A variety of lunar programs are possible within an integrated space program. A reasonable initial program would be an umanned lunar geology laboratory. This might be comprised of satellites, ground stations, and ground rovers, possibly equipped with rockets which deliver collected samples to a station. Sample return to earth might be unnecessary. Since the moon has no atmosphere, freight delivery to t he lunar surface might use 3 phase ion (accelerate, coast, decelerate); and braking rockets for the final phase. Weak ballistic trrajectories might be of use for the ion flight. One advantage of such a program would be as a testbed for a Mars geology laboratory.
Initially at least, there is no need for permanent surface facilities such as telescopes; these are better placed in earth orbit, because they are closer to earth and weightless. Noise elimination for orbiting radio antennas can be achieved with wire screens.
A manned visitation capability can readily be included. Initially at least, a lunar base is not needed. In a basic system all equipment for a manned mission is sent from the earth station, used for the mission, and possibly returned to the earth station for refurbishment.
A basic system might provide the ability to visit the moon for a 10 days. The components for a mission are two crew ferries and a lander. The lander and the return ferry are sent to lunar orbit by ion propulsion, in some large fraction of a year. When they have arrived, the crew of 2 travels in the outbound ferry to the lander, in about 3 days.
The lander contains a crew compartment, storage bay for a surface rover, and storage area for remaining reusable and expendable mission equipment. It flies back to orbit in toto, except some equipment such as power modules and rovers may be left. The two way mass ratio for 30 Km orbit is around 2.5; the dry weight is a perhaps 3 to 4 tons.
The return ferry takes 3 days; it can use aerobraking to achieve Earth orbit. The outbound ferry and lander could be returned to the Earth station by the ion engine.
The SIP and the outbound crew ferry can go into an orbit of any inclination. This allows visits to any point on the lunar surface. The lander can have some of its surface to orbit fuel on top of the crew sphere, for radiation shielding. This probably allows 10 day stays. There should always be enough fuel around for shielding in orbit.
A surface base for longer stays could readily be added to the basic system. This could be a movable platform, which is moved to the landing site by remote control prior to a mission. The capability of "hopping'' could be added to the lander.