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As the mystery surrounding missing Flight 370 moves into its second full week, theories continue to pour in, while data analysis becomes increasingly more critical.
As "Piers Morgan Live" continues its coverage, on Monday evening Guest Host Bill Weir will welcome Radar Expert Greg Charvat for a live, face to face primetime interview.
In advance of his appearance, the author of “Small and Short-Range Radar Systems” took some time to delve into his area of expertise, in the process posing – and then answering – some questions geared toward radars, with the entire experience being presented on the backdrop of the on-going investigation.
1. We've all seen it in our favorite World War Two movies, in laymen's terms, how does radar work?
Radar is a WW2 acronym that stands for Radio Direction And Ranging (RADAR). A radar consists of a radio transmitter and a radio receiver.
Imagine that we can turn on and off a radio transmitter at will. The radar simply measures the time it takes for the transmitted signal to travel from the transmitter, scatter off the target and travel back to the receiver:
The total time measured is proportional to range because the speed of radio waves in air is approximately the speed of light. Range proportional to time.
Conventional radar as we may think of it provides a round image and 'blips' representing all targets within view, angle vs. range. To do this, the radar uses a directional antenna shaped like a parabola (just like a flashlight's reflector). This antenna rotates, thereby 'sweeping' the horizon. Any targets within line of sight are ranged and plotted on a screen as the antenna rotates, mapping these targets and their associated antenna angles onto a screen, providing an image of all targets around the radar:
2. We've all been pulled over once or twice. What is the difference between air traffic control radar, military radar and the radars used by law enforcement?
An air traffic control radar, such as the ASR-9, operates out to ranges of approximately 60 nmi. It's job is to locate and track commercial and civil aircraft. It follows a similar architecture to the figure above.
By contrast, a law enforcement radar is a small short-range device operating out to 100-200m that simply provides the velocity of anything within its field of view. You point it like a flashlight beam, the speed of the fastest and brightest target within that invisible radar beam is displayed. These radars are not capable of ranging nor do they rotate around and plot positions of targets. They are very simple.
Military air search radars are a lot like the air traffic control radars, except that they must work out to significantly longer ranges, must be portable and often meet more rigorous specifications. Published specifications of some older military radar devices (for large aircraft) are on the order of 150 to 200 nautical miles or greater.
There are many more radar types. As many radar types as there are radar engineers, but these are the most common.
3. Can a large aircraft like a 777 really 'fall off the radar'?
Conventional radars only detect targets within direct line of sight. Imagine placing a straight edge ruler on a basketball. Where the ruler meets the ball is the radar location. As you get further from this, the distance between the ruler and the ball surface increases. This area is where you can 'fly below the radar.' The further you are from the radar the higher you can fly to be 'below the radar.'
If the ruler is elevated slightly above the basketball, then the area below the radar is reduced to the ruler's height and where a straight line from that hits the basketball. So when installing an air-search radar sensor, be sure to place it as high as you can.
4. What limits a radar's maximum range on land?
Take a flashlight, place it on your head and turn off the lights in a room. Rotate your body. Whatever you see bouncing off that light beam is within your line of site, this is similar to how a radar 'sees' the world. What if there is a large sofa or other obstacle in the way, can you see around it? No. In fact, there is a shadow behind that object. This is the shadow zone. Radars can be shadowed by obstacles too, like mountains, buildings, etc. It takes planning to locate radar sensors in the right locations for optimum coverage. If blind spots exist, you must add more radar sensors or be willing to work with the blind spots.
Tune in this evening at 9 for Charvat's full interview with Weir. And, for more of the work presented by tonight's guest, check out his book, and follow "Mr. Vacuum Tube" on twitter.
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