Tag: Nilsen Strandskov (Page 1 of 11)

Hey All!

Over the past few weeks Silbo has continued his way past the Cape Verde archipelago and on into the open ocean.  Progress has been slow however as the currents have been strong to the North, North-West and North-East; the opposite of what we see as ideal.

After rounding the most western island of Cape Verde and fighting a pretty strong head current as we tried to make progress south, we moved the way point out west to try and increase the ground covered between surfacings.   By doing so, we are trying to take a more northern route across the Atlantic so that at the later end of the mission, we are in better shape for an emergency recovery off of Brazil rather than being stuck in the middle of the ocean.

Another reason behind this decision, is that at the moment, we have very little options for routes to the south.  For weeks now, the current in our vicinity has largely been flowing to the North.  So as we slowly make progress, we are hoping to find an outlet that may help us in the direction we want to go.

Unfortunately, our road maps are not always as reliable as we would like.  Of the three different ocean models that we have been using throughout the mission, all three are showing a current that disagrees with what Silbo is showing us.  While Silbo is showing the currents moving to the north in a pretty strong jet, the RTOFS, MyOcean and NCOM models all show a current flowing to the south:

Real Time Ocean Forecast System Sea Surface Height & Currents

NCOM Currents & NLOM Sea Surface Height

MyOcean Sea Surface Height & Averaged Currents 0-1000 m

MyOcean Sea Surface Height & Averaged Currents 0-1000 m

As the current continues to look unfavorable, Silbo and our team will persist in our attempts to fight back and try and make progress towards Brazil.  Hopefully a new path will reveal itself soon and Silbo can coast a little after fighting for so long.

Force Wind Sea & Honor

Nilsen & Antonio

Hey All,

sorry about the delay on my end, but here are the photos from Silbo’s inspection mission!

A special thanks to Alvaro Lorenzo and Laura Cardona from PLOCAN for taking part in this mission and getting Silbo ready to cross the Atlantic

Hey all!

Over the past week, I have been looking at a way to check the accuracy of the tools we use to pilot our long duration gliders. So far, we have been using wind mapping sensors and wave height analysis from Marinemet, NCOM geostrophic currents, myocean currents at various depths through the water column,  and the ROTFS model.  This week I was able to run a preliminary analysis on the myocean and ncom data sets.

As both data sets are available in netcdf format, I was able to dissect them and easily pull out the data for the area around the glider.  While the NCOM data is the geostrophic average, there is only one data point to directly analyze, but with myocean, we are able to take a number of points throughout the water column from surface to the depths Silbo dives to (in this case 1000m) to average.  The myocean data is pretty interesting to compare, as in order to do so, I take a number of points and take the average, similar to how we arrive at the currents that Silbo records.

At the beginning of the week, I calculated the the % error of the values for the models using the numbers recorded by Silbo as the accepted value, and both were roughly within 15% from the magnitude of Silbo, and 20% when direction was compared.

Towards the end of the week I began making these plots that I will keep up when I have the chance, visualizing the magnitude and direction or the currents, withe the blue arrow being of the myocean data set, green being NCOM and red being Silbo.

Force Wind Sea & Honor

Hey All!

Well the inspection mission was a success!  Saturday morning, Alvaro and our team from PLOCAN arrived on site to meet Silbo aboard the Islandia after leaving port late the night before.

News from the boat is that there was some barnacle growth on Silbo’s nose cone which we will have photo and possibly video footage of within the next couple days, along with a more in depth play by play of the goings on of the inspection.  However, Alvaro was able to scrape the hitchhikers off and wish our little droid luck as he prepares to cross the Atlantic.

Before he departs on this epic journey, Silbo is doing a lap around Geomar’s mooring that is in our vicinity.  Tomorrow, Silbo will be given instruction to enter into low power mode, proceed to dive to 1000m, head to the north west to round the corner of the western island of the Cape Verde Archipelago and the two seamounts, and leave sight of land as he heads out into the North Atlantic.

Force Wind Sea & Honor

Nilsen & Antonio

Hey All,

So it has been a hectic month, but Silbo and our team are making final preparations for an inspection that will take in the early hours of the morning.

First let us back track a bit and catch up on what has happened in recent weeks.  Since Antonio and I did the barnacle analysis back in June after recovery, we started making projections for potential growth on the next journey.

From our findings, we saw that due to the temperature variations in the water column of the North Atlantic, it would be more likely that we saw substantial barnacle growth between the Canaries and Cape Verde than Cape Verde to Brazil due to the temperatures at depth (seen in the temperature map above).  Another point supporting our hypothesis was that we were flying Silbo through some of the most productive waters in the world, thus why the islands have been called Cape Verde.  This year has also been a very productive year as there have been a number of strong wind events over the Sahara that have deposited iron rich dust into the waters off the African coast which have sparked some large blooms.  So as we flew Silbo through these productive waters, we began to worry that we may start picking up some hitch hikers.

To try and monitor if we were picking anything up, I began looking at Silbo’s velocity with the help of Dave Aragon.  We initially looked at the raw vertical velocity Silbo reported at each surfacing.

As the weeks went on, we saw some slight indications that we were going slower, but we couldn’t be completely sure of what was going on.  We then started filtering data, taking out times that we were at the surface, and then correcting the data for changes in pitch and ballast to try and get a better estimate on what the velocities were.

We also added a 10 day average to see any trends in the data, and we saw that there was a definite slowing occurring over the course of the last three weeks.

We had previously discussed a collaborative 48 hour station keep in the vicinity of the Geomar mooring site just north of the islands of Cape Verde and we proposed the plan for an inspection.  This would be our last opportunity for contact before Silbo would leave the coast and set sail to cross the Atlantic with Rio De Janeiro as our finish line.

