First Mover

Does Aireon’s pioneering space-based ADS-B technology create a problem for UN aviation agency ICAO?

The green light signalled by the World Radiocommunication Conference to protect the 1090 MHz spectrum up to satellite altitude could well pose a headache for ICAO in its mission to develop rules for global flight tracking solutions that are both performance based and technology agnostic, writes Aimée Turner.

The protection means that Aireon, developer of the world’s first space based ADS-B tracking solution, could arguably claim a de facto monopoly in this technology area when it enters into service in 2018.

Space-based ADS-B promotes itself as a new capability that will augment or provide a more cost effective solution for air navigation service providers (ANSP) and airlines in remote and oceanic airspace.

“Given the required low earth orbit (LEO) satellite platform and investment in 1090 MHz receivers brought together by Iridium and Aireon, if they make it to operation their satellite constellation will probably be – for at least a while – the only one capable of receiving 1090 MHz ADS-B signals from existing avionics,” SITA corporate strategist Philip Clinch tells Air Traffic Management.

While Europe’s SES Techcom is understood to be designing a multi-constellation system which it too claims will offer ‘unprecedented’ global ADS-B coverage, for now, Aireon’s only real rival – Globalstar – admits that its LEO satellites cannot pick up 1090 MHz signals without a fair deal of tweaking.

That could be a deal breaker for Globalstar and ADS-B Technologies who have teamed on a space-based ADS-B Link Augmentation System (ALAS), trialling a 7,000 nautical mile public flight demonstration in September 2014. The partners have said that while the trial proved its ability to deliver a 1090 Extended Squitter (ES) or 978 MHz Universal Access Transceiver (UAT) payload between an aircraft and surveillance system, its inability to pick up 1090 MHz signals means airlines would have to modify their ADS-B avionics in order to send position data on a different Globalstar frequency.

Modification

Clinch points out that the need to make such modification underlines the Aireon principal benefit which requires no changes to existing aircraft equipage.

“This is true,” says Don Thoma, Aireon’s chief executive. “Aireon does not require any additional equipage other than what is being mandated by many states and regulators around the world.”

By effectively piggybacking on the Iridium network, Thoma says Aireon will provide those services very cost-effectively for both the airlines and the ANSP. Thoma also touts the powerful Iridium network whose architecture will be a ‘perfect fit’ with space-based ADS-B.

“LEO orbits are at an altitude that enables reception of ADS-B signals with no modification to the avionics, the cross-linked architecture provides global coverage and real-time transmission of aircraft information that is needed to support air traffic control,” he says.

In remote airspace, it is only ADS-C and space-based ADS-B which will fulfil the ICAO mandate – applicable from 2018 – directing airlines to receive position reports at 15-minute intervals. This will deliver a minimal level of tracking and would only help locate aircraft in routine flight scenarios – not in emergencies for which ICAO is planning a far more sophisticated regime called the Global Aeronautical Distress and Safety System or GADSS. This will take many years for the industry to define and install any new autonomous emergency tracking system that would take over working if the transponder and normal communications systems were turned off for any reason.

Even so, any additional level of surveillance must be provided cheaply by ANSPs which are charged with implementing the safest, best performing and most cost effective solutions.

The UK satellite business Inmarsat has already proved its technical and operational capability to track aircraft in real-time using ADS-C technology which meets ICAO’s regulatory requirements for both communication and surveillance at little or no additional cost.

Inmarsat’s Cpt Mary McMillan argues that surveillance of more than 90 per cent of the world’s aircraft already takes place, including over oceans, using ADS-C, which in addition to relaying position reports, gives additional information on the mechanical and environmental status of the aircraft.

Airservices Australia and Inmarsat launched a joint initiative earlier this year to determine if existing ADS-C capability – routinely used over oceanic or remote areas – could meet ICAO’s normal tracking requirements in oceanic airspace without impacting airline communications costs or operational efficiency.

By the end of the trial, aircraft across all oceanic airspace managed by Australia were being tracked at a minimum reporting rate of 14 minutes, something which reduced separation standards, while maintaining a good balance between system limitations, cost and monitoring requirements during normal operations.

