Hello
everyone, and welcome to another episode of Eyes on Earth,
a podcast produced at the USGS EROS Center.
Our podcast 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.
My name is Tom Adamson.
EROS is known as the central location for acquiring, processing,
archiving, and distributing Landsat data.
But how does that data get from the satellites to EROS?
For this episode, we have gotten special access
to the Landsat operations room here at EROS during a live Landsat pass.
Now, a pass means one of the Landsat satellites will be passing overhead
while we're recording this episode.
Hey, thanks for letting me come in here and watch what you
do during a Landsat pass.
I'll let you two introduce yourselves.
My name is Aaron Hensley. Been here
25 years, and we are ground station technicians here in ground station.
You've been here for several of the Landsats.
I have been here for all of them
in this ground station, yes.
And my name is Eric Gaspar.
I am as well a ground station technician.
I've been here for 25 years as well.
So we have a monitor on the wall in here
that says data capture and processing facility.
It shows us when the passes for the Landsat
satellites are going to start and when they're going to end.
Aaron, at the top, it says AOS.
What does that stand for?
AOS is an acronym for acquisition of signal.
Okay. And then the next column says LOS.
Let me guess.
Loss of signal.
Correct. Loss of signal.
Okay.
The next pass that's coming up is going to be Landsat 9.
It's going to be at 16:34 UTC time.
And how long is that pass going to last?
That support will run just about 13 minutes from start to finish.
That monitor is kind of like the arrivals and departures at the airport.
But these are always on time, right?
Yes, they absolutely should be on time.
If not, then we've got bigger problems.
Okay. We don't want big problems.
We kind of want this to be a boring pass, you know, no issues.
Just typical, what normally happens in here.
So how many passes per day do we support?
So the ground station is staffed from 5:30 in the morning
until 1:30 in the morning, in which time we can support up to 18
events, three per spacecraft, totaling nine per shift.
That's not to say that we have a loaded schedule every day.
In some cases, the in-view is so small that it does not make it
onto the schedule.
The norm is 2 to 3 events per spacecraft per shift.
What do you mean by in-view?
When the spacecraft is at a high enough elevation where we can have
a really good communication between it and us, between
the spacecraft and the ground station and call it a coherent support.
We're talking to the spacecraft, and the spacecraft is talking back to us.
I'm trying to catch
some of the jargon that you guys talk about. Support--
I sometimes say, well, during this pass-- Satellite pass. Support. Event. In-view.
Everybody's got a little different word for it, I suppose.
What do we expect to happen first for that pass?
Well, about five minutes prior to the support, we will have
an audible that will start up and alert us that the pass is upcoming.
At that point, the antenna controller will start to set up all of the hardware
and software systems that we will be using and monitoring for that support.
In that time, it will start establishing a connection to the LMOC
so that we can see
any commanding that's outgoing, you know, telemetry flow and whatnot.
So it's basically preparing that event.
It's setting up the antenna, preparing that event for the pass to come.
Okay. You mentioned LMOC.
I know that's another one of our acronyms, L-M-O-C.
Can you explain that real quick?
It's the mission control.
They are located at Goddard Space Flight Center,
and they're the ones responsible for all commanding to and from spacecraft.
Okay. Mission operations.
Landsat Mission Operations Control.
Okay,
and when you say commanding, are we going to be, on this pass,
are we going to be sending commands up to Landsat 9, too?
That is correct.
Typically on any given support, 7, 8 or 9,
you will see commanding coming from the MOC going to the spacecraft.
Okay, sounds good. So it's going to be sending us imagery.
We're communicating with the satellite back and forth here.
What are these audibles you were mentioning? For antenna controllers,
several years ago, we downloaded some WAV files.
So it's just that you're going to hear
some audibles pop up alerting us that the pre-pass is starting.
There are also audibles loaded up to let us know that
that pre-pass check worked, and it will give us an alternatively
a different one if things did not set up correctly, telling us that we need to pay
attention, that something did not happen and we need to take action on it.
Okay.
Some sounds anyway, that alert you to something is going on.
Okay.
Can you explain
what I'm seeing on this monitor
up here with these squiggly lines?
That's a spectrum analyzer.
So what we're watching is the S- and X-band
telemetry both up and down to and from the spacecraft.
It's a monitor for us
just to make sure that the S-band and X-band signals look good
and there's not any errors or problems.
We will expect that monitor to change
once the satellite comes within range and is sending data.
As soon as we can see the spacecraft, you will start to see the S-band telemetry.
And once they turn the X-band on, you will see that modulation pop up as well.
