Synopsis Some Aspects of German Airborne Radar Technology, 1942 to 1945

It is rather curious, that after more than sixty years, there are still ongoing discussions on aspects of German radar technology. This may be also due to the circumstance that, for several decades, most communities were "indulging in the glorious past". What not directly originated from this country was often being considered to have a very minor (obscure) status, and was not worth spending much time on it. I have selected, for this DEHS Symposium, the following aspects: Lichtenstein and Berlin radars as well as, briefly, the passive systems Flensburg and Naxos. Of which Lichtenstein type (version) SN2 had, for some time, a frightening impact on the air battle over Germany. The Berlin radar design was primarily based on what became known the "Rotterdam apparatus". Which actually was the British H2S radar equipment discovered in a crashed Stirling bomber aircraft in the vicinity of Rotterdam, early February 1943? From then on, the sophisticated "electronic warfare" beat the Germans merciless. After the discovery of this revolutionary British radar apparatus, the Germans responded almost instantly by constituting the so-called "Arbeitsgemeinschaft Rotterdam" (AGR), being a coordinating research and engineering committee. Given the bleak early 1943 circumstances they showed new élan, and merely unlimited resources were made available to counter the menace of backlogs in German radar science. It is not that they were backwards in radar theory, though, they considered decimetre wavelengths de facto as most sufficient, whereas in Britain and America centimetre technology was already gaining maturity. Significant was that in the centimetre regions common valve techniques failed to match with new radar requirements.  Nowadays, radar-technology is unthinkable without the application of "FFT" computations (fast Fourier transformations). It is hard to imagine, that early radars could have been operated successfully without micro-processors and comparable facilities.We also may expect that in a few years time, no one will be able to explain wartime technology from own experience. I opt therefore, to explain some underlying facts of German airborneradars in detail.

After the subjects of this paper had been selected, it was not yet clear to me where to start my retrospect and how to approach it. Contemplating, that my website has become rather wideranging and, that one can find various contributions on radar related topics on it (of which several contributed by Hans Jucker of Switzerland, who is also a member of our Society). I have, therefore, decided to deal with particular details, which are more or less complemental to what already have been made available on it. [1] The Germans introduced their first experimental airborne intercept radar sets in 1941. Albeit, against the meaning of many Luftwaffe (German Air Force) pilots and officials. Göring, as well as many German pilots, were considering radar aids disdainfully, as it diminishes the open manto- man air-combat. Others were, nevertheless, very impressed (encouraged) by the new possibilities of radar aids. Unlike to what occurred in Britain, German industry was very much involved in the early stages of design of most new projects (they sometimes even initiated them). In the pre-war years, competitions between the two major German electronic firms C. Lorenz and Telefunken decided who of them should become the chief project contractor. However, after the war proceeded and German industry was being bothered with too many projects, the military services (Luftwaffe, Navy and Army) decided who should work on particular projects. To some extent, the C. Lorenz company was kept out of advanced radar projects, as it was owned by (affiliated with) the American IT & T company (sometimes known as: Standard Electric company). Only later in the war (1942/43), Lorenz became significantly engaged in radar work. Although, not directly in the confidential fields of SHF radar technology.

Lichtenstein airborne radar

Most references on German airborne radar mention type Lichtenstein, though, without distinguishing between the versions. Which used the same code-name, but that had only in 3 common that they had been of Telefunken design. In my opinion, this significant  hortcoming is one of the reasons why it makes sense to discuss aspects of "Lichtenstein radars" today. Glorious stories have been told, as to how cleverly one had been operating by misleading their "war opponent". That the counter side was, sometime, able to trick-out Allied intelligence services for more than eight months, has often been ignored. Regard, however, Hinsley's well balanced comment on SN2, at the end of this Lichtenstein chapter.

Morales Romero Karelis

CI 18089995

CAF

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How does an airborne radar works?

