Abstract
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 220km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5degrees 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. The LRI has operated continuously without breaks in phase tracking for more than 50days, and has shown biased range measurements similar to the primary ranging instrument based on microwaves, but with much less noise at a level of 1 nm/sqrt[Hz] at Fourier frequencies above 100mHz.
Highlights
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
A beam splitter (BS) transmits 10% of the light to be used as the local oscillator (LO) to enable heterodyne detection of the nW-level received (RX) light
The remaining 90% of the local laser light is reflected by the BS and is routed through the triple mirror assembly (TMA), which consists of three plane mirrors, whose planes are precisely orthogonal to each other and intersect in a virtual vertex located at the center of mass (c.m.) of the accelerometer test mass, the reference point for the ranging measurement [17,18,19,20]
Summary
Philipp Hager,4,† Jerome Hauden, Frank Heine, Gerhard Heinzel,5,‡ Mark Herding, Martin Hinz, James Howell, Mark Katsumura, Marina Kaufer, William Klipstein, Alexander Koch, Micah Kruger, Kameron Larsen, Anton Lebeda, Arnold Lebeda, Thomas Leikert, Carl Christian Liebe, Jehhal Liu, Lynette Lobmeyer,. Data processing of the range variations that involved the on-board accelerometer, GPS-based precise
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