  The WASP-148 planetary system has a rare architecture with a transiting
Saturn-mass planet on a tight orbit which is accompanied by a slightly more
massive planet on a nearby outer orbit. Using new space-born photometry and
ground-based follow-up transit observations and data available in literature,
we performed modeling that accounts for gravitational interactions between both
planets. Thanks to the new transit timing data for planet b, uncertainties of
orbital periods and eccentricities for both planets were reduced relative to
previously published values by a factor of 3-4. Variation in transit timing has
an amplitude of about 20 minutes and can be easily followed-up with a 1-m class
telescopes from the ground. An approximated transit ephemeris, which accounts
for gravitational interactions with an accuracy up to 5 minutes, is provided.
No signature of transits was found for planet c down to the Neptune-size
regime. No other transiting companions were found down to a size of about 2.4
Earth radii for interior orbits. We notice, however, that the regime of
terrestrial-size planets still remains unexplored in that system.
