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Notes from the Field

We are still at South Pole Station.

As we were finishing up the preparation of the sleds used on the 88S Traverse, we realized that we were missing a couple of fittings that pair our propane tank to 2 Coleman cook stoves. It seems like a small part, but that part is fundamental in allowing us to cook meals while simultaneously melting water to stay hydrated. So we were stuck…

Amundsen-Scott South Pole Station.

We called the science-support crew in McMurdo that had the fittings and they tried to get the part on the next plane to the South Pole. That plane would be the last one to arrive before a long 2-day break associated with the New Year holiday. The science-support crew in McMurdo went so far as to chase down the vehicles headed to the airfield to hand them this part! But they couldn’t chase them out onto the ice shelf, to the airfield associated with aircraft equipped with skis. So we ended up spending New Year’s Eve at the South Pole.

While time at South Pole is arbitrary, the convention here is to be on New Zealand time, primarily based on the air support through Christchurch. About a couple hundred yards from Amundsen-Scott South Pole Station is a large camp associated with expeditioners that come to the South Pole, with a commercial logistics provider. Their air support is through South America. Thus, people that are just a couple hundred yards celebrated the New Year 16 hours apart.

Expeditioners camp, just a couple hundred yards from Amundsen-Scott South Pole Station.

The coolest thing about spending the New Year at the South Pole is the 1 January ceremony to place a geodetic benchmark on the geographic South Pole, or 90°S. Ice sheets are dynamic; they move under their own weight very slowly, like thick maple syrup moving toward the edge of your pancakes. Thus, South Pole Station is slowly moving away from the geographic South Pole. Every year, on the first of January, a new benchmark is placed on the surveyed geographic South Pole. The benchmark itself is designed by the science-support crew that spends the long, isolated winter at the station, ensuring that continuous scientific observations are kept running!

The 1 January 2020 ceremony to place a geodetic benchmark on the geographic South Pole.

The old benchmarks are removed and put on display inside the station. They often represent current happenings at South Pole Station, such as the year that the new station was completed. The older benchmarks contain the names of the US Geological Survey personnel that used to come down and survey the geographic South Pole; I used to work with many of those folks and it was pretty cool to see their names again! The newer benchmarks often contain the names of all of the winter-over science-support personnel, or the folks that designed the new benchmark.

Geographic South Pole benchmarks on display at South Pole Station. The one in the upper left is the oldest benchmark, dating from 1984.

More recent geographic South Pole benchmarks on display at South Pole Station. Some of these get quite elaborate!

The new 2020 geographic South Pole benchmark! The names of the winter-over science-support personnel are etched into the post.

Happy New Year!

-Kelly & Thomas

Greetings from Amundsen-Scott South Pole Station

January 2nd, 2020 by Kelly Brunt

The third 88S Traverse is about to commence!

For the past couple years, we have conducted a 450-mile ground-based traverse collecting highly accurate GPS elevation data. These data have been used to validate elevations from NASA’s ICESat-2 satellite mission. You can see videos from the previous 2 traverses here and here. And you can see results from the previous traverses here.

Over the past three weeks, we have traveled quite a bit to get to the South Pole. We started in Maryland and flew via commercial airlines to Christchurch, New Zealand. We spent a couple days in Christchurch, where we were provided with special clothing for the extreme cold temperatures of Antarctica. Next, we flew from Christchurch to McMurdo Station, Antarctica, on a New Zealand military C-130 aircraft. That was about a 7-hour flight, with pretty modest accommodations. We spent about a week in McMurdo collecting the gear that we will need for the traverse, such as sleeping bags, tents, radios, etc. Once we had (most) of our gear, we flew from McMurdo Station, which is on the coastline, to Amundsen-Scott South Pole Station, which is in the center of the Antarctic Ice Sheet. That was aboard a US Air National Guard LC-130, which is an aircraft equipped with skis, for landing on the ice sheet.

New Zealand C-130 aircraft.

88S Traverse members Kelly and Callie aboard the US LC-130, enroute to the South Pole.

One comment about the South Pole: It’s very high. We are at about 9300 feet above sea level, but the dryness makes it feel more like 10,000 feet or even more, depending on the barometric pressure. Thus, the first few days here are very challenging as your body tries to acclimatize to the altitude. In general, after we arrived, we took it very easy.

