Wake vortex detection, prediction and decision support tools

New challenge for airports to increase capacity and safety 26/08/2017
Publication REE REE 2013-3
OAI : oai:www.see.asso.fr:1301:2013-3:19546
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Résumé

Wake vortex detection, prediction  and decision support tools

Auteurs

Optimal matching between curves in a manifold
Drone Tracking Using an Innovative UKF
Jean-Louis Koszul et les structures élémentaires de la Géométrie de l’Information
Poly-Symplectic Model of Higher Order Souriau Lie Groups Thermodynamics for Small Data Analytics
Session Geometrical Structures of Thermodynamics (chaired by Frédéric Barbaresco, François Gay-Balmaz)
Opening and closing sessions (chaired by Frédéric Barbaresco, Frank Nielsen, Silvère Bonnabel)
GSI'17-Closing session
GSI'17 Opening session
Démonstrateur franco-britannique "IRM" : gestion intelligente et homéostatique des radars multifonctions
Principes & applications de la conjugaison de phase en radar : vers les antennes autodirectives
Nouvelles formes d'ondes agiles en imagerie, localisation et communication
Compréhension et maîtrise des tourbillons de sillage
Wake vortex detection, prediction and decision support tools
Ordonnancement des tâches pour radar multifonction avec contrainte en temps dur et priorité
Symplectic Structure of Information Geometry: Fisher Metric and Euler-Poincaré Equation of Souriau Lie Group Thermodynamics
Reparameterization invariant metric on the space of curves
Probability density estimation on the hyperbolic space applied to radar processing
SEE-GSI'15 Opening session
Lie Groups and Geometric Mechanics/Thermodynamics (chaired by Frédéric Barbaresco, Géry de Saxcé)
Opening Session (chaired by Frédéric Barbaresco)
Invited speaker Charles-Michel Marle (chaired by Frédéric Barbaresco)
Koszul Information Geometry & Souriau Lie Group 4Thermodynamics
MaxEnt’14, The 34th International Workshop on Bayesian Inference and Maximum Entropy Methods in Science and Engineering
Koszul Information Geometry & Souriau Lie Group Thermodynamics
Robust Burg Estimation of stationary autoregressive mixtures covariance
Koszul Information Geometry and Souriau Lie Group Thermodynamics
Koszul Information Geometry and Souriau Lie Group Thermodynamics
Oral session 7 Quantum physics (Steeve Zozor, Jean-François Bercher, Frédéric Barbaresco)
Opening session (Ali Mohammad-Djafari, Frédéric Barbaresco)
Tutorial session 1 (Ali Mohammad-Djafari, Frédéric Barbaresco, John Skilling)
Prix Thévenin 2014
SEE/SMF GSI’13 : 1 ère conférence internationale sur les Sciences  Géométriques de l’Information à l’Ecole des Mines de Paris
Synthèse (Frédéric Barbaresco)
POSTER SESSION (Frédéric Barbaresco)
ORAL SESSION 16 Hessian Information Geometry II (Frédéric Barbaresco)
Information/Contact Geometries and Koszul Entropy
lncs_8085_cover.pdf
Geometric Science of Information - GSI 2013 Proceedings
Médaille Ampère 2007

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15 REE N°3/2013 Introduction A ircraft creates wake vortices in different flying phases. To avoid jeopardizing flight safety by wake vortices encounters, time/distance sepa- rations have been conservatively increased, thus restricting runway capacity. The concern is higher during taking off and landing phases, as aircraft are less easy to ma- neuver. These vortices usually dissipate quickly (decay due to air turbulence or transport by cross-wind), but most airports operate for the safest scenario, which means that the interval between aircraft taking off or landing often amounts to several minutes. However, with the aid of accurate wind data and pre- cise measurements of wake vortices, more efficient intervals can be set, particularly when weather conditions are stable. Depending on traffic volume, these adjustments can generate capacity gains which have major commercial benefits. Wake vortices are a natural by-product of lift generated by aircraft and can be considered as two horizontal tornadoes trailing behind the aircraft. A trailing aircraft exposed to the wake vortex turbulence of a lead aircraft can experience an Wake vortex detection, prediction and decision support tools New challenge for airports to increase capacity and safety L'ARTICLE INVITÉ FRÉDÉRIC BARBARESCO in cooperation with Philippe Juge, Jean-François Moneuse, Mathieu Klein, Erwan Lavergne, David Canal, Yves Ricci & Jean-Yves Schneider