  For testing gravity and detecting gravitational waves in space, deep-space
laser ranging using drag-free spacecraft is a common method. Deep space
provides a large arena and a long integration time. Laser technology provides
measurement sensitivity, while drag-free technology ensures that gravitational
phenomenon to be measured with least spurious noises. In this talk, we give an
overview of motivations and methods of various space missions/proposals testing
relativistic gravity and detecting gravitational waves, and refer to various
references.
