active craft usually decreases the scatter of initial deviations and velocities. Deviations from the coaxial position are conveniently given (see Figure 1.3) by two linear coordinates and along axes y and z associated with the passive docking assembly (the plane is located along the section of the receiving cone or a section of the control projections) and two solid angles and between the longitudinal axis of the spacecraft, and lying in planes and and the angle of the intersection of planes and into plane The relative velocities of the centers of mass are given in projections on axes x, y, z, and angular velocities and arc given in projections on their associated axes. The total deviations of the docking assemblies from the coaxial postion are added from the errors: 1) errors in the adjustment of the measurement equipment (targets, visors, antennas); 2) errors in the adjustment of the docking assembly; 3) measurement errors; 4) dynamic errors arising in the control process. To decrease the adjustment errors and to avoid significant systematic errors, for example, rotation by 180 verification and tuning are provided for. Thus, when the APDA is used aids are used to sequentially verify the correctness of the two joints (the command module of the Apollo with the docking module during redocking and the docking module of the Soyuz with the APDA); simultaneously, the targets are adjusted (Figure 1.5). As has already been said, control during the approach is structured so that individual channels of the system rotate the spacecraft relative to the , and axes and shift the center of mass of the active spacecraft along axes At the same time the regulating effects in the control system are deviations from the coaxial position, measured, in the general case, in another coordinate system. For example, the observed deviations of the center of the target from the cross hairs of the visor may be due to linear or angular shifts in the line of sight relative to the longitudinal axis of the docking device; angular banking errors cause additional lateral deviations. As a result, the angular and linear deviations are usually interconnected along different coordinates. Nonetheless, due to the random character of the errors, for small values of deviations along different coordinates, in the first approximation, they may be considered independent random values with normal distribution laws.
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