Can you tell me the difference between S-band and X-band?
S-band is going to be probably more important to mission control.
This is where the commanding comes from.
So anything that commands to the spacecraft,
that is going to be on the S-band. X-band is what we like here.
That is the imagery data.
That's the pretty pictures that we collect. That comes down on the X-band telemetry.
Okay.
And these are basically radio waves that-- the data is being carried
on radio waves. Is that a good way to put it? Absolutely.
Think of it as your at-home radio on a grand, grander scale.
Okay.
Or like Wi-Fi?
Yeah, absolutely.
I like how you have kind of a video feed of each antenna,
the 10-meter prime antenna, and the 5-meter backup antenna.
So we're going to be able to see those start to move here imminently.
We're not going to shadow on this support,
so it'll be the 10-meter only that we see move on this.
Oh, okay. Only the--
Oh, there it goes, I can see it moving right now.
It was in its birdbath position and now we can see it move, get into place.
Kind of lets you know that everything's working okay.
Controllers, listen up.
Give me a go, no-go for launch. Surgeon.
Go, flight.
EECOM. We're go, flight.
GNC. We're go. TELMU. Go. Control. Go, flight.
What did that mean exactly?
That is just essentially a system check.
That is, our system is ready and set up and did not encounter any errors.
If it were to encounter an error, it would play a different file
that would say, Houston, we have a problem.
That's the one we don't want to hear, right?
We're happy at this point?
Yes, we are.
There's a little bit of a countdown on here until acquisition of signal.
We have 25 seconds.
Oh, I see the S-band,
squiggly lines as I call it, starting to change.
That looks normal so far?
Yep. We're not quite into AOS, but because
we start a little higher than your typical acquisition,
we have some masking zones.
So as that comes into view, you'll see that signal get stronger
and stronger. Launch control,
this is Houston.
We are go for launch. And now we're into the AOS.
Let's be honest, nothing
really changed inside the ops room when the AOS started.
It made my heart leap a little bit, though, like, it's really happening now.
We're communicating with a satellite.
Since the guys were so calm, though, I figured I could keep asking questions.
Eric, can I ask what you're watching for on this monitor?
I'm watching for
our confirmation of
our X-band signals coming down and our S-band signal levels
and confirmation of good packets being transmitted back and forth.
See, when you're looking at your squiggly lines,
if you watch that one, you'll see it kind of get erratic.
That's an actual command coming across.
You'll see with 8 and 9, you'll see it kind of at random.
Yeah.
But if you watch, you'll see that modulation roll across from one side to the other.
It's pretty quick.
Unless they're doing like a command load where it's multiple.
But if it's like one little command, it'll run across pretty quick.
That's one of the things that we're kind of watching for, you know--
There's some there.
Oh, there's a few little extra waves going across the screen.
That was a command going up? Command going up. So
when you think about it, it's really kind of cool.
You know, we do this every day and you kind of forget that you have somebody
sitting in Washington, DC, that is planning a command load
and they're sending that from the ground to us,
and then we're transmitting that bit of information 500 miles
into space to hit, you know, a small vehicle.
You see it so many times you kind of forget what it is
that you're doing, you know?
But when you really pull it into perspective,
it's really kind of a cool thing that we're doing every day.
Oh, no doubt.
So that command that went from our antenna up to the satellite at that moment
that we saw it, how long did it take to get to the satellite?
Typically the MOC can see the return on that.
So once they send it and issue it to us,
within seconds they can see that it's been received at the spacecraft.
Wow. It's very quick. How often do you communicate
with the flight operations team over at NASA Goddard?
When this program started,
we were in contact with them via what we called a scam-a-phone.
It was, think of it as the presidential red phone.
I mean, you queued up and you could talk to these people immediate.
We've kind of done away with that.
But when Landsat 7 started, we spoke to them every support
throughout the support, and we let them know, we have an AOS.
You're coherent.
You can go ahead and command. Hey, we're commanding.
Your X-band is on. Okay, We see that.
Oh, there's your 256.
Here's your telemetry stuff.
And, okay we're at the end of the support. Today,
it's really not that way.
We do not have to be in contact with them
every support. They see kind of what we see.
If we're talking to them, it means that either we or
they probably saw a problem, and we're trying to get around it.
So if the phone doesn't ring, that's kind of a good thing for us.
But we do--
We have a great relationship with all those teams.
We do speak to them quite often.
We have a daily tag up every morning where we talk to these guys and,
you know, they will tell us kind of what's
on the agenda for that day, what's on the agenda for that week,
what's going on, here are things that worked, here are things that didn't.
