Doesn LISA require formation flying with nanometer precision, which has never been demonstrated?
• No. LISA is not formation flying. Each spacecraft freely follows its own Keplerian path, and the arm lengths vary by ~ 1% or about 50,000km. (See for example: http://arxiv.org/abs/gr-qc/0410093.) • Since the LISA spacecraft are in independent orbits, no station keeping is required. The only propellant required is for the micronewton thrusters that are keeping the GRS drag free.
