AN/TPY-2 Transportable Radar Surveillance
Forward Based X-Band Transportable [FBX-T]
AN/TPY-2 radar is an X-band (wavelength around 3 cm, about 10GHz) active phased array radar, it has two working modes or configurations, namely terminal mode (TM) and frontier deployment mode (FBM) . The former is usually used as the fire control radar of the THAAD missile company. The latter is mainly deployed at the front and is used to provide data to distant missile defense systems, such as the US "Ground-based Midcourse Interceptor" (GMD) system. The United States claims that the TPY-2 radar deployed in South Korea will be deployed in a TM configuration with a shorter detection range, while the TM mode detection range is 600 kilometers. The party that supports the deployment of the "THAAD" system in South Korea says that the detection range only covers North Korea. Can't go deep into mainland China. Critics point out that the radar detection range in FBM mode is much longer, and it only takes 8 hours or less to switch from TM mode to FBM mode.
Although the US military is very open, it is actually very strict with regard to the core parameters of weapons and equipment, including the detection range of THAAD's AN/TPY-2 radar. Of course, first of all, when talking about the detection range of the radar, it must correspond to the radar cross-sectional area (RCS). It doesn't make much sense to talk about the detection range without talking about the RCS or basic attributes of the target. This is like the human eye can observe the object's distance depends on the size of the object and the contrast with the background. Humans can see the moon hundreds of thousands of kilometers away, but cannot see ants tens of meters away.
So, how far can the "THAAD" radar look at targets with different attributes in different working modes?
(1) Hundreds of miles. This is the shortest public report about the detection range of the TPY-2 radar that Yi Chi Jun has seen so far. It comes from Raytheon, the developer of the radar. The company once said in a video that the TPY-2 radar can "track home runs on baseball fields hundreds of miles away." Of course, this home run must be hit. It is high enough-more than 44,000 feet, which can be detected beyond the horizon (about the relationship between flight altitude and detection distance.
(2) 600 kilometers. This is the detection range of the TPY-2 radar reported by the Korean media when deployed in terminal mode. In February 2015, a report in South Korea’s Chosun Ilbo quoted a government official as saying that the effective detection range of the terminal configuration TPY-2 radar is 600 kilometers. In April 2015, "Seoul News" cited a US technology report that also gave this distance. If one considers the hundreds of miles in (1) to be three hundred miles, then the detection distance is about 480 kilometers. The RCS of a baseball is about 0.004 square meters. According to the calculation of the radar equation, for a target with an RCS of 0.01 square meters, the radar detection range is about 600 kilometers. This is consistent with the detection range of the "THAAD" deployed in the terminal mode reported by the Korean media.
(3) More than 1,000 kilometers. This statement is mentioned in the "THAAD" Anti-Missile System Radar Frontier Deployment Operation Manual published by the US Department of War. The original text stated, "AN/TPY-2 (forward deployment mode)...used to detect, track, classify and identify ballistic missiles in the boost and mid-stage at a distance of more than 1,000 kilometers." Of course, this statement is too vague.
(4) 1500 kilometers. The schematic diagram in the 2013 National Academy of Sciences (NAS) report shows that the detection radius of the TPY-2 radar is about 1,500 kilometers. The NAS committee believes that the detection range of 1,500 kilometers is relatively conservative.
(5) 1800-2000 kilometers. The information source of the detection range given by the Korean media for the front-end deployment model TPY-2 radar is the same as in item (2) above. This 2,000 kilometers is currently the most cited data by domestic media.
(6) More than 2900 kilometers. In 2008, U.S. Army Major General Patrick O'Reilly (later became Director of the Missile Defense Agency) claimed that the detection range of TPY-2 was "more than 1,800 miles" (2,900 kilometers). The TPY-2 radar can be used to track China's intercontinental ballistic missiles. There are two main trajectories of Chinese intercontinental missiles against the United States, one is passing through the North Pole and the other is passing over the Pacific Ocean. Judging from the above publicly reported data, the detection range of the TPY-2 radar is five times different. For radar, this is a huge difference. This means that the radar power difference is 5 to the 4th power, which is 625 times. If only the radar cross-sectional area (RCS) of different targets is different, then the RCS of these targets needs to be 625 times different.
George Lewis and Theodore Postol made simple calculations using radar equations in a blog on September 21, 2012. The formula they used for calculation is the following radar equation, but how to determine each parameter is a matter of knowledge.
Among them, Pav is the average power of the radar, and the unit is watts. The antenna of TPY-2 uses the third-generation transceiver module. According to estimates, its peak power is 16 watts and the average power is 3.2 watts. The radar has 25,344 modules, so its average power is 81 kilowatts.
P represents the antenna aperture efficiency and is set to 0.8. Two experts believe that this is a high value.
A represents the area of the radar antenna, in square meters. This number is easy to check, the antenna area of TPY-2 is 9.2 square meters.
G is the radar gain, calculated according to the formula , the gain is 103000. n is the number of dwell pulses, set to 20.
Fi is the radar cross-sectional area (RSC) of the target, calculated as 0.01 square meters. The FN noise figure is estimated by experts to be 1.4.
fP: Pulse repetition frequency. In other words, at what frequency does the radar emit detection pulses. Experts believe that it is 200 Hz, which means that 200 pulses are sent per second. The dwell pulse is 20, which means that the beam has to send and receive 20 pulses in one wave position, and the beam dwell time is 100 milliseconds.
LS is the system loss, which is evaluated as 6.3.
