for the Lockheed U-2 and SR-71 reconnaissance aircraft. The camera photographed the Moon; had the S-IVB failed to fire causing the CSM to not leave earth orbit, astronauts would have used it to photograph the Earth. SIM also had other sensors and a subsatellite. Sector 2 (70°) contained the service propulsion system (SPS) oxidizer sump tank, so called because it directly fed the engine and was kept continuously filled by a separate storage tank, until the latter was empty. The sump tank was a cylinder with hemispherical ends, high, in diameter, and contained of oxidizer. Its total volume was Sector 3 (60°) contained the SPS oxidizer storage tank, which was the same shape as the sump tank but slightly smaller at high and in diameter, and held of oxidizer. Its total volume was Sector 4 (50°) contained the electrical power system (EPS) fuel cells with their hydrogen and oxygen reactants. Sector 5 (70°) contained the SPS fuel sump tank. This was the same size as the oxidizer sump tank and held of fuel. Sector 6 (60°) contained the SPS fuel storage tank, also the same size as the oxidizer storage tank. It held of fuel. The forward fairing measured long and housed the reaction control system (RCS) computer, power distribution block, ECS controller, separation controller, and components for the high-gain antenna, and included eight EPS radiators and the umbilical connection arm containing the main electrical and plumbing connections to the CM. The fairing externally contained a retractable forward-facing spotlight; an EVA floodlight to aid the command module pilot in SIM film retrieval; and a flashing rendezvous beacon visible from away as a navigation aid for rendezvous with the LM. The SM was connected to the CM using three tension ties and six compression pads. The tension ties were stainless steel straps bolted to the CM's aft heat shield. It remained attached to the command module throughout most of the mission, until being jettisoned just prior to re-entry into the Earth's atmosphere. At jettison, the CM umbilical connections were cut using a pyrotechnic-activated guillotine assembly. Following jettison, the SM aft translation thrusters automatically fired continuously to distance it from the CM, until either the RCS fuel or the fuel cell power was depleted. The roll thrusters were also fired for five seconds to make sure it followed a different trajectory from the CM and faster break-up on re-entry. Service propulsion system