Remote Sensing of Real-Time Volcanic Activity Part 2: Spaceborne Sensors

Here, in this article I follow on from Part 1 that focused on webcams and thermal cameras and I report on some of the capabilities spaceborne sensors, which can detect thermal signals, map out volcanic flows and detect/measure volcanic plumes and clouds in real-time. The data from this equipment can then be used for systematically detecting changes in volcanic activity.

Satellite-based remote sensing

Satellite remote sensing has been used for monitoring and analyzing a volcanoes thermal activity, one can even go back to Oppenheimer (1998) who provides an excellent overview. Sensors available today can measure from the ultraviolet (nanometers) to the microwave (cm to m). Here, Ii focus on the use of ultraviolet – thermal infrared wavelengths and report on example from certain satellites on the different volcanic features that one can capture.

For the detection of thermal signals, sensors such as the U.S. National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) can provide measurements at approx 1 km and 90 m spatial resolution respectively. For the MODIS sensor, it is aboard two NASA satellites and as such there are generally four overpasses per day, more in Polar Regions.

ASTER data is collected through a tasked system and as such, for volcanoes, is not routinely collected. Other useful sensors include the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and Visible Infrared Imaging Radiometer Suite (VIIRS), NASA Advanced Land Imager (ALI) and United States Geological Survey (USGS) LANDSAT-8 sensors.

Figure 1 shows some examples, from my blog, http://volcanodetect.blogspot.com/, where thermal signals have been detected in the data from these sensors. Harris (2013) provides an excellent overview of thermal detection of volcanic features.Figure 1A, is an ASTER image of Shiveluch volcano from March 4, 2014 (http://volcanodetect.blogspot.com/2014/03/aster-imagery-of-shiveluch-volcano.html). Here in the thermal infrared range, the temperatures are from +19 to -20 C, hence the ‘white’ and more elevated region close to the summit of the volcano.

Figure 1. A – ASTER TIR data from Shiveluch volcano on March 4, 2014; B – LANDSAT-8 data from Pacaya volcano on March 3, 2014 at 04:40 UTC; and C – NASA ALI data from Pavlof volcano on May 18, 2013.

Figure 1. A – ASTER TIR data from Shiveluch volcano on March 4, 2014; B – LANDSAT-8 data from Pacaya volcano on March 3, 2014 at 04:40 UTC; and C – NASA ALI data from Pavlof volcano on May 18, 2013.

Figure 1B is a LANDSAT-8 view of Pacaya volcano from March 3 2014 (http://volcanodetect.blogspot.com/2014/03/pacaya-volcano-march-3-2014-0440-utc.html). This is from Band 10 at 11 µm. Figure 1C shows a NASA ALI image from May 18, 2013 of Pavlof volcano. This is a Red-Green-Blue (RGB) view of the visible channels, illustrating the thermal signals from the volcanic activity and the water/steam and volcanic ash. Figures 2 and 3 show some examples of the different volcanic ash cloud examples that are possible from the different satellite sensors. Prata (1989), Pavolonis and Sieglaff (2010) and Webley et al. (2009) are just three example of the brightness temperature difference (BTD) methodologies applied for the detection of volcanic ash clouds, using TIR data. Figures 2 and 3 are examples from AVHRR data from the 2006 eruption of Augustine volcano (Bailey et al., 2010) and the 2009 eruption of Redoubt volcano (Webley et al., 2013).

Figure 2. AVHRR data shown as brightness temperature difference images from the explosive events on Jan. 13 – 14, 2006. A, 1734, and B, 1924, Jan. 13, adapted from Bailey et al. (2010)

Figure 2. AVHRR data shown as brightness temperature difference images from the explosive events on Jan. 13 – 14, 2006. A, 1734, and B, 1924, Jan. 13, adapted from Bailey et al. (2010)

Figure 3. Volcanic ash cloud from event 5 on March 23, 2009. Satellite data from NOAA AVHRR at 13:25 UTC: (A) 3.7 μm channel, (B) 10.6 μm channel, and (C) BTD data. Volcano location highlighted by red star; adapted from Webley et al. (2013).

Figure 3. Volcanic ash cloud from event 5 on March 23, 2009. Satellite data from NOAA AVHRR at 13:25 UTC: (A) 3.7 μm channel, (B) 10.6 μm channel, and (C) BTD data. Volcano location highlighted by red star; adapted from Webley et al. (2013).

