Space Photonics: A Platform Technology for Satellite SystemsEfstratios Kehayas - 18 September 2017
Photonics has the potential to transform the space industry and introduce a paradigm shift in the way satellite payloads and communication terminals are designed and built to enhance or enable new navigation, remote sensing and telecom applications. G&H VP of Space Photonics Efstratios Kehayas’s feature – Space Photonics: A Platform Technology for Satellite Systems talks about how.
The use of photonics subsystems for functions such as navigation, remote sensing and telecoms is gathering pace as the advantages related to bandwidth, mass, power consumption, beam size and immunity to electromagnetic interference become apparent. The deployment of 1.55 μm fused couplers from G&H on-board the European Space Agency’s satellite Soil Moisture and Ocean Salinity (SMOS) satellite in 2009 was a watershed in the history of space photonics as one of the first satellites to use photonics for mission critical function. The planned lifetime of SMOS was three years and yet after seven years the satellite and its photonic components and sub-assemblies continues to exceed expectations.Satellite-to-satellite or satellite-to-ground laser communications can allow both high speed connectivity whilst using fewer resources compared to conventional systems. Tried and tested terrestrial photonics are exploited, when necessary using wavelength division multiplexing (WDM). The role of transponder in terrestrial networks is taken up in space by a laser communication terminal (LCT), I which is usually responsible for Layer-1 and Layer-2 functionalities. It is composed of a central processor, a transmitter, receiver and pointing and tracking acquisition assembly. Essential components include lasers, electro-optic modulators, amplifiers and photo-detectors. Photonic components used in space need to be ruggedized compared to their terrestrial counterparts in order to function after launch and in the presence of radiation present in low earth (LEO) and geostationary orbits.
Photonic components used in space need to be ruggedized compared to their terrestrial counterparts in order to function after launch and in the presence of radiation present in low earth (LEO) and geostationary orbits. Semiconductor lasers used for transmission, signal generation and amplification are at the heart of many space photonic assemblies. Not only does their manufacture need to be closely controlled but the compliance and traceability of their components needs to be assured.
The European FP7 project HIPPO (High-Power Photonics for Satellite Laser Communications and On-Board Optical Processing), led by G&H has focussed on developing DFB lasers, high-speed detectors and pump lasers and testing their performance against radiation. G&H also dedicated resources to the development of polarization-maintaining (PM) and non-PM fused couplers and pump combiners suitable for space applications.Integration of HI-REL components and sub-systems, such as amplifiers and transmitters, into an LCT, requires verification through testing according to ESA or NASA standards. Tests include electromagnetic compatibility, thermo-mechanical tests that include shock, vibration and thermal cycling in vacuum.
Integration of HI-REL components and sub-systems, such as amplifiers and transmitters, into an LCT, requires verification through testing according to ESA or NASA standards. Tests include electromagnetic compatibility, thermo-mechanical tests that include shock, vibration and thermal cycling in vacuum. These tests, and specifically in that sequence, mimic the process of launch and operation in-orbit. Within the frames of two European Space Agency (ESA) qualification programmes, G&H followed a test plan to space qualify mid-power booster amplifiers for direct downlinks following ECSS test plans. The unit-level test results were successful and proved that he G&H multi-channel amplifier was ready for an in-orbit demonstration and to move into flight hardware production.
Photonics is coming of age and has indicated proven efficiencies and advantages which can be used to enable the next generation of satellite communication systems. In order to prove commercially viable however cost-efficiencies will need to be found. On this basis the bandwidth hungry applications of satellites can made more viable on the back of the unique performance characteristics photonics offers.