Abstract: An interferometer delay line includes an optical payload displaced along a guide track under the control of a control device including at least one sensing device which senses the position of the payload along the guide track and a drive device acting on the payload. The sensing device includes a linear succession of fixed optical read heads parallel to the guide track and a graduated rule carried by the optical payload in any position on the latter facing at least one of the optical read heads. The sensing device also includes a synchronizing/switching unit causing a counter to count pulses from the heads in succession, the pulses representing distance increments.

Abstract: Method and apparatus for calibration of a set of rate gyros on a three-axis stabilized satellite in orbit, the satellite including an attitude sensing system including the set of rate gyros, a set of actuators and control logic adapted to apply to the set of actuators control signals U derived from measurement signals M supplied by the attitude sensing system. From a time t.sub.0 satellite attitude errors (E1) relative to a reference frame of reference and constant drifts (E2) of the set of rate gyros about three axes (XYZ) of the satellite are estimated conjointly. The estimated values of the attitude errors and the difference between the measured speeds (.omega.) of the set of rate gyros and the estimated values of the constant drifts are applied in real time to the control logic and these estimated values of the constant drifts are stored when they become constant to within a first predetermined tolerance and the estimated values of the attitude errors become constant to within a second tolerance.