Oh, by the way, you know, maybe this ground station
missed a support, you know.
So we're in communication with them daily really.
But as far as
what's going on for each individual event,
we don't necessarily have to talk to them on every event.
They know what's going on and so do we.
When I look at the
antenna on the monitor here, it does not look like it's moving.
You know, it doesn't.
You really kind of have to watch.
The spacecraft is moving along quite speedily, but to see it from the antenna,
yeah, you wouldn't really notice it so much.
But these events take, you know, up to about 15 minutes to complete. So
it's moving quicker than what you would believe.
The antenna is indeed moving.
It just looks very slow here.
Once the imagery data
on the X-band hits the antenna, then where does it go?
What happens to it?
So on a typical support, when we're collecting X-band, you're right,
it starts at the spacecraft, comes down to the antenna,
and then that's hard-lined into the RF equipment,
the hardware equipment that you see out on the computer room floor.
Yeah, there's cable under the ground that's coming in here to the computer
room. Okay.
So that data moves down and, you know, as
we collect it from the spacecraft, then we store it on,
we call them AVPDs.
They're a programable demodulator.
We collect that data from there, and then it kind of sits
until the support is over. That data will collect on a drive.
It'll sit for a few seconds, say, yep, okay, this data is on the ground.
And once that is complete, it'll move into our processing systems where we turn it,
you know, from bits, zeros and ones, into pretty pictures.
And then from there it moves into the archive.
And it's not just the scenes of North America,
wherever Landsat 9 is passing right now, it's scenes that it's collected
from previous orbits. Absolutely.
That's all kind of based on the command load. That's up to the MOC.
The beauty of the new spacecrafts, Landsat 8 and 9,
they've made it harder for us to lose data. With Landsat 7,
if you had any sort of a problem, anything that would interfere with the
support, if you didn't collect that data, it was just gone.
There was no way to recover it.
With Landsat 8 and 9, the story is flipped a little bit.
Now, the equipment in the spacecraft is smart enough to know
this data is on the ground. It is good.
We can go ahead and clean that up off the recorder.
This data did not make it to the ground.
Leave that on the spacecraft.
So maybe it's a rainy or a snowy day, and that data just doesn't look good.
The demodulators are smart enough to say, yeah, I don't like how that looks.
I'm going to throw him out.
And you can see that here on the right.
So you will see like an ACK message and a NACK message, basically saying this
is a good piece of data.
I think by ACK, you mean, acknowledge, is that right?
Acknowledge and not acknowledge.
So it's just saying I don't like this one,
so I'm going to throw it out.
But the beauty of that is we don't lose that data.
It stays on the spacecraft.
So it will go down at the next downlink, whether it's us or it's Alaska
or it's, you know, Germany
or any one of our coordinators that we work with. That data is not lost.
We know if it's on the ground. And the system is keeping track of which is which.
Absolutely, yep.
Eric,
tell me about these lines of-- it looks like lines of code
kind of coming in here on this monitor, now, tell me about that.
That's honestly just, it is our
received acknowledgment and not acknowledgment files
that we're getting, just essentially, it shows the time it was received.
If it was acknowledged, the location it's stored at for temporary purposes.
Are you looking for anything in particular?
Just monitoring to see if we have what we have coming in, making sure
that we do get a majority of acknowledgment messages from this.
We don't have any weather today to worry about.
If it was a rainy, heavy day, I would not be surprised to see a larger
number of NACK messages in the system.
Okay, yeah, it's a nice day in Sioux Falls today,
so everything looks pretty good. When it's raining,
when it's windy,
that has an effect, too? Rain, yes. Wind?
Not so much.
Our antennas are in radomes, so they are protected from the wind.
Wind does not affect our antenna, but atmospheric moisture can.
If it
happens to be raining heavily during this
12- to 15-minute pass
and you miss some of the data, you catch it
next time, it goes to another ground station.
We're not losing anything. Correct.
The biggest concern that you would have at that point,
would be more with, like, the mission control guys,
because they're going to be worried about recorder space.
But to be honest, you would have to lose a lot of data
to really fill that recorder up. It would have to be more than just us,
you know, before that really becomes a problem. We see
that if there's like a ground station failure,
you know, and you start losing some of your coordinators
and then they have more limited in-views across the globe.
That's when that becomes more of an issue.
But if we have a rainy or a snowy day,
we would have to have a lot of them for that to be a real large problem,
as far as missing data or overloading the recorder on the spacecraft.
What are you kind of taking notes on right here?
