78 "Mass Production" 

Gearing towards Mass Production   The ADTM Mk2 has been developed to better answer dual deployment requirements, which is now  becoming the standard. This means that instead of one  large antenna per East/West spacecraft wall, two  large antennas are to be deployed on each wall. A few spacecraft were equipped with ADTM mk1 for dual deployments but as it is a single deployment axis mechanism, heavy and voluminous support structures  were needed to have the right orientation of the mounting plane of the mechanisms.  Once qualified, the ADTM mk2 is intended to be come the baseline deployment mechanism for E3000  spacecraft. It has to cope with any mission, meaning it  has to have a fine angular resolution of 0.0025° on  the whole angular range, be compatible with the to p floor antenna environment (earth-facing wall), and  fulfil the most severe missions like RF-sensing missi ons requiring in-orbit daily trimming operations over  the whole lifetime of 15 years.  Therefore, the number of ADTMs r equired per spacecraft has at least doubled compared to Mk1, and  production of this equipment needed to be scaled up to cope with the demand. The design and development phase of the ADTM mk2 was done taking  into account the expectations of the first  customers. Today (18 months later), we have successf ully passed all major reviews and are close to the  end of qualification. The first batch of 20 units is in manufacturing and delivery and another half from the next batch2 production has been sold. This has been a fast-paced development, only possible thanks to  the dedication of the team and the close co-engineer ing we developed with our internal and external  customers.  Electrical Ground Support Equipment (EGSE)

The ADTM mk1 is a “passive” mechanism for deploym ent which is driven by springs; only the trimming  function is done using electrical actuations. The ADTM  mk2 requires electrical actuations whatever the  operation: deployment or trimming, and this on a wide r angular range. Although the number of ADTM per  spacecraft has increased, the specification requires a lot more data about performance of the units and  family data comparison than in the past with the Mk1. It has been very challenging to conceive, manufacture and validate a new EGSE within the short time between kick-off and the first tests.  To cope with the increased amount of tests, data and analyses now required, three identical EGSE have been developed in parallel to the ADTM Mk2, each c apable of testing up to four ADTMs in parallel  (consistent with most dual deployments spacecraft where four antennas are to be deployed), enabling the  automation of most of the functio nal tests performed on the ADTM Mk2, recording all data and pass / fail  status in a spreadsheet.  The EGSE units programmed under Labview environment produce extremely useful data. The amount of  data collected today is large (~0.5 GB per functional test per unit) but is currently necessary to clearly understand and characterize the behavior of the ADTM. It is planned to make a data reduction exercise in the future once we have a clear understanding of  what parameters are important to monitor. 

Design Lessons Learned   Load through the output shaft

A duplex pair bearing supports the RA output shaft. It is  designed to survive the specification worst case  design loads. These have continuously increased th roughout the project, exceeding the initial allowable  design loads. This led to modifications of the prelimi nary design of some of the screwed joints within the  RA.  These screws are used to preload the RA output sha ft duplex pair bearing and retain a gear onto this  shaft. Due to increased to rsional loads requirements,  these were not strong enough to eliminate sliding  between the gear and the output shaft during spacecraft launch; up to 2.5 degrees shift can occur. The  NASA/CP-2010-216272