Moderadores: Lepanto, poliorcetes, Edu, Orel
En la vida real, los aviones hostiles generalmente van llevar aproximaciones más o menos frontales, en este caso las detecciones caen una barbaridad como muestra la siguiente tabla que sirve de ejemplo.
poliorcetes escribió:Qué pedazo de aportación. Muchísimas gracias, es interesantísimo y se aprende mucho.
14yellow14 escribió:Buen post y dejo esto por aquí
On the use of AESA (Active ElectronicallyScanned Array) Radar and IRST (InfraRed Search & Track) System to Detect and Track Low Observable Threats
https://www.matec-conferences.org/artic ... _04001.pdf
Contra un objetivo stealth respecto a los radares que suelen montar los cazas desde luego el IRST es una mejora importante pero las distancias son mucho más cortas... Y bien dentro del alcance de las armas que puede tener ese caza stealth.
Truquichan escribió:Joerse que currada
Mis agregados, ojo sin conocer como funcionan las tripas de los sensores IR, sensibilidades y limitaciones, pero si tengo idea de procesamiento fotográfico y post procesamiento.
Se puede conseguir realmente mucha (de hecho muchísima) mas resolución o mas "sensibilidad", a costa de tiempo de toma de imágenes y proceso. Se llama supersampling, se puede realizar en el espacio y en el tiempo. Los militares usan desde hace años la segunda para quitarse las distorsiones ópticas atmosféricas a larga distancia. Desconozco si estas distorsiones ocurren en las frecuencias infrarrojas. Al respecto de la resolución, se consigue a base tomar fotogramas ligeramente superpuestos, cuantos más fotogramas, más resolución final obtienes. Obviamente a costa de estar mas tiempo para cubrir una zona mas pequeña y mas tiempo(potencia) computacional.
Probablemente los IRST tengan esto implementado. Es decir, una vez detectas algo, te enfocas en él para verificarlo cubriendo una zona espacial mas pequeña. También he de indicar que el tema de la sensibilidad funciona mejor contra el suelo y objetivos estáticos que contra el cielo. El de la resolución en ambos casos.
Por lo que veo las limitaciones tecnológicas de los sensores infrarrojos son parecidas a los ópticos en el principio de los tiempos:
- Sensibilidad
- Tiempo de refresco a nivel de pixel para distinguir si cambia o no lo que ve.
- Tamaño de la matriz/columna de píxeles
- Velocidad de lectura de la matriz completa para formar un fotograma: uno a uno(lento), por filas o columnas, todo de golpe (lo ideal)
Y todo esto con una señora refrigeración que es crítica para la sensibilidad IR.
Buen currazo Pathfinder muchas gracias.
El Pirate se dice tenía originalmente un array de detectores de 4*768.
Figure 5.20 shows the PIRATE unit and the installation on Typhoon of the left side of the fuselage. The equipment uses dual-band sensing operating in the 3–5 and 8–11 mm bands. The MWIR sensor offers greater sensitivity against hot targets such as jet engine efflux, while the LWIR sensor is suited to lower temperatures associated with frontal engagements. The unit uses linear 760*10 arrays with scan motors driving optics such that large volumes of sky may be rapidly scanned. The field of regard (FOR) is stated to be almost hemispherical in coverage. The detection range is believed to be ~40 nm.
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2.2. Sensor head assembly
The optical path is arranged in a folded configuration to ensure a very compact design (see Figure 4). This was necessary to stay within the space constraints in the front section of the Eurofighter. The IR radiation enters the optical system of the FLIR/IRST through a large window made of zinc sulphite coated with boron phosphate and a diamond like carbon layer. This ensures maximum resistance against mechanical stress and erosion. With this construction an IR transparency of about 80% is achieved. The head mirror controls the line of sight of the FLIR/IRST. The head mirror movement in azimuth and elevation is inertial stabilised as to scan very fast an adjustable scan volume. Required scanning accuracy demands the application of internal solid-state gyros in addition to the LINS data received from the aircraft system. To allow switching between the wide field of view (FOV) for imaging and the narrow FOV for tracking a dual magnification telescope (see Figure 5) is inserted into the optical path. As the detector is a linear CMT detector array, an agile scanning mirror performs the scanning of the instantaneous FOV. To compensate for the image rotation along azimuth scanning direction a de-rotation prism (see Figure 5) is necessary. The telescope of the optical path actively compensates temperature variations while the remainder of the optics is designed to passively equalise thermal variations.
A long linear detector array with 8 TDI stages is mounted in the focal plane of the optics. The 8 TDI stages enhance the sensitivity of the detection. The CMT detector elements are attached to a CMOS ASIC. A conventional Stirling cooling engine keeps the detector at 77 K. This high performance detector array is a new development for the Eurofighter FLIR/IRST.
