Once removed from HGAS, the  tower assembly was delivered to metrology for coordinate measuring machine documentation of tower assembly height and critical feature positions. In doing so, proper fitment of the modified and reassembled tower assembly could be verified. The tower assembly was then  disassembled and the individual  components were modified via CNC  machining. Piece part metrology verification was performed prior and after component modification. Tower reassembly then occurred. The now modified spherical tower assembly itself received metrology  verification. With spherical tower assembly modification complete, it was installed to its previously pinned  HGAS location and its interface to the stowed HGAS constraints was verified by measurement. The element of the gimbal assembly that could interfere with the constraint tower during deployment was  the outboard gimbal cable wrap (see Figure 8). The cable wrap hardware was enveloped in a multi-layer thermal blanket. To maximize clearance at the potential location of contact, a section of blanket was removed from the gimbal harness wrap and replaced with a single layer of vapor deposited aluminum Kapton™ tape. Modification of the blanket was performed in situ. With the trimmed hardware, the baseline simulations now indicated a 19-mm (0.76-in) clearance. Since  the approval metric was based on using the worst case model, another simulation was run, whichpredicted a clearance of 12 mm (0.48 inch). This exceeds the minimum clearance of 6.35 mm (0.25 inch)by almost a factor of two. The design was acceptable. The hand manipulation motion studies were repeated and clearance verified. Spacecraft level  deployments and environmental testing followed. With respect to the component modifications performed, spacecraft environment testing was complete with the successful post-environmental test deployment.  Functional and workmanship verification was achieved. Lessons Learned The late discovery and resolution of a potentially mission degrading interference issue has yielded  several pertinent lessons. The compliance in cable synchronization systems in articulating multi-boom systems may allow significant  non-kinematic behavior. A particular deployment travel path cannot be assumed. Designing to this assumption led to the development of a g-negation system that biases the deployment to the intended path. This can mask interference or other issues that ground testing is intended to uncover. In the present case, this was discovered during the integration and test phase of the spacecraft development, long after the design phase was complete. Assuming the deployment path also led to giving up some clearance during the design phase in order to  accommodate other packaging needs. If the kinematic indeterminate nature of this deployable was understood and appreciated at the time, clearance would not have been sacrificed. For such a system, more clearance should be kept in reserve. Although not always possible due to space constraints, a good “rule of thumb” is to avoid having deploying hardware below the break plane between the LRMs and the deploying hardware so that clearance increases monotonically during deployment.     /g51/g85/g72/g16/g80/g82/g71/g76/g73/g76/g72/g71  /g48/g82/g71/g76/g73/g76/g72/g71   /g3 Figure 11. LRM-C Spherical Tower Assembly

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