a preselected region of the Fra Mauro Formation. Deploy and activate an Apollo Lunar Surface Experiments Package. Develop man's capability to work in the lunar environment. Obtain photographs of candidate exploration sites." The astronauts were also to accomplish other photographic objectives, including of the Gegenschein from lunar orbit, and of the Moon itself on the journey back to Earth. Some of this photography was to be performed by Swigert as Lovell and Haise walked on the Moon. Swigert was also to take photographs of the Lagrangian points of the Earth-Moon system. Apollo 13 had twelve cameras on board, including those for television and moving pictures. The crew was also to downlink bistatic radar observations of the Moon. None of these was attempted because of the accident. Flight of Apollo 13 Launch and translunar injection The mission was launched at the planned time, 2:13:00 pm EST (19:13:00 UTC) on April 11. An anomaly occurred when the second-stage, center (inboard) engine shut down about two minutes early. This was caused by severe pogo oscillations. Starting with Apollo 10, the vehicle's guidance system was designed to shut the engine down in response to chamber pressure excursions. Pogo oscillations had occurred on Titan rockets (used during the Gemini program) and on previous Apollo missions, but on Apollo 13 they were amplified by an interaction with turbopump cavitation. A fix to prevent pogo was ready for the mission, but schedule pressure did not permit the hardware's integration into the Apollo 13 vehicle. A post-flight investigation revealed the engine was one cycle away from catastrophic failure. The four outboard engines and the S-IVB third stage burned longer to compensate, and the vehicle achieved very close to the planned circular parking orbit, followed by a translunar injection (TLI) about two hours later, setting the mission on course for the Moon. After TLI, Swigert performed the separation and transposition maneuvers before docking the CSM Odyssey to the LM Aquarius, and the spacecraft pulled away from the third stage. Ground controllers then sent the third stage on a course to impact the Moon in range of the Apollo 12 seismometer, which it did just over three days into the mission. The crew settled in for the three-day trip to Fra Mauro. At 30:40:50 into the mission, with the TV camera running, the crew performed a burn to place Apollo 13 on a hybrid trajectory. The departure from a free-return