S/N is the signal-to-noise ratio. There were two situations, S/N=20 in tracking mode; S/N=100 in recognition mode
Putting the above values into the formula gives the following results:
R=870km tracking (S/N=20)
R=580km identification (S/N=100)
On this basis, a statement from the National Academy of Sciences (NAS) committee stated that the S/N will be reduced from 20 to 12.4, and the beam dwell time will be increased from 0.1 seconds to 1.0 seconds. If other parameters remain unchanged, the detection range of 1732 kilometers will be obtained.
The key assumptions and parameters of the above calculation are: the RCS of the warhead is 0.01 square meters; the dwell time of the radar beam for each target is 0.1 seconds; the signal-to-noise ratio S/N=20 for detection, and the noise figure is 1.4. This result shows that the radar can track 10 incoming targets per second within a range of 870 kilometers per second, or search for 10 wave positions, or detect 100 targets every 10 seconds.
The dwell time is actually the time that the radar beam stays at a wave position/target. The longer you stay on a wave position, the more target reflection pulses you may receive. After correlation calculations, you can detect farther targets or you can detect more details of the target, but the cost is an increase in the scanning period.
However, the the 0.1 second assumption of beam dwell time may be too large. The beam dwell time of many fire control radars is less than 10 milliseconds. A dwell time of 100 milliseconds means extremely poor search capabilities. For example, for a space of 10 degrees X 64 degrees, if the beam width is 1 degree (the X-band fire control radar beam is usually a very narrow needle beam), the scanning time takes 64 seconds, which is more than a minute. This will cause its search speed and data update rate to drop. For the X-band fire control radar, its beam width is inherently small. If the search speed is reduced, it will greatly reduce its search ability. It may be unbearable. Therefore, at least in terminal mode, the residence time should be shorter. Of course, if it is a radar that relies on external target indications, 100 milliseconds is still tolerable.
According to calculations by American experts, the detection range of the TPY-2 radar on a target with an RCS of 0.45 square meters can reach 3000 kilometers. This value is obviously slightly higherAccording to calculations by American experts, the detection range of the TPY-2 radar on a target with an RCS of 0.45 square meters can reach 3000 kilometers. This value is obviously slightly higher.
A well-known radar expert from China Electronics Technology believes that the noise figure and system loss of the various variables in the above formula are too low. The noise figure is chosen to be 1.4 (that is, 1.2dB), and the total system loss is only 8dB, which is not reasonable. Among them, the noise figure should be increased by at least 1dB, and the system loss should be increased by at least 3dB (mainly because the X-band atmospheric attenuation is large at long distances). Even if the additional system loss due to atmospheric attenuation is not considered, and the noise figure is only 2.5dB, the result obtained by his team is that the detection distance for a target with an RCS of 1 square meter is about 1,800 kilometers, and the detection distance for a target of 0.01 square meters is about 570 kilometers. The expert emphasized that even so, the noise figure and system loss values brought in are still relatively small values based on the principle of "feeding for the enemy". The actual system loss may be greater, and the final actual detection distance may be Lower.
In general, the calculated value of the Chinese expert is still relatively close to the data published by the Korean media, but it is smaller than the data estimated by the American experts (870). According to the radar equation, the American expert's algorithm should have a detection distance of 1 square meter. It is more than 2,700 kilometers.
The expert said that his team calculated the horizontal beam width of 0.37 degrees and the pitch direction of 0.84 degrees based on the antenna size. If calculated based on 20 dwell pulses and a dwell time of 100 ms, it would cover an airspace of 120 square degrees for approximately 30 seconds.
According to calculations, the parameters of hundreds of miles and 600 kilometers mentioned above obviously match the radar's terminal mode, and should be aimed at targets with a reflection area of 0.01 square meters or more but that meet the characteristics of a reentry warhead. From this perspective, the value of 600 kilometers and the calculations of Chinese experts are quite credible.
Now let's look at the terms "greater than 1,000 kilometers", 1,500 kilometers, and 1732 kilometers. More than 1000 kilometers is the clear statement of the US Department of War publication on the detection range of the front-deployed TPY-2. This value is too general, but judging from this, the statement of 1500 kilometers and 1732 kilometers should also be its front-deployed radar. The detection distance. The radar and target parameters used in the U.S. Department of War and NAS reports are classified. But this can be understood as targeting a larger and rising target.
How big is the target at this stage? The 2003 American Physical Society’s boost phase research report quoted a solid-fuel missile that exceeded the horizon and entered the detection range of the TPY-2 radar. The radar cross-section was 0.094 square meters (the liquid-fuel missile was 0.45 square meters). If calculated based on these two values, according to the algorithm of the American expert, the detection distance is 1523 kilometers and 2253; if according to the algorithm of the Chinese expert, the detection distance is 998 kilometers and 1476 kilometers. Obviously, the algorithm of the Chinese expert is more than 1000 kilometers and 1500 kilometers The report is close.
S-band radar cross-sectional area characteristics of the first and second stages of liquid fuel missiles (left) and solid fuel missiles (right) given in the 2003 American Physical Society's boost phase research reportS-band radar cross-sectional area characteristics of the first and second stages of liquid fuel missiles (left) and solid fuel missiles (right) given in the 2003 American Physical Society's boost phase research report.
The main difference between the value of 1732 kilometers and the detection distance of 870 kilometers is due to the longer beam dwell time. The dwell time is increased by 10 times to obtain the detection distance of 1732 kilometers, which is an important factor for the detection distance to increase by 1.78 times. That is to say, the increase in the detection distance is at the cost of reducing the number of tracking targets per unit time to one-tenth of the original, or increasing the detection time for each target ten times.
