Category: Challenger Mission (Page 14 of 37)

Hey All

Challenger has made it as far lateral as we wished to go!

Now we have placed her way point to the south east and will be making our final approach towards the island.  Although her progress was slowed by the currents running to the east-north east over the past week, she will still be arriving to the recovery zone well ahead of schedule. Antonio and I have been bouncing some ideas back and forth for ways to kill the next few weeks as we wait for Scott, Chip and Chuck to arrive on Ascension to recover and one of the most promising ideas may in fact be something out of the past. Check back in in a few days to see what we are cooking up!

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Hey All

As the recovery date looms nearer, Challenger continues to make head way parallel with the Ascension Fracture as we position ourselves for the final approach to the recovery location.  As previously discussed, Collin on Ascension Island told us that his boat which will be our vessel for recovery has a range of 40 nautical miles and that we should park ourselves to the west of the island within the lea.  From this information, I created the green polygon visible in the image above to set as our end zone as we prepare to wait out the arrival of our team that will be present for recovery.

Looking to pinzon, the sub surface current (>200m) continues to flow to the east, slowing us to roughly 22 km/day.  Even at these speeds, we should arrive within the recovery area well before our planned operation for Nov 4.  Until then, we shall continue forcing our way in the right direction as we come up with a constructive way to kill time until the recovery just under a month away

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Hey All,

So over the past week, we have continued to follow the sampling mission described last time: zig zagging our way over the portion of the Mid Atlantic Ridge called the Ascension Fracture as we make the final push to Ascension Island.

As predicted by Antonio, the currents have shown evidence of a rotation on either side of the ridge, clockwise to the south and counter to the north of the fracture

Another surprise we encountered while crossing over the rift was that on the first crossing, the glider reset underwater once again early on a weekend morning.  Unfortunately with these resets, we lose the data from the segment since it was written to the gliders RAM and not saved to the hard drive until the segment is complete.

Then later when we crossed the ridge again, we noticed that as we crossed, the compass began to spin close to when the glider should have been crossing over what is the thinnest part of the earths crust along the ridge, which may have caused a magnetic anomaly that led to the compass freaking out. A strong magnetic field we think could have caused the reset on the first crossing if it was strong enough

However on the third crossing, there doesn’t seem to be much of a reaction as the glider neither reset nor had too much of a wonky compass.

As the glider has been out for just under 9 months, the data on our pages has gotten very congested and so John Kerfoot has helped us out creating a new plot of the recent sampling mission, however, the data is a bit spread out for now so we can not make out any patterns just yet.  Looking at the old plot however, we can see the continued oscillation of the thermocline, although it has become much smaller than it was weeks ago.

Finally, as we are nearly ready to head west towards the island with a month still left before the planned recovery, Antonio and I have proposed to the group that we will fly the windmill pattern within the 40 mile box to the west of the island, which will keep us in range of the boat just in case anything bad happens.

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Hey all!

After this week, we are well underway into our sampling mission above the Ascension Fracture Zone.

With the sampling strategy we have laid out in the previous entry, we will be running a pretty close zig zag pattern over the ridge before running parallel to the north of the island.  With how tight the weaving pattern is, we have outlined the way points we will be pursuing over the upcoming days.

With how quickly we are making our way through this pattern, Antonio and I have been bouncing ideas off of each other just in case we have more time to kill. One idea we have arrived at includes flying a windmill pattern through a possibly eddy in the vicinity of the recovery zone

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Hey All

So since Antonio’s video call last week with the Ocean Observatories class, we have made the decision to sample the Ascension Rift over the upcoming weeks as our team prepares for recovery in the first weeks of November.

Back in April as Silbo crossed the Mid-Atlantic Ridge, Antonio discovered that there was a noticeable counter clockwise oscillation in the depth average currents.  These seem to be localized features caused by the flow of the gyre across the subsurface mountain range.

The plan we arrived upon for Challenger’s last ditch science mission will follow the path outlined below

The path runs us about 550 km from our latest location, which should take up roughly  23 days before we arrive near the western shore of Ascension island.  In preparation for this test, we have bumped up the sampling on the glider, now collecting data on all dives and climbs instead of on the first dive of each segment as we have done previously as a power saving technique.  But now as we have plenty of battery for what we have left to do before recovery, we will take advantage of the opportunity we have been given.  Within the next 6 surfacings, we should be just about ready to change the way point towards the west to make our first crossing of the fracture zone.

As we approach the ridge, Challenger has also come across a sub surface eddy that we have have traversed over the past couple days.

As seen in the depth average current calculated by the glider, we can see a clear rotation of the current following the pattern that could be associated with a warm counter clockwise rotating eddy.

A third oscillation we have noticed, is the depth of the thermocline.

Since the siesta back in May, the thermocline has been moving up and down in roughly two week periods overlaid with 3 day oscillations.  We are bouncing some ideas around with what could be causing this, but with the increased sampling rate, we may even be able to detect smaller scale shifts.