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3.1. IR imaging modes
The imaging modes give visual assistance to the pilot during manoeuvring of the aircraft, visual identification of targets and weapon aiming. The imaging modes flying aid (FLAD) and landing aid (LAAD) will assist the pilot during bad weather, night and low level operation. The image (575 lines per frame and 690 pixel per line) will be displayed on the HUD of the Eurofighter and overlay the outside world. In LAAD the image contrast is optimised for the lower part of the image, which with a high angle of attack landing approach is usually the runway area . In FLAD the image contrast is optimised for the surface along the flight path. Additionally, FLAD provides a thermal cueing function (TC, see §3.2) that allows tracking of hot spots. Another imaging mode is the steerable imaging mode (SIRPH). This mode provides a steerable IR image on a pilot’s Helmet Mounted Display (HMD). The pilot’s head tracking system provides the steering commands for the FLIR/IRST sensor head. In addition to the imaging modes above, the FLIR/IRST may also provide an image for identification (IDENT mode) of the tracked target, when the FLIR/IRST is in the single target-track mode (STT, see §3.2.). This image is displayed on the Multifunctional Head Down Display (MHDD). This image can be electronically zoomed or freeze selected.
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champi escribió:Muy buen hilo, Pathfinder.El Pirate se dice tenía originalmente un array de detectores de 4*768.
Por aquí dan datos algo distintos (2006): https://www.wiley.com/en-us/Military+Av ... 0470016329Figure 5.20 shows the PIRATE unit and the installation on Typhoon of the left side of the fuselage. The equipment uses dual-band sensing operating in the 3–5 and 8–11 mm bands. The MWIR sensor offers greater sensitivity against hot targets such as jet engine efflux, while the LWIR sensor is suited to lower temperatures associated with frontal engagements. The unit uses linear 760*10 arrays with scan motors driving optics such that large volumes of sky may be rapidly scanned. The field of regard (FOR) is stated to be almost hemispherical in coverage. The detection range is believed to be ~40 nm.
Sobre el F-35:
(...)
alejandro_ escribió:Excelente mensaje Pathfinder, muchas gracias por el esfuerzo.
El Pirate dispone de 3 modos principales de búsqueda, uno entiendo que manual, y los otros 2 conocidos como Sector Aquisition, esclavo a otro de los sensores del avión y el Slave Adquisition, esclavo a otros sensores externos al avión, por ejemplo algo que le venga vía datalink.
PIRATE is a complex system that operates radar-like modes in a wide field of regard. PIRATE is capable of operating against several heavily cluttered scenarios in each one of the following IRST modes: Multiple Target Tracking, Single Target Tracking and Slaved Acquisition.
Passive ranging data is also available.
PIRATE is also providing IR TV imaging to cockpit displays in accordance with the following FLIR modes: Flying/landing aid, Steerable IR picture on helmet and Identification.
La capacidad IRST permite al avión de caza disponer de un “radar pasivo”, que barre el espacio frente al avión... La información del IRST es tratada por el ordenador de misión para la asignación y dirección de armas, y para la dirección de otros sensores (principalmente radar) en la fase final del ataque. Es capaz de realizar un seguimiento automático de más de 500 blancos simultáneamente
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5.0 GROWTH POTENTIAL
The growth plans for the PIRATE system are focussed in two main areas; improved performance against surface targets and long range target identification.
Currently the IRST is optimized for air to air operations with air to surface capability limited only by the implementation of the scanning strategy and target extraction algorithm set. Extended data fusion, especially with the terrain data base together with hyperspectral processing of ground target returns will significantly improve the capability to detect, track, classify and identify surface targets at long ranges.
The IRST is currently a totally passive system but can be used to slave a laser onto a potential target for ranging, designation or identification using burst illumination or vibrometry techniques.
Currently, PIRATE has a passive capability for missile approach warning in the front sector. Using upgraded computing capacity this could be extended to cover all sectors by the addition of a distributed aperture staring array set of sensors.
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champi escribió:Otro interesante artículo más sobre el PIRATE (2002): https://booksc.org/book/40212449/644db1
Una de las curiosidades:...
5.0 GROWTH POTENTIAL
The growth plans for the PIRATE system are focussed in two main areas; improved performance against surface targets and long range target identification.
Currently the IRST is optimized for air to air operations with air to surface capability limited only by the implementation of the scanning strategy and target extraction algorithm set. Extended data fusion, especially with the terrain data base together with hyperspectral processing of ground target returns will significantly improve the capability to detect, track, classify and identify surface targets at long ranges.
The IRST is currently a totally passive system but can be used to slave a laser onto a potential target for ranging, designation or identification using burst illumination or vibrometry techniques.
Currently, PIRATE has a passive capability for missile approach warning in the front sector. Using upgraded computing capacity this could be extended to cover all sectors by the addition of a distributed aperture staring array set of sensors.
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