Well, for every pass, we do have a paper checklist.
It's kind of a stats check.
If for some reason something doesn't go as it should, we can record times.
What's failing?
What time things recovered?
Any time we have an issue,
someone always wants to know when it happened.
What elevations, what times,
what was affected, what we did to correct it.
Having something there, right,
for every support to write down on.
It's handy to have.
So just to make notes and to record what we do.
And we save those sheets until our binder
gets full, and then we throw some of them away
because if we're going to have a problem, you'll know
in the next 24 to 36 hours after the event, realistically.
Might still be just a little bit quicker to jot it down quick on a piece of paper.
It is. It is.
This is all pretty routine for you guys, though.
You know,
routine is probably a pretty good word.
You know, when everything is running smoothly.
When things are not running smoothly, routine kind of falls out the window
because every-- there's not a set fix for any one problem.
You know, depending on how things happen, there's an array of ways
to get around and over whatever issue you might have.
But we're one of the few ground stations in the whole globe
that have the capture success rate that we do.
And the team, the entire team is pretty proud of that.
And, you know, and if routine is being
good at what we do with that success rate, I'll take routine every day.
That's fine.
That's right. There we go.
Yeah,
I kind of would hope for you guys that it doesn't get too exciting in here.
Well, it makes the day go faster if it does.
Everything is going along pretty routinely for this pass.
But what would you do
if something unexpected happened?
What if something went wrong here?
The short answer is fix it.
It really boils down to what the problem is
and what systems are affected by the problem.
If we have the unfortunate business of a failure during a support,
we're very limited with time
and have to make decisions and corrections efficiently.
We are quite redundant and we can roll over to backup resources pretty quickly.
Aside from that, we really are a jack of all trades,
watching for errors and assessing what the corrective plan will be
if something comes up.
If this is something that we can correct here or, you know,
or do we need to involve others to get back online?
Does this particular problem require an engineer, system admin, or a database guru?
All these things fall under the eye of the operator.
It was at about this point
that the AOS, the acquisition of signal, ended.
That is, the loss of signal,
the LOS, had occurred.
There wasn't any fanfare for that, no audible for that,
no good-bye from the satellite or see you on the next orbit.
It just ended.
We continued to talk about what they do after the pass is over.
So this pass has ended already.
The next pass is going to be in about 33 minutes,
and that one's going to be Landsat 8.
What do you do until then?
So we've got the data on the ground.
Now what do we do with it. Now we have to process it.
We have to turn it from numbers to pictures.
We're responsible to monitor these data collects and
the successful transfer of that data to its appropriate location.
So we move to the other side of the room and we're watching that data come in.
Data will start moving from the collection point to our processing point.
And then we're watching that data assemble, making sure
that everything looks fine, that the data is what we would expect it to be.
And from that point,
it will go into a success state, and then it moves into ingest,
over to the archive guys. We're very raw here,
so we're just turning raw data into a rough image and gets it into the archives.
So we're watching that.
And it's not just here in Sioux Falls.
Like I said, you know, we've got a handful of other ground
stations that we're watching: Germany, you know, Svalbard, Norway.
As that spacecraft travels around the globe,
these other stations are watching it as well.
So we're kind of a liaison.
So when they collect that data, they have no way to process it.
So it goes very similar to us.
They capture it on a demod, they store it,
and then we collect it from them and we put it into our archive.
And then we assemble that data, process it, and get that moving.
So we're kind of like a first line of defense
if there is an issue. We don't just watch us, we're watching the others too,
just to make sure that all of that data is collected and it gets here
and all materials are going not only for imagery, but the other part of
that is the spacecraft state of health, part of that S-band.
There is a file that is downloaded to us, it's SSOH,
spacecraft state of health.
That file will go out to control as well.
And they can see the statistics of the spacecraft.
We're really watching everybody and making sure that all products
are going to and from where they need to be.
How did we get the data from the other ground stations,
like you mentioned, Germany, Norway and so on.
How did that get here?
That's going to be land line transmission across,
so not quite as glamorous as a 500-mile space trip.
But it is quite,
I mean, it's fast, it's efficient.
And like, what we're seeing on this monitor
right here, there's sort of this--
So here's one--
Ok, this one.
So you can actually see it as, like I told you with the demods,
these are just tail journals.
This one tells me just about everything I need to know.
It's telling me flat out that I'm moving this particular file from the demod,
and I'm moving it out to your storage. You know, so we can see that
as it's coming in and collecting and assembling,
and it'll tell me, hey, I'm sending this particular file out
to the mission control guys so that they have it, you know,
and we see the products that they send back to us,
these assembly files, that all comes through us, and
it's all on hand right there at, on the spot moment.
