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As we head into the 2018 Atlantic hurricane season, now is a good time to reflect on the accomplishments achieved by CYGNSS since its launch in December 2016. Early mission operations focused on engineering commissioning of the satellites and of the constellation as a whole. One achievement in particular is noteworthy. The satellites have no active means of propulsion, yet their relative spacing is important for achieving the required spatial and temporal sampling. The desired spacing is achieved by individually adjusting a spacecraft’s orientation and, as a result, the atmospheric drag it experiences. This technique is referred to as “differential drag”. An increase in drag will lower a satellite’s altitude, thereby changing its orbital velocity. We adjust the distance between spacecraft by adjusting their relative velocities. This is a new way of managing the spacing between a constellation of satellites, and one that can be significantly less risky and lower in cost than using traditional active propulsion. As a result, we were able to afford more satellites for the same price, which ultimately led to better, more frequent, sampling of short lived, extreme weather events like tropical cyclones.
Here is a figure, provided by CYGNSS team member Kyle Nave of ADS, illustrating the change in relative speed between two of the CYGNSS spacecraft that occurred the first time a differential drag maneuver was performed, on February 23, 2017.
The orbital phase rate between the two spacecraft is shown before, during and after the higher of the two had its orientation changed to maximize atmospheric drag. Phase rate measures how quickly the angle between two satellites changes. By increasing the drag on the higher one, it lowers to an altitude and orbital velocity closer to the lower one, thus reducing the phase rate. This was an important first confirmation of our ability to perform the maneuver. Since then, there have been many more drag maneuvers. Five of the eight satellites are now properly positioned relative to one another at a common altitude, and the remaining three are expected to have their drag maneuvers completed later this year.
The primary science objective of the CYGNSS mission is measurement of near surface wind speed over the ocean in and near the inner core of tropical cyclones. In an earlier NASA blog, (15 Dec 2017), I reported on our measurements of Hurricane Maria made in September 2017. Since that time, we have been examining the quality of our measurements both within and away from major storms. Measurements at ocean wind speeds below 20 m/s (44 mph) were found to have an RMS uncertainty of 1.4 m/s (3 mph). Measurements of storm force winds during the 2017 Atlantic hurricane season were found to have an uncertainty of 17% of the wind speed. The analysis that produced these results is reported in Ruf et al. (2018). DOI: 10.1109/JSTARS.2018.2825948.
CYGNSS operates continuously, over both ocean and land, and the land data have been another focus of recent investigations. The quality of some of those measurements, in particular regarding its spatial resolution, has come as something of a pleasant surprise. Here is one example of CYGNSS land imagery, of the Amazon River basin in South America, provided by Dr. Clara Chew of UCAR.
In the image, inland water bodies are prominently visible. This includes not only the major arms of the Amazon River but also its quite narrow minor tributaries. Careful examination of this and similar CYGNSS images suggests that the spatial resolution is markedly better here than it is over typical open ocean areas. The explanation lies in a transition of the electromagnetic scattering from an incoherent, rough surface regime over ocean to a largely coherent, near specular regime over inland waters. The fact that coherently scattered signals have inherently better spatial resolution is a well known phenomenon. What was unexpected is the widespread, global extent to which land surface conditions support coherent scattering. It requires the height of the surface roughness to be significantly below the wavelength of the radiowave signal, which in our case is 19 cm. This is apparently a ubiquitous property of wetland regions. It is a very fortuitous property for us, as it should enable an entirely new direction in scientific applications of CYGNSS measurements over land. NASA has recently added new investigators to the CYGNSS team specifically to study these new and exciting land applications.
A recent article summarizing these and other CYGNSS achievements, as well as some of the future applications of its measurements, is available at <www.nature.com/articles/s41598-018-27127-4>. The mission has demonstrated that smaller, more cost-efficient satellites are able to make important contributions to the advancement of science. In the months and years ahead, CYGNSS will hopefully be able to demonstrate that those advances can lead to practical scientific applications, such as extreme weather monitoring and prediction, that will benefit humankind.
So the challenge of writing the last blog for the NASA NAAMES field campaign has fallen into my hands and I have to admit that I don’t know what to write. There is a ton of exciting science to share and many stories of adventure, but regaling upon these discoveries and outward experiences seems inappropriate for this final entry. I think it instead better to try and capture the deeper personal aspect of seeing this long journey come to an end. And it is here that I find myself at a loss for words. Perhaps a path for describing this experience is to draw upon one of the final scenes from Peter Jackson’s filming of the Lord of the Rings…
After a tumultuous journey, our four heroic hobbits, Frodo, Sam, Merry, and Pippin, finally find themselves back in the Shire at the local tavern, each with an ale in hand. All around them, Shirefolk are laughing and carrying-on, but the four hobbits quietly sit around a corner table looking at each other and saying nothing. They are experiencing the loneliness of a profound shared experience that leaves nothing left to be said between its participants and nothing that can be told to an outsider that will adequately convey the events that have taken place. Each has seen the strengths and weakness of the others and themselves, and this knowing tightens the bonds of friendship. It is a moment that needs no spoken words, but it is also a moment that cannot last. Eventually, the time comes to raise the glasses at the unspoken words and re-engage. This moment comes for the hobbits and each is soon following their new paths in life, but not without the lasting bond of their shared adventure.