Once we arrived at South Pole, we started to rig up our sleds for the traverse. The 88S Traverse is a two-week endeavor using tracked vehicles called PistenBullys to haul sleds that contain all of our equipment needed to live and work on the Antarctic Ice Sheet. The sleds carry our sleeping and eating tents, fully deployed, so we set up camp just once for the entire 2-week traverse! The sleds also carry the survey-quality GPS instruments that we use to collect the elevation data. GPS units in your car are accurate to about 10 to 15 feet. The GPS units that we use are accurate to well within an inch!

The Antarctic summer field season is from about late October to about early February, with the warmest part being in early January. As such, we spent Christmas here at South Pole. The folks here on station do an amazing job to make the holiday great, even though folks are thousands of miles from family. The galley does an especially great job; Christmas dinner was fantastic. The next day, the station hosted the annual Race Around the World, which is a roughly 2-mile running race that intersects every line of longitude. The male winner and the female winner earn a 10-minute shower here at Pole, which is a luxury relative to the usual 2-minute showers that we are allowed, twice a week. Two of the 88S Traverse team members ran the race; Thomas came in second, earning a 5-minute shower!!!

88S Traverse members Thomas and Callie at the ceremonial South Pole, after the Race Around the World.

Belated Merry Christmas to folks back home!

-Kelly & Thomas

More Fun Than a BARREL of Electrons

December 31st, 2019 by Andy Hynous

I realize that, you know, its New Year’s and all.  But while everyone is waiting for that big ball to drop in Times Square, here outside McMurdo, we’ve been working to send balloons UP! We just had a super successful launch of a 0.6 million cubic foot (MCF) balloon. Now, for us at in the Balloon Program Office, that’s a pretty small balloon; we generally launch balloons that are anywhere from 4 to 39 MCF. But the 0.6 MCF platform gives us a capability to support a whole lot of scientists that have small and very sensitive instruments with the ability to go where only we can take them. Up above you can see how these small balloons look just prior to launch. 

This flight really supported two missions for us. First of all, the instrument that we launched on the balloon was a part of a program ran by Dr. Robyn Millan at Dartmouth College. Robyn and her team are using the BARREL instrument to study electron losses from the Van Allen Radiation Belts. The instrument is able to capture when electrons literally fall out of the sky and measure their energy. One of the big things that their work will help everyone with is how to better protect satellites from the radiation in space. 

The second thing we want from this launch is for the balloon to be a pathfinder for a future NASA Explorers Program mission. We will use the trajectory that this flight follows, a similar flight from last year, and another follow on flight scheduled for next year to help bound the expected flight path for the future GUSTO mission.  GUSTO will be studying emissions from the particles that are in interstellar (between the stars) space and help shed light on the lifecycle of stars in our galaxy.

Now, I realize that 0.6 MCF is a pretty abstract number, so for those of you (like me) that think in real dimensions I wanted to give you an idea of just how “small” these balloons really are. When fully inflated, the 0.6 MCF balloon is 72.5 feet by 124.5 feet (yes, I said feet), and it quite frankly looks like a pumpkin! So if you take your average pumpkin from October and make it 55 times bigger then you have a 0.6 MCF balloon. Easy, right?  Another way to visualize it is if you took three full sized school buses and put them end to end, then that’d be the diameter of this balloon. Sounds pretty small to me.

I also want to circle back to that “pumpkin” shape I mentioned earlier.  Another thing that made this launch super was that this was a Super Pressure Balloon.  This design of balloon actually maintains constant pressure during its entire flight (just like a party balloon), and that gives us very good altitude stability during day and night transitions and long flight durations. Our record from last year’s Antarctic campaign was 73 days. 

My picture today is of the BARREL instrument at the foot of our flight line with Mt. Erebus in the background. And if you look behind BARREL, the red plastic on the ground is our balloon in its covering that protects it while we lay it out prior to launch. Thanks again for checking out my Notes from the Field: Balloons for Science blog.  And most importantly, have a happy New Year!

Eye of the SuperTIGER

December 18th, 2019 by Andy Hynous, NASA Balloon Program Office

Welcome again to below the 77th parallel.  I know it’s only been a few days since my last post went live, but I have some great news from WAY down south.  Today, I wanted to cover the picture-perfect launch of the SuperTIGER mission from our Long Duration Ballooning Camp from here outside McMurdo Station, Antarctica. 

