Category: ru29 (Page 20 of 22)

Hey All!

As Challenger turns to fly to the north west with our new way point, she is closing in on the boarder defining the South African EEZ and the international waters!

It looks like the stream of eddies is moving out to the west so we are feeling less of an affect from the warm eddy to our south, however this is causing us to now feel the added effect of the cold eddy to our north resulting in a little more of a northward current at the surface.  Hopefully we will be able to ride this further to the north once we cross into international waters.

To the north, Silbo continues to fight his way through the northern flux created by the cold eddy to the west and warm signature to the east.  However there is some good news: the large warm eddy to the south west seems to be migrating in a north west direction. This we hope will expedite Silbo’s progress into more favorable currents.

Force Wind Sea & Honor!

Hey All!

Today during my discussion with Antonio of the layout of the playing field for Silbo and Challenger, Antonio pointed out something very interesting. The conditions that Silbo and Challenger are flying through are nearly symmetric!

As we fly away from South African waters, Challenger has found the trail of eddies that come from the Indian ocean, round the cape and shoot up into the South Atlantic Gyre, paving the road we plan on taking to the North East towards Brazil.  The depth of the thermocline from the warm eddies in the area also follows a trend Silbo is seeing, where the eddies closer to shore have a deeper signature.

In the north, Silbo again is seeing similar instances with the depth of the thermocline within eddies, but is also seeing a similar trail.  However this trail follows the equator and is formed from the interaction of the Northern and Southern Atlantic Gyres.

The salinity maps also have proven to be symmetric in the North and South Atlantic:

In the south, Challenger is flying away from a region of fresher waters from the upwelling event that has been fueling the plankton bloom we spoke about last week along the coast.

While up in the north, Silbo continues to inch forth towards the prominent Amazonian outflow which yesterday we pointed out causes the concentration of salt to decrease from 37 to 34.

Finally on the next surfacing, we are moving Challenger’s way point further to the north east from the current way point to make an attempt at flying more in a northern direction.  With the way point signified by the red dot in the image below, Challenger has been flying due east.  A heading that we are worried will not be enough to keep us from being sucked into the southern current created by the strong warm and cold eddy to our south and south west.

Force Wind Sea & Honor!

Hey All,

So starting late last week, we began to notice an anomaly with the flight patterns of Challenger.  On down casts, we were seeing a number of heading errors, causing us to fly irregularly.  This spurred a number of questioned followed by a brainstorming session to figure out what could have caused this.  After all, before deployment, the compass had been calibrated and was working well.  Ideas that we bounced around ranged from looking into a recent solar flare, positions of lows in ozone concentration, and high levels of ambient iron in the water; all of which could result in abnormalities in electronic compass readings.  Finally, our team began looking into similar instances we have had where a gliders compass had acted in a similar manor.  One of these instances that came to mind was a few years back when RU26 was flying in the Ross Sea off of Antarctica.  After doing some research, it was discovered that both the region off of South Africa and the Ross Sea are both areas with abnormal lows in the horizontal intensity of the Earths Electromagnetic field.

Now, we think that the problem we are encountering is that this low in horizontal intensity combined with the angle we were diving at causes our compass to have errors in the eastern quadrants, impeding our ability to have complete control of our direction on dives.

Since we have hypothesized this as the reason for our abnormal flying, we have done a number of tests diving at different angles and have now chosen to fly at 20˚ on dives and 25˚ on climbs.

While we were running the tests, we lost a bit of position on the eddy we are flying through, so I have now plotted not only the currents, but the U and V components to find the best route North and West safely into international waters.

U Component blue to the west and red to the east

V component Red being north and Blue to the south

Based off of these maps, we have placed the waypoint up to the North West hoping to weave our way between the fluxes while avoiding crossing into Namibian waters.  Other quick changes we made today were that low power mode has been turned back on at intervals of 30 seconds and current correction has been switched off so we can get a feel of how we can fly.

As for our boy Silbo to the north, he is still pushing along through the northern flux from a cold eddy to our south west.

Antonio has created another fascinating tool with the help of GeoEye and SeaStar showing correlations between the eddies and the depth of the thermocline.

From this map, we can see the presence of these eddies causes changes of up to 100m in the depth of the thermocline as we fly from warm eddy to cold eddy.

With the map above of sea surface height and currents with the overlay of the direction of the eddies, we can see that Silbo is continuing to fly due south between the influences of the large warm and cold eddies to the south east and south west respectfully.

Finally, Antonio left us a 3D map of salinity showing that starting from the Amazon and working out across the North Atlantic showing the range of 34 to 37: an incredible change for distance of 2000km

Force Wind Sea & Honor

Hey All!

So today I began looking into the salinity fields for the North Atlantic in search of any signals that may help fly south towards Brazil.  Our team has been thinking of looking into this to see if the Amazon and its fresh water fluxes may have any extending influences on this area. To start off our investigation, I plotted up some of the myocean data.

