Ep. 460: Earth from Afar: Remote Sensing

Our Solar System, Planetary Science, Planets | 0 comments

The space age has given us the ability to look at every corner of the globe in every wavelength. It’s revolutionized our ability to predict the weather, keep track of environmental damage, and watch the world change. Today we look at what missions and technologies give us the ability to watch our world from afar.
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This episode is sponsored by: Away.

Show Notes

CosmoQuest’s Image Detective citizen science project – go try it out here!
Cameras first taking photos on V2 rockets
Television Infrared Observation Satellite
Stirling Colgate proposed detecting nuclear weapons with satellites
LandSat series of satellites
Landsat History
RadarSat program from Canadian Space Agency
Light Detection And Ranging (LIDAR)
DSCOVR: EPIC – Earth Polychromatic Imaging Camera
Geosynchronous Satellites


Transcription services provided by: GMR Transcription

Female Speaker: This episode of Astronomy Cast is brought to by Away. For $20.00 off a suitcase, visit Awaytravel.com/astro and use the promocode Astro during checkout. Now, any of you who’ve been listening to the show for a long time, know I travel a lot, a lot. And one thing I haven’t had is a hard-sided carry-on bag or checkable bag or hard sided luggage at all. And, it’s not because I haven’t wanted once, since 2008, it’s because I haven’t found one that didn’t weight 10,000 pounds. And when Away offered us a chance to try their luggage, I said, yes. Because here is someone who says we make lightweight luggage, and it has a lifetime warranty, which is one of those things that’s a must have for me and suitcases.
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Fraser: Astronomy Cast Episode 460 remote sensing. Welcome to Astronomy Cast, our weekly facts based journey through the Cosmos, we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the Publisher of Universe Today and with me is Dr. Pamela Gay, the Director of Technology and Citizen Science at the Astronomical Society of the Pacific and the Director of Cosmo Quest. Hey, Pam how you doing?
Pam: I’m doing well, how are you?
Fraser: Doing really well. So, just a couple of things to mention before we get on with this week’s episode. No. 1 Patreon, just to remember there is a Patreon for Astronomy Cast and your support helps us make this show, and there are 60,000 people that listen to Astronomy Cast. If each one of you gave $1.00 a month, $1.00 a year it would totally pay for Chad’s time, Suzie’s time, maybe our time, which has never been paid for. So, it would be amazing if you could go to Patreon.com/astronomycast. In addition, my regular job is Universe Today and we have a patreon on for that, and again we do video editing, we’re trying to increase the production quality, it’s hard and expensive to make these things. Do, if you can go to patreon.com/universetoday kick in, man, it would mean so much to me and the team.
Pam: So, that’s patreon.com/astronomycast or /universetoday all of it helps us out.
Fraser: Or both.
Pam: Yeah, if you can do both $1.00 each, that’s all we want.
Fraser: Yeah, that would be great. Now, image detectives, we’re gonna talk about it more –
Pam: Yes, yes –
Fraser: – but can you just give everyone, because I finally got to play around with it while we were doing the weekly space hangout, and I was totally hooked and just distracted enjoying playing around with the software. So, where do people go to get involved in image detective?
Pam: So, this is our newest citizen science project, it invites you to help us label 1.5 million astronaut photos and determine what the heck the astronauts were taking pictures of. You can get to it by going to cosmoquest.org/imagedetective and I could see in last week’s stats, that a bunch of you during the recording of this episode did go to our website and did do science while we were talking. This is my challenge to outdo last week and all of you while you are listening, go to cosmosquest.org/imagedetective and do science while you learn science.
Fraser: Right on. And actually, it’s got a great guest feature where you can just kind of play around with it without having to totally signup, so you can get a sense of what the work is gonna be like, and it is so much fun. So, again, what Pamela just said go there.
Pam: And I just have to say, this is one of those citizen science projects that has already proven to me, that some of you are way better at accomplishing this task than I will ever be. So, check out cosmoquest twitch channel to watch me failing, we’re getting help from the audience, so our twitch channel, twitch.tv/cosmoquest.
Fraser: The space age has given us the ability to look at every corner of the globe in every wave length. It’s revolutionized are ability to predict the weather, keep track of environmental damage and watch the world change. Today we look at what missions and technology to give us the ability to watch our world from afar. Now, the problem with the term remote sensing, is it just makes me think of psychics.
