41 testing, quasi static and random vibr ation testing, TVAC (thermal cyclin g, deployment testing, cold spike)  testing, final surface mapping, and post environment al RF performance testing. The antenna passed all  tests and was delivered for system integration and testing. All of the design changes made from the EDU  antenna did improve the performance of the antenna. The FM antenna has a measured surface accuracy  of 8.1 mm (0.32 in) RMS and has seen a total of ~3 0 open/close cycles, including 3 TVAC deployments  and 6 in air deployments.    There were additional lessons learned throu gh the build and testing of the FM antenna: 

Gore Cracking

In total the gores on the FM antenna behaved much be tter than the EDU gores. The additional material  added solved the CTE issue that was found on the E DU antenna. Secondly removing the through holes  substantially improved the cracking issue that was seen on the EDU ant enna. However, as expected, the  FM gores were stiffer and proved to be slightly more  difficult to stow. After ~20 open/close cycles some  minor gore cracks have developed. These cracks were very small (pin holes to 1.6-mm (1/16-in) long),  and developed in areas where the reflective material was forced to bend in multiple planes creating “kinks” through the stowing action. This phenomenon can be observed by bending a piece of paper in a similar  fashion. The effect is that a stress point develops and this point has a very tight bend radius. These stress points are worked over time from opening and st owing the antenna and eventually a small pin hole  develops in the material. When left unchecked the pin hole developed into a small crack/tear in order to relieve the stress in the material. To combat this  issue, a patching procedure was developed and tested.  Small (25 mm x 25 mm) germanium sputtered black Kapton tape was placed over the problem areas on both sides of the reflector. This method proved to stop the propagation of t he crack without adversely  affecting the RF performance or the material behavior during the stowing process. In some cases preventative patches were placed in areas sh owing beginning signs of crack development.     Several design changes were considered to solve the cracking problem. These potential changes included changing the gore geometry to give the localized stress areas additional material, using thinner Kapton in the flex circuit to lower the gore bending st iffness, using a different type of Kapton that could  have better resistance to this type of stress, and in creasing the f/D of the reflector. In the end these  changes were not necessary because the patches proved adequate to meet t he mission requirements.   Overall the flex circuit gore material proved to be fairly robust to work with. The material did work very well  in order to meet the low PIM requirements and was easy to handle and manipulate in order to stow the antenna while meeting the surface accuracy requirement of the reflector.     Conclusions   The Naval Research Laboratory has developed a nov el design approach for a low-cost, low-PIM,  deployable UHF antenna. The design has been fully qua lified and will launch as part of the Tacsat-4  satellite in 2010. This new technology is directly applicable to other sub four-meter deployable antennas at UHF and may have application for other missions at higher frequencies.        NASA/CP-2010-216272