There are also methods that can be applied to compare RGB imagery to that from the different TIR bands. The example highlighted here is for the 2014 eruption from Sinabung volcano, Indonesia. The data in Figure 4 is from NASA ASTER and was collected at 03:56 UTC, or local daytime. Figure 4A shows the RGB imagery of the Visible-Near IR (VNIR) channels from Bands 3, 2 and 1 in ASTER. Compare this to the decorrelation stretch using the TIR data from bands 14, 12 and 10 in RGB and the ash is highlighted, Figure 4B. This tool is useful at local night-time, when the RGB data in Figure 4A would not be available. This data can be seen at my blog entry, http://volcanodetect.blogspot.com/2014/02/aster-imagery-of-sinabung-volcano.html

Figure 4. ASTER data collected on February 10, 2014 at 03:56 UTC. A - RGB view of Visible/Near-Infrared channels 3, 2 and 1. Also a decorrelation stretch, B, that used TIR bands 14, 12, and 10. Here the purple/red colors represent ash dispersing off to the east.

Figure 4. ASTER data collected on February 10, 2014 at 03:56 UTC. A – RGB view of Visible/Near-Infrared channels 3, 2 and 1. Also a decorrelation stretch, B, that used TIR bands 14, 12, and 10. Here the purple/red colors represent ash dispersing off to the east.

In addition to the detection of volcanic ash, volcanic gases such as sulfur dioxide, SO2, can be recorded from space, both in the TIR and the ultraviolet. Figure 5 illustrates two examples, one from the 2009 eruption of Redoubt volcano using NASA Ozone Monitoring Instrument (OMI) data in the ultraviolet, Figure 5A, and another example using a MODIS decorrelation stretch on the 2009 eruption of Sarychev Volcano, Russia, Figure 5B. These two sensors have very different spatial resolutions and so the OMI data looks ‘blocky’ in comparison to the MODIS data.

Figure 5. A - OMI SO2 data from March 23, 2009, showing a large SO2 cloud dispersing to the east from Redoubt volcano, adapted from Webley et al. (2013) and B -  High altitude SO2-rich volcanic clouds on June 16, 2009 at 00:50 UTC from Sarychev volcano, Russia, as depicted in the MODIS decorrelation stretch. Here, the SO2 clouds are displayed in yellow and the ash clouds are displayed in red/magenta, with ice crystals are displayed in blue, adapted from Rybin et al. (2011)

Figure 5. A – OMI SO2 data from March 23, 2009, showing a large SO2 cloud dispersing to the east from Redoubt volcano, adapted from Webley et al. (2013) and B – High altitude SO2-rich volcanic clouds on June 16, 2009 at 00:50 UTC from Sarychev volcano, Russia, as depicted in the MODIS decorrelation stretch. Here, the SO2 clouds are displayed in yellow and the ash clouds are displayed in red/magenta, with ice crystals are displayed in blue, adapted from Rybin et al. (2011)

For satellite remote sensing of volcanoes, one can also measure in the microwave wavelength range. This time, the data comes from an active sensor, where a radar pulse is sent to the surface and the time to return to the satellite is record. Using this information, with the wavelength of the sensor, and orbital information, one is able to record the altitude of the ground surface to mm accuracy; Figure 6A shows an example from Merapi volcano of the dome at the summit of the volcano. Combining multiple images together and one is able to watch the change overtime from radar data, analyzing subtle changes in mm to m/yr. This data and methodology, known as satellite synthetic aperture radar (SAR) interferometry (InSAR), see Hanssen (2001), then is critical for mapping small scale changes at a volcano, which could then lead to large eruptive events. Figure 6B shows how, from Lu (2002; 2007), that InSAR measurements can be used  to map out up to 17 cm of uplift at Peulik volcano in Alaska from 1996 – 1997.

Figure 6. Merapi TerraSAR imagery from November 4, 2010, where is highlighted as the dome, adapted from Pallister et al. (2010). Also B - InSAR image (1996 to 1997) showing approximately 17 cm of episodic uplift of Peulik Volcano, adapted from Lu (2002; 2007)

Figure 6. Merapi TerraSAR imagery from November 4, 2010, where is highlighted as the dome, adapted from Pallister et al. (2010). Also B – InSAR image (1996 to 1997) showing approximately 17 cm of episodic uplift of Peulik Volcano, adapted from Lu (2002; 2007)

Final statement

In this report here, the use of webcam imagery, thermal cameras and satellites and their sensors has been highlighted for remote sensing of active volcanoes. Ground based measurements are useful as they can provide continuous views of the volcano and their activity. Short term campaigns can provide more data that can be used to calibrate/validate the long term ground instruments. But not all volcanoes can have a webcam/thermal camera, and so satellite data has been used to analyze in real-time volcanic activity. Whilst not always being able to see the volcano as it erupts, the change over time can be use for those in hazard assessment and to detect significant changes that could lead to large scale activity.

Author

Peter WebleyDr. Peter Webley is an Assistant Research Professor at the Geophysical Institute, University of Alaska Fairbanks. Dr. Webley’s focuses upon using remote sensing data to analyze natural hazards, such as volcanic events, forest fires, landslides and coastal erosion. Dr. Webley has designed new mechanisms to visualize the development of volcanic ash clouds. He has taken the three-dimensional dispersion model simulations that used to be visualized on two-dimensional maps and displayed them in their original three-dimensional form. Dr. Webley has been the guest editor for two special issues of the Journal of Volcanology and Geothermal Research (JVGR) in 2009 and 2013. His paper collaborating on eruption source parameters, Mastin et al. (2009) and listed in his selected publications is the highest cited publications in JVGR since 2008 with over 95 citations.