THALES Land & Air Systems Dans les aéroports, la piste est le facteur limitant le débit global et plus particulièrement les distances minimales de séparation permettant d’éviter les turbulences dans le sillage des avions. Ces distances sont maximisées à des valeurs élevées par l'OACI et ne tiennent pas compte des conditions de vent. Les tourbillons dangereux se dissipent habituellement rapidement en raison de la turbulence de l'air ou du vent de travers. Mais pour des raisons de sécurité, la plupart des aéroports utilisent des distances de séparation entre avions qui correspondent aux cas les plus défavorables, ce qui porte l'intervalle entre avions décollant ou atterris- sant à des valeurs atteignant souvent plusieurs minutes. A partir de mesures précises du vent et des tourbillons de sillage par des radars, des intervalles plus réduits peuvent être définis, en particulier lorsque les conditions météorologiques sont stables. Selon le volume de trafic, ces ajustements peuvent générer des gains de capacité qui ont d'importantes retombées commerciales. Cet article présente le projet européen SESAR P12.2.2 qui vise à développer un système d’évaluation des tourbillons de sillage fondé sur l'amélioration de concepts opérationnels, avec l’objectif de réduire les distance de séparation liées aux turbulences lors des décollages et des atterrissages, ponctuellement ou de façon permanente, afin d’augmenter le débit de la piste d’une manière telle qu'il puisse absorber les pics de demande d'arrivée en toute sécurité et réduire les retards au départ. Cet objectif sera atteint par la combinaison de capteurs radar/lidar qui fourniront la position en temps réel et la force des tourbillons de sil- lage et évalueront les conditions de vent, y compris la turbulence de l'air ambiant par les EDR (Eddy Dissipation Rate). L’article présente l’architecture du système d’évaluation de la turbulence de sillage et la campagne d'essais des capteurs effectuée à l'aéroport CDG au printemps 2011 et l'automne 2012 qui a fourni des résultats sur la possibilité de surveiller les tourbillons de sillage par des radars/lidars. Les principaux résultats ont été probants en termes de détection des turbulences de sillage. La plupart des tourbillons de sillage a été détectée dans les deux domaines critiques. Les résultats montrent que les radars et lidars sont complémentaires en fonction des conditions météorologiques : les performances des radars en bande X sont optimales dans des conditions pluvieuses alors que les performances du lidar sont optimales dans l'air sec. Pour le vent, les résultats permettent de cerner l’aptitude des radars UHF profileurs de vent en fonction de la hauteur au-dessus de la surface (conditionnée par le pourcen- tage du temps pendant lequel la réflectivité est suffisante pour effectuer une mesure et sous réserve que l'atmosphère soit suffisamment homogène et stable). La comparaison statistique entre deux profileurs UHF (et avec des profileurs sodar/lidar) est basée sur des histogrammes de données interpolées, la vitesse du vent, des profils de direction dans des périodes spécifiques, le calcul de biais, d'écart-type et de corrélation de la vitesse et direction du vent en altitude. L’usage combiné de capteurs, de modèles et de mesures réelles permettent de montrer, en prenant en compte les objectifs d’amélioration des capteurs déjà prévus dans le projet (radar E- balayage en bande X), qu’il est possible de satisfaire les exigences opérationnelles d’un système d’évaluation des tourbillons de sillage. ABSTRACT 16 REE N°3/2013 L'ARTICLE INVITÉ induced roll moment (bank angle) that is not easily corrected by the pilot or the autopilot. However these distances can be safely reduced with the aid of smart planning techniques of future Wake Vortex Decision Support Systems based on wake vortex detection/monitoring and wake vortex predic- tion (mainly transport estimation by cross-wind), significantly increasing airport capacity. This limiting factor is significantly accentuated with the arrival of new heavy aircrafts: Airbus A380, stretched version of Boeing B747-8. Radar and lidar sensors are low cost technologies with highly performing complementary wake-vortex detection capability in all weather conditions compared to others sen- sors that suffer of limited one. Radar and lidar are promising sensors for turbulences remote sensing on airport, for all kinds of aviation