Product review: FLIR Duo Pro R camera for drones

It’s not my habit to write product reviews, because I’m rarely in a position to say anything about any product that hasn’t already been amply covered by other professional and/or amateur reviewers.  The Duo Pro R camera manufactured by FLIR for thermal imaging from drones will be my first exception.

The Duo Pro R [640×512 pixel model] camera is a rather expensive (list $7,599) specialty product that came out in late 2017. To date I haven’t found a hands-on review of the camera by any other user, let alone someone attempting to utilize it for scientific research. Yet I know from forum postings that there is considerable interest from at least some other prospective customers in its unique capabilities.  So I’d like to share my experience in the hope that they will help guide others’ decisions.

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First Fixed Wing UAV Mission Successful!

From Saturday, October 13 until Wednesday October 17, we had the opportunity to travel with Prof. Ankur Desai and our ATM OCN 404 (Meteorological Measurements) students to Champaign, Illinois, to participate in the SAVANT field campaign led by Prof. April Hiscox (University of South Carolina).

In addition to the unique opportunity for AOS undergraduates to see a meteorological field experiment in action and to make contributions with their own complementary measurements, it was also our first chance to fly our newly acquired Elanus Duo fixed wing unmanned aerial vehicle (UAV, or drone) carrying a FLIR Dual Pro R camera that captures both visible and thermal infrared images.  The purpose was to map surface temperature at sunrise over the 100-acre farm field, where SAVANT scientists are studying night-time drainage winds.
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Observing boundary layer evolution with the UW ultralight

With winter weather looming and my sabbatical break from teaching nearing an end, I watched carefully last week for conditions that would allow us to make at least one more flight with the Zigolo before the end of the year.  Among other things, I wanted to try to use up the remaining fuel so that the carburetor and fuel lines wouldn’t gunk up  from standing idle for up to several months.  But I also wanted to demonstrate the ability to make meaningful meteorological measurements that could not be as easily achieved with an unmanned aerial vehicle (UAV, or drone), conventional weather balloon, or conventional manned airplane.

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Testing and outfitting the UW ultralight – the view from above

In my previous post, I described our second off-airport test flight. Now I’m belatedly posting video taken from a GoPro attached to my helmet. Unfortunately, the camera was angled slightly too far downward so the horizon is rarely visible; also it quit recording halfway through the flight, just when things were getting interesting again!

Testing and outfitting the UW ultralight – October 26, 2017

This morning, I flew the ultralight for what is probably the last time in 2017 unless we have exceptional weather in December (I will be gone most of November). I took it to
1,100 ft. AGL – about four times as high as my previous flight, loitered for a short time, and landed again after only 8 minutes total time in the air.

I had planned to stay up much longer and to try to burn through most of the rest of the fuel (about 3.5 gallons) before putting the plane away for the winter.  But the winds aloft were quite strong, and for a time, my ground speed (as measured with GPS) when heading directly into the southerly wind dropped to only 2 knots!  Given the 30–35 kt airspeed of the Zigolo,  the winds between ~600 and 1,100 feet must have been pushing 30 kts or so.

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Building an airplane – a photo/video montage

I put together a quick-and-dirty montage of photos and videos covering the period from the arrival and unpacking of the Zigolo kit to its first off-airport flight on October 8. Total viewing time is about 13 minutes.

At the close of the building phase of this project, I’d like to thank Craig Oswald for his crucial assistance during the intensive first week of the build and Jonathan Thom for his substantial ongoing role not only in the build itself but also in subsequent operations. The quality and speed of completion of this phase would not have been possible without their involvement.

And of course we would still be scratching our heads over a large pile of random parts if Chip Erwin (Aeromarine LSA), through his Builder Assist program, hadn’t flown twice to Madison to work with us for several intense days each on crucial parts of the build.  His involvement also gave me considerably greater confidence that the Zigolo wouldn’t fold up and crash the moment the wheels lifted off the runway (or worse, five minutes later!).

I’d also like to thank Bob Paulos and Gary Anderson once again for providing the perfect space at the Physical Sciences Laboratory in Stoughton. I have no idea where and how we would have built the airplane without it.

Sue Foldy in AOS patiently handled all of my orders for exotic materials and tools, and Sonja Johnson continues to help me navigate the reimbursement process.