Recently in 2013, Dr. Webley, along with Dr. Jon Dehn, an Associate Research Professor at the Geophysical Institute, University of Alaska Fairbanks, formed a company called V-ADAPT, Inc [Volcanic Ash Detection Avoidance and Preparedness for Transportation], (www.vadapt.net), from their research at the University in analysis of volcanic activity and dispersion modeling of volcanic ash clouds. V-ADAPT, Inc. provides data, tools, analysis, and risk assessment of volcanic ash for the aviation and other transportation industries. They offer a comprehensive system to help in planning and response to volcanic eruptions for its clients. It is based on over 20 years of the founders’ experience in mitigating hundreds of eruptions in the North Pacific. The company focuses on volcanic hazard assessment and scenario planning through research and development, consultancy and service-orientated web-based tools.

References

Bailey, J.E., Dean, K.G., Dehn, J., and Webley, P.W., 2010, Integrated satellite observations of the 2006 eruption of Augustine Volcano, chapter 20 of Power, J.A., Coombs, M.L., and Freymueller, J.T., eds., The 2006 eruption of Augustine Volcano, Alaska: U.S.G.S. Professional Paper 1769, 481–506

Hanssen, R. F., 2001. Radar interferometry: data interpretation and error analysis. Springer. 308p.
Harris, A., 2013. Thermal Remote Sensing of Active Volcanoes: A User’s Manual. Cambridge Uni. Press. 728pp.

Lu, Z., Wicks, C., Dzurisin, D., Power, J., Moran, S., and Thatcher, W., 2002. Magmatic inflation at a dormant stratovolcano: 1996–98 activity at Mount Peulik Volcano, Alaska, revealed by satellite radar interferometry, Journal of Geophysical Research, 107(B7): 2134, doi:10.1029/2001JB000471

Lu, Z., 2007. InSAR imaging of volcanic deformation over cloud-prone areas-Aleutian islands. Photogrammetric engineering and remote sensing, 73(3), 245.

Mastin, L.G., Guffanti, M., Servranckx, R., Webley, P.W., Barsotti, S., Dean, K., Denlinger, R., Durant, A., Ewert, J. W., Gardner, C.A., Holliday, A.C., Neri, A., Rose, W.I., Schneider, D., Siebert, L., Stunder, B., Swanson, G., Tupper, A., Volentik, A. and Waythomas, C. F., 2009. A multidisciplinary effort to assign realistic source parameters to model of volcanic ash-cloud transport and dispersion during eruptions. Journ. of Volc. and Geo. Res: SI on Volcanic Ash Clouds, eds. Larry Mastin and Peter Webley, 186 (1–2), 10–21

Oppenheimer C., 1998. Volcanological applications of meteorological satellites. Review article. International Journal of Remote Sensing. 19 (15), 2829 – 2864.

Pallister, J. S., Schneider, D. J., Griswold, J. P., Keeler, R. H., Burton, W. C., Noyles, C., Newhall, C, G., and Ratdomopurbo, A., 2013. Merapi 2010 eruption—Chronology and extrusion rates monitored with satellite radar and used in eruption forecasting. Journal of Volcanology and Geothermal Research, 261, 144-152.

Pavolonis, M., and Sieglaff, J., 2010. “GOES-R Advanced Baseline Imager (ABI) algorithm theoretical basis document for volcanic ash (detection and height).”NOAA CSTAR Tech. Doc. Version 2, 72pp.

Prata, A., 1989. Infrared radiative transfer calculations for volcanic ash clouds. Geophysical Research Letters, 16. 1293-1296.

Rybin, A., Chibisova, M., Webley, P. W., Steensen, T., Izbekov, P., Neal, C., and Realmuto, V., 2011. The June 2009 eruption of Sarychev Peak volcano, Matua Island, Central Kuriles. Bulletin of Volcanology, 73 (9), 1377 – 1392. DOI: 10.1007/s00445-011-0481-0

Sparks, R. S. J., Bursik, M. I., Carey, S. N., Gilbert, J., Glaze, L. S., Sigurdsson, H., and Woods, A. W., 1997. Volcanic plumes. Wiley, 574 pp.