Well Airborne RADAR works in similar manner as their Ground counterpart , the differences typically lies in mode of operations, processing software , physical size and functions .usually Airborne RADAR's , especially for those who's required to detect target that flies at low altitude uses Doppler measurements to differentiate between target and steady objects like grounds . It's also may have a "compensations" to correct tracking error caused by the carrier's own movement 

EDIT- It seems the previous answer is bit too complex for some people

Air to Air airborne radar uses combinations of range ambiguous and Doppler ambiguous modes. High Pulse Repletion Frequency (HPRF) modes which are range ambiguous, to measure Doppler unambiguously. Low Pulse Repletion Frequency (LPRF)modes measure range unambiguously both of these modes still measure both Range and Doppler and resolve the ambiguous measurement using Chinese remainder theorem. This resolving of the ambiguous measurement uses different measurement parameters that are not related provide a measurement remaining that can be related to unfold Range or Doppler measurements. In between the HPRF and LPRF is the Medium Pulse Repetition Frequency Mode which are both Range and Doppler ambiguous. Repetition Rate of Pulses adaptation can be mixed together and sequenced. Some modes are have better properties then others for measuring particular targets or characteristic of some targets. The question of ambiguity, and therefore what defines a Pulse Repetition Frequency as High Medium or Low is dependent on the target characteristic and the range you wish to measure to.

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CI 18089995

CAF

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NASA Airborne Radar Catches Glimpse of Haiti

It was scheduled to conduct a three-week ission over Central America, but NASA officials decided to include Haiti in the observation plan, given the scale of the devastation that struck the impoverished island nation. The new photo clearly shows the Enriquillo-Plantain Garden fault line, the area where the massive, 7.0-magnitude earthquake originated. It stretched East to West (left to right in the photo), below the dark feature that represents a section of the Atlantic Ocean. The fault extends from the western tip of Haiti past Port-au-Prince into the Dominican Republic to the right of this radar image.

"Satellite interferometric synthetic aperture radar measurements show that the January 12 earthquake ruptured a segment of the fault extending from the epicenter westward over a length of about 40 kilometers (25 miles), leaving the section of the fault in this image unruptured. The earthquake has increased the stress on this eastern section of the fault south of Port-au-Prince and the section west of the rupture. This has significantly increased the risk of a future earthquake, according to a recent report by the US Geological Survey," the JPL team writes on its official website.

This is the first of a series of observations that will be conducted above Haiti. The map will be merged with others that will be obtained through similar processes. The purpose for that is to use a technique called interferometry to analyze the differences that occur in this region during the time frame that elapses between the moments each of the images are taken. "The interferometric measurements will allow scientists to study the pressures building up and being released on the fault at depth," JPL experts add.

Morales Romero Karelis

CI 18089995

CAF

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Airborne Radar That Tracks Missiles

Two giants in the airborne radar field have joined to develop a new radar that can detect and track, not only ground targets and aircraft, but also cruise missiles. It's a unique system designed by a unique partnership.

James W. Ramsey

Existing airborne radars can detect and track moving ground vehicles and aircraft. Now the U.S. Air Force is developing the first airborne surveillance radar capable of detecting and tracking low-flying cruise missiles. And despite budget uncertainties, the development program is on schedule.

Two leading U.S. radar providers, Northrop Grumman and Raytheon, are teamed in a unique partnership to develop the new sensor in the Multi-Platform Radar Technology Insertion Program (MP-RTIP). Northrop Grumman is the prime contractor, but it splits development and initial production work on the new radar system 50-50 with Raytheon. This arrangement to develop the radar for the new E-10A wide-area surveillance (WAS) aircraft and the Northrop Grumman Global Hawk unmanned air vehicle (UAV) seems to be working. "The program is progressing well," declares Col. Joseph Smyth, commander of the E-10/MP-RTIP systems group at the USAF's Electronic Systems Center.

The radar program successfully completed its final design review in June 2004, and a laboratory-based prototype system was tested at Raytheon's El Segundo, Calif., facility last September.

Following the award of a six-year, $888-million contract for the program's system development and demonstration (SDD) phase, the companies have been procuring components and preparing to build the first flyable system, scheduled to be tested on a Global Hawk surrogate aircraft in October 2006. At the same time a larger version of the modular scalable radar will be produced for test flight on a Boeing 767-400ER test bed, the anticipated aircraft platform of choice for the E-10A program.