Throughout 2016, Ben Griffiths in the UW-Madison Legal Affairs office, Hartley Murray in Purchasing Services, and Jim Bogan in Transportation Services were critical in navigating the university and state bureaucracies,  aided by helpful individuals in the Wisconsin Department of Administration (e.g., Cheryl Edgington), and culminating with a signed memo from Gov. Scott Walker authorizing the University to acquire its own airplane.

Last but not least, none of this would have been possible without the Ned P. Smith Professorships that were awarded to Ankur Desai and me; these collectively provided one half of the flexible funds that allowed us (and me in particular) to embark on this exotic quest, with the remaining half divided equally between Prof. Tristan L’Ecuyer’s flexible research funds and from our partners in the Space Science and Engineering Center, especially Hank Revercomb and Fred Best.

And now, on to the testing and operational phases!

Building an airplane – leaving the nest, October 8, 2017

Unbelievably, it’s been almost six weeks since I made those first crow hops down the grass strip at the Verona Air Park (W19). First, I was away in Arizona for four weeks as a part of a sabbatical stay at Embry Riddle Aeronautical University in Prescott, where I’m working with colleagues in the Applied Meteorology program there to brainstorm meteorological applications of UAVs.  After my return, I was disappointed to learn that we still had not received the rocket for our BRS (ballistic recovery system) due to a licensing glitch with the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

This meant that I would either have to continue waiting to fly the Zigolo to any significant altitude, or I would have to take my chances on the airplane we just built hanging together through whatever turbulence or moderately stressful maneuvers I might expose it to.

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Building an airplane – MY first flight, August 30, 2017

Recap: Yesterday, within minutes of tightening down the last bolts and setting the last rivets, Chip Erwin took the newly built Zigolo MG12 out of the hangar at Verona Air Park (W19), started it up, taxied it to the grass strip and did a few crow hops to verify that everything was in working order. It was a thrill to see it fly, however briefly, but the major milestone that was still missing was for me to fly it myself.

I wasn’t at all sure when that would happen. Not only did conditions have to be just right – which basically means calm winds (for now), but I also had to have confidence that I could safely get it down on the ground again.  As they say, takeoffs are optional, landings are mandatory.  And landings are by far the most demanding of flying skill, relative to other routine maneuvers.

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Building an airplane – first flight, August 29, 2017

Two months ago today, the Zigolo MG12 kit arrived as a 200+ lb. crate of parts (plus a bundle of long aluminum tubes) packing hundreds of seemingly random plates, bolts, rivets, cables, brackets, and fittings.  Today, with Chip Erwin at the controls, it flew for the first time.

Chip Erwin “crow hops” the newly completed Zigolo MG12 down the grass runway at the Verona Air Park (W19).

Last Thursday, Chip had found an unexpected break in his schedule that allowed him to come to Madison on very short notice for the final push. The five days since then have been intense: Chip, Jonathan, and I worked together through Thursday and Friday, Chip and I worked all day Saturday, I worked alone on Sunday from noon to midnight covering and painting the wings, and yesterday Chip and I madly worked from 8am to 7pm to complete everything on our list in time to cart the aircraft components out to our rented hangar at the Verona Air Park (W19) for final assembly.

It turned out that the bed of the University Fleet’s Ford F350 pickup was too short to be usable for our purposes, so we rushed out to find a 20′ flatbed utility trailer we could rent for the afternoon to transport everything in four trips between Stoughton and Verona. Paint was literally drying on one wing while we were driving the other one down the back roads.

This morning, the push continued starting at 7am at the Verona hangar; we needed to finish a number of items that had had to wait for resupply of the appropriate rivets; we also installed the ailerons, and Chip rigged the aileron cables. At 10:30am, we gave the plane a thorough preflight, checking for bolts that might still be loose and rivets that might have been missed. 

With everything looking good, Chip grabbed the Zigolo without ceremony and pushed it out onto the grass and started the engine. Wind was light and more or less straight down the grass runway.  Chip throttled up from mid-field and was airborne fairly quickly.  He stayed within a few feet of the grass and touched down again after maybe 100 yards. Turning sharply at the end of the runway — using a burst of power to bring the rudder into play — he repeated the crow hops in the downwind direction.