Webley, P.W., Dehn, J., Lovick, J., Dean, K.G., Bailey, J.E. and Valcic, L., 2009. Near Real Time Volcanic Ash Cloud Detection: Experiences from the Alaska Volcano Observatory. Journal of Volcanology and Geothermal Research: Special Issue on Volcanic Ash Clouds, eds. Larry Mastin and Peter Webley, 186 (1 – 2), 79 – 90. doi:10.1016/j.jvolgeores.2009.02.010

Webley, P. W., Lopez, T.M., Ekstrand, A. L, Dean, K. G., Rinkleff, P., Dehn, J., Cahill, C. F., Wessels, R., Bailey, J. E., Izbekov, P., and Worden, A., 2013. Remote observations of eruptive clouds and surface thermal activity during the 2009 eruption of Redoubt volcano. Journ. of Volc. and Geo. Res., 259, 185-200, http://dx.doi.org/10.1016/j.jvolgeores.2012.06.023

Peter Webley

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82 thoughts on “Remote Sensing of Real-Time Volcanic Activity Part 2: Spaceborne Sensors

  1. First of all, a big thank you to Dr Peter Webley for his fantastic summary of how Satellites can be used.
    Second thank you to Spica who edited the piece while I was suffering from the Plague.
    Also, the list of references, lots of goodies in there.

    Do not forget to write suggestions for additional pieces and questions to Dr Webley now that he is around and we all have the opportunity to ask all those really tricky ones.

    • I’ll be on travel this week so i’ll check in again early next week and see what could be another topic. One might be on how to measure effusion rates from satellite data.

      • Oooh… that would be cool and usefull. A lot of us have tried to figure that one out on our, but not with a lot of success really.

    • I know that many will love that piece Boris! Me among them of course, especially now that Etna seems to have changed her pattern again.

    • Ooh! yes please Dr Boris 🙂 Waiting with anticipation. Thank you. All these wonderful posts are greatly appreciated here as I am sure others feel the same.

  2. Are these the satellites that do the flyovers to see which way a volcano is being lifted up prior to an eruption?
    Do the Ground GPS work together with the satellites to get an overall picture of what is going on?

  3. Interesting stuff, thanks. Just one teeny thing – might you have transposed ASTER and MODIS when discussing spatial resolutions? ASTER is 90 metres (in the TIR band) while MODIS is 1000 m.

    • Yes i did. Apologies. Carl, could you edit the article.

      from

      For the detection of thermal signals, sensors such as the U.S. National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) can provide measurements at approx 90 m and 1 km spatial resolution respectively. For the MODIS sensor, it is aboard two NASA satellites and as such there are generally four overpasses per day, more in Polar Regions.

      to

      For the detection of thermal signals, sensors such as the U.S. National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) can provide measurements at approx 1 km and 90 m spatial resolution respectively. For the MODIS sensor, it is aboard two NASA satellites and as such there are generally four overpasses per day, more in Polar Regions.

  4. Thank you, Dr. Peter, this is very interesting! Two questions coming to my mind:

    1. There are countries who have lots of volcanoes but due to grave financial and political restrictions they can only install a very limited number of ground equipment to watch them. Is it possible for them to draw on the various satellite imaging instead, perhaps getting more and better data? Or is it also too expensive for such countries to get access to the original and/or very specialised images?

    2. In the search for flight MA370 satellite imaging played a substantial role. Is has been said often that the published images are never the high resolution originals delivered by the sensors or cameras, because countries would not reveal their imaging capabilities (“You can read the number plate on cars in the originals…”). Is that also true for all the scientific remote sensing equipment? – I can imagine that the ones we get on the internet are not the originals due to file size, but are the originals available to the international public?

    • I will answer a small part of this and leave the rest to Dr Webley.
      The intelligence community fervently wish that satellites would have that kind of resolution. They do not.
      As far as I know the Aster and Modis does not have higher resolution than what Dr Webley stated above. But there are other satellites up there with higher resolution.
      The latest KH-11 Kennan Block IV (Misty) satellite have a resolution that makes it able to pick up objects less than 1 meter in size during perfect conditions, but you can’t read the headline on a newspaper. I am not going to blurt out the specifics better than that. But no car plate.

      Just so you understand (and using declassified data). The first KH-11 satellite used a CCD capable of 800 by 800 pixels. This was the satellite that started that little rumour about car-plates. Anyone with the knowledge of CCDs knows that a camera with that poor resolution would not be able to get high resolution graphics regardless of the optics you wham on (and the optics are basically the same as on Hubble). Caveat: All information written in this answer is from declassified sources.

    • I’m gonna echo Carl on this. If you can do the formulas, go grab the published data for the Hubble space telescope and work out the minimum resolution on targets 300 miles away. Essentially, use the Hubble’s info, but pointed at the earth. You’ll find that about 1 meter is the limit for resolution, or pretty close to that. (I grundged my way through the calculations once, just out of curiosity) Sure, it’s theoretically a bit better than that, but you also have to account for the perturbation’s in ray path that the atmosphere causes. Those twinkling stars that you see at night do that for the same reason. Ground based telescopes are getting to where they can compensate for it, but they have to fire a laser into the sky to get a read on the turbulence of the atmosphere so that they can adjust the optics as needed to compensate.