There's a lot to watch when everything is good.
But you know, when you have issues that stumble across
us, whether it's a data issue or a product delivery issue.
When we were sending some of the X-band information out there,
it was kind of overlapping.
So we would get this assembly file come in.
So we put together
all of these, this data, and we get it pushed off the archive.
Well, here would come another file and say, hey we need you to assemble
these files. Well, the processing system is smart--
smart enough to know that that data has already gone through.
So it's going to throw a flag and say, I can't send it again,
it's already been gone.
So now we need to go into these, these files
and decipher what was good and what was not.
So then we have to edit them, and the file is,
it can be a little daunting. It's quite large.
There's a lot of information in there.
So we're watching a lot of things.
I mean, it's a process.
So this would be like one file that we get,
this is kind of that assembly file that I told you about.
So when you open this up, there is a lot of information in there.
And that's what we would look to see what is good and what is bad.
And this kind of relates back to those RFIDs that we saw on the demod.
They are all assigned a name and a place and a time.
And if I can find one here, it's quite a large file.
So we'll see like these interval IDs.
And it'll tell you if it's an OLI or a TIRS image.
It'll tell you which part of the spacecraft is actually being used here.
And as you go down further, it starts identifying
which scenes were pertinent to that particular interval.
So there is a lot, a lot of information here.
It tells you what type of data it is.
You know, what the resource is.
So here's our data from that last pass.
Oh let's look at that, yeah.
So we have received this assembly file from Goddard.
A majority of that imagery that we collected on that last support,
that's all right here.
So it is in the process of assembling. It's kind of putting all that data together.
What you see here in white is still waiting to go.
Files are--
Files are kind of collecting in,
and it'll tell you if it's a success.
So now this one is delivered. So this data,
all these that are in green, all of that data is now in the archive.
These are scheduled,
so we're still kind of waiting on them. As quick as that was--
That just came in a few minutes ago. Yeah.
It's really quite, quite quick.
And so for each one of these IDs, you know, you got a handful of scenes
that are part of it.
But that assembly file, that's what it says.
It's like, okay, take this, this ID and take these scenes in that ID,
and this one needs to be attached to this guy and this guy and this guy.
And that's what's going to collect that particular packet of scenes.
So how you can order it. And there again,
so now they went from that, scheduled to delivered, just that fast.
Yeah. Just as I was looking at it,
it changed to delivered. It's in the archive.
I'm glad this Landsat 9 pass that we just witnessed was one of the ones
that was routine.
Is that fair to say?
That's fair to say, absolutely.
That was textbook
Landsat 9, Landsat 8 pass, as we would hope for them to be.
And very rarely do we have problems. On occasion,
but, you know, as I told you before, our system is very redundant.
So not only do we have a very good team, but if you look like anywhere in the room
or even out on the hardware rack, you don't see one of really anything.
There's always 2 or 3.
And the reason for that is, if one fails,
we can roll over to a second one and say, okay, this one broke.
Let's get this guy
fired up and get it moving so that we don't lose any more data or any more time
than we have to.
What do you
like best about working here in the ops room?
We're pretty proud in here of, you know, of what it is that we do.
When you look at the grander scale of what this mission is and what it supports,
you know, we're a small cog in a big wheel and it all starts
right here in the ground station.
And, you know, they rely on us to get this data on the ground without a problem.
And, you know, it's just a very neat mission,
and I'm happy to be a part of it.
Eric, what do you like best about working here?
I'm going to echo about the same thing Aaron said.
You know, we're a very small part
of a very big mission that's changing the world, that we can have,
on a day-to-day basis
from our seats in here, we see very little of the actual change of it.
But our impact of it on a grand scale is huge.
For me, it's a little world tour every day, you know,
you get to see imagery from all over the globe, you know,
and it's-- we're not rock stars, but we sure get
our way around the globe.
You know, it's a neat thing. The mission,
it's a good one,
it really is.
Well,
it may not be a historic feat, like a moon landing,
or a hair raising flyby of a distant planetary body.
But most of us do think it's a pretty neat thing that we communicate with Earth
observing satellites
from this little room here just north of Sioux Falls, South Dakota.
Thank you to Aaron Hensley and Eric Gaspar
for letting me in the Landsat ops room for a live Landsat pass.
Aaron and Eric, you're a big part of helping
to keep Landsat flying and the data flowing.
You are rock stars to us.
And thank you, listeners.
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