Pam: I know, I know.
Fraser: Do we have a better term, than remote sensing?
Pam: No.
Fraser: Earth Observation.
Pam: But the problem is that remote sensing is the term, the actual term for any time you take your senor and you put it somewhere and you don’t touch the thing you’re observing. So, when we put a spacecraft in orbit around mars, and we’re studying the surface of mars, that’s remote sensing. When we have LRO in orbit around the moon, that’s remote sensing. Now Maven, which is also an orbit of mars is only sometimes doing remote sensing, because it actually has the ability to like open itself up and take samples. And that act of taking sample of directly sensing things, that’s like normal sensing.
So, we have sensing, with like mass spectrometers and things like that, and then we have remote sensing, which is where we’re trying to understand a distant thing without touching it.
Fraser: Right.
Pam: Which is also what psychics claim to do, but we’re not gonna talk about that.
Fraser: Yeah, see, this is the problem they –
Pam: I know, I know, they stole our word.
Fraser: Aww, they stole the word, yeah.
Pam: It’s kinda like skeptics got stolen by the climate people.
Fraser: Yeah, all right. Fine, so we’re just gonna –
Pam: Our word, it’s our words.
Fraser: We’re just gonna reclaim it right now.
Pam: Yes.
Fraser: So, let’s talk about it. Now you talked about sort of saying things from afar. What was sort of the first usage, when you can sort of think, what’s the first time that we’ve ever been able to remote sense? You know, from space. I’m not gonna really think about stuff, you know, setting up a camera here on earth. But, what’s sort of an early kind of remote sensing instrument that we’ve had up there?
Pam: Well, this is where you have to go back to the earliest days of spacecraft, and here we’re starting to look back at 1947 when we were able to get picture of earth from 100 miles up. So, we weren’t quite in orbit, but 100 miles up is still pretty darn good. So, this is where we were using V2 rockets to launch cameras and look down instead of bombing what’s below. I’m much happier taking the photos.
Fraser: Right. Yeah, that’s putting Von Brun’s weapons of war to a better use. So, that’s kind of really when the space age, let’s talk about the space age starting with Sputnik, but once you cross that 100-kilometer height, you’re in space, you get your astronaut wings. Every one of those V2 rockets got their astronaut wings before they exploded, and that’s when the space age really truly began and that’s when we started to get this information from afar.
Pam: So, this was the US Vanguard program, which had a combination of German scientists and American soldiers and scientists out in the desert of New Mexico, which is again where we’re going with the American space port that’s now being built out there. And they were launching V2 rockets, and they put cameras on them and looked down, and we’re still continuing to do this kind of ballistic trajectory with some of our instruments on what we call sounding rockets. So, these re rockets that go in to sub orbit, which basically means they don’t go all the way around the plant.
And you can do all sorts of cool science by getting above the bulk of the atmosphere to look in wavelengths that normally you can’t see, because the atmosphere blocks them. Or you can get high enough to get really cool views down on the earth.
Fraser: When did we start to, like I guess, really start to use this technology for staying on top of the environment of the earth, the weather, things like that?
Pam: So, there are a whole variety of different kinds of satellites doing different kinds of things. We had in 1960 the first television and infrared observation satellite, which was one of the first that allowed us to start monitoring our planets weather. But we also had weird satellites that did things, like try and confirm whether or not the soviets were testing nuclear weapons, and these weren’t imaging so much as they were looking for gamma rays, which is actually how the first gamma rays bursts got detected.
Fraser: Right, yeah, yeah, yeah.
Pam: So, remote sensing sometimes senses unintended directions.
Fraser: Yeah. Can you just take a second, I mean, we did a whole episode on this, but that sort of is so interesting about those first spacecraft, can you just go in to a little more detail about that story?
Pam: Back in the 1960s the Vela satellites were designed to look for nuclear tests. Our concern was that the Soviet Union would break the international treaty saying, though shalt not test nuclear weapons, we are done blowing up atolls and deserts and things like that. And, because, they’re kind of on the other side of the planet, the way we were going to monitor whether or not they adhered to these treaties, was we were going to look for the effects, in the form of gamma ray radiation that would be given off by a nuclear test with orbing satellites. Thus, the Vela satellites that were capable of detecting gamma rays.