      By far, better imagery can be obtained from drones or surveillance aircraft. Probably the best platform for that would be the U-2 or SR-71, but they have been retired and are no longer operable. (Specifically the SR-71 due to the massive area it could cover in short order)

      I’ve seen some pretty remarkable things done with radar imaging, but when you have a surface (ocean) that is constantly in flux, occasionally forming nearly ideal reflecting surfaces that disappear just as rapidly as they form, it gets really complicated.

      • The atmosphere do weird things. It is effectively the show stopper for getting higher resolution on earth. I have though seen a test image aimed at Tranquillity. You do not see the first step, but you see the junk they left behind quite well. Difference here being that the moon has no atmosphere to hinder top resolution.

        I find it odd that the same people who do not believe in the moon landing do believe that satellites can watch their dental hygiene status in real time.

        Oh bother, while I am at it. People are idiots. At the same time the Americans went to the moon the Soviets had an equal capacity space program. They watched and tracked every little minute detail of what the Americans did. If the Americans had fibbed it, it would have been the Soviets that pulled down their pants and gave them an Atomic Wedgie Communist Party Style. And any one who do not beleive that the Soviet Union would not have should truly wear a tinfoil hat. Oh wait, they allready do…

        • Yeah, your definitely on the money with regards to the Soviets. At the time, the stakes were quite high and bragging rights is what it was all about. Anything that one side could do to smear the other side was put on high priority.

          • It was the most expensive pissing contest in history, and the Soviets would have loved to say “Hey, that is not piss, that is apple juice!”

          • Cool! So that’s not a US specific colloquialism!

            I have on occasion referred to it as a pecker waving contest. 😀

            I’m glad to see that other people recognize the concept for what it is.

            • Yepp, we have the same colloquialism. And we also have bright white snow to write our names in… Let us just say that beer has most often been involved prior to this actual contest.

            • It’s also an advantage to have a short name like Per or Carl. Hjalmar or Sigge is at a definite disadvantage.

            • Bruce, you are supposed to write your full name… I have my first name (Carl) a middle name and an ancestral name (name of my paternal grandfather) and then comes my last name. Lots of yellow snow there.

      • I guess the inadequacy of satellite based systems for military reconnaissance is corroborated by the moves to find a replacement to the U2 and SR-71.

        • Makes sense to me.

          I foresee a drone based solution to this problem. The optical packages on those aircraft were phenomenal, it was just hazardous to stick a human in the airframe and send them into the territory of them that don’t want to be looked at.

          An interesting coincidence is the Air Force’s continued testing of hypersonic airframes.

          http://en.wikipedia.org/wiki/NASA_X-43

          • The SR-71 was an awesome piece of machinery. Just outran any threat. I never understood why they terminated the program.

          • Me either… but taking one down was becoming a matter of getting the anti air missile up and into the projected flight path. It was just a matter of time before that communications juggle was worked out. If you can get the intercept missile into the right position, something like an expanding rod warhead could probably do it. Expanding rod is essentially the high speed military equivalent of whacking it with a fly swatter. At that speed all you have to do is nick it and it will fragment into pieces. Expanding Rod is one of the warheads used by the Standard Missile family.


            Portions of the aircraft intercepted by the expanding ring will receive a continuous cut through the skin, light structure, underlying cables, hydraulic lines, and other plumbing if present. This may cause a structural failure, or, if not, can be sufficient for defeating the redundancy of aircraft systems. The effect is only pronounced as long as the ring is unbroken, so multiple layers of rods are employed in practical weapons to increase the effective radius.

            • scramjets are cool but only 300 seconds of flight to date? sounds like they have lots of work ahead of them.

            • Well, remember that when an SR-71 was at speed, it’s engines were effectively operating in a ram jet mode. All those adjustable spikes on the engines were for slowing down the airflow while it was operating as a turbojet. Above a certain speed, most of the the thrust came from using the bypass airflow in ramjet fashion.

            • Unfortunately, I don’t have an unclassified reference to give you about some of the more nasty thought processes of killing aircraft. Lets just say that some tactics involve using your instincts against you.


              Ref: the EA-6B. Tragic, though we aren’t the only ones who have cut cables there. August 1961 a French aircraft did something similar. As for the EA-6B, it’s a highly capable system that can really mess up your electronic sensors. It does what it was designed to do quite well. The airframe is also quite rugged, something that probably allowed the pilot and copilot to be convicted of destroying evidence and obstruction of justice. Otherwise they would have cratered.

            • Random notes:

              * Aster has a 15-metre resolution in the visible/near infrared bands

              * Much as I love the SR-71 (and lucky enough to do the tanker ride 🙂 🙂 ), it was FRIGHTENINGLY expensive to operate, and the advent of the later Russian S-300 SAM versions meant it would never be able to overfly anywhere ‘hot’ with any degree of safety. Notwithstanding its quick-reaction capability, having something so expensive in the stand-off role just didn’t make much sense.

