|Aura Webcast: Dr. Phil DeCola, Aura Chief Scientist|
Host Tiffany Nail: Now that we've heard about the launch vehicle, let's learn about the science of the Aura mission. The chief scientist for the Aura mission, Dr. Phil DeCola, takes a closer look.|
DeCola: Hi! I'm Phil Decola, NASA's chief scientist for the Aura mission. So, we just heard Dr. Asrar tell us Aura is a mission dedicated to the health of Earth's atmosphere. We need a healthy atmosphere because in addition to giving us the oxygen we breathe for life, we know that it plays other important life-sustaining roles. The Earth's ozone shield in the upper atmosphere, known as the stratosphere, protects all life down here at the surface from destructive UV radiation.
The Earth's air quality in the lower atmosphere where we live, known as the troposphere, is fundamental to our health and the health of ecosystems.
The Earth's climate is affected by changes in atmospheric composition. How will Aura help us to understand and protect the very air we breathe? It does so by measuring the Earth's atmospheric composition as it orbits above the Earth. Trace gases such as carbon dioxide, water vapor, ozone, methane, nitrogen oxides, chlorofluorocarbons and aerosol particles, just to mention a few, are the only parts of the mixture that have a strong influence on -- and response to -- the Sun's radiation and Earth's radiation.
For example, the Sun's radiation -- peaked in the visible wavelengths -- warms the Earth's surface. And the warm Earth emits radiation -- infrared and longer wavelengths -- back out to space. If it were not for the greenhouse effect, caused by trace-gas absorption of Earth's radiation, the average global temperature would be 60 degrees colder than it is -- making for a much less hospitable climate.
So you begin to see the importance of these trace gases -- the gases that are the focus of the Aura mission. They are as important as the oxygen we breathe to sustaining life on Earth. From Aura's vantage point, as it orbits over the poles 16 times per day with the Earth rotating beneath, Aura gazes down through the atmosphere beneath the spacecraft, allowing us to survey on a daily basis the 3-D distribution of trace gases over the entire surface of the Earth. This is needed information for answering the scientists' questions and supporting policy decisions that affect the health of Earth's atmosphere.
On the Aura spacecraft, there are four instruments that comprise the orbiting laboratory: the Tropospheric Emissions Spectrometer (TES), the Microwave Limb Sounder (MLS), the High-Resolution Dynamics Limb Sounder (we call that HRDLES), and the Ozone Monitoring Instrument (OMI).
Each of the instruments is a technological marvel with unique capabilities and science goals, and I would like to tell you about a few of their features. The MLS instrument contains sensitive radio receivers that listen to natural microwave signals emitted by about 15 important chemical species in the atmosphere. It does this all at once, looking toward the horizon in front of the spacecraft.
The breakthrough for the TES is that it is the highest resolution mission spectrometer ever flown in space. It looks at infrared emission from the atmosphere behind and beneath the spacecraft to make unique, brand new measurements of pollutants in the troposphere. Ozone is a key product of pollution, which is hazardous to human health and ecosystems. With these kinds of measurements, we will be able to make the first global air quality assessment.
HRDLES measures infra-red emission as it scans across the horizon behind the spacecraft. The scan mirrors can be positioned so accurately that we can point at a dime halfway around the world. What does this buy us? It buys us the ability to study the mixing of trace gases, such as water vapor.
Thin filaments of water vapor in the atmosphere, like the cream when you begin to stir your coffee, get longer, break off and mix into the surroundings. With HRDLES' high resolution, we will be able to observe this mixing for the first time and begin to understand it on a fundamental level.
OMI is a wide-swath imaging spectrometer which stares beneath the spacecraft. It is the only instrument that uses the Sun's light directly to make its measurements. It does this in the visible and ultraviolet wavelengths. The big breakthrough with OMI is in its spatial resolution, the best ever for this kind of measurement, allowing us to make urban-scale, air-quality measurements from space.
