NATS looking at multistatic as radar alternative

Tracking commercial aircraft using TV signals could become standard following a proof of concept trial led by UK air traffic control NATS in conjunction with Thales ATM UK and Roke Manor.

Read How can TV signals be used as radar?

Over the last two years NATS, working with Thales and Roke Manor, has been testing whether the same signals delivered to televisions across the country could simultaneously be used to detect and direct aircraft.

The trial, part funded by Innovate UK, was carried out primarily over London with a Thales concept demonstrator using signals from the Crystal Palace transmitter. The results of the trials were then validated by Roke Manor. Up to 30 aircraft were tracked at any one time at altitudes of up to 10,000 feet, although more would have been possible had additional equipment been used.

The results demonstrate that not only can TV transmissions be used to locate aircraft; they can do it well enough to meet the standard separation requirements for air traffic control of three or five nautical miles. That makes TV signals a potentially viable alternative to radar.

Nick Young, NATS system engineer, said: “It may sound incredible, but we’ve been able to prove this really works and could one day be a real alternative or complement to using standard primary radar. The benefits could be enormous, including big reductions in the cost of ground based infrastructure.”

The concept works in exactly the same way as traditional radar, where a beam of radio energy – in this case a TV signal – is sent out and is reflected by an aircraft.  Specialist receivers then measure the directions of the signal echoes and the time taken for them to arrive in order to calculate the aircraft’s location.

A second phase of the trial in Liverpool also demonstrated that the signals were seemingly less susceptible to the interference wind turbines cause to traditional radar, an issue that has affected the renewables industry in recent years.

However, despite the excitement, NATS admits a lot of work still needs to be done before the X Factor is being used to direct the 8.25 from Glasgow to Heathrow.

Young adds: “There are a number of technical and regulatory hurdles to overcome before this could be considered for operational use. Questions around resilience and service standards need to be answered and we’d need to explore formal agreements with the broadcasters, but this is very exciting and we’ll be looking to further develop the concept over the next five years.”

There are additional reasons for the civilian air traffic management industry to be looking at multistatic radar technology.

One senior ANSP engineering chief told Air Traffic Management that the UK provider NATS was likely motivated by the UK government’s recent move to introduce spectrum pricing.

“Primary radar is a key part of NATS’ overall concept of operations. If their government was to introduce pricing on the radar band and particularly on the broad spectrum covering the primary radar band, that could be very painful. So cost is basically incentivising NATS to look at other technologies that would not use the same bandwidth as its normal radars use at the moment.”

NATS currently uses primary radar as a back-up to secondary surveillance radar and it is used principally for monitoring infringements by general aviation aircraft in controlled airspace.

Its chief advantages are its superior resilience, its lower cost and its better environmental impact in terms of its being far less obtrusive.

“If primary multistatic radar has the detection capabilities to ensure separation standards that means when NATS comes to renewing its next fleet replacement of radars – certainly in the en route area in around 10 -15 years’ time, then it may well look at primary multistatic radar with ADS-B and multilateration capability.”


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