  We propose a set of experiments in which Ramsey-fringe techniques are
tailored to probe transitions originating and terminating on the same ground
state level. When pulses of resonant radiation, separated by a time delay $% T,
$ interact with atoms, it is possible to produce Ramsey fringes having widths
of order 1/T. If each pulse contains two counterpropagating travelling wave
modes, the atomic wave function is split into two or more components having
different center-of-mass momenta. Matter-wave interference of these components
leads to atomic gratings, which have been observed in both spatially separated
fields and time separated fields. Time-dependent signals can be transformed
into frequency dependent signals, leading to ground state Ramsey fringes
(GSRF). The signals can be used to probe many problems of fundamental
importance: a precise measurement of the earth gravitational acceleration $g$
and residual gravity in a microgravity environment with an accuracy $6
10^{-9}g;$ the rotation rate measurement with an accuracy of 6 10^{-3} deg/h;
the recoil frequency measurement.
  Since only transitions originating and terminating on the same ground state
are involved, frequency measurements can be carried out using lasers
phase-locked by quartz oscillators having relatively low frequency. Our
technique may allow one to increase the precision by a factor of 100 (the rf-
to quartz oscillator frequencies ratio) over previous experiments based on
Raman-Ramsey fringes or reduce on the same factor requirements for frequency
stabilization.