So this is just a quick look into how these measurements each do their job, but our plan is to use them in concert. Links exist between the issues of climate change, air quality and ozone depletion. Understanding these connections is important for understanding change on regional and global scales.
As the spacecraft orbits at about seven kilometers per second, the four instruments will look ahead, beneath and behind the spacecraft and be able to see the same parcel of air within about 13 minutes -- a small enough time that chemical changes and mixing will be inconsequential. So, we're essentially able to look at a parcel of the atmosphere with all four instruments simultaneously. Combining the data from all four instruments will help us to unravel the complex interactions among climate, air quality and ozone depletion.
I look forward to our launch with great anticipation of the scientific payoff, and the resulting benefit to our nation and our neighbors on the planet.
Nail: We're pleased to have Dr. DeCola with us now live on NASA Direct! This sounds like an incredible mission and I know the team out here at Vandenberg is ready to get Aura off the ground this weekend.
DeCola: Yes, we're all very excited and very happy to come to this day, and thank you for inviting me to come and speak with you about the Aura mission.
Nail: Over the past several weeks we've had our NASA Direct! question boards open, and we've received many questions about Aura from all over the globe. Dr. DeCola is here to help us answer them.
Our first question comes from Sara from Riverdale. What planet will Aura be studying?
DeCola: I really appreciate that question, because I think many people may be more familiar with NASA's role in exploring the Solar System and the universe beyond, and less familiar with the fact that NASA plays a very important role in studying the Earth, as well, as a system from space, because we're able to get global observations from our NASA satellite missions observing the Earth.
So, it's really a great question and, in fact, the information that we gain about Earth through these missions to study Earth are very important in enabling some of NASA's work in exploring the rest of the Solar System and the universe beyond.
Nail: Our next question comes from Damian from Florida. How will Aura help improve our life here on Earth?
DeCola: Another really good question. Thanks for that one. You know, the atmosphere, which the is the focus of Aura -- Aura is a mission designed to study the very air we breathe, to understand it in a better way and then as a result be able to protect it.
Earth's atmosphere, as I think most of us know, provides us with the oxygen we need to breathe. The oxygen and the nitrogen which comprise 99 percent of the Earth's atmosphere, are certainly important. But it's not that that Aura is studying; we're studying the fraction of the one percent that's left -- the so-called trace gases and aerosols, particles in the atmosphere, that really are also very important in sustaining life on Earth. The Aura mission will provide us with a wealth of information about those trace gases and aerosols.
Nail: Yavor from Swarthmore tells us a little bit about something and asks questions. How will the analysis performed by Aura be different from previous ozone layer surveys? I've seen many images showing the progression of the hole in the ozone layer; is that analysis not sufficient? Given the fact that we're already imaging the ozone layer, do we need this expensive new satellite?
DeCola: Great question. You know, we have had many missions before to study, in fact, the very important life-protecting stratospheric ozone layer. It protects all life from harmful UV radiation at the surface, and we've learned a great deal. The scientific research and the observations we've obtained in the past have led the nations of the world to form treaties to protect the ozone layer, limiting the production and release of ozone-depleting chemicals.
As a result, we see that those ozone depleting chemicals are on the decline and that the ozone layer should respond, but we have new questions: What's the relationship between global warming, climate change and ozone recovery? And we see evidence that there are strong connections there. For that reason and others, we need to continue observations and to gain more information, and Aura will provide enhanced information for studying stratospheric ozone.
And, of course, what's also important for Aura is that it's also going to provide a wealth of information about other life-sustaining aspects of our atmosphere, such as air quality and climate.
Nail: Chris from Manila asks: If ever Aura detected that our ozone layer is in danger, what can NASA do to improve the ozone layer?
DeCola: Well, similarly, I will answer that in fact, we have observed in the past that the ozone layer has been negatively affected by ozone depleting chemicals such as chlorofluorocarbons. And because of the research that we've done and the information we've been able to obtain, the nations of the world have taken steps to protect the ozone layer. The Montreal protocol and its amendments regulating ozone depleting chemicals is having beneficial effects. So, things have been done to protect the ozone layer as a result of our observations.