weather hazards (wake vortices, wind shear, micro-bursts, atmospheric turbulences) with ability to work operationally in a collaborative way, in different severe wea- ther conditions like fog, rain, wind, and dry air. Wake vortex hazards The wake vortices shed by an aircraft are a natural con- sequence of its lift. The wake flow behind an aircraft can be described by near field and far field characteristics. In the near field, small vortices emerge from that vortex sheet at the wing tips and at the edges of the landing flaps. After roll-up, the wake generally consists of two coherent counter-rotating swirling flows, like horizontal tornadoes, of about equal strength: the aircraft wake vortices. Empirical laws model tangential speed in roll-up Classically, velocity profile (tangential speed at radius r) is defined by: (1) where is called circulation. This wake vortex circulation strength (root circulation in m2 /s) is proportional to aircraft mass M and gravity g, inversely proportional to air density , wingspan B and aircraft speed V [1] with: (2) Additional factors that induced specific dynamic of wake vortices: wind shear effect (stratification of wind), ground effect (rebound), transport by cross-wind & decay by atmo- spheric turbulence and crow instability. Rational for wake vortex hazards mitigation on airports Wake vortices are a natural by-product of lift generated by aircraft and can be considered as two horizontal tornadoes trailing after the aircraft and their encounter is the main cause of loss of control by pilots. A trailing aircraft exposed to the wake vortex turbulence of a lead aircraft can experience an induced roll moment/bank angle that is not easily corrected by the pilot or the autopilot. Most recent referenced accidents are: November 12, 2001 - AA Flight 587 crashed shortly after takeoff from John F. Kennedy airport, due to pilot error in the presence of wake-turbulence from a Boeing 747; Novem- ber 4, 2008 - Mexican government LearJet 45 with Secretary of the interior, flying behind a Boeing 767-300 and above a heavy helicopter, crashed before turning for final approach at Mexico City airport. To characterize critical area of wake-vortex encounter, we can use results of NATS1 enquiry that shown that highest occurrences of wake-vortex encounters are at the touchdown (behind 100 feet in altitude) and at turn onto glideslope (between 3 500 -4 500 feet in altitude). But severe wake vortex encounters mainly occur at less than 500 feet in alti- tude and should be monitored in this critical area with an associated alert system defined as a safety net. As given by statistics, main occurrence and severity of wake vortex encounters are concentrated at low altitude. One can also observe that impact of wake-vortex encounter is more critical at low altitude due to roll angle, due to flying command limits, more especially during final approach and initial climb phases. As previously underlined, critical area of wake vortex en- counter is localized at low altitude. But this area is also cha- racterized by complex behavior of wake vortex hazards due to ground effect: 1 NATS is the UK’s leading provider of air traffic control services. Figure 1: (Left) Wake vortex encounter severity versus altitude indexed by roll angle – (Right) Critical phases of wake vortex encounters at low altitude during Initial climb or final approach. REE N°3/2013 17 L'ARTICLE INVITÉ Wake vortex behavior differs significantly depending on altitude: in high altitude, out of ground effect, wake vortex behavior is affected by the wind, but remains stable and pre- dictable by “wake vortex predictor”. At low altitude, ground effect can lead to unexpected wake vortex behavior. These phenomena are very difficult to predict and to model. In ground effect, wake vortices behaviors are driven by very instable causes: rebound of vortices on the ground, strength enforcement of a vortex due to low level wind shear induced by airport infrastructure, generation of secon- dary vortices and decay of wake vortex due to low altitude atmosphere stratification. Because of high severity of wake vortex encounter at low altitude where wake vortex have also complex behavior due to ground effect, it is very important and requested to moni- tor wake vortex by sensors in all weather conditions. Project phases of Wake Vortex Decision Support System development The SESAR project is the European