NATS safeguarding – overcoming radar objections via technical mitigation

By Danny Scrivener

Overview

Building developments and wind turbines in the vicinity of NATS’ radar infrastructure can receive an objection where a technical and operational impact is expected. Whilst UK wind development has slowed in recent years, the development of large buildings continues, and these can also impact upon NATS’ aviation infrastructure. This article presents an overview of the most common technical radar mitigation options available for NATS radar where a wind or building development impact has been predicted.

London Skyline with Tall Buildings Figure 1: London skyline comprised of many large buildings.

Blanking

Blanking is a mitigation technique for Primary Surveillance Radar (PSR) typically implemented for wind turbines rather than building developments. Blanking prevents a radar return from within a predetermined area being displayed on a radar screen. This is so that a radar operator does not become distracted by the presence of clutter produced by the wind turbine. This is feasible in less operationally sensitive areas and where the maximum number of blanks within an area has not already been allocated. More on blanking can be found in our previous news article.

Radar Reflections Fix

This mitigation technique is suitable for building developments near NATS’ Secondary Surveillance Radar (SSR) rather than PSR. This solution may be suitable for all static structures. A radar objection is typically received where a development is in close proximity to a radar installation or is within operationally sensitive airspace. This solution involves programming the location and orientation of a known reflector i.e. the façade of a proposed building development, into the radar. The radar’s internal processors can then calculate whether or not a radar return is likely to have been caused by a known reflector rather than the direct path from aircraft to radar. This solution ensures that an aircraft’s position is not incorrectly displayed on a radar operator’s screen.

Project RM

This is a wind turbine only fix, not suitable for mitigating the impact of building developments. This solution is a technical mitigation solution for all of NATS’ En-Route radars which are supplied by Raytheon, a radar manufacturer. A number of internal radar modifications and techniques are employed, including:

  • Comparing the radar high beam with the radar low beam;
  • Doppler filtering techniques;
  • Digital signal processing.

This solution has been applied to existing UK radar and is now a suitable mitigation technique whereby NATS will withdraw objections if the parameters required to ensure Project RM work are met. More on Project RM can be found here.

Radar Infill

This is a wind turbine mitigation technique for PSR where coverage from an affected radar is replaced by coverage from an alternate unaffected radar. This is only suitable where the alternate radar provides adequate low level coverage above the location of the wind development. The alternate radar feed is then supplied to a radar operator, replacing the coverage of the affected radar with the unaffected radar’s feed. This removes the clutter which would otherwise occur whilst also maintaining coverage over a defined area. More information on the in-fill radar mitigation solution can be found here.

Conclusions

A number of technical fixes exist for solving wind turbine radar issues with more solutions available for wind turbines compared to building developments. The good news is that radar based objections for building developments are rare… but they do happen. This is because objections for building developments are typically only received where it is to be located in very close proximity to an SSR and/or where the building development is located in sensitive airspace e.g. an airport control zone. The solutions available to SSR and PSR also vary, however where an objection is received, it is worth investigating technical mitigation options if mitigation through design is not possible.

Posted By: Danny Scrivener

on 26 April 2018

danny@pagerpower.co.uk

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