What it looks like from this perspective, is that the waters close to Brazil and along the shelf become much fresher and spill out a little into the North Atlantic, however subsurface, we see the Antarctic Intermediate Water creeping north.  This will need much more investigation as we get our other products up and working.

As for the currents, we still have some weak flows to the north, but to the south there is a strong jet that may prove to propel us towards the equator and maybe speed us up a bit.  But only time will tell and as for now, Silbo will continue to fight his way south on his journey across the Atlantic basin.

Today, we also did some testing on Challenger’s compass, which caused us to drop a little to the south due to the influence of the small cold eddy I mentioned last night.

This evening however, once the testing was completed, the waypoint back to the north was reassigned and so on the morning surfacing we should have some new northward progress.

Force Wind Sea & Honor

Hey All!

I just wanted to leave everyone with a quick update before bed.

18 days in, Challenger is continuing to make progress towards the way point to the North West.  The image below shows the sea surface temperature and surface currents:

As we can see, the warm eddy we have been chasing has collapsed a bit, resulting in a small cold core clockwise eddy that has produced a minor counter current that is slowing us down a little bit and pulling us a little to the south.  Over the next day, we will see how this current continues to affect us and may follow up with some changes.

In the north, Silbo is continuing to fight a head current.  Similarly we look at the sea surface temperature where we see a a cool jet rising to the north resulting in the head current and leading into the cold eddy to our west.

This current however is not too strong and so we may just try and power through it towards the large warm jet to our south west.  But we will have more on that soon after we talk more with the team

Force Wind Sea & Honor

Hey All!

Well the hover test we ran last night didn’t give us the positive results we were hoping for:

The idea behind this test was that given the deeper we go, the more northern the current shifts, we wanted to take Silbo and only dive for the first couple hundred meters effectively avoiding the bad currents.

So instead of diving to 1000m on two consecutive yo’s, Ben gave our little droid the command to dive to 200m, and then do his best to maintain a depth of 300m, +/- 100m (defined as the deadband).  Although Silbo was able to follow these commands reasonably well, we made no southern progress and instead drifted just a little bit west.

We also thought that this test would not be very energy intensive.  This turned out not to be true.  On that dive, Silbo used over 3 times as much energy as normal.  Thus we will have to go back to the drawing board to see if we can come up with any other creative ideas to get Silbo out of this head current.

As for Challenger down South, last night she had a bit of an oddity in her flight, but overall is still flying very well.  Last night Challenger made a strangely low amount of progress on a 12 hr mission.  We noticed that although the depth average current was pointed almost directly at the way point, we flew off more to the north.  We think this oddity may have been an error with the current correction command so we may play around with that over the next week to see if we can get some better results.

As the crow flies, we are now just 108 km from leaving South African waters, however the path we will take will be a little longer than that:

Over the next week or so, we will follow a path similar to the white line outlined above. For the next couple of surfacings we will continue to fly towards the way point to the north west, until we reach the outer edge of this counter clockwise warm eddy.  Once we each that northern boarder, we will move the way point out to the west towards a way point Antonio outlined late last week that will carry us from South African Waters safely into the open ocean.

Force Wind Sea & Honor

Hey all!

As our title suggests, our team is still looking for solutions to the head current  Silbo is continuing to contest with.

Later today at the next surfacing, we are going to try a hover mission, where theoretically, Silbo will dive to ~200m and maintain that depth for a few hours.  With this strategy, we intend to dive below the euphotic zone while riding a more favorable current rather than diving deep and hitting the northern current that has been slowing us down.

As for Challenger in the south, she is continuing to make good time as rockets towards the new way point to the North West:

Looking at the surface currents and sea surface height from GeoEye/SeaStar, the new way point lines us up to fly the outer edge of this warm core eddy as we make our way out into international waters.

The presence of this eddy is again supported by the aggregation of chlorophyll a levels to the north of us.  This gives us another view of the way the waters are moving, as the organisms that produce these signals move at the will of the currents.

Finally I will leave everyone with the impressive 3D representation of the sea surface height, showing the path ahead for Challenger:

Tomorrow I will update on the progress of the hover test

Force Wind Sea & Honor!

Hey All!

So today our team bounced some ideas around to see if we could find a solution to Silbo’s predicament.  For the past few months, Silbo has been faced with a strong current ranging from North North-West to North North-East that has slowed us to half of the speed we have flown in the past.  One idea that we had stemmed from an event that happened last week, when Silbo had an error that caused him to only dive to 600m.  When he surfaced he reported that the currents were closer to what the model is telling us: flow to the south west!  So the initial idea thrown around was only having Silbo dive 500m, however this would cause the pump to move twice as often, bleeding the battery.  Another option suggested by Ben from TWR, is to have Silbo dive to a depth we feel would have favorable currents, and maintain that depth and have that favorable current push us for a few hours.

