Eyes on Earth Episode 81 - Tour of the EROS Radome

Hello everyone and welcome to another episode of Eyes on Earth. We're a podcast that focuses on our ever-changing planet and on the people here at EROS and across the globe who use remote sensing to monitor and study the health of Earth. I'm your host for today, Tom Adamson. 

ADAMSON:

Landsat's fifty-year archive helps scientists around the world study land change. For this episode we are going to talk about a key piece of equipment here at EROS that brings the data from the satellites to the archive-so that you all can use it. Behind the building is a 10-meter antenna which sits underneath a radome. That's R-A-D-O-M-E: radome. We're going to take Eyes on Earth on location to learn more about the antenna, radome and how they fit into the Landsat story. And the best person to take us on this tour is Mike O'Brien, the Ground Station Engineer. You've been around antennas like this for a while.

0'BRIEN:

Yep, I've been working on these antennas for forty plus years. I've worked on them on every continent on the planet, Antarctica included. So, I am familiar with the antenna and the structures and how they work and operate.

ADAMSON:

You've been to the other Landsat Ground Stations?

O'BRIEN:

Absolutely. I did most of the installation at the other Landsat ground stations called the LGN - Landsat Ground Network. Fairbanks, Alaska; Svalbard, Norway; Neustrelitz, Germany; Alice Springs, Australia.

ADAMSON:

Were you here when the EROS antenna was installed?

O'BRIEN:

I was. We installed the antenna in 1996. It was immediately destroyed that spring by a hailstorm. Which destroyed the reflector and all the electronics. So, we had to had to rebuild it again that following year in 1997 in February-it was really cold. And then we installed the antenna but at that point because the hail had destroyed the first one, that's why we got the radome to protect the antenna from the elements here in South Dakota.

ADAMSON: 

Ok. Well, let's start heading out the back door. We will talk as we walk a little bit more.

SOUND OF DOOR OPENING......

O'BRIEN:

So, we rebuilt the antenna in 1997. Then we installed that radome as you can see, that is over the antenna. We'll talk more about that as we get out to the antenna site itself. But just so you can that the antenna is covered. And we also have a five-meter antenna which you can't see because of the trees right now. One of the unintended side effects of putting the radome on the antenna is that both of them stopped aging. The wear and tear from the South Dakota elements (wind, dust dirt, birds, vermin) stopped attacking the antenna. Hail, you know. We had a problem recently in that we couldn't get any of the motor or gear drive systems replaced or repaired anymore. Because they were so far out of production. We actually had to replace all the motors and gearboxes inside the antenna structure to get something modern and supported that we could get replaced or repaired. That's an unusual thing. Usually on these antennas you replace motors every five to seven years, depending on the environment. However, five to seven years is about the extent. When we replaced those motors under this last action because of the age, those were the original factory installed motors. So, thirty years old. And they weren't even showing signs of deteriorating. They were still going strong, but we would have run into problems. If we would have had an electronic problem. We never would have been able to get those repaired or replaced. So, we had to replace them with something supportable. Before an accident happens. 

ADAMSON:

How long do we expect the antenna to last now?

O'BRIEN:

Probably until we run into this problem again in twenty, thirty years. When we can't get these motors repaired or replaced, we'll have to go through it again. A lot of times these antennas are installed for a single mission, a single purpose or used to be. So, you only expected to get five to seven years out of it because that is what the mission life was. Well, with the Landsat missions Landsat 5 lasted thirty years. It's entirely foreseeable that we have this antenna system out here for the next fifty, sixty years.

ADAMSON:

Nice

O'BRIEN:

And still using it. But we plan on buying/purchasing more antennas as time goes on. But we totally anticipate having this antenna for forty to sixty years.

ADAMSON:

Ok. Cool. Well, we didn't count on them mowing the lawn back here. Let's start walking a little bit. How tall is the dome?

O'BRIEN:

It's a sixty-foot radome. So, it is sixty-foot plus whatever the twelve-foot cement that it sits on, ringwall. cement. Early on when we first started this project back in the late 90s, the cafeteria for the building was on the far side of the building. But then in 2002 or 2003 they moved to where it is now in the middle of the building. At the time they were putting in this parking lot because they needed a way to deliver groceries to the cafeteria which is right here. When they were doing the excavating, they broke some of our conduits. These manhole covers underneath are pole vaults. They are 12 x 12 cement rooms basically. Where cables come in from conduits out underneath the door. And then another set and another set until we get to the antenna.

