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 Returning to the transposition and docking sequence, Figure 26 illustrates the separation of the CSM from the S-IVB-LM. The adapter panels are deployed as part of the separation sequence and are held at a 45° angle with respect to the longitudinal axis. This is sufficient to clear the LM and allow a clean ex­traction maneuver. If the petals are folded back completely, then they shroud the S-IVB antennas located around the periphery of the Instrument Unit.

The Service Module RCS is used to translate some 100 feet away from the S-IVB. At this point, the translation is stopped and the CSM is rolled to the proper indexing for docking and then pitched 180° so that it is pointing back at the LM ( Figure 27). The roll-pitch sequence rather than a pitch-roll sequence is used to avoid placing the spacecraft omni antenna null zone at the MSFN station during the 180° pitch maneuver. In the case of the spacecraft, yaw maneuvers must be restricted to less than ±70° to avoid gimbal lock. Unlike maneuvers during the rest of the mission, the turnaround is done at the rapid rate of 5 degrees per second in order to reduce the time required for transposition and docking; and, in particular, to minimize the time the crew is out of line of sight of the launch vehicle in the separated condition.

Having turned around, the crew will now deploy the spacecraft high gain steerable antenna and orient it to earth before closing on the LM for docking. This is required because the spacecraft omni antennas will be blanketed by the adapter petals once the CSM gets in close to the LM for docking; therefore, communications with the ground will have to be maintained using the high-gain antenna.

The docking operation continues under the manual control of the spacecraft crew as the final translation is made and the CSM slowly closes on the LM/S-IVB. Initial contact is made when the docking proble on the CM engages the drogue mounted on the LM; the docking mechanism pulls the two vehicles firmly together the final few inches, four latches automatically engage, and the initial soft docking is completed (Figure 28). The next step will be to manually hook up the CM-LM umbilicals, and complete the latching operation by manually engaging 8 more latches. The functions of the umbilicals are twofold: first to supply the hardline connec­tion between the CM controls and the explosive ties which attach the LM to the adapter. These ties will be severed by crew command when they get ready to withdraw the LM. The other function of the umbilicals is to supply a small electrical power level to certain LM equipnent from the CSM power source during the translunar coast phase of the mission. The chief user of this power are small heaters in the LM IMU which needs to be maintained within narrow temperature limits at all times. This permits use of smaller