air traffic control in- frastructure modernisation programme. SESAR aims at de- veloping the new generation air traffic management system capable of ensuring the safety and fluidity of air transport worldwide over the next 30 years. Wake Vortex Decision Support System (WVDSS) architecture will be defined and validated during the following development phases of the P12.2.2 SESAR project: Phase 0 The preliminary system architecture will include wake vor- tex sensors and weather sensors. During this task, a theoretical study and a sensor benchmark campaign will be performed in Paris CDG airport (XP0 campaign) in order to select the nee- ded sensors set. The recommendations on sensor technology selection and deployment delivered by this task will be used to refine the system architecture in the following phases. Phase 1 – Time Based Separation (TBS) The aim is to verify the position, strength and behavior of the wake vortices depending on headwind strength in arrivals in order to evolve from distance based separation to time based separation. As well, a first release of the WVDSS pro- totype will be developed, which will demonstrate this capa- bility. This demonstration will include an in situ verification campaign in CDG. Phase 2 - Weather Dependent Separation (WDS) The system will be updated with all the components lin- ked to weather nowcast and forecast, including real-time pre- diction of micro-scale terrain-induced turbulence close to the airport. The goal is to assess in real-time the position and Figure 2: Wake vortex in ground effect (vortex rebound, vortex enforcement by wind-shear, secondary vortex generation). Figure 3: Weather dependent safe separation by wake-vortex monitoring. 18 REE N°3/2013 L'ARTICLE INVITÉ strength of the wake vortices and to predict their behavior for both departures and arrivals, in order to demonstrate the possibility to evolve from a time based separation to a wea- ther dependent separation taking advantage of any favorable meteorological conditions (e.g. crosswind). This demonstra- tion will include an in-situ verification campaign in CDG. All building blocks regarding weather monitoring will be deve- loped/customized. Phase 3 - Pair Wise Separation (PWS) The system will be refined to reach two main goals: concept. With a partial aircraft wake vortex characteristics database, it will be demonstrated that the WVDSS could determine a dynamic pair wise separation, taking in account the real-time weather conditions as well as the aircraft sen- sitivity to wake vortex; layouts. These demonstrations will be performed in platform tests and verified in an in-situ campaign (XP3 in Frankfurt). Building blocks related to pair wise separation (aircraft characteristics database, algorithms…) will be developed or customized. Preliminary system architecture of runway wake vortex detection, prediction and deci- sion support tools The system architecture development is based on SESAR requirements in terms of safety & operational use. ANSPs2 & EUROCONTROL Advices & requirements will be also taken into account. Since no operational WVDSS is currently avai- lable, this first framework architecture is based on existing building blocks coming from partners. As main external inputs, the WDDSS receives: - cribing the current traffic and aircraft data. This function pro- vides the air traffic flow situation to the WVDSS; provided by National Weather Forecast Services. The me- teorological center provides data from the operational wea- ther forecast model “LM” of national Weather Service (e.g. Météo France, DWD…) covering most of Europe. The system is in charge of elaborating decision ads to sup- port: the supervisor, the approach controllers & the airport tower controllers. HMI (Human Machine Interface) towards Supervisor and controllers are considered as outside WVDSS Architecture. Components of runway wake vortex detection, prediction and decision support tools are the followings: 2 ANSP(s): Air Navigation Services Providers. Local meteorological sensors function A combination of sensors, which are typically weather dependent, will be used for wind & air turbulence monitoring. The local meteorological measurements are used for wea- ther nowcast and forecast, through following parameters: or Eddy Dissipation Rate (EDR) level of the atmosphere; Wake vortex sensors function The wake vortex measurements will be performed with two