relativsats

Relativsats are a proposed class of spacecraft whose primary mission is to study and exploit relativistic effects predicted by general relativity and special relativity in orbital environments. They carry ultra-stable onboard clocks and high-precision communication links to perform time transfer and ranging between satellites and ground stations. By comparing clock rates for satellites in different gravitational potentials and with varying velocities, Relativsats aim to test gravitational redshift, time dilation, and other relativistic phenomena.

A Relativsat system would typically use a constellation approach to enable cross-checking measurements and to map the spacetime curvature and gravitational potential around Earth or other planets. Key design elements include drag-free or ultra-low-drag spacecraft to minimize non-gravitational accelerations, precise orbit determination, and long-baseline optical or microwave links for centimeter-level ranging and nanosecond-level timing accuracy. Cross-link communications between satellites support differential measurements and improved error control.

Scientific goals encompass rigorous tests of general relativity, measurements of frame-dragging effects such as Lense–Thirring precession, refinement of the gravitational redshift constant, and constraints on alternative theories of gravity. The resulting improvements in timekeeping and navigation accuracy could also benefit geodesy and fundamental physics experiments.

History and status: Relativsats as a named program are not part of a widely implemented mission today, but related techniques and instruments are used in existing relativity tests, including satellite laser ranging, clock experiments, and gravity-field missions. Proposals envision future missions that integrate optical clocks and drag-free technology.

See also: General relativity, gravitational redshift, time transfer, drag-free spacecraft, satellite laser ranging.