Sprites 2013: Update #5

We flew again tonight, but kind of got burned by the storm. There was a large number of positive charge-moment-change around 8:00 when we were planning, and just the lightning map in general looked like an unusually high number of positive strokes. Normally we see about 1 positive stroke out of every 10 or so, but tonight it seemed like it was around 50/50. And that was reflected among separate storms across the US, making you think there must be something larger controlling the fraction of positive strokes. It's interesting.

Anyway, we took off around 9:00pm, based on the fact that there was a very cold storm with lots of positive CMC, which is exactly what we look for. But it just died almost as soon as we were in the air. There was still a lot of lightning, but the big positive CMCs almost disappeared. I don't know what happened, and I actually don't think anyone knows enough about what sets the fraction of positive lightning strokes to really explain what happened. We had a long discussion about this over post-flight beer - someone should really figure this out.

But long story short, we only recorded two sprites to high speed tonight, neither of which was very good. One we only got the upper halo part of (which is pretty useless as spectra goes), and the other saturated the intensifier, so we can't use its spectrum either. We called the flight early, and now have about 10 flight hours left. Enough for two 5-hour flights, or, if our next flight is good, we'll just stay in the air as long as we can and call that the end.

On the plus side, I got another sprite in my dSLR. This whole time I've wanted to use a tripod to place my camera in a window and just let it shoot, but the NCAR folks are pretty strict about stuff like that. Well everyone was interested enough in my shots from last time that I was able to ride the good spirits into putting my camera into the window with a gorilla pod, using my bandanna as a dark cloth. Looks like this:



The first of the two sprites tonight was too far forward to catch in the Nikon, but I did manage to catch the second one:



And, since we caught it on high speed as well, here's the same sprite at 10,000 frames per second, slowed down by about 666x:

So that's pretty cool. Since we still have 1 or maybe 2 flights left in this campaign, I'm still hoping to capture something that puts this to shame :P but if this is the best I get, it's still pretty damn good. And, the PI's are so impressed that they want me to put some real effort into this on the next campaign. It's a great public outreach opportunity, as demonstrated by the fact that my Flickr page got more than 10,000 views on the day I put the first pictures up. So if I don't get the shot to end all shots this campaign, I'll be well ready for it next time...

Edit: Oh yeah! In the sprite excitement I almost forgot we had some quite nice evening light while fueling the aircraft and waiting for dark:

Sprites 2013: Update #4

Last night we got out on the north edge of the storm and ran 'racetrack' paths back and forth. Scientifically, it wasn't a great night. The storm was nice and productive when we arrived on station, but the activity was spread out along a line, rather than focused in a hotspot, which makes pointing the cameras much more difficult - we basically wait to see sprites in the wide angle context cameras, then point in the spot they just happened. Well when the sprites are occurring all over the place that doesn't work so well. We only captured 7 sprites to high speed, and only one had a really usable spectra. After the first two racetracks the storm died off and we didn't really see anything for the next two, so we called it a night and went home.

Flight path in green.

However, I'm thrilled about last night for other reasons: I managed to capture both jets and sprites with my dSLR! I only know of a couple examples off the top of my head where people have captured sprites in SLRs, and I can't find any examples of jets captured with SLRs - am I the first? Since jets tend to hug the top of the clouds it's understandable that they're more difficult for a ground observer to see/photograph, so it makes sense that being up in a sprite-chasing aircraft would give me a serious advantage. The photo at the top of this post is, IMO, the cream of the crop, despite the strong motion blurring (the pilot would pick that moment to hit a bump...) It shows three jets shooting out of the cloud top just above some lightning, and it's even fairly well composed. Magic. Here is a good shot of a single jet - it looks like a blue butane lighter flame sticking out of the top of the cloud:



And here's the sprite I got, it's the red alien jellyfish on the top right:



Since I have a good starfield in both images, and I know we were about 200 kilometers from the electrically productive part of the storm, I can estimate the size of these things... but it's far easier to wait for the astrometry.net solver to give me a degrees/pixel solution than to figure it out myself, so we'll just wait for that.