We will keep everyone updated on our project as it develops and we come to any conclusions

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Hey All,

Challenger is making quick work of this last stretch before recovery on the shores of Ascension Island.

With less than 260 km remaining between our brave little glider and the end zone, we could potentially make it to shore within 10 days with our average speed being around 26 km/day.   However, we do have some battery left and the potential to do some creative sampling around this little oasis in the middle of the Southern Atlantic.

This will be a topic of discussion in class today, but so far Antonio has proposed two branches of ideas: to circumnavigate the island to study the wake created by the island being in the path of the flow of the gyre, or ahead of us is a region called the Ascension Fracture which is part of the Mid-Atlantic Ridge- the topic of study here would be to look into the oscillations we saw with Silbo crossing the Mid-Atlantic Ridge some months ago in the north.

And the third option which could also be incredibly valuable to our cause would be hiring someone to go out and recover for us sooner rather than later- when Scott and Chip arrive in Ascension there will be a number of tasks to get done on a very limited time frame and if there is less than ideal weather, that could make things much more difficult. However, if we were to recover now that gives us a much larger window to find out what needs to be fixed on the glider, what needs to be in Ascension for the operation to be successful, and more time to get the glider in the water just in case the weather is stormy upon our teams arrival.

We will update later today on what is discussed during class

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It may be a slight exaggeration, but Challenger has picked up her game in the final hour of her mission.

Over the past week, our team has worked very hard meeting deadlines to get all of the necessary equipment for recovery and redeployment slated for arrival in Ascension Island in november. However, Challenger has kicked it into high gear, reaching speeds close to 25 km/day once more.  If this continues, we should be very close to shore within the next two weeks!  Yesterday, as Antonio predicted over 10 days ago, she crossed into the EEZ officially leaving international waters for the last time while on this mission.

Looking at Antonio’s 3-D bathymetry, the Ascension Fracture Zone is all that lies between Challenger and her finish line.  We plan on taking evasive maneuvers around this area even though our maps say it doesn’t rise further than 1600m from the surface just in case the maps are not in a high enough resolution to pick out small points that may be hazardous, and because we have loads of time to kill.

Once we get to the island, we plan to kill time in one way or another.  This will be discussed in class amongst the undergraduate students next week on Tuesday

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Fish & Chips and Roast Beef for all!

Just 350 km from the shores of Ascension, we should be in range for a recovery within the month!

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Hey all

The end is nigh!

Challenger is now just under 500 km from the shores of Ascension, and just 130 km from leaving international waters for the last time on this mission. Over the past week or so, we have noted that she has had what seems to be a head current.

While the currents appear to have changed, Challenger is still making good time, flying over 21 km/ day.  This leads us to believe that there may be a new cohort of barnacles causing drag  once again resulting in the gliders calculation to think there is a head current. This may be problematic over the course of the next few weeks.

As we look at our schedule, our team will be arriving for the recovery of Challenger on the shores of Ascension, however if Challenger continues to keep up the pace (21 km/day) she should be in the area roughly a month ahead of the recovery team.

Because of this we are now weighing our options of way to pass the time until recovery. Two options that have come to mind thus far have been flying a circle around the island, keeping away from the fishing vessels; or revisiting the eddy sampling technique we tried near Madeira in spring of last year where we would fly a wind mill pattern through an eddy- effectively sampling its thermal structure.  As of right now theses are just ideas we are discussing and there is always the option of stationkeeping for the remaining time, however that option is by far less fascinating

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Hey All,

With Silbo now safely on shore and preparations being made  for his safe return to Teledyne Webb Research in Massachusetts, we now can focus solely on Challenger and her mission to cross the South Atlantic.

Now, just under 800 km from the southern shores of Ascension, we set our sights on what is seemingly the last stationary obstacle standing between Challenger and her destination: one last ridge of seamounts.  To prepare for their presence, we set a way point to the north of the island to account for the ~11˚ offset we have grown accustom to flying with over the past months, and with the way point being close to 900 km away we don’t have to worry about hitting it any time soon.

One oddity we have noticed while flying past the previous subsurface mountain range was that there was a noticeable oscillation in the currents

As there was little evidence in the surface current forecast to confidently say what was the cause of this, we delved deeper into the data and found two interesting clues:  the thermocline had deepened and we were flying slightly faster on dives than on climbs.

Antonio pointed out that this was a similar flight scenario as to what a glider sees when crossing a strong warm eddy which sparked an idea in his mind.  To the south west of the island of Gran Canaria, there is an eddy that remains for the most part stationary in its location and is caused by drag as the currents flow through the island chain.

Sea Surface Height

Sea Surface Temperature

Now in our scenario, the sea mounts came within reach of the subsurface flight pattern of Challenger, but did not breach the surface as the islands of Gran Canaria and Tenerife do.  Because of this fact, this warm eddy that we believe we flew Challenger through would not have a signature at the surface and would cause the thermocline to be substantially deeper

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