The LISA spacecraft must thus be designed and built with the gravitational requirements of the free-falling test masses in mind.
The usual structural and thermal analysis of the spacecraft has therefore been extended to include gravitational effects as well to ensure that the requirements on gravity gradient at the position of the test masses is fully met. In addition, the payload controls the position of the spacecraft during science operations, rendering the spacecraft effectively a part of the instrument.
The importance of the co-design and the co-operation of spacecraft and payload is captured in the term “sciencecraft”.
The core features of the payload have been stable for more than a decade: the interferometric measurement system, the telescope, the gravitational reference sensor. Their design has evolved and reached maturity. Many of the design features of, e.g., the optical bench have been shown in laboratory prototypes, during testing of the LISA Pathfinder (LPF), and will finally be demonstrated on orbit.