ADAMSON:

So, we are standing on top of those rooms at this time? Ok.

O'BRIEN:

Yep. And then when the excavators were digging and making all this level, they dug through our conduits right where the sidewalk meets the parking lot. They literally had their scoop dig through the conduits, break them apart, and then break a bunch of cables. So that was pretty traumatic. It's something that you joke about on a sat-com site, but you never actually have happen, because it is really catastrophic. Lucky, we recovered from it. We didn't actually miss any data or passes. Tom Senden and I reused some other cables and were able to restring the antenna, the communications from the antenna to the control room without losing anything.

ADAMSON:

So, the data, it's coming into the antenna back there. And comes through these conduits. That's how it gets into the building?

O'BRIEN:

That is correct. Early on all the trees that we have out here were saplings. They were planted at the time the antenna was planted. What's happened over time is the trees actually grew up. Now, you see some big trees. Well, now they are starting to affect our data reception at the lower elevation. They get in the way of the data.

ADAMSON:

They get in the way of the data?

O'BRIEN:

They do get in the way. And when we started having this problem, we worked with the facilities group to get some of the larger trees cut down. So, the facilities manager came to me at the time and said, "Mike, here is a roll of yellow duct tape. I want you to put this on everything that you want cut down." So, the first thing I went and put it on was the water tower. Wrapped duct tape all around the base of the water tower. Because I really wanted to have that cut down.

ADAMSON:

Why did you want the water tower cut down?

O'BRIEN:

You can't have a worse object on a sat/comm facility than a large metal a large metal object filled with water attached to the ground. You can't see around it. You can't see through it. We have to basically, when we're tracking or transmitting, we notch out a space where we have three to four degrees on either side or above it. So, we don't cause problems.

ADAMSON:

So, we don't miss any data because of the water tower though, do we?

O'BRIEN:

Correct. We plan around it. So, it's notched out. In the overall sphere, you know hemisphere that we have here, we only lose a really small (like less than 1%) of what we normally take. Because it's low to the horizon anyway. When EDC was established, we did a lot of film processing. So, you needed hot water, sewage processing and stuff.

ADAMSON:

So, there is a reason the water tower is here.

O'BRIEN:

That's right. And it was to support the film processing. This entire backyard was covered with solar panels that were also destroyed by the hailstorm that took out the antenna. Because you needed hot water for film processing. Now we've all switched to digital about the same time that hailstorm hit. So, we never put the solar array back in. But it's mainly used now for the surrounding local communities' water pressure.

ADAMSON:

Ok. We are getting pretty close to the dome here. 

O'BRIEN:

One of the first questions that I get asked here is the ropes. There's ropes that come down off the  top of the radome and they tie down near the bottom towards the ground. And a lot of people assume that is for climbing. But it's actually for snow removal. So, when the snow and ice get built up on the top and doesn't fall off, we have the young new guy come out. He has to undo the cables and then he smacks the rope onto the radome and then runs before all the ice and snow come down and smoke him on the ground.

LAUGHING

ADAMSON:

I have to ask you this too. If it's raining, does that interfere with the signal? 

O'BRIEN:

Rain does interfere with the signal. The frequencies that we use it doesn't impact it too bad unless it is one of the really heavy rainstorms where you can't even see 10 feet. Beyond that the signals that we use aren't really impacted by rain.

Adamson:

What is the dome made of?

O'BRIEN:

This particular radome is made by a company called Raytech out of Reno, Nevada. It's made out of a fiberglass material. There's two pieces of fiberglass with a foam core sandwiched in between them. There's 13,866 bolt pieces that hold this radome together. It has to be sub-sampled. We sub-sample the tightness of the bolts. We get it washed and waxed every five years. They just use a regular hydrophobic wax. It doesn't have metal parts in it. You can't go get Teflon and coat your radome in Teflon because it affects the signal going in and out. You have to use a hydrophobic wax that has no metal in it. That is just so that the radome doesn't build up debris. Dust, dirt and even snow for that matter during the winter. When it's freshly waxed the snow and ice just slide right off on its own.

SOUND OF DOOR OPENING

ADAMSON:

Ok. We are inside the dome now. It looks like the antenna is already moving.

