Ground Surveillance Radars enable operators to perform persistent surveillance over wide surface areas from high altitude, manned or long endurance unmanned air platforms operating at considerable stand-off distances and in any weather or daylight condition. Using advanced radar sensors, the AGS Core will continuously detect and track moving objects throughout the observed areas, as well as providing radar imagery of areas and non-moving objects. The collected surveillance data can be disseminated in near-real-time (NRT) to ground stations through line-of-sight and beyond-line-of-sight data links for exploitation, use, and further distribution to interoperable NATO and national command, control, intelligence, surveillance and reconnaissance (C2ISR) systems.
Weather is a driving consideration in the selection of a sensor payload suite. Although aircraft usually operates at high altitude above the weather, the sensor suite must be able to see ground targets through adverse weather. Cloud cover is a particular concern because clouds are pervasive in the world-wide weather. The global average annual cloud cover is about 61 percent, with an average cloud cover over land of about 52 percent and an average cloud cover over the oceans of about 65 percent. The best sensors in looking down through cloud cover and rain are radar sensors. Radar sensors have negligible attenuation at tiequencies below 10 GHz. At higher trequencies, passive millimeter wave sensors operating in cloud cover and rain are limited from about 2 to 5 km length of path through the clouds and rain. Cloud droplets, which are much smaller than mmW wavelengths, absorb mmW radiation (much like a microwave oven).
Ground Moving Target Indicator (GMTI) provides continuously updated radar detections of moving or stationary rotating targets within the field of view of the radar sensor and in any weather condition, enabling users to track moving objects over time and to assess movement characteristics and trends. GMTI is typically used to enhance situational awareness with up-to-date information on movements within a wide area, and may be used to cue other ISR capabilities or even weapon systems onto objects of interest.
Synthetic Aperture Radar (SAR) imagery is radar-generated images of stationary ground features and targets of interest in a specific area at a specific time. Although similar in appearance to other imagery types, SAR is independent of weather and light conditions, and may contain non-visible information enabling processing algorithms e.g. to detect changes over time or to find concealed objects. SAR imagery is often generated in response to cueing by other information, such as GMTI data or intelligence reports indicating suspicious activities in specific locations.
STANAG 4607, "NATO Ground Moving Target Indication Format (GMTIF)" addresses a GMTI format interface for NATO. The format provides a flexible format fortarget information, such that simple GMTI systems can use a small subset of the format with limitedbandwidth channels, while robust systems can encode all aspects of the output data for use withwideband channels, including high range resolution (HRR) and pulse Doppler modes. It is also configured to be used as a stand-alone format, or can be encapsulated in either STANAG 4545 or 7023 data streams. Target reports include such information as target location and radial velocity. Further value-added processing of the target movement can produce track histories of the individual targets.
STANAG 4545, "NATO Secondary Imagery Format" (NSIF) establishes the format for exchange of electronic secondary imagery. Secondary imagery is sensor data that has been previously exploited and/or processed into a human readable picture. This format enables an operator at one workstation to compose and capture a multimedia image on his workstation, and send it to another workstation where it is capable of being reproduced exactly as it was composed on the origination workstation. The NSIF format can be composed of images, graphics and text. Because of the wide variety of display capabilities, the implementations of NSIF readers and writers are classified by their level of complexity, where the highest level will handle every large images with many bands of data, and the simplest level will only handle small, single band images. For interoperability considerations, a reader of an NSIF file must be greater than or equal to the complexity level of the image it is reading in order to display it. There are reserved segments at theend of the NSIF file and within the different segments of the file for other types of information not currently defined in the baseline standard (e.g. GMTI data or motion imagery). For example a reconnaissance exploitation report (RECCEXREP) formatted in an ADatP-3 format could be attached to an image segment through a text segment.
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