Dr. Bruce Wielicki, Senior Earth Scientist, Langley Research Center, Hampton, VA
- Created: Wednesday, 01 February 2012
NTB: What are these “risks in technology?”
Dr. Wielicki: All NASA missions are trying to do something new, so the risk is really “Can you take from the laboratory an actual instrument that’s going to go into space, through launch, through contamination in orbit, through all of the other things that it might go through, and then achieve what it is you’re doing?” In our case, it’s pushing accuracy to levels to a factor of 5 beyond what current instruments do, and that really requires more care, detail, and independent verification systems. It’s a lot more like what the metrology world does actually —NTB: What are the different instruments that you’re building in the laboratory, and how are they each used in the CLARREO mission?
Dr. Wielicki: One of them is a reflected solar spectrometer, and that one will have about a ½ kilometer field of view. It’s a 2D detecting array, so it’s kind of a push-broom in orbit. Imaging NTB: How are the work and the responsibilities divided up? What’s it like to work in that coordinated approach?
Dr. Wielicki: That has really been a fantastic collaboration for us, because NIST, of course, is really interested in pushing metrology, in terms of accurate standards that really can benefit the world. When we brought CLARREO to them, the real advantage was we needed improved standards out into some wavelength ranges that they had done in some original explorations. They were slowly moving into that direction, but we gave them a lot more impetus for why it was important to get there now.
So, in particular, the far infrared wavelengths beyond about 15 or 20 microns out to 100 microns, and then in the near infrared. They had things really well understood out to 1100 or 1200 nanometers, but as you started to get out to 2300 or 2400 nanometers, they still needed some work to do. We have regular meetings with them. We have a formal agreement with NIST, we also have formal agreements with the United Kingdom with their National Physical Lab, with their climate modeling center, and also with some of their universities that are involved as well.
NTB: What is your specific role in the program? What is your day-to-day work?
Dr. Wielicki: NTB: You mentioned infrared spectra. What kind of work is being done there?
Dr. Wielicki: One of the more exciting things with the infrared is we’re getting into about half of the whole infrared radiation that the Earth is emitting out to space, seeing it for the first time in a spectrum, out there beyond 15- to 50-micron wavelengths. It’s called the far infrared. It’s where most of the water vapor greenhouse is. The atmosphere holds more water vapor. That itself is a greenhouse gas, and it therefore amplifies the carbon dioxide warming we get almost by a factor of 2.
This will be the first time we really see this globally everywhere in spectra as well at high accuracy. The transform spectrometer has about a 25 kilometer field of view at nadir. One of CLARREO’s visions here is to not only work as a sort of a transfer radiometer in orbit to calibrate other instruments, but also our own spectra by themselves. NTB: What are the radio occultation teams working on?
Dr. Wielicki: Current GNSS (global navigation satellite system) radio occultation meets CLARREO accuracy goals for temperature changes at altitudes between 5 and 20 km. NTB: What has the CLARREO been able to determine about how the Earth is changing?
Dr. Wielicki: The very process of deriving more rigorous observing requirements for a diverse set of high-accuracy decadal climate change observations has led to new methods of understanding climate observing system requirements and how to derive them.
CLARREO has pioneered new ways to use climate models to simulate future observing system simulations. NTB: Are there similar missions that are providing complimentary data?
Dr. Wielicki: Not right now. This is really a new concept. There are other groups that have tried to propose similar things. For example, there’s a UK group, led by Nigel Fox, at their National Physical Lab, and we proposed one called TRUTHS, and that was to do pretty much the reflective solar part of our CLARREO mission. That was proposed to the European Space Agency (ESA) about 4 or 5 years ago, and so we’ve been working actively with them. And ultimately what you want really want is for the US to put up one of these, and then the international community to put up their own version of it, and then just like metrology labs for international standards, you “shoot it out” between those different laboratories for who really has the accuracy on climate change. And given the critical nature of climate change accuracy, this is just kind of fundamental, basic scientific practice to do this.
NTB: What would you say is the biggest challenge from a technical perspective when you’re developing these instruments in the lab?
Dr. Wielicki: The biggest challenge is not to get too fancy on the technology, so in general we are not using cutting-edge detectors or other things that you might have, like huge optics. The optics on our instruments are about an inch —NTB: Given the budget cuts, do you ever get impatient with getting these projects off the ground?
Dr. Wielicki: Yeah, we get frustrated all the time. It was a year ago when we did our mission concept review, and we just got rave reviews. The engineers said they’d never seen a mission with the engineering and science melded together that rigorously before, and we were all just glowing until we knocked on the door: “There’s not any money to do this right now.” But this is not new. This happens to satellite missions all the time. The cost is high. You can’t get to space cheap. Inevitable glitches in funding profiles will delay you. The global precipitation mission has been going through this for years. They’re finally getting their mission together. You can’t get too depressed by it. If you do, you’re not going to last in this business. You have to be a master of delayed gratification.
NTB: In an ideal world, with all the funding necessary, what would be accomplishing with CLARREO?
Dr. Wielicki: We would’ve launched about 2017 or 2018, serving as that anchor of much of the climate observing system and taking it to a new accuracy.
Another way to explain what we do: If you have observation and climate change over decades, you have error sources in those observations, and those error sources have to be compared to natural variability. So you can actually ask yourself: If I had a perfect observing system, how quickly could I have seen climate change and understood what it was over natural variability? CLARREO is designed to be so accurate that those observations would flow down that perfect system by only about 10 or 15 percent. So let’s say you needed 10 or 20 years to see that trend above natural variability. If it was 20, with CLARREO, you could see that in 22. With a normal observing system, it might take you easily 30 years to see the same trend. As we advance toward trying to control climate change, we’re going to want to see as soon as possible the response of the climate system to those changes, and CLARREO is one of the steps we can take to get that information, not 30 years out but 20 years out, or not 20 years out, but 10 years out.
NTB: What would you say is your favorite part of the job?
Dr. Wielicki:I guess it’s just working with such a talented team: the scientists and engineers. We really have had an almost magical group on CLARREO. It’s not that it has been easy, but the dedication and talent on that team has just been extraordinary. The biggest charge for me is to watch us, over the last three years, evolve a very solid understanding of what this mission ought to be – and even what it shouldn’t be.