LISA Pathfinder as alternative for the Michelson and Morley interferometer experiment.

In the Quantum FFF Model, mass is the capacity of rigid stringy Fermion particles to mutate 

oscillating Higgs vacuum field particles into as many rigid gravitons per time unite in a continuous 

collision process. (FFF = Function Follows rigid paticle Form)

The collision process is assumed to be the origin of the spin and eigen energy of Fermions and fully in line with General Relativity (GR).

Around massive objects like star and planets, the Higgs field oscillation strength is diluted and polarized by the graviton radiation influence creating a “Local Anti Symmetric Oscillating vacuum Frame” ( LASOF) as the origin of a so called lightspeed mass/drag effect, which is not in line with GR. and the origin of the so called “Michelson Morley null result”

Outside the LASOF ellipsoidal area around the earth however, this effect should be observable by Michelson interferometers.

This difference with GR is subject to future (LISA) research in space.

 As a consequence, it is assumed that the LISA (Pathfinder) satellite soon will be able to test light speed differences around the sun even at its orbit location L1 ( Lagrangian L1) and as a result its absolute speed related to the local LASOF vacuum of the sun.
see:

http://sci.esa.int/lisa-pathfinder/

ESA/NASA Laser Interferometer Space Antenna ( LISA)
see also: https://www.flickr.com/photos/93308747@N05/albums/72157651418365380 
and:  https://www.academia.edu/8467271/The_O_Connell_effect_in_eclipsing_binaries_explained_by_mass_related_light_speed_extinction_distances_LASOF_of_stars_and_even_planets