Now the thing about gamma rays is that they’re super hard to focus to detect. So, you basically throw out a detector, and it’s going to detect gamma rays coming from all sides, and sometimes through the planet and things like that. it’s – well it’s more neutrinos that go through the planet, but the gamma rays go through the spacecraft. And so, these early detectors didn’t have directional orientation, you might say. So, we started detecting gamma rays, we started realizing that they weren’t coming from trust real sources. And after we got angry at the soviets and then realized we shouldn’t have, we realized the universe was doing something weird. But there was that intermediate step of getting angry at the soviets and trying to figure out what was going on.
Fraser: Right.
Pam: And, instead of leading to war or other bad things, ended up leading to an entirely new field of astronomy. And now we know that gamma ray bursts are associated with things like gravitational waves, with super novae, with neutron stars with magnetars that are reorganizing their magnetic fields. There are all sorts of amazing things out there. Mostly far, sometimes near that our generating these high energy wavelengths of light, and we know this because we were trying to remotely sense the soviets testing nuclear weapons above the surface of the planet.
Fraser: Now, one of the most successful series that I sort of think about are the land sats. And I remember seeing land sat images, even when I was a kid, you would see land sat, these amazing photographs of the earth from space, but they would have sort of interesting colors. And those were one of the most successful, and there are still land sats going up, new missions going up, you know, every couple of years.
Pam: So, we have a whole variety of different series of spacecraft that get used by a variety of different space agencies and science agencies to monitor our changing planet. And the land sat satellites are, I think, probably the most well-known of all of these. So, the name land sat, first came about in 1975, but the program started in 1966, and the work was really pushed forward in the late 70s by Jimmy Carter. So, it was through the ecological movement of the 60s and 70s, that NASA and the National Oceanic and Atmospheric Administration, this is NOAA, was involved in getting these images.
And they have this beautiful full color imagery which you referring to, and it’s used to monitor river flooding, to monitor changes in forests, to look at the combined wavelengths. What happens when these forest fires tear through Canada and that American west, the first of this series was launched in 1972, and like you said, these are still going today. We’re currently up to using land sat 8, it was launched back in 2013, and we’re kind of hoping that in 2020 we’ll be able to launch land sat 9. So, these are our fairly long-lived spacecraft, not all of them have survived, land sat 6 didn’t exactly make it to space.
But, what is really great about this series is they build on that same tradition that we saw with Cassini of taking a past space craft model, tweaking it a little bit. Cassini built on the mariners series, and with the land sat series, it’s its own series of spacecraft, and each of these is either identical to the predecessor or just an incremental update. Spacecraft wear out, they break down, but the technology is rock solid. So, we just keep updating a little, but keeping the core design to keep the costs down and the science coming.
Fraser: Yeah, and it’s such a great way, I mean, we think about some of the ways that we explore other worlds, mars, things like that. To just have this platform that just gets used again and again and again, but they put a better CCT array, a better camera on it, better faster communication, things like that. And the thing that’s great about a lot of these devices, as you said. They’re looking in wavelengths that the human being can’t see, and different wavelengths reveal different kinds of this here on earth and on other worlds. Can you talk a bit about, sort of what kinds of other wavelengths are useful for different kinds of observations that you’re trying to make?
Pam: So, right now, one of the wavelengths that’s getting used a lot to monitor the [inaudible] [00:16:32] and I’m probably destroying the pronunciation of that. A volcano down in Bali, which is probably going to erupt shortly, yes, this is me being excited about death and destruction. They’re monitoring this volcano and the infrared so they can see the place in the volcanic crater that are heating up, omitting steam, they can see the flanks of the volcano. And so, here by looking at wavelengths that our eyes can’t see, we’re able to systematically see that this volcano is hopefully going to do something really cool shortly.
So, it’s beyond just using plain old infrared, we also sometimes do net and interesting things, where instead of looking in a straight color of light, we do things like we look for neutrons. So, we look for scattered neutrons coming off of the moon for instance, because that is indicative of there being water beneath the surface. So, we when we do remote sensing we are studying things in colors of light, so we use infrared, we use ultraviolet, we use plain old eye ball colors, the visible colors of light. We also reflect radar off of things.