After a couple more passes, Chip taxied back to the hangar and declared himself extremely happy with the flight characteristics.  Unfortunately, that was it for testing this morning,  as Chip had already generously extended his stay through this morning after we were unable to complete all the necessary work in time for a test flight yesterday, and now he was facing a 7-hour road trip back to Ohio.

The next step will be more me to repeat the crow hops on a day with little or no wind, possibly as early as this evening or tomorrow.  This will allow me to get familiar with the handling during the critical phases of takeoff and landing.  I’ll be low and slow enough (maybe 10 feet at 35 mph) that the risk of serious miscalculation will be low — again, assuming little or no wind.

On Chip’s recommendation, the Zigolo won’t be taken to higher altitude until we have received and installed the BRS rocket-propelled parachute system  (we were supposed to receive it months ago, but a supply chain problem has held up delivery).  After that, I will be guided in part by the recommendations of Facebook friend (and experienced ultralight pilot) Bill Esker, who wrote 

Remember three things while flying lightly loaded wings.

[1] Airspeed is everything. Even more so than GA. When you pull power get that nose down and maintain airspeed.

2. Forward penetration inertia is almost zero. You have no weight!

3. You will be far more subject to turbulence. No big deal, but you will be bounced a bit more.Your takeoffs will be short, your landings will be short!

Enjoy because you now have a “motor-floater” and can go play with the thermals! … Even though you are a GA pilot fly only calm days for the first ten hours. Very light aircraft are a little weird to get used to, and no pulling the power half a mile from the numbers like GA , keep power on until you are 50 yards out! Once you get some circuits under your belt, then do some deadsticks right over the runway at first. You need to know what it feels like gravity only for your motor. It’s fun, you will enjoy it, but remember airspeed!

I had fully intended to blog more regularly about the build process leading up to this point, but that proved impractical. On the one hand there were sometimes week-long periods of time where nothing much was happening at all with the build, either because we were waiting on parts or because we were tied up with other things. On the other hand, the busy periods were so busy that I not infrequently worked 10–14 hour days at PSL and had no energy left for blogging by the time I got home at midnight! I apologize to those who might have been hoping for blow-by-blow commentary on the specifics of building this plane.  If you’re building a Zigolo kit, I’ll be happy to answer any questions that come up.  I had plenty of questions myself, and Chip’s on-site oversight and assistance saved us countless hours of head scratching and likely mistakes!

PS:  In the excitement and haste of the moment, I failed to get decent photos or any usable video, despite having good equipment with me (most of it still in the car).  There should have been a third person along whose sole job was to capture the moment. Or, in any case, more planning.

Total eclipse 2017

Antje and I pose with our eclipse glasses during the early partial phase of the eclipse.

Yesterday, my wife Antje, older daughter Annika, and I had the once-in-a-lifetime experience of being at the center of the path of the August 21 total eclipse. Our location: the Crab Orchard marina just east of Carbondale, Illinois.

The partial eclipse began at 11:52 AM and progressed slowly. Wearing our eclipse glasses, we could see the growing bite taken out of the sun’s disk, but there were no remarkable changes in the ambient lighting until the degree of coverage was well past 50%.  Only at that point did it start to become noticeable that the light was unnaturally muted relative to normal noon sunlight – but without either the warmer colors or the long shadows of late afternoon. 

(Interestingly, the effect of the reduced light during a partial eclipse is completely undetectable in photographs using automatic exposure metering, because the camera compensates by increasing the shutter time or opening the aperture by a stop or two, and there are no other visual clues in the light that the sun is partially blocked.)

Now, I have to admit, I have seen a number of partial eclipses in my lifetime, and I don’t find them terribly exciting. Unless you view the sun’s disk through a filter, it could easily escape your notice that an eclipse is happening at all.  Indeed, the only real clue might be the crescent shaped shadows that commonly occur where sunlight is filtered through a tree or other small openings.   I would not drive hundreds of miles to catch a glimpse of a partial eclipse.

