honeycomb design and reducing the torque output and energy absorption. The overall design would have  been much simpler, reducing drawing, fabrication, and installation costs and schedule with the removal of  the Energy Absorber structure and simplification of the Hinge mechanism. Additionally, the crushable  honeycomb would have been replaceable without disassembly of the Energy Absorber mechanism.  GALEX placed the Latch mechanism on top of the cover due to mounting surface constraints and  contamination control. However, the proposed configuration could have allowed the Latch mechanism to  be mounted to the Cover Ring instead of on the cover. This would have removed the necessity of routing  Latch cabling over the Hinge, eliminating cable parasitic torque drag. Additionally, the simplified cabling  could have received cable stiffening micrometeorite shielding. With the Latch mechanism mass removed  from the cover, the crushable honeycomb could have been placed close to the hinge axis instead of along  the canister.  Cover deployment depended on Latch Arm rotation. The GALEX latch arm was positioned close to the  instrument aperture opening and was rotated away from the aperture to reduce stray light issues. The  rotation of the latch arm rotate introduced some potential single point failures. After the GALEX latch arm  was adopted, it was discovered than an earlier mission that originally designed the Latch mechanism  instead utilized a fixed latch arm with a slot in the path of cover deployment. Because the proposed  design did not face the same stray light issues as GALEX, a potential failure mode was unnecessarily  adopted and additional work was necessary to reduce risk.  The Latch mechanism is zero-fault tolerant in some cases as it depends on a single actuator (with  redundant heaters) and a single set of pistons to translate prior to cover deployment. An alternate latch  mechanism design using two Starsys pin pullers in a toggle type configuration could have been more  desirable and would have been fully single fault tolerant. Additionally, the mechanism would have been  less complex and would possibly have fewer parts and less expensive to fabricate.  Both the Latch and Hinge mechanisms were complex, with many tightly toleranced parts. These  mechanisms were expensive and schedule intensive to fabricate. Simpler alternate designs described  above would have potentially saved more schedule than building the heritage designs.  The Hinge mechanism is only capable of cover deployment with the Hinge axis aligned with gravity  (vertically). It would have been preferable to incorporate a hinge mechanism that was capable of  deploying the cover in any orientation as the instrument will not be positioned vertically during I&T and  ATLO, making an end-to-end test impossible. Instead, cover deployment tests will be conducted before  CDLM delivery to I&T. Once in I&T and ATLO, first motion tests will verify Latch mechanism functionality  and the cover will be sweep to ensure there are no obstructions.  The Energy Absorber honeycomb was finalized before flight-like cable was installed over the Hinge axis  during prototype cover deployment tests. It was expected that the cable could be wrapped in a way to  provide a positive torque to aid the cover rotation, but was initially found not to be possible. Further  prototype deployment tests with the cable showed that the honeycomb needed to be changed.  The crushable honeycomb Energy Absorber prototype effort cost significant schedule. In keeping the  Energy Absorber housing similar to GALEX (and thus limiting the redesign of the support structure), the  Energy Absorber still must be disassembled to be reset after a cover deployment test. This disassembly  is only moderately less time consuming than a GALEX Energy Absorber reset.  While the residual end-of-travel Hinge torque output and magnetic latch provide enough force to keep the  cover captured during spacecraft maneuvers, a positive latch mechanism would have been more  preferable.  73