For the technical aspect (skip this paragraph if you don't care about photography), I was shooting 1 second exposures, from a moving aircraft, handheld. I butted the camera up against the window glass and put my weight on it to get rid of most of the wobblies and light leaks, but the motion of the aircraft itself still showed up, especially when we hit a patch of turbulence  (we are, you know, flying right next to a thunderstorm). The city lights on the ground showed quite a bit more motion trailing than the stars so I cropped them out, but it was interesting to notice. For purposes of focus you think of both the city lights and the stars as being 'at infinity', but for purposes of parallax they really aren't. The instantaneous phenomena, the lightning, jets and sprites, show no motion blur. I used a 35mm f/1.8 lens held wide open, ran the camera at ISO 6400, subtracted a dark frame from all of them to get rid of the systematic noise, then ran strong noise reduction to help with the random noise. Some light dodging on the TLE's to make them a little more visible, but they are otherwise pretty much as-shot.

I was also able to see quite a few jets with my naked eyes! That's a first for me, and I'm always excited to see a new sky phenomenon for myself. I still haven't been able to see a sprite naked-eye, and it impresses me just how difficult that actually is. I'm flying in a private jet, right next to a thunderstorm, for the specific purpose of imaging sprites. I have very good low light eyesight, and I've watched tons of sprites in real time on the context cameras so I know exactly what and where to look. I was watching intently out the window while I snapped these shots, and the camera caught a sprite that I didn't see. Garggghhh! Since a typical sprite only lasts a couple of milliseconds, it's entirely possible it happened during a moment I looked away, or blinked. But still... Takeshi did manage to see one by eye last night, his first, so I'm not giving up yet.

Sprites 2013: Update #3

We flew again last night, the route shown above. More trouble with high cirrus clouds on the south and east sides of the storm, but eventually we came into clear air on the north side and were able to record 13 sprites in the high speed cameras. Fiddling about in the clouds for a couple of hours seems to be par for the course for this campaign. We used another 6 hours of flight time, leaving us around 18 more hours in the campaign. We're currently sitting at NCAR RAF and waiting to see how the weather will be tonight before making a decision to fly again: There currently isn't a lot of storm or electrical activity out there, much less the large positive charge-moment-changes we want to see, but the CAPE indicates huge instability out over the middle of Kansas, so we're hoping something will pop up.

I drove up through some of the canyons in the mountains today: It's really quite nice up there away from all the traffic and subdivisions. Because I have nothing else to add, here's a barn I saw today:



Update: As hoped for, a storm has formed in the middle of Kansas. It's very cold in the IR satellite imagery and the cirrus clouds are pretty confined this time. Pretty much exactly what we're looking for. Planning to take off at 10:30.

Sprites 2013: Update #2

We flew again the other night. The storm, over much of the Oklahoma / Missouri / Arkansas area, was massive and producing a ton of lightning.

Hans and Ryan looking at weather data and planning a course before takeoff.

We took off and headed that way, but cut a corner too close and got stuck in the cirrus clouds, unable to see either stars in the sky or cities on the ground. Just a black void out the window. After turning south and flying for a while, we came into clear air, cut north and ran up the east side of the storm through western Tennessee. At this point, after wasting ~2 hours of flight time, we started seeing a few sprites, and managed to record 11 on high speed with spectra. Not bad, but not really that good either. At least it was something.

Me sitting in the trigger seat with the log in my lap and my thumb on the trigger.

Later on, I saw a bright meteor - or at least it was bright on the low light camera. I trigger the high speeds so we got spectra of the meteor as well. Totally unrelated to what we were doing, but neat anyway. Also, while sitting and watching the screen for sprites, I watched a pixel die and become 'hot'. I've never seen that before.

Last night the weather was unpromising so we stayed on the ground and fixed an issue with light leaks: The dark cloth we had attached around the windows to keep reflections out of the cameras wasn't working too well. So we hung some new dark cloth which I think is a much better design, and that has nothing to do with the fact that I designed it. We then finished up the night by walking into a bar 10 minutes before close (at midnight... : / )

Weather looks dull tonight and tomorrow too, my guess is we won't fly tonight and will call a down day tomorrow so we can be ready to fly anytime this weekend, when the potential for big storms increases again.