Nail: Nancy from Naples has an excellent question. We have all been told of global warming and the dangers of the ozone layer being depleted. If these are related could Aura possibly make the world stand up and take notice and action to the problems and could it not correct itself if given a chance?
DeCola: OK, it seems like everyone is rightly concerned about the ozone layer. This is, as we've already said, a complex problem and our understanding that we're gaining over time shows us that there are very strong interactions between important atmospheric properties, such as global climate change, global warming and ozone depletion. And so it's really important for us to continue to study this problem and to monitor how ozone is responding as the atmosphere continues to change.
Nail: Bill from Miramar: Will the EPA use any of the information gathered from the Aura mission to employ any future policy?
DeCola: Great question. This gets us to another important aspect of the Aura mission, it's a study of global air quality. In fact, we are working closely with our partners at the Environmental Protection Administration and at the National Oceanic and Atmospheric Administration, who both have responsibilities in forecasting air quality.
The global data from Aura will be of great use to modelers who use this information to improve their ability to forecast air quality. This is a very, very important goal of the Aura mission to provide that kind of information and for the benefit of society to have better air quality forecasts.
Nail:: Sagar from Mumbai: Can Aura study or check the presence of the atmosphere on different planets as well as Earth? Can Aura predict the time it will take for our ozone to become depleted?
DeCola: Very good question. Of course, since Aura is orbiting Earth and the four instruments onboard Aura are trained on Earth's atmosphere, it will not provide direct information about other planets. But the kind of information we get about understanding Earth's atmosphere and its evolution really is very useful in looking for signatures of life in other places in the universe.
We know that we have life here on Earth, and the atmosphere and the study of it, provides us with signatures that we can look for in other planetary atmospheres in our Solar System and beyond that can tell us about the presence of life. And so, while we're not looking directly at other planets with Aura, the information that we derive is relevant to that.
Nail: Jean from Florida: How will Aura be able to study the chemistry of the Earth's atmosphere if it's 400 miles above the planet?
DeCola: Ok, that's a really good question as well. What Aura is using is instruments that do what we call "remote sensing" of the Earth's atmosphere. Three of the instruments on Aura are looking at the radiation that's emitted by species in the Earth's atmosphere, and one of the instruments on Aura is looking at the way solar radiation comes into the Earth's atmosphere in ultraviolet, invisible wavelengths and scatters back to the spacecraft.
So, by looking at the radiation -- the infrared and microwave radiation that's naturally emitted by Earth's atmosphere as it goes through the atmosphere and back out to the spacecraft as it orbits in space, and the scattering of ultraviolet, invisible wavelengths coming back to the spacecraft -- we're able to analyze that light coming into those four instruments on Aura and then interpret that information, interpret those signals to derive what the composition was in the atmosphere at the time when the signals were passed through to the spacecraft.
So, this is what we call remote sensing, and that's how we get the information that we're hoping to get from Aura.
Nail: Rich from Elk Grove, Ill.: How will Aura help in weather forecasts? Will Aura find a link between the ozone and the weather patterns here on Earth?
DeCola: This is a very hot topic of research. How can information about atmospheric composition improve weather forecasting? Right now, scientists are looking at how, for example, taking information about stratospheric ozone and importing that information -- what we call assimilating that information -- into numerical weather prediction models can actually improve forecasting. This is a hot topic of research. It was not a principle goal of the Aura mission, but it's something we were hoping to learn more about through Aura.
Nail: Junichi from Niihama-city: Suppose a decreasing ozone layer above Earth is the cause of ultraviolet rays. If human beings and other living things are exposed to the rays, what kind of damage could be caused?
DeCola: Well, indeed, we know that ozone plays a very important role in controlling ultraviolet radiation at the surface. It's not the only controlling element, of course there's cloudiness in the atmosphere, aerosols and the angle of the Sun's rays that varies with seasons in location to the globe, all contribute to the intensity of solar radiation, ultraviolet or otherwise, hitting the surface of the Earth.