Sub 1-minute

Even so, in a future envisaged by ICAO where airlines flying over the ocean will be required to obtain position reports at update rates of under a minute in GADSS-type scenarios, that superior level of performance will only realistically come from ADS-B avionics, argues SITA’s Clinch.

He therefore suspects that other satellite operators will probably try to build their own business case for adding ADS-B receivers – although ANSP appetite may be lacking as several major providers have already thrown their hats in to the ring by investing in Aireon and so would hardly want to pay for the use of a second network.

That could present a headache for ICAO which was charged with presenting the airline community with a technology agnostic, performance based solutions for 15-minute flight tracking following the disappearance of Malaysian Airlines Flight MH370.

Steve Creamer, director of ICAO’s Air Navigation Bureau tells Air Traffic Management that the UN aviation agency is ‘extremely pleased’ with the outcome of the WRC deliberations as expanding the protection of ADS-B 1090 MHz services into space offers tremendous potential benefits to the industry not only for tracking, but for surveillance, flow management services and other SWIM-based solutions. “It’s a win for the industry on many fronts,” he says.

He is not fazed by the lack of current competition in the space-based ADS-B segment and is satisfied that there are already a variety of global streaming solutions available that can fulfil the standard.

“We’ve been exposed to several offerings that more than fulfils it,” he says, adding that it is not ICAO’s intention to limit potential solutions strictly to the 1090 MHz ADS-B architecture. “We do believe that future innovations using this and other technologies will be able to meet the requirements that are envisioned for distress tracking. We also believe market forces will help clarify the cost-benefit of the various offerings.”

De Facto

Thoma similarly sees few problems, simply because current and planned mandates have made ADS-B the de facto equipage standard anyway – which is why both ICAO and the ITU supported the primary allocation for reception by satellite.

“All commercial aircraft are being built with ADS-B as standard equipage,” he says. “There are many different technologies that can support sub-minute tracking, however ADS-B is a natural solution as all new aircraft come equipped and many older aircraft are being mandated by their respective regulators/states to be equipped in a certain timeframe, limiting the need for additional investment by the airlines or the ANSP.”

Clinch does point out that aircraft flying over the ocean are not in fact required to be ADS-B equipped and that a significant proportion are not equipped with ADS-B capability.

“If satellite ADS-B is coming anyway, maybe ICAO and its member states should change tack and develop ATC aircraft separation reduction plans requiring all aircraft flying over the oceans to be equipped with ADS-B capable transponders, the same equipage the Federal Aviation Administration and other ANSPs are requiring for their domestic airspace,” he says.

He believes that guaranteed ATC benefits in oceanic airspace could motivate aircraft operators to add ADS-B capability to their transponders – more so than simply a mandate to have tracking in case of an incident that will hopefully never occur.

He adds that making the aircraft operators comply with an ATC-based requirement for ADS-B equipage combined with Aireon going into operation would have the indirect benefit of making tracking data available – so long as transponders kept transmitting reliable data in the event of any incident.

If an ATC justified mandate for ADS-B equipage over the oceans fulfilled the need of routine tracking, the future Global Aeronautical Distress and Safety System or GADSS which envisages real-time tracking for aircraft in distress could concentrate on systems that detect abnormal incidents and send extra data enabling incident diagnosis as well as autonomous distress tracking which employs independent avionics and frequencies – most likely the ELT and its COSPAS/SARSAT frequency.

Meanwhile, Inmarsat’s McMillan says the satellite operator is more than willing to stand with efforts to improve aviation safety, although doubts that the recent ITU spectrum allocation is anything more than a red herring.

“Anything that can enhance aviation safety or flight safety, Inmarsat is very supportive of, but my opinion on space-based ADS-B is actually a solution in search of a problem,” she says.

The prospect of ICAO launching plans for ATC-based requirements to have ADS-B avionics in oceanic airspace that will solve the routine tracking needs remains some way off but as Clinch points out, ‘time and the inertia of aircraft equipage may make things end up that way’.

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