A key technical challenge of the joint European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) LISA mission has been solved: how to maintain precise pointing of a laser beam across 5 million km of space (figure 1).

The next-decade Laser Interferometer Space Antenna (LISA) mission will look for ripples in space-time—their existence predicted by Albert Einstein—known as “gravitational waves.” To do this, a trio of identical spacecraft will fly 5 million km apart in an equilateral triangle formation, linked by laser beams (figure 2).

Figure 1: LISA satellite connected by laser

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