Eyes on Earth Episode 90 – Landsat 8 Turns 10

TOM ADAMSON:

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. My name is Tom Adamson, your host for this episode. In 2022, we celebrated the 50th anniversary of the Landsat project.

We had the excitement of the Landsat 9 launch the year before that, and we have the 50th anniversary of EROS coming up this year. There's a lot going on. In all of these commemorations, there's another significant milestone right now. Landsat 8 launched 10 years ago. Our guest today is Keith Alberts, acting Landsat flight operations project manager. Keith, did we expect Landsat 8 to still be operating after 10 years?

KEITH ALBERTS:

Thanks for the intro, Tom. Yes, Landsat 8, or some of you may recall at the time it was called the Landsat Data Continuity Mission. It was called that until the launch, and it launched on February 11th, 2013. Yes, I think it was expected that Landsat 8 would still be operating after 10 years. And in my experience, if the Landsat satellite can still collect useful science, the Landsat program is going to continue to operate as long as they possibly can. So we hope that it continues to operate for many years to come.

TOM: 

How long do Landsat satellites typically last?

KEITH: 

It's a little hard to answer that in general terms because there's many factors that come into play. For example, one key aspect is the satellite's design life. So in the case of Landsat 8, it was designed with a five-year design life and 10 years of consumables. So what that means is that when the engineers built Landsat 8, they designed it to last five years. So in doing so, they look at things like individual components, expected lifespan and things of that nature. That in turn drives decisions for things like inclusion of redundancy in certain subsystems for the spacecraft. And then the 10 years of consumables basically means fuel. So there is enough fuel to last at least 10 years, and generally there's enough to go well past that 10 years. So those requirements are kind of examples of what drive the design. But we've been really fortunate with Landsat that we've often exceeded that design life. And just as an example, Landsat 7 also had a five-year design life. And as you're aware, that is now around 24 years old and still collecting science data. And actually, Landsat 5 had a three-year design life, and that provided science data for nearly 29 years and, in doing so, set a Guinness World Record for the longest operating Earth observation satellite.

TOM: 

Landsat has a pretty good pedigree for long-lasting satellites, especially since Landsat 5 onward. 

KEITH:

Yes.

TOM: 

Well, I just checked in the USGS Earth Explorer website. Landsat 8 has now acquired over 2.5 million images. That seems like a lot of work. Are the instruments showing any signs of wear?

KEITH:

So that might be a better question for the calibration and validation team, since they're the ones that regularly measure instrument performance. But I will say from the physical instrument aspect that the flight operations team monitors daily, both instruments continue to operate well. Of course, TIRS did have, and TIRS being the thermal infrared sensor, did have an anomaly back in, around, I think it was 2014, 2015 timeframe. The engineers were able to come up with an ingenious way to overcome that limitation, and it continues to provide quality thermal data today.

TOM:

You mentioned the thermal infrared sensor anomaly from a few years back. Have there been any other challenges that the flight operations team has had to overcome?

KEITH:

Yeah, in flight operations there, and probably with any operations, there's always challenges, probably from a daily perspective. Just as a few examples, you know, if there's a ground station that's down, you know, they need to work to schedule around that and find other sites to downlink. Or, as you've maybe seen in past website postings, we may have to plan a mitigation maneuver to avoid space debris. And then another big obstacle, of course, or challenge was COVID. And that especially impacts an operational environment where you have people working on shift and need to be there to perform operations. But from a satellite perspective, you know, we occasionally might have an anomaly on the spacecraft. And when that happens, the flight operations team works around the clock or as long as it is needed to investigate and recover from that anomaly. Sometimes it might even be a more extreme instance, an example of, like, the TIRS anomaly that required quite a bit of analysis and engineering to come up with a way to work around that, which ultimately changed, kind of, our operations concept, how we operate. But that's the benefit to have then really, really good engineering team and this cross matrix team that can overcome issues like that.

TOM:

Okay, Keith, time to try to predict the future. How much longer can Landsat 8 continue to operate?

KEITH:

Well, I'm not good at predicting in the future, at least not with any certainty, I guess. But at this time, there's no reason to believe we don't have many more years of operations. And we'll certainly do what we can to set it up for all the success we can. In an ideal scenario, we'd continue to operate until the limiting factor is the the remaining fuel.

TOM:

Is that typically what would be expected to happen with any Landsat satellite, that the instruments would function until it runs out of fuel?

KEITH:

Again, that's that's the ideal scenario. That's not always the case. But if you can make it till you run out of fuel, that's certainly, you know, considered a win.

TOM: 

Okay. I mentioned that Landsat 9 launched recently. That was September of 2021. And the Landsat 9 has the same design as Landsat 8. Does Landsat 8's longevity give us a good idea for how long Landsat 9 will last?

KEITH: 

It does in a way. So it does have a very similar design, and it has the same design life as Landsat 8 does, with the exception of the TIRS instrument, or TIRS-2 for Landsat 9. That has a five-year design life, whereas the Landsat 8 TIRS instrument had a three-year design life. Otherwise it's the same. I think one benefit we have, or advantage, I guess, is that we have operating both Landsat 8 and Landsat 9, and given that they have very similar designs, if we notice something on Landsat 8, or experience some sort of anomaly, one of the first questions that the flight operations team asks themselves is, "Could this apply to Landsat 9?" And we go look at that. So in that regard, it kind of sets us up with some insight that we maybe normally wouldn't have. So nothing, of course, is certain, and space can be a harsh environment, but we hope to get many more years out of Landsat 8, and Landsat 9, too, of course.

TOM:

What does having 10 years of data from Landsat 8 mean for the remote sensing science and the 50-year archive of Landsat data?

KEITH: 

So, I'm not an expert on all the various ways that science can be used, but from my perspective, every Landsat mission has played a major role in that. Of course, with Landsat 7, 8 and 9, continue to play a crucial role in that, that add data to the archive, and that's of course available to the public for free. As far as the importance to science, I'm always amazed at the different ways that the Landsat data can be used. So you previously mentioned that there's around 2 and a half million scenes that have been added to the archive from Landsat 8, and that's, in very simplistic terms, in my mind, if we didn't have Landsat 8, that's 2 and a half million scenes that wouldn't otherwise be available for that analysis that the scientists perform.

TOM:

I think it's important to remind everybody that, as you said, Keith, Landsat 8 was originally called the Landsat Data Continuity Mission. LDCM is what they called it until it reached orbit. So there was a big focus on continuity with Landsat data. That was sort of the purpose at the time - we're going to make sure that we have a continuity of Landsat data connecting the older Landsats to this current Landsat and into the future?

KEITH:

Right. That's especially important for temporal analysis, to have that continued continuity of the land Earth change.

TOM:

So there's really no signs of old age with Landsat 8?

KEITH:

There's nothing that I'd characterize as concerning or unexpected after 10 years of operations. It's pretty nominal operations.

TOM:

OK. Well, I suppose boring is good in terms of keeping it operating.

KEITH:

That's actually what we always say in operations is a boring day is a good day.

TOM:

That's great. I'd like to thank Keith Alberts for talking with us today about Landsat 8 and commemorating its first 10 years of operation. 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 to Apple or Google podcasts.

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