On the 16thof December, we left McMurdo Station at 1 p.m. to catch a ride to our camp for a 10 p.m. launch attempt. Once we got there, our Weather Wizard (most people would call him a meteorologist, but what he does seems like magic to me) told us that the time we could launch the balloon would be later than we thought. How much later you ask? Try four hours later!!  So with that bit of good news, the launch crew and science team that were there to support launch did what they could to get ready and then we waited. Once we finally had a handle on how the winds were blowing, we started our launch operations. Aside from the delay, everything went as smooth as silk.

The fist picture shows the SuperTIGER instrument on our Mobile Launch Vehicle. Because we like our acronyms so much, we usually just call it the “MLV.”  The first thing that is done on a launch day is we take the instrument out and put in on our launch vehicle so the science team can make some final checks of their communication systems. Down here in Antarctica, we use a lot of satellite radios for transmitting the data from the instrument back to the computers that the scientists use to do their work.  All of this happens on the launch vehicle. 

The second picture shows SuperTIGER, the almost quarter mile flight train, and the very top section of the balloon waaaaaaaay in the back! Between SuperTIGER and the balloon is all the equipment we need to make the mission safely fly. There is a parachute, some more communication systems, and other stuff that allows us to track the balloon and make sure that it’s flying just fine.

The last photo for today is from the actual launch right after the balloon was released from the ground. It was a bit of a cloudy day, but for us all that really matters is that the winds aren’t too strong. 

I know… I know… Enough of this launch stuff, now you want to know what SuperTIGER does. Well, once again I’m just completely blown away but what our scientists can do. The SuperTIGER instrument is trying to see what kind of elements (like hydrogen, helium, iron… Stuff from the periodic table) are created when stars go supernova. SuperTIGER is primarily wanting to measure elements that are heavier than iron. The scientists that are taking these measurements are trying to understand how our own (home, sweet home) solar system was made. In the words of the principal investigator Brian Rauch: “It is true that the information we gather will help us understand how the stuff that we, our world, and indeed the rest of the visible universe are made of is created from the basic building blocks left over from the Big Bang. We are after all made of star dust, and we are measuring individual pieces of that.”  That’s pretty out of this world if you ask me!

Happy Birthday, CYGNSS! Three years on orbit

December 16th, 2019 by Chris Ruf

CYGNSS was launched on December 15, 2016 at 13:27:21 UTC and today marks the completion of its third year on orbit. Much has happened in that time and the future looks very promising, with all eight microsatellites healthy and operating continuously in their nominal science data-taking mode. Year 1 was spent on engineering commissioning and initial ocean wind measurements. In year 2, the ocean wind retrievals were refined and characterized and investigations of observations over land began in earnest. This past year has seen progress on several fronts. An important refinement to the engineering calibration has been developed. Ocean wind measurements in tropical cyclones have been successfully introduced into numerical hurricane forecast models. And the ability to image inland waterbodies with high resolution has been leveraged to demonstrate two new measurement capabilities.

CYGNSS measures the strength of GPS signals reflected by the Earth surface, from which properties of the surface are derived. To do this accurately requires knowledge of the signal strength transmitted by the GPS satellite. The original approach to calibration assumed each GPS satellite had a unique transmit power level and that it did not vary in time. The unique power levels were estimated using measurements averaged over several months. Subsequent analysis has revealed that GPS transmit power can vary significantly, depending on the particular satellite and on its position in orbit. In order to compensate for the changes, the direct signal GPS receivers on all eight CYGNSS satellites were reprogrammed in 2018 to act as power meters which can monitor the variations in transmit power [Wang et al., 2019. A Real-Time EIRP Level 1 Calibration Algorithm for the CYGNSS Mission using the Zenith Measurements. Proc. IGARSS 2019]. The impact of this change is illustrated in the following figure. The top panel shows the geographical distribution of the average error in CYGNSS wind speed for a single GPS transmitter (SVN 63) assuming its transmit power is constant. The center panel shows the actual GPS transmit power as measured by the new on-board monitoring system. Clear localized differences in the measured power are evident which correlate with the errors in wind speed. The bottom panel shows the distribution of average wind speed error after the monitored power is incorporated into the calibration. The discrepancies have been largely removed.

CYGNSS wind speed bias before (top) and after (bottom) a dynamic correction was added for variations in GPS transmit power.

