International Space Station program with on-orbit refurbishment in mind. According to the Outer Space Treaty the United States is legally responsible for all modules it has launched. In ISS planning, NASA examined options including returning the station to Earth via shuttle missions (deemed too expensive, as the station(USOS) is not designed for disassembly and this would require at least 27 shuttle missions), natural orbital decay with random reentry similar to Skylab, boosting the station to a higher altitude (which would simply delay reentry) and a controlled targeted de-orbit to a remote ocean area. The technical feasibility of a controlled targeted deorbit into a remote
Halo orbit 1996. It used an orbit similar to ISEE-3. Although several other missions since then have traveled to Lagrange points, they typically have used the related non-periodic variations called Lissajous orbits than an actual halo orbit. For example, Genesis, launched in 2001, which also pioneered the use of dynamical systems theory to find low-energy transfers to and from its orbit. In May 2018, Farquhar's original idea was finally realized when China placed the first communications relay satellite into a halo orbit around the Earth-Moon point. In January 2019, the Chang'e 4 spacecraft is scheduled to land in the Von Kármán crater