              * U-2 has not been retired yet – sure Hagel is very publicly trying to kill it in the FY15 budget but the battle is far from over and the old girl still has a lot of friends in high places (pun intended). Just see how far you get trying to operate the unmanned Global Hawk alongside everyday airliners at Akrotiri, for instance!

              * don’t forget the RQ-180!
              http://www.aviationweek.com/Article.aspx?id=/article-xml/awx_12_06_2013_p0-643783.xml

            • The SR-72 may face significant challenges to being accepted by the Air Force, as they are opting to develop the Northrop Grumman RQ-180 stealth UAV to perform the task of conducting ISR missions in contested airspace. Compared to the SR-72, the RQ-180 is less complex to design and manufacture, less prone to problems with acquisition, and can enter service as soon as 2015

              http://en.wikipedia.org/wiki/Lockheed_SR-72

            • I have a friend who has tried his darnedest to get his hands on an SR-71. He has a pretty convincing case that he can transform the engine so that the old bird would function as a SSTOS (Singe Stage Take Off to Space) with a single air tanking.
              He is not someone who is a joke in the business, but so far he has had no luck in even getting a single engine to test it out. But he has done scale versions operating in a 3-operations mode configuration so he is definitely onto something.

            • Well, if this guys engines disappear… I’ll know somethings up.

              30.465823°N – 86.562010°W

              For the Google Earth users. That’s a great place for comparing the outlines and dimensions of stuff you find at various airfields to actual USAF aircraft.

      • Aside from pixel count and atmospheric turbulence there is the fundamental issue of diffraction limiting. There’s a handy little formula for the limiting resolvable separation of two objects s=lambda/2NA where lambda is wavelength and NA=numerical aperture = sine of the half cone angle from the optic aperture to the object. Say we pick lambda=0.5 microns (blue green, about as short as you can get through that much atmosphere) and low earth orbit of 160km to give it the best possible chance. Then we apply Johnson criteria for identification on a 100mm licence plate character to get s~8.3mm. This requires that the optic has an aperture of at least 9.6 metres. That’s a big lump of glass to get into orbit!

    • you can get specialist satellites that in panchromatic bands go down to 50 – 60 cm. But these have a very narrow swath view with each overpass. Its like looking down at the earth through a straw. if you want to see the earth at very high resolution, spatially, then you have to trade off with the area that you can see at this resolution.

    • GeoLurking, this is right in my neighbor town! They have a yearly tradition at midsummer celebration to build this monster bonfire… it seems to being bigger and bigger every year! I’m wondering about how close they are to reach the critical height of a building like this, they seems like they don’t care…

      • Well, Texas A & M had an annual bonfire tower that kept growing in size. Eventually, they had a mishap during it’s construction that killed 12 and injured 27.

  5. @Peter Webley
    A question, is it possible to monitor via satellite for changes in gas-release prior to an eruption? Or even monitor changes in release in a volcanoes normal changes?

  6. OT. A while back I posted a video by RedNex, the manufactured Swedish techno/folk/bluegrass band. that pushes a stereotyped redneck persona. The song was Cotton Eyed Joe.

    Carl and others agreed that it was a bit of a lowpoint in art.

    Here is a more accurate rendition of that song that better fits the way that it was originally played.

    You’ll notice a decided lack of “eye candy” in the band. That’s because you are supposed to bring your own “eye candy” to the show. 😀

    Asleep at the Wheel is better known by their Texas Swing styled House of Blue Lights.


    About that “redneck” persona stereotype. Having be born and raised and lived in the deep south for pretty much all of my life, I feel that I likely have an air of authority on the subject. We are not all the inbred knuckle dragging idiots that we are made out to be in most media. I think comedian Jeff Foxworthy inadvertantly hit the nail on the head with his definition of redneck is a “Glorious lack of sophistication.” Using that definition means that many, many cultures have their own version of being a redneck. We don’t all chew tobacco (I do), and we don’t always wind up in a drunken brawl over the honor of our sister… though honor, in some shape or fashion, weighs heavily on many of our actions. At it’s core, for me, being a redneck is being very comfortable with yourself despite what someone else’s opinion may be. They can go to hell for all you care. Sure, we have some social oddities that invite derision from others, but that’s part of what being a redneck is. Again, going back to Foxworthy’s take on it, “we just can’t seem to keep the most ignorant of ourselves off of the TV.”