complementary sensors, one X band radar and one 1.5 µ lidar. The rational is that lidar sensor performances are limited in adverse conditions as in rainy or foggy weathers. The ability of radar to detect & monitor wake vortices in rainy weather will complement lidar in adverse weather situations. Radar and lidar are good complementary sensors, which can be used for turbulence remote sensing as well. They are able to work in a collaborative way, in different weather conditions like fog, rain, strong wind, turbulent atmosphere and dry air. Local weather nowcast/forecast function Local weather nowcast & forecast function will be able to predict atmospheric state variables within a coverage area of e.g. 100x100 km² centered on the airport with an increasing vertical spacing from e.g. 25 to 50 m throughout the boundary layer. Output variables are vertical profiles of horizontal and vertical wind, virtual potential temperature, TKE and EDR. Wake Vortex Advisory System function The Wake Vortex Advisory System (WVAS) will be com- posed of: The WVAS will be able to: or reduced separation and time applicability of separation mode; system track to provide spacing (chevron position for dis- play purpose); against system tracks and provide encounter advisories to controller’s HMIs for display purpose in case of actual or predicted danger; REE N°3/2013 19 L'ARTICLE INVITÉ sensors function. In case of discrepancies between wake vortex sensors and predictor, an alert is generated. The Decision Support System functional architecture is described in the following figure: Sensor simulators To study best sensor parameters/modes tuning and best sensors deployment on airport, simulators are mandatory. A customized 1.5 µm lidar wake vortex simulators will be developed with UCL (Belgium). Radar wake vortex simu- lator activity is relatively new and specific tasks are actively engaged on their development in collaboration with UCL (Belgium). In parallel to the SESAR program, THALES collaborated with ONERA & SAE that developed a wake vortex radar simu- lator in rain. ONERA used THALES SESAR data to calibrate this simulator. The motion of raindrops in wake vortices was modelled and simulated. The equation of the motion was derived and a methodology to compute the raindrops’ trajec- tory and distribution in the flow induced by the wake vortices was proposed. Two simulators were developed for evaluating the radar signatures of raindrops in wake vortices. One simu- lator is based on the simulation of radar signal time series, by superimposing the radar backscattered signal from each rain- drop in the wake vortex region. The other one is based on the raindrops’ number concentration and velocity distribution in wake vortices, enabling the computation of radar signatures much more efficiently. Those simulators have been used to reproduce experimental configurations and the comparison between measured (from SESAR trials at CDG) and simula- ted signature. The Doppler spectrum width is representative of irregula- rities of raindrops’ motions due to wake vortex flow. Doppler Figure 4: Decision Support System functional architecture. Figure 5: Wake vortex radar simulator in rain (list of parameters). 20 REE N°3/2013 L'ARTICLE INVITÉ spectrum width is correlated with circulation. This method could be used to calibrate radar retrieval of wake-vortex cir- culation. Weather and atmospheric turbulences models Météo-France will develop a new advanced weather fore- cast model (resolution: 500 m) for airport applications: Meteorological High-Resolution Prediction System (MHRPS) MHRPS development will be based on the French non- hydrostatic AROME model. The MHRPS will be imple- mented on the Météo-France super-computer and will assi- milate not only dedicated airport sensors data but also all the routine data coming from the European meteorological Infrastructure. MHRPS Requirements are the following: W), temperature (T), humidity (Hu), Eddy Dissipation Rate (EDR), Surface Pressure (PS); airport; to 1000 m, 1000 above; Turbulence high resolution forecast model NATMIG will develop turbulence forecast model. A Rey- nolds averaged Navier-Stokes model (SIMRA) has been de- veloped by NATMIG member SINTEF3 in order to predict local wind and turbulence around airports. Forecast EDR/TKE model will be adapted to airport infras- tructure (buildings…). Local weather data cube The MHPRS software of Météo-France