Three Telescopes, a 1.6-Million-Mile Triangle, and the Hunt for Gravitational Waves

NASA has taken the next step in developing a new all-glass telescope for the LISA mission — the Laser Interferometer Space Antenna, a space observatory designed to detect gravitational waves, the ripples in space-time. The instrument is strange by the standards of astronomy. LISA will deploy a trio of satellites into an Earth-following orbit, forming a vast triangular array with sides stretching 1.6 million miles, or 2.5 million kilometers. Each spacecraft carries a telescope, and those telescopes do not collect starlight: they simultaneously transmit and receive infrared laser beams, measuring the mutual distances between spacecraft to extremely high precision across that enormous gap. The measurement itself is the instrument — the array is less a camera pointed at the sky than a ruler laid across the solar system.