O'BRIEN:

Yep. It is prepositioning for a pass. What it is doing is it's setting up to look at the horizon where the spacecraft will come up over the horizon. Then it will start to follow it as soon as it can see it. And then will lock onto the signal of the spacecraft and follow it from beginning to end. But the antenna system builds a pre-predicted track path to guess where the spacecraft is going to be. So, that's called program track. That's what we do in the beginning of the pass. We have a precalculated track that the antenna is going to follow until it sees the signal from the spacecraft. Then it locks onto that signal and uses that to follow the spacecraft. To receive and send data.

ADAMSON:

Are we ok to be in here?

O'BRIEN:

Yes, absolutely. The signals that come in from space are so weak. Thousands and thousands of times less than what your cell phones put out. So, it's kind of in the background of universal noise. It's not even really seeable or it wouldn't hurt humans. But, when you transmit from here, we have a 100-watt transmitter on this antenna. The transmit signal has to hit a target the size of a spacecraft 400 miles away.

ADAMSON:

The spacecraft is like the size of a UPS truck. And it's 438 miles away.

O'BRIEN:

Right. So, the beam that we send to it is extremely well focused. So, by the time that it hits the spacecraft that beam is about 60-70 meters wide at that point. So down here it's literally tiny.

ADAMSON:

I feel safer being in here despite that fact there is a red light on. But we're fine.

O'BRIEN:

Most of these are designed to sit outside. So, they have red lights to indicate that they are transmitting. This is a Datron 3-axis 10-meter antenna that was purchased in 1996. The reason why it has three axes, I am going to try and explain this with voice. You have one axis that moves the antenna left or right. Then you have another axis that moves the antenna up and down. Now, one of the inherent problems with an antenna like that is, if you are tracking passes that go directly overhead, the antenna doesn't come up and then flip back over. It has to come up and spin and come back down the same way that it went up. So, the point at which it spins at the top is called a keyhole effect and you lose data there. You never want to lose data directly over your ground station because that's some of the best prime imagery. You get to see your ground station in the imagery. So, you never want to do that. So, what they do is put in a third axis. That's the third point that has a built in seven-degree tilt. Now, the antenna thinks that it is pointing straight up, but you can obviously see that there is a tilt in the antenna path going up. That way it only achieves eighty-three degrees, and you don't lose data at the keyhole. Inside of the reflector itself, the reflector is extremely smooth. It's ten meters. It weighs about 8,000 pounds. There's 8,000 pounds of counterweights on the backside of the antenna. It makes this antenna extremely well balanced. I can move this antenna around with my hands when I turn off the brakes. There's two structures that I want to point out inside the reflector. There is the large structure that is attached to the reflector itself. That's where all the image data is received when it's a higher frequency. So, all the pictures that we get come through that structure. Now, at the end of the four bars there is another smaller structure out here. And that is the S-band feed or the low rate. We do command and control here. So, we check the spacecraft's temperature, voltages. We tell the spacecraft when we want it to turn on, when we want it to turn off, all that stuff. All that happens through the low rate, which is the structure out at the end of the four legs here.

ADAMSON:

I also see that we are standing on a significant portion of cement. How far down does this base go?

O'BRIEN:

That's a good question. Originally, when we put the antenna in, when you do an antenna this size, 9-meter or larger, you go down 30 feet or until you hit bedrock. In this case we hit bedrock at 29.5 feet. So, we were right there either way. So, that cement pad runs that whole depth-29.5 feet, right down to bedrock. Inside the radome there is a set of 16 or 24 steel rods that go the length, the 29.5 feet. And then there are threads that stick up through the bottom of the radome. And that's how it's bolted to the ground. So, it is extremely well attached to the ground. I mean the antenna pedestal itself.

ADAMSON:

You were talking about the back-up antenna that's smaller. It's a 5-meter antenna. What's that one used for?

O'BRIEN:

That's correct. Originally, it's a 5.4-meter antenna from Viasat. We originally purchased the antenna to support Terra, Aqua and Aura for MODIS direct reception. 

ADAMSON:

Ok, these are NASA earth observing satellites.

O'BRIEN:

Right. And it started from the OhioView project that eventually morphed into AmericaView. And then we support a lot of college institutions...

WHIRRING NOISE

O'BRIEN:

It is repositioning to go back to stow, ehich is its easiest position of rest. That's why we point them up like that. Because it is the least amount of stress on any given part.