Over the past year, CYGNSS ocean wind measurements have been added to the HWRF numerical forecast model used by the National Hurricane Center and compared to the standard operational forecast, which does not yet use CYGNSS. To forecast a hurricane, HWRF is first initialized with satellite, airborne, and ground based measurements. The storm is then allowed to develop in software, guided by underlying physical principles of thermodynamics, radiation and mass and energy conservation. An example of this is shown in the following figure, which presents three versions of the horizontal wind speed at 3 km altitude for Hurricane Harvey on 25 Aug 2018 at 06Z. The left panel is the 24 hr forecast predicted on 24 Aug by the operational version of HWRF without CYGNSS data. The center panel is the HWRF prediction with CYGNSS winds included. Note the azimuthal shift in predicted peak winds into the northeast quadrant when CYGNSS winds are included. The right panel shows measurements made by NOAA’s airborne doppler radar of the actual winds at 3 km. The predicted azimuthal shift is confirmed, suggesting that the storm’s development is being more accurately modeled [Cui et al, 2019. A Preliminary Impact Study of CYGNSS Ocean Surface Wind Speeds on Numerical Simulations of Hurricanes. Geophys. Res. Ltrs.].

HWRF 24 hr forecasts of wind speed at 3 km altitude: (left) without; and (center) with CYGNSS winds used as inputs. The right panel shows actual 3 km winds measured by a NOAA/HRD airborne doppler radar.

More accurate modeling of storm development should help forecast the intensity of its surface winds, and this has been demonstrated by another study using HWRF [Annane et al., 2018. Impact of CYGNSS Data on Tropical Cyclone Analysis and Forecasts Using the Operational HWRF. 33rd AMS Conf. Hurricanes Trop. Meteo.]. In this case, a 120 hr forecast of minimum sea level pressure (MSLP) in the eye of Hurricane Michael was conducted on 8 Oct 2018 at 00Z without and with CYGNSS winds included as one of the inputs. The left panel in the following figure shows the true (best track) MSLP in black and the operational forecast (without CYGNSS) in red. The rapid drop in MSLP that occurred between ~30-60 hr is not well forecast. The right panel shows the HWRF forecast with CYGNSS winds included and can be seen to more accurately predict the rapid intensification of the storm.

HWRF forecast of minimum sea-level pressure in the eye of Hurricane Michael shown in red: (left) without; and (right) with CYGNSS winds used as input. Best track MSLP shown in black.

CYGNSS measurements over land are able to provide high resolution tracks across inland waterbodies when the surface is calm enough to support coherent specular scattering. A new land/water mask has been developed which leverages this capability as well as the ability of CYGNSS to penetrate through clouds, rain and vegetation canopies. As a result, dynamic changes in waterbodies (e.g. due to flooding, seasons or human development) can be resolved better than existing water masks that rely on optical satellite imagers. [Gerlein-Safdi and Ruf, 2019. A CYGNSS-Based Algorithm for the Detection of Inland Waterbodies, Geophys. Res. Ltrs.]. An example of this new capability is shown in the seasonal watermasks of the Okavango Delta in Botswana derived from CYGNSS overpasses in 2018. The left panel, for Dec/Jan/Feb, shows the typical river boundaries that are present during the dry season. The mask in the right panel, for Jun/Jul/Aug, captures the widespread flooding which occurs during the rainy season.

CYGNSS water masks of Okavango Delta in Botswana during the dry (left) and rainy (ight) seasons.

CYGNSS overpasses of rivers also produce high resolution tracks that can be used to measure a river’s width and infer its streamflow rate. This has been successfully demonstrated using overpasses of the Pascagoula River in Mississippi during a major flood event in April 2019 [Warnock and Ruf, 2019. Response to Variations in River Flowrate by a Spaceborne GNSS-R River Width Estimator, Remote Sens.].  Streamflow measurements by a USGS river gauge made before, during and after the event are shown in the upper panel below, together with markers at the times of each of five overpasses by CYGNSS. The lower panel shows the Associated GNSS-R Width (AGW) of the river derived from each CYGNSS overpass, together with the Pascagoula’s streamflow rate at the time.

Associated GNSS-R Width of the Pascagoula River measured by CYGNSS overpasses during a flooding event. The AWG is highly correlated with flow rate measured by a USGS streamflow gauge.

The two are highly correlated, suggesting that another new type of CYGNSS data product may be possible over inland waterbodies.