Fortunately, NAAMES has not required us to cross middle-Earth, fight impossible battles, and cast a cursed ring into the fires of Mount Doom, but I believe that, beyond the science accomplished, it has created bonds of friendship linked by a common experience. Perhaps it is here that the greatest value of NAAMES can be found. Like the hobbits, we will soon arrive at the shire of Woods Hole and meet together for a final celebration. As at the end of the first three NAAMES campaigns, I expect this final celebration will once again be similar to the above described scene from Lord of the Rings. We will be a group of friends celebrating a common adventure that those outside our group cannot fully understand. We will share stories, relive particular moments, appreciate each other’s company, and raise a glass to a wildly successful cruise and mission before we all depart to reintegrate into our separate lives back home.
Beyond this, I believe there is little left to say other than to extend my personal and profound gratitude to all the loved ones back home who have follow our blogs and waited for us to return safe from the sea, to the captains and crew of the Atlantis and the shore support at WHOI who have made the NAAMES campaigns possible, and to all the scientists involved in NAAMES who have enabled this mission to be successful beyond my wildest dreams. I simply cannot wait to see and read about all the new insights gained from our work as it emerges over the final year and a half of the NAAMES project!
My deepest thanks to you all,
Written by Michael Behrenfeld
Shifting Seas, Shifting Science
The ocean is wildly emotional,
often shifting within short periods of time.
Those emotions easily permeate into the psyche,
but they come and go.
A cloudless afternoon with gentle seas brings a soothing warmth,
an invitation for an embrace.
But the next morning brings howling winds that bites at my bones.
Following is a sea foaming at its waves, angrily lashing out,
driving me to seek some semblance of safety inside the ship.
View of the Atlantic Ocean from a window of the R/V Atlantis
In that moment, I realize that what appears to be a large steel vessel
is actually a small thimble in a vast desert expanse.
I, those around me, and those at the helm,
are all subject to the passing moods of the ocean.
All that we can do is roll with it.
This can be challenging when the ground moves beneath us,
constantly nudging us off balance,
changing the trajectory of where we were planning on going,
on what we had planned on doing.
Now here’s this.
Wise not to become too attached to plans when voyaging the high seas.
When storms brew confused currents,
best to change course before getting caught.
Though forced to retreat to waters once visited,
this tack from intention may seem less than ideal,
but new opportunities are presented.
Signatures of change can be diagnosed:
things grew,
some things grew better,
things died,
some things survived,
things ate,
some things were eaten.
things were infected,
some things escaped detection.
We’ll uncover who, how, and why.
The ocean is immense.
What’s happening here might be similar to what’s happening there,
or maybe what will take place later,
or maybe what has already taken place.
It’s hard to really know.
To piece the puzzle,
we collect hundreds of liters of water,
filter it, fix it, freeze it,
then repeat.
Again, again, and again.
This is the tedious effort that drives great strokes of progress,
as long as the ocean allows.
No matter how the ocean feels,
It’s always humbling
to see it,
to be in and on it,
to explore it,
to wonder about it.
To pay heed to its emotions is to respect it.
Only then do opportunities arise to learn from it.
Sunset over the ocean, as viewed from the deck of the R/V Atlantis.
Written by Nicholas Huynh
Transiting
As we are transiting back to Woods Hole, a calm and fresh atmosphere can be felt in the mood of the ship’s life. People start asking all sorts of questions about the first thing you will do on land, as a nostalgic reflection of the things that we miss. We have left behind the rush of the intense science days and a space for contemplation and thinking opens. Although some of us keep sampling during the transect, this is the time to read the books that were carefully selected before the cruise while we enjoy surfing the waves and sunlight. Calm in the labs can be suddenly disrupted by a “pilot whales on starboard side” shout, followed by a stampede of eager scientists carrying their cameras running towards the ship’s bow. Most of the times it’s difficult to spot them in the vast oceanic blue and the only shot that we have is that of a big wave splashing the ship’s front, which is awesome by itself (no complaints).
This free time led me to write on this blog about a frequent question asked by family and friends; what do you do in your spare time aboard? Unless you have been in a research vessel as the Atlantis, it’s difficult to have a picture of what it means living at sea. Each shipmate has it’s own way to spend free time, so I will write about some of the most popular activities.