That said, the progression of the partial eclipse was not without its excitement. We warily monitored the increasingly widespread cumulus congestus clouds that had begun developing throughout our area starting around 11 AM.  These were large and slow-moving, and I worried that one might block out the sun during the critical 2 minutes and 38 seconds of totality. Indeed, as we got to within 10 minutes of the start of the total eclipse, our tension was heightened as one towering cloud edged ever closer to the sun’s disk.  At that point, I sadly reckoned that we had at best a 50/50 chance of directly observing the total eclipse.  Would the 950+ mile round trip have been worth it? But fortune was with us, and the clouds remained more or less clear of the Sun’s disk.

As we got to within a couple of minutes of totality, the reduction in light accelerated rapidly.  Recall that the Moon slides over the Sun’s disk in linear fashion with time, while the eye responds logarithmically to light and thus to each factor-of-two change in the amount of uncovered area of the Sun’s disk.  The first factor-of-two took around 45 minutes, the next factor-of-two required maybe 20 minutes, and each successive factor-of-two required about half as long as the one before (these are crude estimates; the exact math is complicated).  Only on the brink of total eclipse were we able to perceive the rapid change of  ambient light as if someone was working the slider on a dimmer switch.

Through our eclipse filters, we watched as the uncovered portion of the Sun’s disk became an impossibly thin sliver and then, briefly, a residual bright spot known as the “diamond ring” (more on that below).

Seconds later, even that was gone.

As we removed our eclipse glasses, a collective gasp of appreciation went out from all those in our vicinity as we all beheld a sight that I have  never seen adequately capture in either print or photograph. This blog post will be no exception. 

The sky was dark, though not the dark of the midnight sky; more like pre-dawn.  The corona of the sun was suddenly visible in all its other-worldly glory.  This photograph shows the exact same corona we saw, but without capturing the fine fibrous texture or subtle coloration we saw with the naked eye. I think no photograph can.

Looking around us, we saw that the towering cumulus clouds and sky low on the horizon were illuminated with an orange glow – in all directions. It was as if the sun had just set to the north, east, south, and west, and all points in between, all at the same time.

At our location at the center of the path, we had a full two minutes and 38 seconds to appreciate the spectacle of a total eclipse, and I was grateful for every second. For a brief period, it partly disappeared behind a shred of cloud, only to reappear through a gap.  If anything, the proximity of clouds only enhanced the beauty of the scene.

I allowed the sun to begin reemerging from behind the moon without putting on my eclipse glasses again.  I did not look at the sun itself during this time but instead took in the environment around me during this critical transition back to a partial eclipse.  And that’s when the next surprise hit me.

When the “diamond ring” phase occurs, the intense light of the sun comes from an exceedingly small, almost point-like source rather than from the  half-degree diameter disk that we’re used to. Why is this significant?  It’s because the “large” unobscured disk causes shadows to have blurry edges. Look at the shadow of  the leaves of a tree on an ordinary sunny day, and you’ll have a hard time making out the individual leaves; the shadows are all smeared by that half-degree variation in the direction from which the light is coming. 

During that “diamond ring” phase, however, that blurring effect is almost entirely eliminated – shadows are exceptionally sharp and detailed.  A co-worker who also traveled to see the eclipse told me that he was able to discern the shadows of the hairs on his own head.
In fact, the lighting during the “diamond ring” phase reminded me of that cast by someone operating an arc welder during my shipboard days – the light is unnaturally white and the shadows are unnaturally sharp.

But what really drove that observation home for me was the shadows cast by the cloud wisps that passed in front of this point-like source of intense light: I could see astonishingly fine-scale texture in the clouds’ shadows as they moved across the ground before me, even though the clouds casting the shadows were some 2,000–3,000 feet above ground level!  I don’t know why I had never previously seen mention of this truly striking phenomenon.  I did retroactively find this page, which describes “shadow bands,”  which I believe are closely related to what I saw, but the latter apparently result from turbulent inhomogeneities in the cloud-free upper atmosphere.  The thin sliver-like source of sunlight is central to their occurrence as well.

You’ll notice that I have not posted any eclipse photos of my own.  I did not believe I could capture the experience in photographs well enough to compensate for the distraction. If you want to see images professionally captured by NASA from approximately the same vantage point, you can check out this YouTube video.

Rainbow photographed from the car as we headed back north through Illinois on the way to Madison.