Comparison to JSTARS

Both contractors and the service claim that the new radar will enhance the USAF's ability to track and identify stationary and moving vehicles, as well as hard-to-detect cruise missiles. It also will perform battlefield command and control functions.

Unlike currently fielded airborne systems, such as the E-8C Joint Surveillance Attack Radar System (JSTARS), the MP-RTIP radar will be able to collect ground moving target indicator (GMTI) imagery and synthetic aperture radar (SAR) still images nearly simultaneously. The radar also will be able to detect, track and identify more targets faster and with higher resolution than ever before, according to Dave Mazur, MP-RTIP program manager at Northrop Grumman's Integrated Systems sector in El Segundo.

"The key difference in this radar over the JSTARS radar is the fact that it includes missile defense. That capability doesn't exist today in an airborne platform," says Mazur. "And this radar, in comparison, offers increased range, accuracy and resolution, and faster revisit time."

The Air Force concurs. "The MP-RTIP being designed for the E-10A will provide five to 10 times the air-to-ground surveillance capability of JSTARS," Col. Smyth adds. What assures this capability is the new radar's larger aperture, the increased available power to the system, and its active electronically scanned array (AESA) antenna, which automatically scans in both azimuth and elevation," Mazur explains. "That means we can almost instantly revisit several areas at one time. Each pulse can be doing a different technique."

"Not only can you run [software] modes in sequence, you can interleave them," adds Tom Bradley, Raytheon's MP-RTIP program manager. He explains that, with one asset tasked to carry out significantly different missions, the platform will be able to collect and integrate "all types of intelligence on ground moving targets, imagery and low-flying threats," and provide the user with a comprehensive threat picture.

Both contractors bring considerable AESA antenna experience to the table. Northrop Grumman has developed radar systems for the new F-22 and F-35 fighters, while Raytheon is providing similar radars for the F-15 and F/A-18E/Fs. (The first operational unit equipped with Raytheon's AESA radars is an F-15 squadron based in Alaska). Raytheon also is upgrading the active array radar for Northrop Grumman's B-2 bomber program.

While not planned to replace the E-3A Airborne Warning and Control System (AWACS) radar, MP-RTIP can track conventional aircraft as well as cruise missiles. "The frequency we operate at--X-band--is different from [that used by] AWACS," says Mazur. (The Air Force's AWACS uses S-band radar.) "This allows us to have a very narrow beam, which allows [the radar] to be very accurate. We need that to track cruise missiles. This is a feature we can exploit to augment the AWACS capability."

An AESA includes thousands of transmit and receive modules that are assembled onto "subarrays" inserted into the antenna. The antenna then sends the radio frequency (RF) signals to a receiver, and the radar support electronics processes them.

While the antenna remains stationary, the beam is steered electronically. And the radar's electronic scanning capability moves the beam much more rapidly than previous systems, promoting improved radar searching and multiple tracking capabilities. By removing gimbals and other moving parts associated with manually scanned antennas, AESA offers increased reliability, Raytheon and Northrop claim.

Radar Size

The MP-RTIP radar being developed for the E-10A is a side-looking radar, whose antenna aperture units and associated avionics are mounted in a pod underneath the fuselage, forward of the wing root. While the antenna doesn't move in azimuth or elevation, it does rotate on gimbals 180 degrees to look out the other side of the aircraft.

The radar antenna for the Global Hawk measures 1.5 feet (0.46 m) tall by 5 feet (1.5 m) long. On the E-10A the antenna is considerably larger: 4 feet (1.2 m) tall by 20 feet (6.1 m) long. (The JSTARS pod measures 2 by 24 feet [0.6 by 7.3 m]).

The MP-RTIP requires a widebody aircraft such as the B767, primarily because of the radar's height. "You need something with a big enough landing gear, to account for a hard landing with all tires blown, and you are riding on the rims, and your shocks are fully compressed," Mazur explains. "You must have adequate clearance, so you don't go in there and scrape off the radar."

Most of the electronic equipment supporting the radar--including receivers/exciters, power conditioning units and processors--are mounted inside the E-10A's cargo bay. A separate (helicopter) jet engine, mounted in the cargo bay in a fireproof enclosure, powers the radar.

