Author: admin (Page 4 of 36)

On March 31 2016, RU29, Challenger was recovered by a team of scientists and students off the coast of South Africa, completing the circumnavigation of the South Atlantic.  When the team arrives back on land tomorrow afternoon, we will get more details on the recovery.

Force Wind Sea & Honor

Early this morning, Antonio sent over this picture of the boat as the team was moving the equipment on board and preparing to set sail.

The glider is currently 230 nautical miles from Cape Town, so the team will have about a full days steam to get on location.  If all goes well, early tomorrow they will be on location and preparing for recovery.  After 282 days at sea, its time to get this glider out of the water

Force Wind Sea & Honor

After spending the weekend following Antonio’s waypoint, our luck continued to get better as the currents continued to shift in our favor rotating from West to North North-East.

With this favorable current, 29 managed to get back up to speeds of 1km/hr vs the 1km/10 hrs progress we were making last week.

By Monday however, the current continued to rotate around – the result of how hectic the landscape is of quickly moving eddies through the area.  Even with the 180˚ change in current direction, the glider continues to make good progress in the direction of Cape Town.

With the latest forecasts, the British GLOSEA is the closest to what the glider is reporting, showing a medium sized warm eddy to the south of 29 resulting in the currents shifting back to the west.

GLOSEA Mar 29

Since recovery is quickly approaching, we have shortened 29s flight pattern to 4 yos and turned the ctd on for both up and down casts so we can gather a nice data set upon approach for data comparison with the recovery vessels on board ctd.

Finally looking at the AIS data in google earth, the RV Algoa is waiting at the port for this weeks activities

Over the past day, the team has been arriving in Cape Town and this afternoon will be meeting at the Algoa to load up some equipment and discuss the plan for recovery.   Then, weather permitting, the team will set sail early tomorrow with the intent of arriving at the glider early Thursday where they will get the glider out of the water after 282 days at sea and 6700 km.

Force Wind Sea & Honor

Now less than a week away from when the team will arrive in Cape Town and set sail to recover Ru29, we continue to fight the oceans currents as we look for the best way to get the glider closer to shore.

On Tuesday, 29 was given a new way point and almost immediately we saw a change in the direction of the currents as they rotated from West to North-West, and as the week continued this rotation moved further and further north.

A reduction in the number of yo’s per segment also led to a decreased number of oddities from the pump.  As of last week, the pump was holding steady at 32 oddities; we reduced the yos by 25%, so we would expect the oddities to then drop to 24.  However the result was 19, so 19/24= .79 so they effectively dropped by 21%.  The more well behaved pump has also lead to the power usage dropping back down a bit allowing the team to rest a little more easily.

By Wednesday, the persistant West North-West current had slowed Challenger down to a crawl of about 1 km/10hrs while the glider continued to try and push east to the cold core eddy.  It seemed though that the warm eddy in the image above had shifted and the northern edge was what was causing the strong westward current.

Antonio however suggested we move the waypoint to the North East of the glider citing the Copernicus salinity data overlayed with the current fields.  The water that spills over from the Indian ocean into the South Atlantic is significantly more salty and shows up very nicely in the data:

Copernicus Depth Average Current with 260m Depth Salinity

With the new waypoint set to 32º30`S, 14º30`E, Challenger regained some pep in her step as the currents rotated further to the north and she covered a significant distance compared to the progress made over the past few days

With this change of luck we will keep Antonio’s way point and see if we can continue to make better progress while the recovery team makes final preparations for their travel to Cape Town

Force Wind Sea & Honor

The image above shows that RU29 is about 95 kilometers from South African waters. However, the currents are the wrong direction flowing more west than anything else. And it is hard to rely on what the glider is reporting.  The waypoint is northeast, the reported currents are mostly west, even when you account for the persistent difference in magnetic versus true. Yet the glider is traveling slowly southeast.  The following are todays forecast products

Oscar Mar 21

OSCAR says if we can just get a bit more east, we will begin to feel that large cold core eddy that will bring us around clockwise into South African waters.  That means we should soon see currents to the north. Dave’s suggestion of flying ESE will aid in getting us there.

GLOSEA Mar 21

GLOSEA agrees with the OSCAR forecast, also showing the large cold eddy to the south east.

HYCOM Mar 21

HYCOM says we should have had a favorable current to SE that last few days, and we did not. It also says if we fly south, we will enter a current to the west. But we are already in a current to the west – our present issue. HYCOM further says that if we continue east, we will find ourselves in a strong southward current, the exact opposite of OSCAR.

RTOFS Mar 21

RTOFS is showing the same as HYCOM but with slower currents. ROTFS does however start with the same initialization as HYCOM, but uses different winds to complete the forecast.

So we have two products saying we should go ESE, and two products saying there lies danger. The Copernicus product however is not yet available for a tie breaker on the guidance side as they are in the process of doing maintenance on their site.

Despite what the models are saying, Challegner is telling us East North-East is not working, and that straight East will not work.  29’s track is telling us to try ESE to see where it gets us regardless of the guidance.  Hopefully the model guidance from OSCAR and British are more correct.

For the gliders status, the power plots have to be adjusted.  We are up to about 3.2 AH/day, and down to about 50 days left.  That is end of April/early May if nothing else happens, like the need for shallower dives or more pump leaks.  Luckily we are all set to recover in just over a weeks time.

Communications and steering are holding steady, but the oddities and pump issues on climbs outlined last week are still the main problem and the source of the increased power draw.  At some point this week we would like to try and pull more data from the glider to see if there is anything that can be done, however that would require a more prolonged surface time and at the moment we are in a pretty high trafficked area

Force Wind Sea & Honor

105 km to South African Waters, and Challenger is looking like she is ready for a very well deserved rest.

Lagrangian Flow Map using Copernicus Forecast Data from Antonio Ramos

The reported currents are 19 cm/sec to South West, but the glider is flying South East – our East-North East waypoint is still having a significant influence, even when the direction is corrected from the magnetic to true north rotation.

Recently the power consumption has skyrocketed to 3.25 AH/day compared to 2.1-2.2 AH/day during majority of the mission.  At this rate,  the power consumed over the course of a day is worth 1.5 days from early in the mission.

This we believe is largely due to the pump slipping and having to repump throughout the flight rather than moving to one position per dive or climb.  Lately segment oddities are up to 30 per segment as the pump has been all over the place having to pump multiple times on climbs through the water column.

Steering holding steady at 15 degrees rms. Constant offset of +5 degrees with Fin offset partially compensating at roughly -7 degrees.

Comms back to good after a small bad patch.

The waypoint for now seems to be doing well keeping us on a path with Eastward Progress.  Below is a current map comprised of the average output from the Five Forecasts we have been taking into account for piloting.

5 Forecast Average Output

oscar – head east, not too much south, perhaps a tad north, if we take turn too tight we could go west or if we come in hot into the eddy we we might not get back out.

copernicus – head E, shows route to the south isn’t too great as the eddy we’re trying is moving west quickly.  also too much north could put is in an unfavorable eddy to the north

Copernicus Mar 18

HYCOM – head ENE and fast or else we find west currents again

HYCOM Mar 18

GLOSEA – says were ok just keep heading east

GLOSEA Mar 18

And finally RTOFS has us also in the midst of a south east current that we must continue to try and make our way east across.

RTOFS Mar 18

Force Wind Sea & Honor