Aug
26
Filed Under (Chile, gliders, Iquique, MOOMZ, OSU, seagliders, sg158) by shearmar on 26-08-2009
Track line for glider sg158 lauched at the beginning of August

Track line for glider sg158 lauched at the beginning of August

After performing a very nice “butterfly” pattern during the MOOMZ cruise, we sent sg158 offshore to start cross-shelf transects. Shortly after that, we started getting loads of roll retries and even a few roll errors – this means the internal motors were trying to shift the batteries and execute a roll to turn the glider and the motors either did not respond enough or did not respond at all. We panicked a bit a called Fritz at UW. He gently chided us for not digging a little deeper into the log files, and then suggested some glider magic:

Create a pdoscmds.bat file with these 3 lines and let the glider execute it during next phone call:

menu hw/pitch/read
menu hw/roll/read
menu hw/roll/rolls

This ran the glider through a series of tests on the roll mechanism. Things seemed ok, but the problem continued to worsen as we made more and more dives. Eventually, the glider was stuck rolled partially to the starboard side, meaning all dives now executed as a slow clockwise spiral on the way down and counterclockwise spiral on the way up with no real control of heading.

Last 1000 m dive from sg158 stuck rolled to starboard

Last 1000 m dive from sg158 stuck rolled to starboard

Now, this meant sg158 had to be recovered. It wasn’t in imminent danger, but it was way (30+ nautical miles) offshore. Once again, Gadiel Alarcon sprang into action (on a Saturday and Sunday no less), and late on Sunday August 23 sg158 was safely recovered and brought back to Iquique.
On Monday, Laura emailed with Ruben Moraga at UNAP and they got sg158 turned off and stowed away. Now we’ll need to get the gliders shipped back to the US to replace sg157’s batteries and figure out what went wrong with sg158.

Jul
21
Filed Under (Chile, gliders, Ha ha, Iquique, OMZ, seagliders, SG157) by Amanda Whitmire on 21-07-2009

We continued to have communication problems with SG157, so we decided to call on our Chilean colleagues to help with a rescue on July 10th. The Seaglider was close to the coast at the time, so the pilot worked to keep it as close as possible to the port of Iquique despite a current pushing it to the south.

The plan was to have a student, Nadin, fly from Concepcion to Iquique to help with the recovery, since he helped us with the deployments and recoveries back in March. We communicated with our Chilean colleagues mostly via Email, so sometimes things were happening there faster than we could follow. It turns out that before Nadin could get from Concepcion to Iquique, the Chilean Navy was already on sight and recovering our glider! Jack’s words were, “Chilean Navy to the rescue!” We were all surprised that they had gotten involved, but I guess it’s not every day that a misbehaving Seaglider needs to be rescued off of the Chilean coast. We were (are!) very grateful for their assistance, and they did a great job on the recovery. By the time they got the glider back to shore, Nadin was able to get there and shut the glider off with the magnet. All’s well that ends well in the world of Seagliders!

We received this clipping from a Chilean newspaper yesterday (click for bigger)…

Chilean newspaper article on the SG157 recovery

Chilean newspaper article on the SG157 recovery

We’re famous!

Jul
03
Filed Under (Chile, gliders, Iquique, MOOMZ) by shearmar on 03-07-2009

sg157 stopped communicating with the basestation sometime late last Friday (06/26/09). sg157 disappeared for 4 days, and then finally called in Tuesday evening. Anatoli and Justin handled it like pros, and figured out that the glider had happily continued to dive and receive GPS fixes, during it’s seclusion. This means there’s nothing wrong with the antenna and that the antenna is getting far enough out of the water. It also means that there’s nothing mechanically wrong with the glider.

The problem appears to be isolated to the Iridium satellite phone communications.

sg157 has been calling in more consistently since then, but misses a scheduled call in every now and then …

Out plan is to continue to fly sg157 onshore. If we get another big disappearance, then we’ll have to figure out an emergency recovery. If things continue to go OK, then we’ll send Laura out at the beginning of August to put sg158 in before the MOOMZ cruise, and we’ll send Justin out at the end of August to recover sg157.

Jun
11
Filed Under (Chile, gliders, Iquique, MOOMZ, OSU, power, seagliders, SG157) by shearmar on 11-06-2009
Energy usage plot for sg157 since the beginning of the deployment.

Energy usage plot for sg157 since the beginning of the deployment.

We’ve been experimenting with some power saving strategies on sg157 this week. In the plot of energy consumption, you can see that the blue 10V battery is draining a lot faster than the red 24V battery. The 10V battery powers the onboard computer and the scientific sensors. The 24V battery mainly powers the buoyancy pump. So, our energy consumption for science is rapidly outpacing our energy consumption for flying.

How to fix that? Shut off the science sensors! So we tried that starting MondayJun 08 by uploading a one-line science file:

// Science for OSU sg157 and/or sg158 with PAR sensor
/depth  time    sample  gcint
1000    600     0000    600

This file determines that from the surface to 1000 m the sampling interval is 600 seconds (10 minutes), none of the sensors are turned on (0000), and the guidance and control interval (time between steering) is also 600 seconds. This had an immediate affect:

10V battery energy usage by sensor, major consumers are optics and TT8 (computer)

10V battery energy usage by sensor, major consumers are optics and TT8 (computer)

Notice the major drop near dive 540. This is great, it extended our mission duration from end of August to end of October! Nevermind the fact we are no longer collecting data … and this had an added complication of suddenly erratic flying by the glider. With the glider checking in only every 10 minutes to steer and make flying decisions, sg157 would fly past 1000 m, go to deep and rocket up to the surface in what I’m assuming is an emergency manuever.