In terms of radar hardware, Global Hawk bears a "two box" system, with the antenna mounted below the aircraft and the signal processor inside an avionics bay. The radar mode software resides in the signal processor, which is responsible for controlling the radar, running it and processing the data.

Scalable Radar

The USAF's original intent was to make MP-RTIP a radar upgrade for JSTARS--the service's airborne ground surveillance, targeting and battle management system--which has been used effectively in the Iraq war. But MP-RTIP evolved into an advanced system that a widebody platform could best accommodate. (JSTARS uses the narrowbody Boeing 707.)

MP-RTIP was designed to be a scalable radar, using the same basic architecture and common software, but with a smaller aperture to accommodate later model Global Hawks. (A scenario is envisioned using both the Global Hawk and E-10A together for battlefield surveillance and air-to-air detection.)

Teaming Arrangement

Northrop Grumman Integrated Systems is the prime contractor for MP-RTIP, although its program management, modeling and simulation, and Global Hawk flight test activities account for only about 10 percent of the program. The other 90 percent involves the radar's design, development and testing. These activities are split evenly between Raytheon's Space and Airborne Systems unit in El Segundo and Northrop Grumman's Electronics Systems sector in Baltimore and Norwalk, Conn. All work on MP-RTIP falls under Mazur's realm of responsibility.

"Northrop Grumman and Raytheon are fierce competitors in the radar world, so bringing these two teams together to work on this program smoothly has been a challenge. But we've been very successful at it," boasts Mazur. (In fact, the Air Force granted the two contractors 100 percent of incentive award fees for successful teamwork in the contract's first phase.)

As for hardware, Raytheon is providing the MP-RTIP's "front-end" RF aperture unit (RFAU) antenna assemblies on the E-10A, while Northrop Grumman Electronic Systems provides the radar back-end. "We build the aperture assemblies into an antenna and provide receivers/exciters, cabinets and a radar signal processor," says Russ Conklin, MP-RTIP program manager for Northrop Grumman Electronic Systems. Northrop Grumman is responsible for the E-10A's radar integration and testing at its systems integration laboratory in a former Norden facility in Connecticut.

On Global Hawk the contractors' roles are reversed. Northrop Grumman builds the antenna elements and Raytheon, the back-end. Raytheon is responsible for integration and testing at its systems integration lab in El Segundo. There the software modes are added prior to flight test--and for testing on the Global Hawk.

"We at Raytheon build the currently used Global Hawk radar sensor, which has SAR and MTI [moving target indicator] modes, and we have a lot of experience putting it out in the field," says Raytheon's Bradley. "Northrop Grumman is doing Joint STARS and brings that system experience forward."

"Global Hawk is reconnaissance, and Joint STARS is really surveillance," he adds. "Now you're creating a platform that can do both. And by adding some air-to-air mode support, it also is going to be doing cruise missile defense."

The basic MP-RTIP software on the E-10A and Global Hawk are common. Both Raytheon and Northrop Grumman, together, are writing the radar operating services (ROS), built-in test (BIT) and calibration. One team member or the other is writing independently each of the three major radar modes: GMTI, SAR and airborne moving target indicator (AMTI).

Fitting MP-RTIP on Global Hawk is a plus for the E-10A program, Mazur says, because a number of the MP-RTIP modes are common between the two platforms. "We can do a lot of the integration and testing and validation before we get to the E-10A platform, so it helps us save test time on the E-10A portion. It is more expensive to run a B767 than to fly a Global Hawk."

Raytheon also brings its transmit/receive (TR) module manufacturing capability to the program. "We have a dedicated factory down in Texas [attained when Raytheon acquired Texas Instruments in Dallas]," Bradley points out.

Both Raytheon and Northrop Grumman Electronic Systems work closely with Mercury Computer Systems, a commercial off-the-shelf (COTS) vendor in Chelmsford, Mass., that provides processors for radar signal processing and the receiver/exciter hardware.

Morales Romero Karelis

CI 18089995

CAF

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NASA Airborne Radar to Study Quake Faults in Haiti, Dominican Republic

PASADENA, Calif. - In response to the disaster in Haiti on Jan. 12, NASA has added a series of science overflights of earthquake faults in Haiti and the Dominican Republic on the island of Hispaniola to a previously scheduled three-week airborne radar campaign to Central America.

NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar, or UAVSAR, left NASA's Dryden Flight Research Center in Edwards, Calif., on Jan. 25 aboard a modified NASA Gulfstream III aircraft.

During its trek to Central America, which will run through mid-February, the repeat-pass L-band wavelength radar, developed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., will study the structure of tropical forests; monitor volcanic deformation and volcano processes; and examine Mayan archeology sites. After the Haitian earthquake, NASA managers added additional science objectives that will allow UAVSAR's unique observational capabilities to study geologic processes in Hispaniola following the earthquake. UAVSAR's ability to provide rapid access to regions of interest, short repeat flight intervals, high resolution and its variable viewing geometry make it a powerful tool for studying ongoing Earth processes.

"UAVSAR will allow us to image deformations of Earth's surface and other changes associated with post-Haiti earthquake geologic processes, such as aftershocks, earthquakes that might be triggered by the main earthquake farther down the fault line, and the potential for landslides," said JPL's Paul Lundgren, the principal investigator for the Hispaniola overflights. "Because of Hispaniola's complex tectonic setting, there is an interest in determining if the earthquake in Haiti might trigger other earthquakes at some unknown point in the future, either along adjacent sections of the Enriquillo-Plantain Garden fault that was responsible for the main earthquake, or on other faults in northern Hispaniola, such as the Septentrional fault."

Lundgren says these upcoming flights, and others NASA will conduct in the coming weeks, months and years, will help scientists better assess the geophysical processes associated with earthquakes along large faults and better understand the risks.

UAVSAR uses a technique called interferometric synthetic aperture radar, or InSAR, that sends pulses of microwave energy from the aircraft to the ground to detect and measure very subtle deformations in Earth's surface, such as those caused by earthquakes, volcanoes, landslides and glacier movements. Flying at a nominal altitude of 12,500 meters (41,000 feet), the radar, located in a pod under the aircraft's belly, collects data over a selected region. It then flies over the same region again, minutes to months later, using the aircraft's advanced navigation system to precisely fly over the same path to an accuracy of within 5 meters (16.5 feet). By comparing these camera-like images, interferograms are formed that have encoded the surface deformation, from which scientists can measure the slow surface deformations involved with the buildup and release of strain along earthquake faults.

Since November of 2009, JPL scientists have collected data gathered on a number of Gulfstream III flights over California's San Andreas fault and other major California earthquake faults, a process that will be repeated about every six months for the next several years. From such data, scientists will create 3-D maps for regions of interest.

Flight plans call for multiple observations of the Hispaniola faults this week and in early to mid-February. Subsequent flights may be added based on events in Haiti and aircraft availability. After processing, NASA will make the UAVSAR imagery available to the public through the JPL UAVSAR website and the Alaska Satellite Facility Distributed Active Archive Center. The initial data will be available in several weeks.

Lundgren said the Dominican Republic flights over the Septentrional fault will provide scientists with a baseline set of radar imagery in the event of future earthquakes there. Such observations, combined with post-event radar imagery, will allow scientists to measure ground deformation at the time of the earthquakes to determine how slip on the faults is distributed and also to monitor longer-term motions after the earthquakes to learn more about fault zone properties. The UAVSAR data could also be used to pinpoint exactly which part of the fault slipped during an earthquake, data that can be used by rescue and damage assessment officials to better estimate what areas might be most affected.

