In-Orbit Performance of the GRACE Follow-on Laser Ranging Interferometer.

The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degrees of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wave front sensing compensates spacecraft attitude fluctuations.

Coherent range-gated laser displacement metrology with compact optical head.

We describe a new architecture for laser displacement metrology with a drastic reduction in the size and complexity of the optical head. Connected by a single optical fiber, the compact heads are easy to integrate and readily multiplexed to support applications requiring large numbers of sensors. The approach is made possible by modulating the outgoing laser light with a binary random noise code, allowing the detected signals to be discriminated based on their propagation delay.

MSTAR: a submicrometer absolute metrology system.

The Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor permits absolute distance measurement with subnanometer accuracy, an improvement of 4 orders of magnitude over current techniques. The system uses fast phase modulators to resolve the integer cycle ambiguity of standard interferometers. The concept is described and demonstrated over target distances up to 1 m.

A laser Doppler instrument for in vivo measurements of blood flow in single renal arterioles.

A laser Doppler instrument has been developed to measure the blood flow in single vessels for the study of the dynamics of local control mechanisms. A commercial blood perfusion monitor, designed to measure blood perfusion in a vascular field containing many randomly oriented blood vessels, was modified to perform measurements of blood flow in a single arteriole. In vitro tests of the instrument revealed that the relationship between blood flow and Doppler shift was not a simple linear function.