Pre-Phase A Report - Lisa - Nasa

2.7 Heliocentric versus geocentric options 45
Auxiliary Spacecraft Auxiliary Spacecraft
10 6 km
120°
Master Spacecraft
10 6 km
Figure 2.4 Early version of the LAGOS concept. Top: Central spacecraft.
Bottom: The configuration of three drag-free spacecraft in interplanetary
space.
be sensed optically, and the signals could be used to servo-control the position of the
spacecraft against perturbations.
2.7 Heliocentric versus geocentric options
An alternate gravitational wave mission that uses geocentric rather than heliocentric orbits
for the spacecraft has been suggested by R.W. Hellings. An earlier version of this mission
called SAGITTARIUS was proposed to ESA in 1993 as a candidate for the M3 mission.
A similar mission called OMEGA was proposed to NASA in 1996, and is expected to be
proposed again in 1998 .
Our understanding is that the 1996 OMEGA proposal involved six spacecraft in retrograde
coplanar geocentric orbits with semi-major axes of roughly 600 000 km and periods
Corrected version 2.08 3-3-1999 9:33