TV room and library: dynamics in the TV room are quite intriguing during the day. You can see sporadically one or two shipmates hanging around without paying attention to the TV. During lunch and dinner this room gets crowded and people enjoy their meal while watching a movie. Both spaces are famous due to the presence of the popular “blue comfy seats”. Blue comfy seats are present also in the library and have become a highly demanded luxury during science meetings. People even start occupying them as long as 20 minutes before our daily gathering, reminding me those concerts where you got early to get the best spot. Most of the time, library is occupied for working, reading, and napping.
Board games in the mess: this is other popular activity that takes place usually after dinner and sunset. Some games can go very late.
Launching meteorological balloons: yes, this is a very fun activity. During good weather you can collaborate launching balloons from the O2 deck. This activity has become a highly competitive sport during this campaign and rumors say that even chocolate and chips are being bet to the balloon that reaches the highest altitude. Participants require a set of skills involving grace, wind control, strength, and lots of luck.
Reading: as mentioned before, reading is one of the most popular pastimes in the cruise. During sunny days, you can see people sitting in the aft deck enjoying the sunshine and their favorite books. Naps and reading have had a huge improvement this year due to the presence of the most comfortable beanbag.
Caitlin, Bryce, Eric and Ali enjoying a morning reading.
Notice how books can have a double function.
Watching sea creatures (from micro to macro): this activity includes all sizes of creatures. We can spend hours watching the pictures of microorganisms retrieved from the Inline Flow Cytobot. As you can imagine, we always are paying attention to the ocean and trying to spot whales, dolphins, birds and any other creature that decides to show up and say hi to us.
Sunset and sunrise: most of our lives aboard are determined by meals and sun cycle. Sunrise and sunsets are simply amazing. Watched from the middle of the ocean, there’s always a new beautiful picture to take. Even more, some kind of ritual has been established. I had never heard so many times “My heart will go on” by Celine Dion.
Writing this, I realized how lively NAAMES has been and how lucky I’m for having the opportunity to share the passion for science and ocean with an awesome group of people. As the last NAAMES field campaign is coming to an end, I can only thank the Atlantis research vessel crew, the science team, and the people in charge of logistics for making of NAAMES a wonderful, successful and enriching experience.
Written by Luis M. Bolaños
The rhythms and routines that form at sea are dictated more by our daily tasks than by a weekly pattern, as often is the case on land. Monday, Wednesday, Saturday…these words do not have meaning while living on boat, whereas meal times, science meetings, and sunsets do. The balance between monotony and routine is delicate; a routine gives me some purpose and is the framework to build a productive day around, but too much of the same and you can lose the spark needed to push forward with the science, the brainstorming, the attention to detail.
We are all “stuck” on this boat, with nowhere to go – but to stand on deck (or on the bridge, four levels above the main deck and where the boat is driven from) and watch the power of the sea all around – it never gets old, for me. Sure, I have my reasons for wanting to be back on shore, as we all do, but to stare at the ocean and sky all around…it makes me feel small and humbled and grateful to exist on this planet. Deep, I know.
Looking down at the ocean from the deck of the R/V Atlantis.
The past few weeks have brought challenges to our work in the form of weather and equipment failures, and yet people keep smiling, laughing, running new experiments, and generally embracing the situation. The work we do is real and raw and unpredictable…and for all the prior research that has been conducted to study this part of the world ocean, we still have so much to learn. The beauty of research is that we don’t know what we don’t know. Being at sea is poignant reminder that studying the ocean and atmosphere is a blend of organized and calculated experiments with creative openmindedness. The data collected from this expedition, and in combination with the results from the first three NAAMES cruises, will allow us to add our piece to the scientific puzzle and push the bounds of our knowledge forward by another increment.
Views of the Atlantic Ocean from the R/V Atlantis.
I try to make a conscious effort to take pictures of something aside from the ocean view, which without a doubt is the most photogenic option around…but the reality is that most of our hours are spent in the labs, futzing around with instruments, filtering water, or staring at screens. For example, once a day we clean and calibrate the suite of instruments that we have installed in a “flow-through” set-up, which means that they run continuously and collect data around the clock from seawater that is continuously pumped from the surface waters beneath the boat. See the pic below for the usual daily instrument-cleaning scene.
Nils performing the daily instrument cleaning.
After nearly three weeks we are fairly well adjusted to the sea-going lifestyle, so to give you a small insight into what that means, I’ll leave you with a short list of things that rarely or never occur on land but that are 100% acceptable at sea:
• wearing the same outfit for several consecutive days
• prolific swearing anytime, anywhere
• lying down on the floor beneath your lab bench to catch a quick nap
• top-of-your-lungs singing Celine Dion’s “My Heart Will Go On” with colleagues (sober…)
• lamenting the logistical challenges of remaining upright while showering and without flooding the bathroom floor (I’m still working to achieve this goal…)
Written by Ali Chase