Study of high power L-band space transmitters for 2nd generation INMARSAT

The developmental status and historical record of high power L-band traveling wave tube amplifiers (TWTAs) in applications relevant to the requirements of the INMARSAT second generation space segment were studied. Visits to ESTEC, Hughes Space and Communications Division (HSC), Hughes Electron Dynamics Division (HEDD), ANT-Nachrichtentechnik (ANT), AEGTelefunken Professional Tubes Division (TFK) were included for up to date briefings on their current work. The technical and schedule risks are reviewed, and reliability estimates given for the two major competing concepts, namely six for four linearized TWTAs (four 70 W saturated output power 291HA TWTs) and two for one linearized 300 W saturated output power TWTA (TL 2400 or, possibly, 8281H). Each approach, with its set of differing risks, can basically meet the requirements of INMARSAT's (International Maritime Satellite Organization) draft RFP. A few critical areas are proposed where it is thought that further study would be useful.