After coordinating with our team,  PLOCAN was able to secure a boat and a crew of scientists and technicians to go out on a boat, while our friends Ben and Lauren at Webb provided ground support for an inspection.   The tricky part it seems will be communication as the boat does not have internet and our team is without a satellite phone.  So what we plan to do, is to use Silbo’s iridium and freewave connection as a sort of instant messaging service, with Ben and Lauren leaving messages for Alvaro via iridium and Alvaro responding through the freewave.

Alvaro and our friends have left harbor a few hours ago now, and plan on being on site by 8am gmt, so as they near the area, Ben and Lauren back in the US will be ready to catch Silbo and stop his mission so that the ship can find him.  While Silbo waits for the boat, he will drift with the currents it looks to the west (red is surface whiel orange and blue are 250m and 500m respectively).

News of the inspection will be relayed back throughout the morning, so over the next couple of days we will make sure to update everyone and release the pictures!

Good luck to our team!

Force Wind Sea & Honor

Nilsen & Antonio

Hey all!

As we head into the Labor Day weekend, Silbo is continue to fly along as he continues to keep up a good pace of over .3m/s

With the new way point we set last week, we really started to cruise to the southwest setting our speed record for the mission thus far and keeping an average speed up of roughly .3cm/s.

Looking at the Satellite imagery (curtsy of Antonio &  http://www.afrimet.org/marinemet/ ) although there is quite a bit of cloud coverage blocking our view, we can see there this is quite a bit of productivity in the waters to the south east of Silbo.  Relative to the image below, Silbo currently is flying through the upper left corner of the map, where the imagery cut off.

As for our data, this week we will have a new way of looking at the data we have been using all along.  I have been working on getting the code that Mike Smith uses to visualize the CODAR data we have along the Mid Atlantic Bight and applying it to the data sets Antonio has been supplying us with since Silbo’s deployment off of Iceland over 16 months ago to create kmz’s that will allow us to see satellite and ocean model data accurately visualized in google earth along with Silbo’s latest position, allowing us to see what the conditions of the water are like not only at the surface, but throughout the entire water column.  Although there are still a few more things to work out, below I have an image the currents at the surface, 100m, 300m, 500m and 1000m in the area around Silbo.  This along with temperature, salinity and wave height data will allow us to make more accurate decisions for glider piloting, which will really prove its value as we continue to grow our global glider fleet.

Force Wind Sea & Honor

Nilsen & Antonio

Hey All!

well it is hard to believe, but Silbo has been back at sea for a month already as he voyages south towards Cape Verde.

Granted we have had a bit of a sluggish start as we have had unfavorable currents basically since deployment, I have made an estimate of where Silbo will be on the first of each month as he crosses the Atlantic basin.

If we can keep Silbo in more favorable currents (which will easier in the coming weeks) we will undoubtedly fly faster than this projection shows, but Silbo should make landfall in Rio sometime in late spring 2013.

As for our current flight, the currents are pretty mundane and so we are nearly flying at our own will, allowing us to fly a nearly straight line towards the way point.  In the coming days as we move further south, we plan on swinging the way point out west to catch some south westerly currents that will carry us out further from the west african shelf.

Force Wind Sea & Honor

Nilsen & Antonio

Hey all

After our little bought with the strong north east currents, Silbo has gotten back on course towards the south west.  Looking onwards, Silbo has a long and winding road ahead, as he flies south past the Cape Verde Islands, across the Equator and on the Rio de Janeiro.

The distance between Silbo and our ideal recovery sight is roughly 7,400 km, with our only safety net being Cape Verde.  This leaves us with nearly 5,000 km of open ocean flight where if we run into any trouble, it will be tough to get ourselves back out.  But in the name of science and adventure, Silbo is backed with a team that are determined to safely navigate him through the Atlantic and assure his safe arrival.

One way in which we have prepared Silbo for this journey is we have crammed his hull to the brim with lithium batteries, which when coupled with the new low power mode setting released by TWR has given Silbo over a year of energy!

In the plot above, we can see that Silbo’s batteries are projected to last somewhere between 14 and 16 months from now giving us the potential to fly until January 2014.  How low power mode works is that instead of leaving the flight computer on 24/7, the computer is only turned on every 30 seconds during dives and climbs (after becoming situated during the process of inflection).  This conservation of energy has now given Silbo a very nice cushion, relieving us all of the stress of running out of power.

Force Wind Sea & Honor!

Nilsen & Antonio

Hey All,

I just wanted to update everyone on what happened last week when we flew backwards.

Last week, Chris DeCollibus (TWR) looked into the surface dialogs from Silbo around those surfacings and found the answer.  It seems that Silbo miscalculated the currents that it was encountering which resulted in the flying backwards.  When the mission was reset after we gave Silbo a new way point, the calculations of the current showed a significant difference, and so when Silbo was flying towards the way point, he flew using his dead reckoning and the incorrect currents.  This lead Silbo to believe that he would surpass the way point and needed to turn in order to arrive in the correct location.  If he were to continue flying without turning, the logic of  the glider believed that it would fly well beyond the way point.  This mishap combined with the strength of these currents resulted in Silbo then flying 14km “backwards”.

Now we have new questions to answer: how can we speed Silbo up?

In the image above, I have taken the average velocity of Silbo for each segment he flies: red indicates the trip from Azores to Canaries and blue is the current mission.  So far on this mission, Silbo has been flying significantly slower than on the previous mission.  This potentially could be from the increased weight from the batteries over the previous configuration, but we need to discuss means of speeding up a bit.  On another note, in figure above, the red line from the previous mission shows how towards the end of the mission the velocity decreasing by nearly 1/3.  This correlates with the presence of the two barnacle cohorts described and analyzed here: http://www.i-cool.org/?p=11984

Force Wind Sea and Honor All!