Fraser: Right, and that’s what I was sort of gonna bring up next. Is there’s a sort of famous Canadian mission called Radar Sat, and we talked a bit about this with Cassini, how it had a ground penetrating radar. We talked about those with Arecibo, radar lets you see some things that you just wouldn’t normally be able to see in any other way. So, let’s talk about that.
Pam: So, with radar, what you’re doing is you’re sending out a pulse of light in the same color as the radio that you detect with the radio in your car. I just used a wavelength name to define the wavelength, sorry about that everyone. So, with radar you’re sending out a pulse of radio light, and then you’re detecting how long it takes to come back. And, you do this in a geometric sweep, if you’re trying to measure something out or you move the thing that’s omitting the radar, which is what they do with spacecraft. So, as your spacecraft goes along, it omits a pulse of radio and then you measure how long it takes for that pulse to come back.
If it comes back faster, something is closer that’s doing the reflecting, it if takes longer to come back, the thing that it’s reflecting off is further away. And, nowadays, we’re doing this radar technology in more than just radar, and this is where we start to get in to lidar, which is lesion versions of radar. So, the shorter the wavelength of light that you use to do the reflecting, the smaller you’re able to measure things. And so, as we get to visible colors of light that we’re reflecting, which we’re not quite there yet, but as we get towards that we’re able to measure smaller and smaller differences.
So, the key is send a pulse of light, count how long it takes to come back, and that tells you how far away something is.
Fraser: Another great technology is some kind of spectrometer, so that you can actually determine the chemical constituents of something. How do those work?
Pam: So, in this case, it’s not as much if you’re doing mass spectroscopy, that again is not remote sensing.
Fraser: That’s hands on, that’s regular sensing.
Pam: Exactly, now if you’re doing light spectroscopy, this is where you’re looking at the colors of light that in general are reflected off of something in the case of remote sensing. So, sunlight reflects off the moon, you measure the spectrum of light that’s reflected. Some colors are going to be absorbed by that surface, some are going to be omitted by the surface. Sometimes the light that hits the surface is absorbed, re-omitted as a different color and by measuring these colors you’re able to get hints of what’s in the surface, what’s doing this absorbing, and you’re able to get at the temperature of that surface, but looking at the overall black body distribution or how it’s reradiating light.
Fraser: That is really cool. There was sort of an interesting mission planned, we talked about this in the weekly space hangout, that they could send 50 separate little five-kilogram satellites to observe 300 different asteroids, they’d be the equivalent of a tiny little set of binoculars sized lens, and a spectrometer. So, they could just know what the chemical composition of each one of these asteroids was, at a reasonably high level of resolution. But, this is the kind of thing I know, like, curiosity has the ability to just look around with its eyes and see the chemical makeup of the rocks around it. And it can even shoot a laser.
Pam: And, this is this strange mix of do you call this remote sensing or local sensing with curiosity because you’re imaging it instead of touching it, but curiosity has the ability to go zoomp and touch something and grind away on it. Which is kind of rude, but it has that capacity.
Fraser: But it can see with its eyes the landscape around it, and map out the chemical constituents of it, I think it does it with ultraviolent, anyway and then, as you said, it can go right up and then grind on something interesting piece of mineral. But, it’s a really handy way to sort of quickly look at the whole landscape, find what you want and then move close. I think, you know, when I think about what’s happening now here on earth, there are so many amazing missions and satellites, both from NASA and the Europeans.
I’m sure there’s a bunch from the Chinese and the Russians that we don’t know about, but, and I’m sure there’s a bunch from NASA or the US Military that we don’t know about. But, you know, Terra, Aqua, there’s all these satellites that are mapping out the ground and mapping out ice flows and mapping out river systems, and water systems and everything, like, weather systems –
Pam: Discover.
Fraser: – discover, yeah. Which is one I always point to whenever someone’s like, you know, [inaudible] [00:22:53] well, how come there’s no live picture of the earth? And I’m like, okay, just go check out the discover pictures, those should be what you’re looking for.
Pam: And it has the best named instrument. I really want to meet the person who came up with this acronym, and like shake their hand and buy them a coffee. Because, EPIC stands for Earth Polychromatic (which is a fancy way of saying multicolor) Imaging Camera. And just the fact like that came up with the word polychromatic, so that it would be EPIC is epic.
Fraser: That’s awesome. So, what does the future hold for remote sensing? What are some ideas of missions? I mean, is any of this coming up on the Decadal survey do you think? What re some sort of big ideas, missions, capabilities for the future of remote sensing?
