T2L2 Flight Model Metrological Performances

Abstract

The T2L2 (time transfer by laser link) space instrument developed by CNES and OCA will permit the synchronization of remote ultra stable clocks and the determination of their performances over intercontinental distances. The principle is derived from laser telemetry technology with dedicated space equipment T2L2 embarked on the satellite Jason 2. The T2L2 instrument has just been integrated on the satellite that should be launch in mid-2008. The T2L2 scheme will allow an improvement of one to two orders of magnitude as compared to the performances of existing time transfer systems. This paper focuses on a detailed description of the T2L2 flight model, its electronic and optical sub-systems and its functionality. The T2L2 space instrument is based on photo-detection of laser pulses by avalanche photo diodes and therefore equipped with two optical subsystems located on the outside of the satellite, in the vicinity of the LRA retro reflector of the Jason 2 satellite. The electronic subsystem is housed inside the satellite and principally consists of an event timer, a signal conditioning and delay adjustment system, a controller and respective power supplies. We report on the global performances of the whole instrumentation that were measured during an exhaustive test campaign with a dedicated test bed.