    About that tobacco thing. I used to smoke, it’s a nasty habit. I stopped smoking due to a conscious decision. I went back to chewing tobacco when I was a volunteer firefighter. Smoking yields carbon monoxide, and co has a cumulative effect on the body, lowering your blood’s ability to carry oxygen. I figured that being exposed to the byproducts of combustion from house fires would be exacerbated by me being a smoker. I had chewed tobacco when I was younger, so I went back to it. Neither is acceptable from a biological point of view, but that’s just the tack that I took. (long term nicotine exposure can lead to an accelerated heart rate)

  7. question for doc webley 🙂
    would it be possible to get inSAR images for the globe – on say an annual basis – possibly just to a low tolerance ?

    so comparing a series of photos from this year to a similar series the year before
    and then flag up any areas that have more than a certain amount (30cm annually? is that a decent criteria?) of uplift over a large (10km square ?) area

    the idea being to allow ‘coarse grain’ monitoring of ‘unmonitored’ volcanoes

    technically I’m guessing it would be feasible – given the pelud image above, but practically speaking?

    do inferometry images require a tasked system?
    do satelittes that have the facility to take suitable images orbit in a manner that lets them cover the globe once a day?

    can you only get inferometry for land areas – can this detect the sea bed too ?

    • edward, this can be done with InSAR technique. As we can get overpass with 16 – 32 day repeats, and some times less time, we can then look for changes. We need to make sure we have good coherence, or no signal loss from changes in ground surface, i.e. compare same seasons, hard if we have big changes in surface cover, like loss of vegetation.

      • hmm, interesting, yes ok I see annual ice/vegetation cycles might be tricky if spring ‘comes early/late’ somewhere, is there a way to remotely assess the season change line’s progress and factor that in – allowing you to compare this year when spring reaches a volcano, with last year when spring reaches the same volcano ? – or does that require ground based observations?

    • this is a active sensor technique so it sends radar pulse and measures return. as a result the sea surface looks like a very flat surface and actually with certain sensors we can see waves on surface.

        • That’s a tough nut to crack. Radar operates as an intercept of reflected signals. That reflection is caused by an abrupt change in dielectric constant, (my opinion) that causes most of the wavefront to be reflected. Additionally, seawater is conductive. That makes wave traversal even more difficult since the seawater tends to massively attenuate the wavefront. It is nearly impossible to get a signal to penetrate is that is of any use. Ultra low frequencies may be able to do it, (ELF comes to mind) but the wavelength is so horkingly large that you probably can’t get any resolution smaller than a planet in the return signal. ELF is used in submarine communications since it can make the penetration… but it can’t really carry much data. Once a sub get’s the code, it has to find someway to communicate with it’s command center in order to find out what they want. (Comm bouy etc)

          • thanks for the the clear answer Lurking that makes sense – I figured that would alas be the case, but I was hoping for some funky tech that might not use “radar type stuff” I’d not thought of 🙂

          • Well, if you can find a coating or design that fully eliminates that abrupt change in dielectric constant, you’ll have the worlds military beating a path to your door. That’s one of the ultimate goals of stealth. “Free Space” has a constant of about 377 ohms. Sheet metal, about 0 ohms. Plessey did a lot of research work in the field for several years, as well as other manufactures. See, if you can control that you can control how much interference your antenna has to deal with in forming it’s beam. Eliminating reflections at one frequency is easy… the problem is coming up with a solution that is broadband and operates across a wide frequency range. What is invisible at one frequency is usually quite visible at another frequency. That’s one reason for the odd angular designs of some attempts. The idea is to control what direction the reflected energy goes, reflect it away from the sending radar and you seem to be much smaller to it. With some radars able to track the equivalent of a sparrow, it gets to be a high stakes technology race.

            Now… ponder this. Some radars are designed to track water droplets and snow. (NEXRAD). If your radar is tracking what is essentially perturbations in the atmosphere, how do you eliminate the turbulence and condensation trail of your aircraft moving through air?

            One of the first “clean sheet” stealth designs using stealth coupled it with obscene speed to improve it’s chances of not being shot down. That was the SR-71. This was after they came to the realization that back fitting the U-2 with stealth was likely going to yield a very unstable and unmanageable aircraft. As it is, the U-2 is essentially a glider design with a jet engine strapped on it’s ass.

            Now.. for the fun part. The Chevy corvette is an ultra sleek design that is reminiscent of the smooth lines of an SR-71. Guess what? It’s about as obvious to a speed radar as a pickup truck. All the pretty skin is made up of fiberglass. Fiberglass is transparent to radar. What the radar sees is a collection of highly reflective engine and chassis components with many angular surfaces. A 90° angle is an ideal reflector and is used in many sailboats and small craft as part of their rigging so that they don’t get run over out at sea. (called a corner reflector) It’s that small diamond shaped gizmo attached to a halyard.

  8. Thanks again for letting us have a glimpse into your field of work!
    Had to look up “decorrelation stretch” and found it´s also very useful in archaeology and elsewhere to bring out elements almost invisible to the naked eye.
    http://www.dstretch.com/AlgorithmDescription.html
    I really appreciate your articles and hope for more (especially “how to”s 🙂 )!

