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REQUESTING A TOUR

I wasn't sure if it'd be possible to get a close-up view of a NEXRAD site; all I really wanted was maybe something inside the fenced area, a close-up view of what we normally see from afar. As such, I emailed the National Weather Service WFO (Weather Forecasting Office) in Pueblo Colorado and asked them if it would be possible to take up-close pictures of the radar, preferably within the fenced area under escort. I received a response that, yes, they could arrange that and I should pick a day to visit the WFO and then travel out to the radar site with the electrical technican to get the pictures I wanted.

ARRIVING AT THE WEATHER FORECASTING OFFICE (WFO)

Pueblo WFO

NEXRAD Server

On March 29th, 2004, I drove the 1.5 hours from Denver down to the Pueblo WFO which is just southwest of the Pueblo Memorial Airport (I took the linked picture of the Pueblo Airport a few days earlier when I flew into Pueblo in a Cessna). At the WFO I met a number of people that were working at the time and all very friendly. I was also offered (and accepted!) the opportunity to see a home video that was taken during the construction of the Pueblo NEXRAD back in 1994. The video included the process of constructing the tower, lifting the unassembled radar dish to the top of the tower, and then lifting the radar dome "ball" with a crane and placing it on top of the tower. It was fascinating to see the construction of the site and then see the operating site within an hour.

Forecasting Terminals

The WFO, of course, is primarily to monitor and forecast the weather. Many sources of information, including satellite, radar, and local observations, are used. In the pictures to the left you can see two of their forecasting stations which each consist of three separate monitors all presenting different weather data and imagery. I was given a demonstration of the different types of information and imagery that can be selected and viewed in different formats. As a software engineer I was quite impressed with the flexibility of the software and how it allows the forecaster to view all the information available to them in the format and level of "zoom" that the forecaster requires.

I was then taken to the WFO's computer room which consists of a number of racks of computer systems. To the right is a picture of the computer system and rack which is responsible for receiving radar data from the NEXRAD site, processing it, and converting it into the various radar products that the NWS offers (reflecitivity, velocity, etc.). The system to the left is the computer which receives the radar data directly via a dedicated data line from the radar which, in the case of Pueblo, is about 20 miles away from the WFO itself. The system then automatically relays the data to the NOAA where it is published on the Internet and relayed to other users of the radar data.

DRIVING TO THE NEXRAD SITE

Arriving at site

Outer gate of site

In the case of many WFOs around the country, the NEXRAD site is located at the WFO as is the case in Milwaukee, Marquette, and Knoxville, to name just a few. With many other WFOs, however, the NEXRAD site is not at the same location as the WFO. In the case of Pueblo, the radar was located elsewhere since the eventual site of the NEXRAD was preferable due to its distance from the mountains and relatively high altitude which gives the radar a greater useful range than had it been placed at the WFO.

Since the Pueblo NEXRAD was some distance from the WFO, we agreed that I would follow the electrical technican out to the site. The technican was also going to have to wait for a contractor to do some work on the air conditioning so it made for sense for us to go in two vehicles so that I could leave when I was done taking pictures and not have to wait for the contractor to finish his work.

Upon approaching the NEXRAD site we first had to stop while the technican opened a cattle gate (since cattle often graze in the surrounding field). We then proceeded about another 1/4th of a mile to the NEXRAD site itself which, of course, had its own internal gate (to keep the cows from trampling all over the radar site!).

NEXRAD SITE OVERVIEW

Map of NEXRAD Site

The NEXRAD site, within the fenced area, consists of three small buildings, some external air conditioning ducts, and the NEXRAD tower itself. The layout is depicted in the site map to the right (not to scale).

The first building, "UPS & Spare Parts" contains the Uninterruptable Power Supply. This includes a large UPS that is capable of running the site for a minute or two during a power failure as the power generators kick in. The building also contains a number of spare parts and a small office.

The "Backup Generator" building contains, not surprisingly, a backup generator. The generator is capable of running the site for over a week in the event of a prolonged power failure.

The "Xmitter, Receiver, and and Small Office" building holds the major electronics including the transmitter and receiver. To the east of this building is a relatively large air conditioning unit which cools the electronics in the building.

The "Nexrad Tower" consists of a base of concrete upon which the tower structure is built. There are a number of tubes and cables that leave the xmitter/receiver building and go to the center of the NEXRAD tower and then up to the radar dome itself.

