  Chameleon mechanism appearing in massive tensor-scalar theory of gravity can
effectively reduce locally the non-minimal coupling between the scalar field
and matter. This mechanism is invoked to reconcile large-scale departures from
general relativity (GR), supposedly accounting for cosmic acceleration, to
small scales stringent constraints on GR. In this paper, we carefully
investigate this framework on cosmological and solar system scales to derive
combined constraints on model parameters, notably by performing a non-ambiguous
derivation of observables like luminosity distance and local post-newtonian
parameters. Likelihood analysis of type Ia Supernovae data and of admissible
domain for the PPN parameters clearly demonstrates that chameleon mechanism
cannot occur in the same region of parameters space than the one necessary to
account for cosmic acceleration with the assumed Ratra-Peebles potential and
exponential coupling function.