and the “Turbu- lences calculation” of NATMIG will update the “Local weather data cube”. The data stored in the Local weather data cube are computed by MHPRS within a volume centered on air- port containing following areas of interest: Derisking 2008 trials and SESAR XP0 campaign at Paris CdG airport In a derisking phase in 2008 [3-6], THALES BOR-A radar was deployed at Paris CDG Airport, and co-localized with a Eurocontrol 2 µm lidar. In a first step, antenna was used in a staring mode for vertical exploration by exploitation of 4° beamwidth. In figure 16, wake vortex detection is illustrated 3 SINTEF is the largest independent research organisation in Scandinavia. Figure 6: Doppler velocity spectrum of raindrops in wake vortices at different ages. REE N°3/2013 21 L'ARTICLE INVITÉ by Doppler entropy in time/range coordinates axes in rainy weather. After each departure on the first nearer runways, wake vortices are monitored. In vertical scanning mode, individual roll-up of each wake vor- tex were tracked in range and elevation axes. In figure 7, above the first nearer runway, wake vortex generated by aircraft during departure can be observed. These detections of wake vortex are coherent with classical behavior close to the ground. Each roll-up from scan to scan (with one scan every five seconds) can be tracked as proved by the trials. Close to the ground, trajectory of each roll-up can finely and accurately been followed and their strength been estimated by circulation computation. More recently, from mid-May to end of June 2011, first XP0 Sensors Campaign of SESAR P12.2.2 was carried out at Paris CDG Airport with the following sensors: Wake vortex sensors: X-band radar BOR-A (THALES), Win- dcube 200S scanner lidar (LEOSPHERE) [8-9]; Weather sensors: Windcube 70 wind profiler lidar (LEOS- PHERE), C band weather radar (Météo-France), SODAR (Météo-France), UHF Wind Profiler radar-PCL1300 (Météo-France), UHF wind profiler radar-PCL1300 (DE- GREANE). X-band Wake vortex radar detection in rainy weather & 1.5 m lidar in clear air With the deployment under the east glide of CDG, the ra- dar was scanning a plane orthogonal to the glide axis. During rainy weather conditions, 34 aircrafts crossed the scanning plane ; 13 aircrafts taking-off: 4 heavy (B777, A340, A330, B767), 9 medium (B737, A319, MD80, EMB190); 21 aircrafts Figure 7: Wake vortex roll-ups tracking from scan to scan in rainy weather (CDG derisking campaign in 2008 with BOR-A radar). Figure 8: SESAR P12.2.2 XP0 Sensors Campaign at Paris CDG Airport. 22 REE N°3/2013 L'ARTICLE INVITÉ landing: 9 heavy (B777, MD11, A330), 12 medium (B737, A320, A321, B717, EMB170). We compared these results with wake vortex radar simu- lation in rain in collaboration with ONERA & SAE. In rain, the BOR-A X-band radar was able to detect wake vortices for all of them, via the Doppler analysis of the rain- drops. The observation duration of the wake vortices varies from a few seconds up to 250 s. This time seems to be limited by two factors: when the rain rate is too low, it is more difficult to detect raindrops and then wake vortices; in most configurations, vortices are lost when they go out of the radar scan (in range or angle) after some time. The X-band radar has successfully detected wake vortices generated by aircraft of categories HEAVY and MEDIUM in rainy conditions, radar up to 1 350 m height. The X-band radar was able to distinguish the two vortices in some cases (in par- ticular for heavy aircrafts for which lateral separation of the two vortices is higher than for other aircrafts). However its angular resolution limits its capabilities to provide accurate vortex core positions. For future campaigns, the new X-band radar will be designed with a narrower beam width to investigate this issue. Detection in dry air requires a higher power budget. This point offers room for improvement and will be assessed during future measurement campaigns, (power budget increased by 10, beam width divided by 2). The ability of the wake vortex sensors to detect aged vortices depends on: is scanning and thus on the dimension of scanning sector and crosswind; - lence) would also result in shorter vortex detection times; (they are also assumed to affect wake vortex decay and transportation, but are not included in this study). With the X-band radar, wake vortices have been observed up to 250 s after the airplane (wake vortices