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Objectives & applications

OBJECTIVES

To deliver High speed broadband via satellite is key to complete the coverage of European citizens unserved or underserved by high speed terrestrial network. Indeed, Vice‐President of the European Commission Neelie Kroes recognised on October 17th 2013 at the Broadband‐for‐All event that: “Thanks to the extra coverage provided by satellite broadband, we have achieved our 2013 target of broadband for all”.

This has been made possible by the drastic enhancement of satellite broadband services which took place in the last few years with the arrival on the market of High Throughput Satellites.
The first generation of broadband satellites was providing a total capacity up to 20 Gbps in a first attempt to make satellite communications suitable for broadband market.
Since 2011, the 2nd generation of Ka‐band satellites is achieving an economy of scale, reaching total capacities from 90 Gbps to 140 Gbps.
However, while this generation of Ka band HTS satellites can cover consumer demand up to 30 Mbps, it will not be provide a viable economic model to fulfil DAE 2020 objectives stating that all Europeans get access to internet speeds of 30Mbps and 50% of European households subscribe to internet connections above 100 Mbps by 2020.
This generates the need to start now designing broadband satellite systems reaching the Terabit/s capacity or beyond while drastically reducing the cost of the Mbps in orbit. ”quote BATS or TERABIT programs”

 

In addition, since most operators have now experienced the fact that the broadband market is very difficult to predict, it is important that this large increase in capacity is accompanied by the possibility to reallocate capacity after launch or even dynamically to follow the daily evolution of internet connection demands through various time zones of the covered areas. Such flexibility has become a must for operators to adapt to the market evolution throughout the satellite life‐time and secure their business plan.
With Telecoms payloads based on traditional RF equipment, increase in capacity and flexibility has always translated into a more or less linear increase in equipment count, mass, consumption and heat dissipation.
The main challenge of this next Terabit/s generation of HTS is therefore to provide a ten‐fold‐increased capacity with enhanced flexibility while maintaining the overall satellite within a “launchable” volume and mass envelope. And this envelope is only expected to grow by a fraction of this 10x factor in the meantime.
For example, by 2020, the next Airbus DS GEO platform Eurostar Neo will be able to carry payloads of up to 22kW of DC power for a total satellite launch mass of up to 7.7tons, while Eutelsat Ka‐Sat, which entered commercial service in May 2011 and provides about 80Gbps of broadband services over Europe and North Africa already had a launch mass of 6.15 tons for a DC power of 11kW.
A very promising way to tackle these issues is the introduction of photonics payload.
Photonics technology refers to techniques and equipment that convert RF signals at the input of the payload into optical signals.

 

These optical signals can then:

  • Be transported on lightweight, ultra‐broadband, EMC‐robust optical fibre,
  • Undergo multiple transformations (multiplexing, frequency translation, filtering…) in ways that cannot be achieved by conventional RF equipment (WDM multiple frequency translations)
  • Be routed through compact optical switch matrices offering full interconnectivity between very large number of ports (>100s) with minimal losses
  • Be converted back to RF before amplification to be retransmitted to users.


  • These techniques are often referred to as “RF‐over‐ fibre” or “microwave optics” and have been widely used for terrestrial applications such as CATV distribution or more importantly Fibre‐To‐The‐Home applications, where the end‐user modem connects to the optical fibre network via a coaxial cable.
    More generally Fibre Optics has largely contributed to the booming development of the internet over the 2 last decades.

    However, while the corresponding components, devices and equipment are nowadays mass‐produced for terrestrial applications, they remain mostly inaccessible to the space industry.

     

    This is mainly due to the contrast between the high level of effort required to produce equipment qualified for the harsh and peculiar space‐environment and the relatively low volume of units required for space applications compared to space applications.
    Nevertheless, in the recent past, several joint initiatives between European companies from the both terrestrial optical communications and space industries have emerged, with a view to bridge that gap and adapt some of the terrestrial products to space environment.

     

    However, so far, these initiatives have remained mostly isolated and cannot on their own fulfil the midterm goals of:

  • Creating a European industrial network able to provide the space industry with mature, affordable space‐qualified photonics products
  • Offering a new path for growth to terrestrial optical communications actors with a new line of high added value products targeting space market, with potential extension towards other markets such as defence

  •  

    The OPTIMA project aims at giving a strong initial impulse to the photonics payloads for telecommunication satellites by focusing the efforts of various industrial and academic actors from the photonics and space European landscape towards the concrete goal of demonstrating the validity of the photonic payload concept and associated benefits in a real‐world working organization.