Entering the site	The 3 buildings	UPS Building (left)	Entering Xmit/Rcv Building
Generator (left), Xmit Building, & Tower	Tower, A/C, and Xmit/Rcv Building	A/C east of Xmit/Rcv Building	A/C east of Xmit/Rcv Building

THE UPS BUILDING

NEXRAD UPS

The northeast building on the site is the UPS building. This contains what is essentially a typical, but large, Uninterruptable Power Supply (UPS). It works in pretty much the same way as any other UPS--just a large battery--but is relatively large and can power the radar for about a minute in the event of a power failure--during this time the power generator (in another building) will start up and is able to power the site for over a week.

The picture to the right shows the UPS that provides instant-on power in the case of a power failure.

THE GENERATOR BUILDING

In addition to the UPS in the UPS Building (above), the site also has an on-site backup power generator. While the UPS is battery-based and can instantly provide power in the event of a power failure, the generator will be activated in the seconds following a power failure. This starts up a gas-powered generator that can create the power necessary for the site for over a week in the event of a prolonged power failure.

Entering the generator building

Gas tanks on right side of building

Generator in middle of building

Power panel on left side of building

THE TRANSMIT/RECEIVE BUILDING

Of the three buildings, the transmit/receive building is the most interesting. This building houses all the electronics necessary to generate the radar beam, controls the radar with a PC, receives the return echos form the radar, and transmits it to the WFO for processing and the generation of the various radar products.

In the set of pictures below we first see a view of the xmit/receive building as taken from the door. As you enter the building the radar electronics is right in front of you. On the left side we have the hardware that is responsible for receiving and interpreting the radar echos (the receiver) and on the right side we have the hardware that is responsible for producing the radar beam (the transmitter/klystron). The second picture shows the electrical technican entering commands into the PC in preparation for shutting down the radar. In the third picture we see the control panel for the transmitter hardware and in the last picture we see the electrical technican shutting down the radar beam--shutting down the beam was accompanied by an impressive reduction in the sound in the building; there was no doubt something was being powered down as the "hum" and noise in the building faded away.

View from door of xmit/recv building, xmiter on right and recvr on left

Electrical tech shutting down the radar

Control panel for xmit hardware

Shutting down radar beam

The klystron itself is pictured below as the leftmost picture. Next, we see the klystron on its "base" which contains oil to cool the klystron unit. To the right we then see the black "duct" that leaves the top of the klystron and heads up out of the unit to the top. The rightmost photo shows the beam duct which is no longer a black flexible duct but rather a beige metal duct (the one with the blue wire) which then goes to the right and then back again to the left. This is actually a hollow duct which, due to the radar wavelength, allows the radar beam to reflect around inside the duct towards the radar dish. In the first picture in the second row we see where the beam duct becomes a black, plastic-looking tube (just to the left of a gague). Finally, we see the black curved beam duct leave the building on its way to the radar tower in the last picture.

The Transmitter, Klystron, and Beam Duct

The klystron	The klystron oil base	Duct heading up from klystron	Beam duct above xmit hardware
Beam duct	Black beam duct leaves building

Facing the transmitter, to the left as you walk in the building, is the receiver hardware. In the middle is the PC that operates the radar and which the electrical technican used to power down the radar. To the left, we can see where the radar return echos come back from the radar dish into the receiver hardware. The hardware itself is visible in the middle two pictures. On the otherside of this rack we have the Automatic Gain Control (AGC) which is pictured in the rightmost photo. The AGC takes the incoming return signal and automatically adjusts it so that it is not too weak or too strong for the rest of the receiver hardware to handle.

The Receiver

Cables leading into receiver hardware

Inside the receiver hardware

Lower half of receiver hardware

Automatic Gain Control (AGC) unit

THE RADAR TOWER

Having seen all the electronics in the xmit/receive building, the electrical technician phoned the WFO to see if it would be possible to briefly take the radar down so I could see the inside of the radar dome. Luckily, there was absolutely no weather of interest anywhere in the Pueblo area so the technican was authorized to take down the radar so we could climb the tower.

I followed the technican to the base of the radar tower. From there, in the first picture, we can see the radar ducts leaving the xmit/receive building and curving up the tower. These ducts carry the radar beam that is transmitted and also carry the return signal back to the receiver hardware. The next picture is a view looking directly up at the radome from the base of the tower. Next, we can see as the technican unlocks the access gate to the stairs that lead up the tower. The stairs themselves are a comfortable climb except for the last flight, pictured in the rightmost photo, which is significantly steeper than the first two flights of stairs. In all, the floor of the radome is approximately 50 feet high. The exact height of the tower at any given NEXRAD site will depend on the elevation of the site as well as the relative height of the surrounding terrain. Since the Pueblo site is already relatively high in relation to surrounding terrain the tower itself is not as tall as many.

