9 research outputs found
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. The LRI has operated continuously without breaks in phase tracking for more than 50 days, 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/Hz at Fourier frequencies above 100 mHz. © 2019 authors. Published by the American Physical Society
GRACE-Follow On Laser Ranging Interferometer: German contribution
The Gravity Recovery and Climate Experiment (GRACE) is a joint US/German
mission that has been mapping the Earth's gravity �eld since 2002 by measuring the distance
variations between two spacecraft using a micro-wave link. GRACE is reaching the end of its
lifetime. For this reason and in order to minimize data gaps, an almost identical mission will be
launched in 2017. This mission is called GRACE-Follow On (GRACE-FO) and it will include
an additional instrument as a technological demonstrator to monitor distance changes between
the spacecraft. This instrument is the Laser Ranging Interferometer (LRI), which is based on
heterodyne laser interferometry at 1064nm and takes advantage of many technologies developed
for LISA. In this paper a short overview of the current status of the German contribution is
presented
LASER RANGING INTERFEROMETER ON GRACE FOLLOW-ON
The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched
in 2002 consisting of two identical satellites in a polar low-Earth orbit [1]. The distance variations between
these two satellites are measured with a Micro Wave Instrument (MWI) located in the central axis. In data postprocessing
the spatial and temporal variations of the Earth’s gravitational field are recovered, which are among
other things introduced by changing groundwater levels or ice-masses [2, 3, 4, 5]. The Laser Ranging
Interferometer (LRI) on-board the GRACE Follow-On (GFO) mission, which will be launched in 2017 by the
joint collaboration between USA (NASA) and Germany (GFZ), is a technology demonstrator to provide about
two orders of magnitude higher measurement accuracy than the initial GRACE MWI, about 80 nm/√Hz in the
measurement band between 2 mHz and 0.1 Hz. The integration of the LRI units on both GFO S/C has been
finished in summer 2016.
The design as well as the functional, performance, and thermal-vacuum tests results of the German LRI flight
units will be presented
Testing the GRACE follow-on triple mirror assembly
We report on the successful testing of the GRACE follow-on triple mirror assembly (TMA) prototype. This component serves to route the laser beam in a proposed follow-on mission to the Gravity Recovery and Climate Explorer (GRACE) mission, containing an optical instrument for space-based distance measurement between satellites. As part of this, the TMA has to meet a set of stringent requirements on both the optical and mechanical properties. The purpose of the TMA prototype testing is to establish the feasibility of the design, materials choice and fabrication techniques. Here we report on co-alignment testing of this device to the arc second (5 μrad) level and thermal alignment stability testing to 1 μrad K-1
European laser development for LISA
We present the European development of an engineering model Laser Head for LISA. This single box includes a seed
laser, an electro-optical phase modulator, a fiber amplifier and all PCBs to operate the Laser Head
The design and construction of a prototype lateral-transfer retro-reflector for inter-satellite laser ranging
The Gravity Recovery and Climate Experiment (GRACE) mission, launched in 2002, is nearing an end, and a continuation mission (GRACE Follow-on) is on a fast-tracked development. GRACE Follow-on will include a laser ranging interferometer technology demonstrator, which will perform the first laser interferometric ranging measurement between separate spacecraft. This necessitates the development of lightweight precision optics that can operate in this demanding environment. In particular, this beam routing system, called the triple mirror assembly, for the GRACE Follow-on mission presents a significant manufacturing challenge. Here we report on the design and construction of a prototype triple mirror assembly for the GRACE Follow-on mission. Our constructed prototype has a co-alignment error between the incoming and outgoing beams of 9 μrad, which meets the requirement that this error must be less than 10 μrad