     
    Objective 1:

    Demonstrate and validate the photonics payload concept and its benefits in a relevant industrial environment

  • To define a photonics payload demonstrator aligned to the requirements of the Terabit/s satellite based on equipment currently developed by members of the consortium
  • To develop and build TRL6 version of each of the building blocks of the demonstrator
  • To assemble the building blocks into a demonstrator
  • To test this demonstrator in the premises of a prime satellite manufacturer member of the consortium, Airbus Defence and Space
  •  
    Objective 2:

    Establish specifications of each building block of future photonics payload

  • Those specifications should make sure the building blocks are fit for a 15‐year lifetime on board a geo‐stationary satellite
  • Those specifications should ensure the building blocks are consistent with the objective of a Terabit/s satellite in terms of mass, footprint, power consumption, dissipation, performance and cost.
  •  
    Objective 3:

    Establish a roadmap towards in‐orbit demonstration of photonics payload by 2020

  • To identify potential showstoppers blocking further development of each of the building blocks and ways to tackle these issues
  • To propose further development plan of each of the building blocks up to TRL8
  • To leverage on the experience acquired through the OPTIMA project to pave the way for a future in orbit demonstration program within the EC context

  •  
    Objective 4:

    Increase general knowledge and raise the interest for photonics payload among the space industry

  • To communicate on the project, its goals, its implications and its contributors in publications conferences, workshops and through a dedicated website
  • To reach towards potential new industrial or academic partners for future development
  • To reach towards satellite operators for future commercial deployment of this technology
  • To propose ways to extend the use of this technology further than Terabit/s satellite, such as other space or even military applications that could largely benefit from using similar building blocks
  •  

    APPLICATIONS

    Currently there is no photonic payload being used in communication satellites. The hardening and integration of the photonic payload elements, the reduction in power dissipation and the reduction in size will enable this technology to be applied on a next generation of high capacity communication satellites which have very demanding requirements with respect to size, mass, power and bandwidth.

    OPTIMA aims at making innovative photonic key technologies for broadband satellite communication more mature and less costly. The photonic broadband payload demonstrator can be applied in satellites and terminals on the ground. The application in ground terminals makes broadband satcom available to a larger population due to the lower cost. Optical technology can be applied in the payload elements of communication satellites due to the broadband performance and the increased efficiency.

    Over the last decades, microwave photonics has been investigated as an alternative to RF systems for a number of applications. MWP now aims at exploiting the specific features of photonics in microwave systems, such as wide bandwidth, immunity to electromagnetic interferences, low propagation loss and distortion, low phase noise, and extremely high frequency flexibility. These features make them attractive for next generation flexible satellite payloads which require high flexibility and high capacity, for instance aiming to use beamforming of wideband signals in phased‐array antennas.

    Application of multibeam satellite concept with narrower beams and exploitation of the frequency reuse schemes have enabled a significant increase in the overall system capacity and instantaneous user data rates “as high as 100 Gbps” total capacity in the second generation of High Throughput Satellites in Ka band, for example used on Ka‐Sat or Viasat‐1 missions.
    Demand rate for higher and higher peak data continues to maintain pressure on communication infrastructures since Fibre to the Home has replaced Asymmetric Digital Subscriber Line as the new reference in terms of performances, especially in areas where the connectivity was critical or non-existent.

    The high throughput ‘Terabit/s’ Satellites will incorporate payloads with very large quantity of payload equipment, co‐axial cables, waveguides, harnesses and ancillary equipment, making the payload mass and power consumption very high and the Assembly, Integration and Test very complex. Use of ‘RF over Fibre’ and associated photonics payload equipment can make the process of AIT much simpler with the added benefit of significant reduction in number of payload equipment with inherent reduction in payload mass and power consumption.
    Disruptive techniques and technologies have been applied in order to define such satellite, including very large platforms, highly efficient RF power amplification, large reflectors, and usage of new frequency bands including Q/V band and optical links as well as advanced air interface techniques.

    The system scenario that has been investigated assumes a user beam layout of 260 beams of 0.21° over EU27 coverage area. This number of beams has been selected through a top‐down approach so as to approach the Terabit/s capacity based on the selected frequency plan and assuming realistic spectral efficiencies.


     

    According to the frequency plan selected, this leads to 33 active gateways.
    To mitigate the propagation attenuation for the Q/V band feeder links, a diversity solution called N+P has been selected. In this scheme, in a given feeder beam, only one gateway is deployed. However, the system implements more feeder beams and deploys more gateways than the required active gateways. It is assumed that for N active gateways, P additional gateways are deployed as back‐up, leading to a total of N+P gateways. The additional gateways are deployed sufficiently far apart from other gateways in order to ensure full decorrelation of rain events.

    After assuming full‐decorrelation of rain events between sites, the problem has been modelled by a random variable following a binomial law. In order to ensure a single feeder link availability of 99.99%, a total of 4 back‐up gateways have been identified.