FIGURE 30 ROLL AXIS The baseline rigid body mass properties of the SSPS about the X axis are listed in Table 9. TABLE 9 ROLL AXIS MASS PROPERTIES The structural dynamic analysis about the spacecraft's X axis identified two roll-axis bending modes that would fit the requirements of the math model discussed in Reference 35. The mode shapes of both of these modes are given in Figures 31 and 32. As indicated, the mode shape in Figure 31 is symmetrical, while Figure 32 represents an anti-symmetrical mode. Table 10 gives modal characteristics for these modes at the actuator and sensor locations located at the axial extremities. A detailed discussion of the roll-axis bending modes is given in Reference 36. With the SSPS in the nominal orientation with the spacecraft X axis perpendicular to the plane of the synqhronous orbit [Reference 35], the SSPS experiences a constant gravity gradient disturbance torque, Tdx as well as a solar pressure torque Kdx0x which is proportional to the offset rotational angle 0x about the X axis. These torques were evaluated in Reference 31 and are repeated in Table 11.
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