Climbing the Radar Tower

Cables leading to radar tower

Looking up from tower base

Opening gate to radar tower

Last flight of stairs to radome

Cables leading entering radome from below

INSIDE THE RADAR DOME (RADOME, THE NEXRAD "BALL" ITSELF)

Upon entering the radar dome (radome), the first thing that catches your eye, of course, is the large radar dish. It is so large that it almost touches (within a foot or so) the protective fiberglass "ball" that protects it. Hence, when you enter the radome what you actually see is the pedestal (the construction that supports the actual radar dish) and the back of the radar dish.

In the pictures below, we first see the top of the pedestal and the backside of the radar dish. The structure above the area with the black strip on it is what actually rotates when the radar is on. In the rest of the pictures in the first row we can see various views of the "base" of the radar dish--where the radar connects to the supporting pedestal. In the rightmost picture you can clearly see a ladder which scales the radar dish itself towards the top of the radome structure. This allows a technican to access the top hatch at the top of the radome. The five black cables that go out from the center of the top of the radome are part of the lightning rod structure that protects the radar from lightning strikes.

In the second row we see the electrical technican pulling the radar dish down manually. Although the radar dish itself weighs 3000 pounds, it can be moved quite easily due to the very delicate balance that is achieved with the counterweights. Pulling the radar dish down allowed me to get in between the radar dome wall and the radar dish to take the remaining two pictures. These pictures show the radar dish itself as well as the concentrator from where the radar beam is both transmitted and the echo return is focused back at for subsequent detection.

The Radar Dish

The radar dish and pedestal	Base of the radar dish	Base of radar dish	Dish, pedestal, and ladder to top of dish
Pulling radar dish down for better view	Face of radar dish	Dish concentrator

The radar dish itself is not the only thing of interest inside the radome.

In the following pictures we first see the floor hatch through which one enters the radome from below. A chain is placed in front of the hatch to (hopefully) keep people from accidentally falling out. In the next picture we see a picture of the floor of the radome where it is apparent how the external fiberglass radome wall is bolted at the base of the radome floor.

In the next picture we see a close-up of one of the many fiberglass tiles that make up the characteristic radome "ball." Although they are bolted in place with normal metal bolts, this does not present a problem for the radar since they are so close to the radar they are not picked up as an echo.

The final picture is the base of the pedestal which supports the radar dish. The pedestal includes a number of power units along with a telephone.

Other Points of Interest in Radome

Floor hatch that gives access to radome from below

Floor of the radome

One of the many fiberglass panels that make up the radome

The base of the pedestal that supports the dish

The radar pedestal is of interest, too. It is made of iron that is strong enough to support the radar dish and its counterweights. The pedestal contains two access ports that can be removed to look inside the pedestal.

The first picture shows the lower access port removed. In this picture we can see the radar beam duct (the white rectangular duct that heads left, then up, and then down and right) as well as the return signal cables (the two black cables with yellow tape on them). The second picture was taken from within the access port looking up. Again, the radar beam duct can be seen as well as the return signal cables.

The third picture shows the upper access port removed. This access port is 90 degrees counter-clockwise from the lower port, and higher up--i.e, the lower access port is right about at floor level while the upper port is about 5 feet off the floor. In the third picture the radar beam duct can again be seen. However, peering inside (in the rightmost picture) the most interesting item is the electric motor which causes the radar dish to turn when it is in operation.

Radar Pedestal

Lower access port

Looking up in lower access port

Upper access port

Radar dish motor

Having had a good look around inside the radome and taken dozens of pictures, the electrical technican and I began our descent back down. In the first picture we can see the technican closing the access hatch that provides access to the radar dome from below. In the second picture I'm on the last flight of stairs just elowthe radar dome floor. The third picture is a shot of the electrical engineer descending from the top landing. Finally, the fourth picture is a view of Pike's Peak in the distance as seen from the top landing of the radar tower.

Descending from the Radome

Closing the access hatch as we had down

Me descending from radome

Electrical Tech descending from radome

Pike's Peak in the distance

In addition to the above pictures, I took quite a few pictures of the site's perimeter and longer-range pictures of the entire site which can be seen in the following images.

The NEXRAD Site

North Perimeter	East Perimeter	South Perimeter	West Perimeter
Radome backlit by sun	Radome from southwest	Site from southeast	Site from south
Site from west	Site from north	Site from northeast, leaving site	Site from end of access road

ACKNOWLEDGEMENTS

I'd like to extend my thanks to everyone at the Pueblo WFO who were so kind and accessible and made this entire visit, and subsequent "Online NEXRAD tour page," possible. The visit was most educational and very memborable given my interest in software, meteorology, and my newfound interest in weather radar. THANKS!