Morales Romero Karelis

CI 18089995

CAF

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Airborne radar

Radar equipment carried by commercial and military aircraft. These aircraft use airborne radar systems to assist in weather assessment and navigation. Military systems also provide other specialized capabilities such as targeting of hostile aircraft for air-to-air combat, detection and tracking of moving ground targets, targeting of ground targets for bombing missions, and very accurate terrain measurements for assisting in low-altitude flights. Airborne radars are also used to map and monitor the Earth's surface for environmental and topological study.
Airborne radars present unique design challenges, mainly in the severe nature of the ground echo received by the radar and in the installation constraints on the size of the radar. The peculiar clutter situation governs the nature of the signal processing, and the installation limitations influence the antenna design and the radio frequency to be used (the two being strongly related) as well as the packaging of the rest of the radar. Similar considerations influence the design of space-based radars as well.
A particularly valuable use of airborne radar is weather assessment. Radars generally operating in the C or X bands (around 6 GHz or around 10 GHz, respectively) permit both penetration of heavy precipitation, required for determining the extent of thunderstorms, and sufficient reflection from less intense precipitation. See also Meteorological radar; Radar meteorology.
Another basic and valuable airborne radar function is altimetry. The aircraft's altitude can be continuously measured, using (generally) C-band frequencies (around 6 GHz), low-power transmission, and a downward-oriented antenna beam. Sometimes, information from additional beams (looking somewhat forward, for example) is combined with measurements of the Doppler shift of the ground echo received to further aid in navigation. Another type of radar used in navigation is the radar beacon, in which a ground-based receiver detects an interrogation pulse from the aircraft and sends back a so-called reply on a different frequency, to which the receiver on the aircraft is tuned. See also Air-traffic control; Altimeter; Doppler effect; Surveillance radar.
Airborne radars are used effectively to provide high-resolution mapping of Earth's (or other planetary) surface, with a technique called synthetic aperture radar (SAR). The processing uses the fact that surface objects produce a Doppler shift (due to the aircraft's flight) unique to their position as the aircraft passes by; this Doppler history is indicative of the scatterer's lateral, or cross-range, position at the particular range determined by the usual echo timing. With very stable radars and well-measured flight characteristics (and other focusing methods), picture cells (pixels) of 1 ft × 1 ft (0.3 m × 0.3 m) can be formed in the processed images from radars tens or hundreds of miles away. The resolution is somewhat like that possible had the flight path itself been used as a huge antenna, the synthetic aperture.

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Airborne Radar

Airborne Radar

Airborne Radar Simulation, in the present context, is the real-time generation of radar displays and other radar outputs, such as data exchanges with the flight computer or other avionics subsystems, consistent with the actual radar and in response to the interaction with the operator, ownship, targets, and the environment.

The application is flight simulators for man-in-the-loop training of pilots and radar operators, and engineering research simulators for designing radars, avionics systems, and cockpits. Engineering research simulators are frequently used to aid integration and so may incorporate additional aircraft hardware. Otherwise, the requirements are similar to flight simulators. This paper addresses the Airborne Radar Simulator for flight simulator application. The focus is Air-To-Ground radar modes and thus the Digital Radar Landmass Simulator (DRLMS). Keywords: DRLMS, flight simulator, modeling, radar, remote sensing, simulator, training.

The radar contains a Radar Data Processor (RDP) and a Programmable Signal Processor (PSP). The RDP provides control of all the radar functions, tracking, motion compensation, and communications to the avionics computer. The PSP provides predetection and postdetection signal processing, display processing, range/azimuth compression, and other high-speed processing.

The exciter creates the modulated waveform that is amplified by the transmitter and radiated into space by the antenna. The A/D converter translates the receiver output from analog to digital for PSP processing. The gimbal servo unit is driven by the RDP and maintains antenna scan and stabilization.

Table 2 lists the three primary radar modes. The RBGM mode is a conventional radar mode. The only distinction is that with modern technology it is possible to match the radar resolution to the display resolution by variable pulse compression, and thus eliminate the collapsing losses present in earlier radars. The DBS mode is a scanning mode, providing constant azimuth resolution throughout the field of regard. It is generated by sequential batch processing of short, fixed-length FFTs performed at a variable PRF and combined (as adjacent segments) to give the continuous scan display. The SAR mode is a spotlight mode, providing constant cross-range resolution at any designated range/azimuth location. It is generated by a single, long FFT that is performed with motion compensation at a constant PRF. (In reality, several FFTs are used to provide adequate azimuth coverage and several looks, performed at different RF frequencies, are noncoherently combined to improve image quality.)

Both DBS and SAR modes require motion compensation. The aircraft motion is acquired from the inertial navigation system. Then the receiver Local Oscillator (LO) is offset by appropriate frequency to remove the instantaneous Line-Of-Sight doppler from the radar signal that is due to the aircraft.

Morales Romero Karelis

CI 18089995

CAF

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