Pam: It’s hard to know exactly what will come out of the Decadal survey process, which is something that’s probably about to start spinning up this year. We know that we don’t have the full suite of weather satellites that we really need to get very accurate far out forecasts, and a lot of our weather satellites are getting kind of old and need replaced. So, what we’re looking at is a future where we need a suite of sun synchronist satellites, these are orbiting imagers that always have the same sun, earth angle beneath them, and sweep across the entire planet.
We need to have our full suite of GEO stationary satellites that are always sitting there looking down. And, right now, we’re augmenting all of this, also by, well as we brought up at the top of the show, asking the astronauts to hang their head in a window, not out a window, you don’t do that on the space station, and look down at the earth and grab hand held photos of our planet if they happen to be what’s straight above what we’re most interested in. It would be awesome if we could have more spacecraft up there, so that we had better time coverage from different angles.
And, it’s that time coverage that, at the northern and southern latitudes is most difficult, because the GEO synchronist satellites just can’t get a good view on the top of the world.
Fraser: It’s pretty amazing the resolution of even the [inaudible] [00:25:26] Google maps. I mean, some of it’s aerial, some of it’s space based. But these new, even private missions that are going up and mapping the earth at higher and higher resolutions. I forget what we’re down to, a couple of meters in resolution now, a meter, meter and a half, smaller than that even.
Pam: Yeah, I have to admit, I’m not sure, and they do just to reinforce this, Google maps is largely aerial photography.
Fraser: It’s largely aerial photography, but there’s a new missions digital globe, I think. And even Google bought one of these –
Pam: And Terra Server.
Fraser: – and Google bought one of these companies, and so, because there’s so many commercial private uses for this kind of data for surveying, for agriculture use, for city planning, things like that, there’s a pretty busy industry of putting these satellites up and selling the imagery to various services. So, we’re not quite at the point, you know, that Simpsons episode, where it’s in real time and Homer looks up and sees the satellite looking down at him, but we’re getting close.
Pam: And there’s a lot of real need for this. For instance, right after the Puerto Rico disaster with Hurricane Maria, a lot of people were frantically trying to get imagery to look down on places that we hadn’t been able to get cars in to yet. A lot of the interior of Puerto Rico is still basically cut off, because the roads have been destroyed. And, again, with all of the disasters going on around the world, if we can have a spacecraft getting a safe UN, it helps us figure out where to direct the helicopters. So, having that view really helps, and having that view beforehand helps us better figure out exactly where storms are going.
We’re currently several days out on the newly formed tropical storm, Nate, at south of the Gulf of Mexico and we’re already starting to able to see that people need to be battering their hatches on the Gulf and there’s a chance of a direct hit on New Orleans. Being able to pre-ahead of time is the reason that lives haven’t been lost in the numbers they might have been, with Irma and Maria and all of the terrible weather that we’ve had this year.
Fraser: I’m more and more worried about what’s going on in Puerto Rico, and –
Pam: I’m horrified.
Fraser: – yeah, and I really really hope that they can get back to some kind of power, without power you get chaos. And peoples’ lives – so, this is a time when remote sensing is more important than ever, to know exactly where – I mean, have you seen the pictures of Puerto Rico at night, and that it’s just dark –
Pam: It’s dark.
Fraser: – compare to what it was, back when it had full power. That is a great indication to show you where people are in trouble. In addition, as you said, the aerial photography, the satellite photography, and using some of the other wavelengths to see things like vegetation damage, flood zones. We’re gonna need this technology for these kinds of disasters more than we ever have.
Pam: And in the past, we’ve used remote sensing of scattering light off of foliage to do things like look for pot crops hidden in the forest, this is like legit, a thing that we’ve used remote sensing for, as a species. Now, instead what we can start to do is look to see where has the foliage been completely destroyed, what is left? And because of our insistence of trying to find marijuana crops, we actually have a good understanding of how different kinds of foliage and plants reflect light. It’s amazing what we can do, and it’s now proving that we need to be able to do this for law enforcement, for civil protection and just for humanitarian reasons of finding that person that is out there still needing help.
Fraser: Thanks Pamela, we’ll talk to you next week.
Pam: Sound good Fraser.
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[End of Audio]
Duration: 31 minutes

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