  9. Great series! Enjoying this. I’m busy with my efforts to fly for my
    new boss appears to be on track! I should be more relaxed
    By the week end.😁

  10. Thanks again Dr Webley. I usually get very lost with the physics side of things but I can more follow this post thanks to your excellent explanations. Your writing is easy to understand as it is so well written aand so it reaches a wide audience.
    I saw Edward’s comment about the sea acting like a mirror, presumably deflecting any waves back.
    I would like to know if changes in the temperature of of the sea or if emissions and particles from a submarine eruption can be detected. I resume they can as we saw when Bob erupted off the coast of El Hierro. I also presume that satellite imagery is very useful for spotting events in the Oceans as they are such vast areas.
    Just a note that there have been quite a few small quakes around the Öræfajökull /Skaftafell area in Iceland. Most unusual.
    http://en.vedur.is/earthquakes-and-volcanism/earthquakes/vatnajokull/#view=table
    There are some interesting tremor plots too!
    http://en.vedur.is/earthquakes-and-volcanism/earthquakes/vatnajokull/#view=table

    • Lurking gave a pretty good explanation above that gave a simple view on why it is hard to get signals out of the ocean that a satellite can detect.
      Best way is through a hydrophone. Back when I used to designe them for a living I had the joy of hitching rides with a few subs. Ocean water is an amazingly good sound carrier, and volcanic and seismic activity is increadibly noisy, so you can pinpoint activity rather well. Sadly volcanologists rarely have a submarine craft with a 100 million hydrophone.
      I used to ask nicely and sit on the night shift if we were close to the MAR. It is increadible hearing all that noise created from black smokers, small volcanoes known to no one, minute earthquakes… it is like sitting for hours hearing Earth talking to you. I so wish I could put up a few audiofiles I have so you guys could listen.

      That is why I am driving Lurking nuts having him making weird MP3s all the time :mrgreen:

      • Want to drive someone nuts? Have a bored sonar tech hold his electric razor up to the underwater microphone and turn it on. Ships in formation tend to scatter. Evidently it sounds like someone dropped one in the water.

        (almost as funny as when they we firing air slugs and forgot to take the torpedo out and landed one in a car on the pier.)

        • My favourite is the noise as water rushes in to a steel tube. It is the weirdest sound ever and there is nothing on the planet that sounds that way. I have always wondered why no navy and no shipyard have come up with a way of quieting that one down, or changing the noise signature. (flooding the torpedo tube as the forward gate opens)

      • Sounds fantastic….A perfect lullaby for when I can’t sleep. Keep trying I’d love to listen. Thanks for the answer Carl.

        • Do not forget whales talking to each other across 100ds of kilomters as they traverse the ocean. I have always wondered what on earth they are talking about.

        • “Fantastic” she says….

          In Chula Vista, I woke up from a nightmare on a Saturday, thinking for all the world that I was still on watch and had never pulled into port. That was what my dream was about. The incessant droning of a long range air search radar nagging at you. The dream seemed to be so ultra vivid, like I was actually still sitting the equipment stack out at sea.

          Then I noticed that the radio next to my bed was sounding out the signal from an air search radar on a ship just off the coast.

  11. Briefly encountered a genuine asshole today. She was pissed off that the control room staff were busy and couldn’t immediately let her in through the gates. The control room was quite busy with doing maintenance on their control panel, and had the lid lofted high into the air so that their maintenance guy could mess with the wiring. She just stood there quietly cursing their very existence. Dunno if the twit realizes it, but if that panel they are working on isn’t operating correctly, they aren’t letting her anywhere, no matter how important she thinks she is.

    What would have been cool would have been if they had let her into the sallyport but couldn’t let here in any further, or back out. “Just stand in that little pen until we get it working.” 😀

    • I know the feeling Lurking. I get it every time some twit drives up and wait immediately behind me as I start to reverse out of a supermarket parking slot. They want my place but I can’t move because they are right behind me. My answer to this is to move back in. Start clearing out my handbag (This can take some time) and as soon as I see them move on I quickly reverse out and hopefully someone else slides in before they do! 😀

  12. OK so here endeth my comments for the morning. It’s sunny and I am off to cultivate the wilderness in my Allotment. Twelve months of inability to do any major improvements due to dodgy knee ligaments and other assorted body failures have created vegetable plots from hell. Sis in law told me to give my plot up as at my age it was too much for me. Told by the Docs and family not to use a spade, as digging would knacker knees up again I thought laterally and have purchased a heavy digging hoe, adze, mattock whatever you want to call it. I don’t dig. I now heft and pull and it’s proving to be quicker and easier than using a spade. Going through clumps of established couch grass like a knife through butter . I will have an upper torso Mr Universe would be proud of by the time I have finished 😀 Moral of this mini rumination……
    Think laterally and you won’t loose the plot. 😀

    • For those not into horticulture here’s what I am chunttering on about. It’s been used for cultivation for thousands of years . Considered a primitive tool and very basic, here’s another guy that has rediscovered it’s usefulness.

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