Anatoli did some experimentning, and now we are flying with shorter gcints and the CT sensor on, consuming only slightly more power than everything off, and having no more erratic dives.

May
11
Filed Under (gliders, Iquique, seagliders, SG157) by Amanda Whitmire on 11-05-2009

Hey all – just realized that Seaglider 157 made it’s 400th dive off of Iquique on Saturday (9 May, 2009). Very exciting! The glider is now on it’s usual onshore-offshore route, about 2/3 the way through the seventh ~135 km, cross-shore transect. The eastern south Pacific oxygen minimum zone has never been sampled over these time and space scales, so I hope you all can share some of my enthusiasm for these unprecedented data. Now, if we could just find a research vessel so that we could get out there and do some discrete sampling…

Anyhow – thanks to everyone involved for your continued efforts.

Apr
22
Filed Under (Chile, gliders, Iquique, MOOMZ, seagliders, Video) by Amanda Whitmire on 22-04-2009

In this post we share a short video documenting how we launched the gliders in Chile.

Before we get to the video, though, I’d like to extol one of the [major] benefits of using gliders as a tool in Oceanography: they are easy to launch and recover from small vessels. “Traditional” oceanography takes place on large research ships (well over 100 feet long), which is problematic in terms of the costs involved (very expensive) and their limited availability. Launching or retrieving a glider from a small boat is simple and inexpensive, and if we need to get out on the water for an unplanned emergency rescue, small boats are relatively easy to come by. Case in point: this was our small-yet-capable Chilean launch vessel, which belongs to the Universidad de Arturo Prat (UNAP):

R/V Antares

R/V Antares

We launched two gliders and recovered one from this nimble little vessel. While the rest of the research team was stranded on land after our larger research vessel blew an engine, the OSU Glider Research Group was still able to get out there and save the day with gliders (fist bump!).

Okay, on with the video:

Thanks to Laura for sharing her photos and video from the trip!

Apr
13
Filed Under (Chile, gliders, Iquique, OMZ, seagliders, SG157) by Amanda Whitmire on 13-04-2009

Here is a plot of the upper 400 meters of the latest seaglider section off of Iquique (27 March – 07 April 2009, onshore to offshore track). On a hunch I plotted salinity contour lines on top of the oxygen (upper right) and backscattering (middle right) data. It seems that there is tight coupling between salinity and both O2 and bb. Before seeing these data, I would have guessed that variability in the deep oxycline would be driven by intrusions of water masses with different density and oxygen characteristics. Likewise with the bottom boundary of the intermediate depth scattering maximum. However, given what we see here, the story seems to be a bit more interesting than that! Why would salinity be more influential than density in regulating these distributions?

Apr
08
Filed Under (Chile, gliders, Iquique, MOOMZ, OMZ, seagliders, SG157) by shearmar on 08-04-2009

Dive 236 uploaded new science file to decrease energy consumption and match buoyancy energy rate.

// Science for OSU sg157 and/or sg158 with PAR sensor
/depth time sample gcint
50 4 1111 60
150 4 1111 120
250 16 1110 180
600 52 1110 300
1000 104 1100 360

The projected recovery date is currently end of July, this may buy us some more time.

Mar
25
Filed Under (Chile, gliders, Iquique, OMZ, seagliders, SG157) by Amanda Whitmire on 25-03-2009
Full profile (0-1000m) below \/, surface to 400 meters above /\

Seaglider 157 recently completed it’s first complete onshore to offshore section, and the data are fantastic! As you saw in the profiles, the oxycline is consistently very near the surface, ranging from 30 to 75 meters depth. Becasue the oxycline is so shallow, we often observe a second chlorophyll peak within hypoxic waters (oxygen below 20 umol/kg or 1 mL/L). We also see consistently elevated backscattering signals throughout the OMZ, from the oxycline to about 300 meters depth. We hypothesize that this signal is at least partially derived (if not mostly) from enhanced microbial activity in the OMZ, and look forward to ship-based sampling to test this idea. We have observed these same features in data from Apex profiling floats that were released in the area last March (Whitmire et. al., in prep.; link to data, link to plot).

Mar
17
Filed Under (Chile, gliders, Iquique, MOOMZ, OMZ, seagliders, SG157) by shearmar on 17-03-2009

Yeah, Anatoli! He got the dive speeds down from 180 minutes to 260 minutes (30 cm/s to 10 cm/s), and the results is extended mission duration and better vertical resolution in the profile data! Check out the latest profiles and you’ll see a much clearer picture of the small scale subsurface maxima in chl or DO:



Here’s the cmdfile that did the trick:
$D_TGT,990
$T_DIVE,470
$T_MISSION,390
$HEAD_ERRBAND,30
$ROLL_ADJ_DBAND,3
$ROLL_ADJ_GAIN,0.03
$ALTIM_PING_DEPTH,400
$ALTIM_PING_DELTA,20
$ALTIM_SENSITIVITY,4
$MAX_BUOY,100
$SM_CC,300
$C_VBD,2630
$C_PITCH,2500
$C_ROLL_DIVE,2500
$C_ROLL_CLIMB,2400
$GO

A new ratio for D_TGT and T_DIVE (not 3 anymore) and limiting the buoyancy range from 200 down to 100 with MAX_BUOY. This slows the dive thru buoyancy without altering the range.