On-board processing (OBP) is a key differentiating technology for telecommunication satellites, enabling fine granularity channelisation, and routing, as well as more advanced functions such as on-board spectral analysis and regenerative communication links. At the time this project was initiated the OBP market primarily consists of mobile communications at L-band or UHF, where the ability to use congested spectral resources efficiently is worth the cost premium of including a digital processor within the payload. This activity moved this trend forward by developing and then demonstrating in-orbit on the SES-12 Commercial Telecommunications satellite a Transparent Digital Processor (DTP). The activity included development of all the technology and control system required to support utilising the flexibility of such a payload in an operational system.
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The key challenge for this project was completing the development and manufacture of a flight hardware within the timeframe of a commercial telecommunications satellite.
Another challenge was to develop the ground software to support the operations of an extremely flexible but complex processor such that the operations team could make the most of the flexibility without being an expert in the details of how a DTP works.
On-Board Processors that provide the ability to selectively route different amounts of spectrum from uplink beams to downlink beams, such that the limited spacecraft and spectrum resources can be used efficiently.
The processor for the SES12 program is based on the Alphasat heritage ( NGP 3rd Gen ) and is equipped with 12 Input/output ports each with a useful bandwidth of 250MHz and subchannel resolution of 330KHz.
The DTP Ground Control Unit is a ground based system that contains the hardware and PCS software required for Command Generation. This unit has full knowledge of the DTP functions and how to route channels and maintains a copy of the in-orbit DTP state.
The System architecture builds on Airbus’ long history of providing flight processors for mobile and UHF commercial payloads. Thus it follows the traditional architecture of an ADC followed by a channelising filter based on an FFT algorithm to provide the ability to selectively route different frequencies. A 3 rank non-blocking switch matrix is then used to route the different frequency elements to different outputs, where an FFT based channeliser is used to form the spectrum to be transmitted. This is then converted back to the analogue domain via a baseband centered DAC.
The project is now complete.
The processor was integrated into the SES-12 spacecraft which was launched on 28th May 2018. Following orbit raising and commissioning of the payload including the processor, the spacecraft entered commercial service. Data on the Processors performance over the following 12 months was then collected and confirmed the Processor operated as expected in its operational environment and with real traffic.