight
near the Lagrange points indicates that:

1. Formation flight near L2 is dynamically possible for the TPF Mission.
2. Linear control around a nonlinear baseline libration orbit near L2 is 
   adequate for the TPF Mission.