ADAMSON:

Yeah, the antenna was moving back into its birdbath position, I think you call it. 

O'BRIEN:

Yes, that is what the operators have termed it. Technically it is called the stow. Because when these antennas sit outside, they have something that is called a stow pin, that if you come up to a hurricane or a tornado or heavy environmental... You can put in these large pins that hold the antenna steady. They go through the structure, the support structure itself and hold it steady. And they are called stow pins. So, this position is technically called stow. But, yes, everybody calls it birdbath.

ADAMSON:

That's what it ends up looking like. Well, we're going to real quick go into the Ground Stations Operations Room and talk about what happens in there.

SOUND OF DOOR OPENING AND CLOSING

ADAMSON:

Ok, we're inside the ground station and Mike, honestly there are a lot of monitors here. What's going on?

LAUGHING

O'BRIEN:

Ok, this is where the magic happens. This is the Ground Station Operations Room. So, the guys in here run the passes. So, every time we can see a spacecraft, these guys are on board. Every time something needs to be done. Images need to be processed, resent, packaged, whatever. These are the guys that do it. We have a front row of monitors here. And these are the monitors that are attached to the systems that control the antenna. This particular one to my right is the one that controls the 10-meter antenna that we were just at. And you can see on the monitors here, this is the antenna we were just at.

ADAMSON: 

We see a video of what it looks like inside the radome.

O'BRIEN:

Right. I forgot to turn off the lights. And then this other monitor is the 5-meter antenna. We have the ground station control system. So, during a given pass - which the next pass is in about 15 minutes. We will have a Landsat 9 pass. And we'll have to get out of the way. Cause operations guys will come in here. They monitor all the received signal levels and the data that the spacecraft is outputting. Whether it be imagery or command and control or health and welfare.

ADAMSON:

So, the stuff on the monitors will mean something to them.

O'BRIEN:

That's correct. And they will be right on top of it. So, if something looks out of the window, they either handle it themselves or give me a call. One of the stories that I like to tell when we are in here is, early on in the Landsat 7 days, it took three days to process a received piece of data. In that three days if you found out at the end of the third day that a piece of equipment was bad, you went three days with capturing nothing but bad data for three days. And that was horrible. It caused problems. We didn't like that at all. So, we had a set of smart people come up with a way to show us the data as it was being received. Showing the live imagery. At the time, it was unheard of because the processing power requirements just were not there. So, we had this new tool called moving window display. That showed the data as it was being received. So, that way the operator could say, "hey that looks like image data. Or nope, there's something wrong. You guys need to do something." Well, technology has moved a long way since then. And now were able to do that with hardly any processing power. And we can share it with the general public. There's a free USGS government website EarthNow@usgs.gov that anybody can go to and see live imagery as it comes down from the spacecraft. And in the interim when there is no live imagery like right now for instance, there is no pass going on, it will play a recorded file that happened earlier today. That way it's always moving and showing people stuff. Moving around to the backside of the room. There is just a lot more monitors. Most of the monitors deal with the processing of the Landsat imagery once it's been received. And then the distribution and archive of that data. So, we kind of set-up different environments. You have a Landsat 7, Landsat 8, and Landsat 9 processing system. And then we have a Dev. And that way the operators can sit here, and they can see how things are processing. If there's any errors, the errors will come up as red messages. And then they just keep and eye on this stuff to make sure that it's all being processed and entering the archive. That's the most important thing that it gets  to the archives. And beyond that we have different tools and different set-up for different levels of processing, which I won't get into. That's another podcast. We process the data to different levels. So, the rest of the monitors are for the different tools and things that the different scientists use. Which I'm not familiar with.

ADAMSON:

That's ok. We have plenty of podcasts that describe what we do with all of this perfectly processed and calibrated Landsat data.

MUSIC PLAYING

Getting accurate data from Landsat counts on all of these ground station systems working properly, including the 10-meter antenna here at EROS. Thank you, Mike, for leading us on this entertaining tour of the radome. And thank you listeners for joining us on Eyes on Earth. You can find all our shows on the USGS EROS website. You can also follow EROS on Facebook or Twitter to find the latest episodes or to subscribe on Google or Apple podcasts.

This podcast, this podcast, this podcast, this podcast is a product of the U.S. Geological Survey Department of Interior.