Antonio and I suggested that if we try this ‘hover’ strategy, we should try for 200m.  It seems that the currents  towards the surface may be closer to what the models are telling us, so we chose a depth that wouldn’t take us too far into the unfavorable current.  Another aspect to take into account is that we want to stay out of the productive surface waters.  From our experience and the word of others, the rule of thumb seems to be that barnacles stick to waters >15˚C.  As seen in the temperature time series above from Silbo, 200m keeps us in waters that are roughly 12˚C.  We may not get to this test tomorrow, but I will update you guys on our progress over the weekend.

Down south, Challenger continues to shoot through South African waters on her way towards open ocean.

Tomorrow, we may move the way point more to the north to take better advantage of this northward current we are seeing and ride it out for a few years.  It seems the counter clock wise spinning eddy is slowly moving off shore, so we are trying to bring Challenger towards the outer edge to avoid the possibility of being dragged south when we reach the other side of the eddy.

Force Wind Sea & Honor

Hey All,

I just wanted to leave everyone with a quick update before the end of the night.

In the North Atlantic, Silbo is still muscling his way through the northward flux as we brainstorm ideas to find a more favorable route to take.

Tomorrow, we may make the way point change I had mentioned

Although it looks like there is a clear path for us to take based off of the model, this overlay is only of the surface and tomorrow I will focus on getting subsurface currents to see if that picture gets any better.  This subsurface northward flux has plagued Silbo now for months and we really need to figure a way out.  One glimmer of hope was during an oddity that Silbo encountered late last week.  Silbo’s mission file reset mid segment resulting in a short dive that prevented Silbo from going the full 1000m.  On the short dive, Silbo recorded currents that were in fact flowing in the general direction of what the model was showing, providing us with the theory that the subsurface currents are what is slowing Silbo’s progress.

If we can pin point where these negative currents are, we may be able to adjust the depth Silbo is flying to to try and make some more favorable progress.  This however will cause a trade off with power consumption as we will move the pump more by making shallower inflections so we will have to weight the consequences when there is enough evidence to make a decision.

On the other hand, in the South Atlantic Challenger is still making good progress as she flies towards international waters.

Challenger is now 175 km away from international waters.  Once there and free of the danger of interfering with another countries boundaries, we will expand our view and find the most ideal path onward towards Brazil.

The way point given towards the end of last week is still proving its worth as it now allowing us to fly along the top of this warm eddy that will essentially carry us out of South African waters.

This is also seen in the maps from GeoEye and SeaStar that Antonio has gotten for us that show the warm eddy is similar proximity to the glider, providing that current to the north west that will carry us out to sea.

Over the past couple days, Dave has also been doing some fine tuning to Challenger’s flight parameters.  For example, we have been adjusting the cc’s on the pump throw to make adjustments to our dive and climb angles, changing the gains on the steering parameters, and testing out the low power mode.  The last one here is key as we will need to conserve power if we want to make it all the way across the Atlantic Basin on these batteries.  She has impressed us so far, but she still has a long road ahead.

Force Wind Sea & Honor

Hey All!

As Challenger makes more progress away from the shelf break and towards international boards, we cant help but be proud of how well she is flying.  After brushing the cobwebs off of our knowledge of geometry, we found that Challenger has been hitting speeds of up to 40 cm/s horizontal velocity- nearly twice the speed of what we have had with the older G1 gliders!

We are also collecting some beautiful data as we delve into the depths of the South Atlantic.  Above, is a time series of temperature since deployment recorded by Challenger, and aside from some false hits telling us the depth, the data set looks amazing.

As for the way point that was given to her last week, it looks like it is working perfectly.

With the way point set at the northern edge of the warm core eddy, we are getting dragged up and around the counter clockwise circulation, keeping us from being pulled into the center of the eddy.

We are very pleased to see that the eddy field we are edging ourselves into seems to be accurately depicted by both GeoEye/SeaStar and the RTOFS model.

Both agree with the positions of the counterclockwise spinning warm/clockwise cold eddies in our immediate vicinity and although the intensities differ, they show similar patterns of eddies further out to see.  Both also show similar positions for the warm eddies outlined in the 3d GeoEye/SeaStar image, which we hope will provide us with the path of jumping from warm eddy to warm eddy that will lead us out of South African waters and to the North West once we are out into the open ocean.

As for Silbo in the North, we are still plugging away trying to fight our way through this strong under current.  It looks like we may have a chance ahead as I am proposing a new way point to our team.

Hopefully if we can turn Silbo to the South at some point over the next couple days, we may be able to catch the signature of the small cold eddy to our south west allowing us to cut back to get good position on the large warm eddy south of that point.

Soon Silbo will be encountering the equatorial currents and we need to make sure we can gain good position before that point so we dont get swept up the northern shores of Brazil.

Force Wind Sea & Honor!