Aborting after LOI
Retro’s second offering eoncerned the abort situation when the spacecraft had already entered lunar orbit. For the entire period that an Apollo spacecraft flew in orbit around the Moon, mission control ensured that the command module pilot always had the data he needed to return to Earth, even if an extreme situation meant that he had to come home on his own following the loss of the LM. These were trans-Earth injection (TEI) burns, one of which would eventually be used in the normal course of events to bring the entire crew home. Before they attempted LOI. Retro prepared details of these get-you-home burns suitable for use after one and two lunar orbits. Then, as their time around the Moon progressed, he continued to supply regular updates to ensure that they were never without a return ticket’.
Meanwhile, if all was going well, the fruits of FIDO’s efforts could be brought to play; first to refine the spacecraft’s approach to the Moon, and then to execute the LOI burn and place the spacecraft in lunar orbit.