531 The FWG seemed better on every criterion except heritage. So a development testing program was  implemented to evaluate the FWG for PSP requirements . The FWG performed successfully  in these tests  and was chosen for the HGA assembly . The development test details are discussed later in this paper.  

Flexible Waveguide  

The flexible waveguide considered for this application is made by Custom Microwave. Inc. of   Longmont, C O. The flexible part of the waveguide is Ni-Co alloy  and is manufactured by electroforming.  This waveguide was built to length specified by JHUAPL. The interior of the waveguide is coated with silver  to improve RF performance. The development test article had copper flanges that  were attached to the  waveguide by soldering . Operational high temperature of the waveguide was limited to +180°C due to this   soldered joint . The exterior of the waveguide was nickel plated . 

During the development phase, the qualification temperature range was - 125°C to +100°C and t he  development article successfully survived these temperatures . However,  by the time the flight articles were  procured the qualification temperature limit had changed to - 105°C to +170°C. At this time the manufacturer  had improved processes available, but  the program decided to stay with the qualified  version of the  waveguide , since the revised temperature was still within specifications . The first batch of flight waveguides  were identical to the development article and was tested to the revised temperatur e limits. During thermal  cycling some discoloration was observed at the soldered joint, along with significant degradation in RF  performance.  Investigation by  the manufacturer determined that this was due to a processing defect that  resulted in incomplete removal of the flux from the solder , and this was also confirmed by radiography . This  problem  was further exacerbated by the higher revised qualification temperature. The manufacturer   proposed waveguides with electroformed flange joints, which were considered superior to the soldered  joint. After a thorough review of all options it was decided to change the waveguide configuration to the  electroformed flange joint  as proposed by the ma nufacturer . The program also decided to switch the exterior  finish to black paint inst ead of nickel plating to lower  the temperature of the middle section  during operation.  

Figure 2. WR -34 Flexible Waveguide  

The flight waveguide was made up of electroformed Ni-Co flexible section with the copper flanges  attached  by the electrofor ming process. T he interior surfaces were silver plated and the exterior surfaces  were  painted with BR -127 black paint . Following a successful  batch qualification and acc eptance program, these  waveguides were installed to flight HGA assembly.  The development and flight waveguides are shown in  Figure 2.  

Waveguide Analyses and Test s  

The FWG was subjected t o a comprehensive evaluation program that included testing in three phases,  development test, flight batch qualification test and acceptance tests. These test s consisted of  environmental tests and mechanical functional  tests. The condition of the FWG was monitored by  RF