could be obser- ved in relation to the crosswind, which transported the vor- tices more or less quickly out of the scanning domain). The relationship between EDR and wake vortex decay could not be finally analyzed. For the time being, algorithm to compute wake vortex circulation from a Doppler effect on raindrops is not yet available, but will be developed based on multi-physic simulation: an algorithm of inversion should be developed and calibrated on wake vortex simulation based on a fluid mechanical model coupled with an electromagnetic model. The main results were convincing in terms of wake vortex detection. Most of wake vortices were detected in both criti- cal areas with detection ranges that have been demonstrated to be over the detection needs. Wake vortex was detected as long as it was in the sensor’s scanning domain, except for some cases where detection algorithms must be tuned. For radar sensor deployment, two principal sensor posi- tion options can be distinguished: separated due to the angular resolution. However it requires a large scan angle when the vortex is close to the sensor; axis. This setup is well suited to track vortices down to the ground. The two vortices could be separated due to the range resolution. Both concepts have their strengths and weaknesses. The optimum geometry should be chosen depending on the se- lected operational concept. Radar has more restrictive limits with respect to small scan angles in order to avoid ground clutter, but this shortcoming can possibly be compensated because of the radar’s longer range. Thanks to XP0 results, it has been demonstrated that, in high altitudes, wake vortex behavior, being affected only by the wind, is predictable. Out of ground effect, wake vortex pre- dictors will be able to compute wake vortex behavior based on theoretical models. They need as input an accurate wind speed and direction. In these areas, no wake vortex monito- ring sensor is recommended. On the opposite, close to the ground – where wake vortex behavior is affected by IGE (In Ground Effect) and by low wind shear that can lead to unex- pected wake vortex behavior like complex rebounds and en- forcements that cannot be accurately predicted and modeled – a wake vortex monitoring is mandatory. Sensors scanning domain must be large enough to cover both landing & take-off. The best sensors position is demonstrated to be sideways, few hundred meters upstream from the touchdown area. Results show that radar and lidar are complementary de- pending on weather conditions: X-band radar performances are optimal under rainy conditions and lidar performances are optimal in dry air. In consequence, for wake vortex mo- nitoring, the recommendation is to deploy an X-band radar (electronic scanning) coupled with a 1.5 µm lidar, monitoring in a collaborative way as meta-sensor, both located perpendi- cularly to the runways, a few hundred meters upstream from the touchdown area. Nevertheless, some improvements have to be made on these sensors to reach the performances needed by an opera- tional system. Update rate needed to scan the wake vortex 3D volume should be around 10 s. This capacity is already avai- lable for lidar, but should be developed for radar by electronic scanning. Both lidar and radar have evaluated the circulation of wake vortex but this part needs further algorithm development to be able to assess accurate initial circulation and decay. A gap in data availability has been observed in particu- lar weather conditions, after a raindrop when air has been cleaned from aerosols. Thus, the radar power budget must be increased in order for it to detect wake vortices in the REE N°3/2013 23 L'ARTICLE INVITÉ whole domain where lidar data are not available. These deve- lopments were already planned within the project. Thus, the campaign results confirm the theoretical analysis. SESAR XP1 campaign at Paris CDG airport A new multifunction X-band radar (wake-vortex, weather, traffic) with electronic scanning capability was deployed in September/October 2012 at Paris CDG Airport for XP1 trials campaign of SESAR project, for simultaneously monitor wake vortex close to the runways and assess wind in the glide and around the airport. Conclusion and perspectives SESAR XP0 and XP1 campaigns confirmed the feasibility of a prototype based on existing sensor technologies. Using combinations of sensors, models and real