But we also know for sure that ozone plays an important role, and we of course we know that certain ultraviolet wavelengths can be very damaging to our DNA and therefore to life. So, ozone isn't the only thing that controls it, but it's a very important element in the equations that control surface ultraviolet radiation.
Nail: Danny from Allendale: I have some questions about ozone and Aura. How thick is the ozone? If Aura finds that ozone is not recovering by itself, is there any way to add ozone molecules at the right altitude?
DeCola: Interesting question also. You know, ozone we think about mostly in terms of the stratospheric ozone layer, but ozone is present in all of our atmosphere. It's present at the surface, which is a bad form of ozone because as we breathe it and we're exposed to it, it's an irritant and can damage living tissue.
As you move up in the atmosphere, in the middle troposphere, where ozone is important and good for cleansing the atmosphere, it plays an important role in oxidizing and removing pollutants, converting pollutants to a form where they're more easily removed from the atmosphere. Then, moving up to the upper troposphere, it can be an important greenhouse gas, which could be considered to be a bad influence. Again, in the stratosphere, where we're all familiar with its important good role of protecting life at the surface.
Now, if you take the amount of ozone -- most of the ozone is in that stratospheric ozone layer -- if you were to take it from the upper stratosphere and bring it down to the surface, at the surface temperature and pressure, it would be a very, very thin layer, only about three millimeters thick. So, you can see how, given the important role it plays, it really is a very fragile resource we need to be mindful of.
Nail: I totally agree. Michael from Belgium: Will Aura be able to make a map of the molecules we have in our atmosphere? Are we expecting to find a new type of molecule? If yes, what instrument will be used for this?
DeCola: Well, for example, the Tropospheric Emissions Sounder, nicknamed TES, one of the four instruments on Aura... We have some important primary goals with TES, certain molecules we are going to derive for certain, such as ozone, methane, water vapor, nitrogen oxides, nitric acid, very important molecules in our atmosphere. However, because of the high resolution and breadth of wavelengths that TES is going to measure coming from Earth's atmosphere, there will be a wealth of other molecules that could be derived.
Scientists will be able to, in the future, take that data and continue to derive and study molecules that we may become aware are very important to derive in the future. It's almost like an ice core of the atmosphere; it's almost like what we're doing say, for example, in the Antarctica, deriving ice cores; this will be a data set that will be able to be used for a long time and be mined for information in the future that we may not even realize its importance today.
Nail: Very fascinating. Robert from York: What kind of future forecasts/predictions can be made for the next millennium and further on the atmospheric conditions or ozone depletion rates since this is a limited sampling?
DeCola: That's right. The Aura mission has a design life of five years, but the information that we are getting will help us improve our ability to model the atmosphere and the whole, entire Earth system, which will then continue to give us benefits into the future. As we improve our ability to understand and model the Earth's atmosphere, then, as you say, on into the millennia, we'll be able to have a better understanding of what the future holds for our atmosphere and the whole Earth system.
Nail: Our last question comes from Palak from Chicago: Will Aura warn us of high ozone levels? What is the difference between Aura and weather satellites?
DeCola: Well, as I mentioned earlier, Aura is not, per se, a weather satellite, although we may derive some benefits in regards to weather prediction from the Aura datasets. Aura is measuring atmospheric composition and as a result, the main topics again that we are looking at with the Aura are: stratospheric ozone and how it's responding, air quality and how global climate change and air quality interplay, and also climate itself, and the sources and syncs of greenhouse gases.
So, although it's not primarily a weather satellite -- we will derive some benefits hopefully for weather -- but the main things are stratospheric ozone air quality and climate change.
Nail: Thank you, Dr. DeCola, for participating in NASA Direct! We greatly appreciate it.
DeCola: It's been my pleasure. Thanks very much.