measurements, and thanks to some improved sensors already planned wit- hin the SESAR project (e.g. more powerful radar), it should be possible to meet current operational needs. Considering the state of the art of sensor technology and the needs for operational monitoring of wake vortices, it is recommended that further developments on sensor technology focus on the performance of the selected technologies on a long-term basis, which will allow verification of the overall reliability of the sensors and their maintenance needs, evaluation of the opportunity for upgrading or replacement of some sensors with current R&D sub-systems. For the future, Wake Vor- tex Decision Support System (WVDSS) performances should take advantage of technology progress on sensors and asso- ciated algorithms. Bibliography [1] F. Holzälpfel & al., “Analysis of wake vortex decay me- chanisms in the atmosphere”, Aerospace Science & Technology, n°7, pp. 263-275, 2003. [2] K. Shariff, “Analysis of the Radar Reflectivity of Aircraft Figure 9: (Top left) Multi-function (wake vortex, weather) electronic scanning X-band radar – (Top right) Multi-function Leosphere 1.5 micron 3D scanner – (Down) Radar sensors deployment for XP1 Trials. Figure 10: (Left) Doppler/range spectrum of A380 Wake-Vortex Radar signature - (Right) 3D Radar monitoring of wake-vortex. 24 REE N°3/2013 L'ARTICLE INVITÉ Vortex Wakes”, J. Fluid Mech.,vol.463, pp. 121-161, 2002. [3] F. Barbaresco & U. Meier, “Wake Vortex X-band Radar Monitoring: Paris-CDG airport 2008 Campaign Results & Prospectives”, International Radar Conference, Radar’09, Bordeaux, October 2009. [4] F. Barbaresco, “Interactions between Symmetric Cone and Information Geometries”, ETVC’08 Conf., Ecole Polytechnique, Nov. 2008, published by Springer, in LNCS, vol. 5416, February 2009. [5] F. Barbaresco, “Radar Monitoring of Wake Vortex: Electromagnetic reflection of Wake Turbulence in clear air”, Comptes-rendus Physique Académie des Sciences, Elsevier, 2010, http://www.wakenet.eu/fileadmin/ user_upload/News%26Publications/ CRPhys_article.pdf (preprint). [6] F.Barbaresco,“AirportRadarMonitoring ofWakeVortexinallWeatherConditions”, EURAD’11,EuMW,Paris,September2010, http://www.wakenet.eu/fileadmin/user_ upload/News%26Publications/EURAD- Wake-Vortex-Barbaresco.pdf(preprint). [7] M. Steen, S. Schönhals, J. Polvinen, P.Drake,J.P.Cariou,A.Dolfi-Bouteyre, F. Barbaresco, “Airport Radar Moni- toring of Wake Vortex in all Weather Conditions”, 9th Innovative Research Workshop & Exhibition, EUROCONTROL E.C, France, December 7-9, 2010, http://www.wakenet.eu/fileadmin/user_ upload/News%26Publications/INO-WS2010_148_48085-1. pdf (preprint). [8] A. Dolfi-Bouteyre, B. Augere, M. Valla, D. Goular, D. Fleury, G. Canat, C. Planchat, T. Gaudo, C. Besson, A. Gilliot, J.-P. Cariou, O. Petilon, J. Lawson-Daku, S. Brousmiche, S. Lugan, L. Bricteux, B. Macq, “Aircraft wake vortex study and characterization with 1.5 µm fiber Doppler lidar”, Journal of Aerospace Lab, December 2009. [9] S. Schönhals, M. Steen, P. Hecker, “Surveillance Systems On-Board Aircraft: Predicting, Detecting and Tracking Wake Vortices“, Proc. of 8th Innovative Research Workshop, pp. 65, Dec. 2009, Eurocontrol. [10] D. Vanhoenacker-Janvier, K. Djafri, F. Barbaresco, 2012, “Model for the calculation of the radar cross section of wake vortices of take-off and landing airplanes“, EURAD’12 Conference, Amsterdam. [11] Z. Liu, N. Jeannin, F. Vincent, X. Wang, 2012, “Modeling the Radar Signature of Raindrops in Aircraft Wake Vortices“, submitted to Journal of Atmospheric and Oceanic Technology. Frederic Barbaresco was born in France in 1966. He is graduated from high engineering school SUPELEC. From 2002 to 2005, he was in charge of ATC- WAKE simulation platform development in the framework of European FP5 Pro- gram. He was in charge of “Wake vortex/ wind monitoring sensors” research needs for WAKENET-3 Europe. He is scientific authority for SESAR P12.2.2 project. He is technical manager of FP7 UFO study (Ultra-Fast wind sensOrs for wake-vortex mitigation). He is author of more than 150 publications and has published five book chapters. His main research topic is on weather hazards monitoring by radar sensors. He is SEE Emeritus member and was awarded of Ampere Medal. He was also awarded in 2012 by NATO SET Panel Award. He is a senior expert in radar signal processing and multifunction radar resources management.