MED-GLIDERS experiment

MED-GLIDERS experiment

Pierre Testor & Uwe Send

WP5MFSTEP Partner 7

1) Gliders are driven by positive and negative buoyancy created by a change in volume. No propeller is required.

2) Wings convert vertical velocity into forward velocity.

3) Glide downward when denser than surrounding waterand upward when buoyant, in a sawtooth pattern.

buoyancy and internal mass distributioneffect on vertical velocity, roll and pitch

Control of :

Control of :angle of descent/ascent and direction

General objectives of WP5

Explore the capabilities of gliders by operating one real-time continuous glider repeat-section feeding the overall system

1/ Evaluate and choose which of the available gliders prototype should/could be used

2/ Determine the optimal application, capabilities and mission parameters in the MFSTEP application

3/ Develop a real-time data dissemination system for glider data

4/ Obtain data from the unattended glider repeat transects along one section in the Mediterranean

5/ Disseminate real-time data to the community and to the forecasting system during the TOP

6/ Analyze the data and assess the value of gliders

7/ Establish a European capability for operating gliders

A

BC

VOS XBT network

local support base : CNR-IST (Messina)

Priority to section A with a deep glider (0-1000 m) : 800 km + 800 km = 40-80 days

~3-4 autonomous repetitions of the section in 6 months (TOP phase)

Months 3 6 9 12 15 18 21 24 27 30 33 36

Pre - TOP TOP Post - TOP

5100 Glider choice and mission parameters5200 Glider purchase and preparation5300 Development of real-time data system5410 Deployment during TOP5500 Dissemination of real-time data5610 Analysis of data5620 Technical analysis of glider data5700 Assessment of gliders in overall system

MFSTEP-WP5 Planning

- scientific objectives / observations needed- bathymetry and expected currents- capabilities and endurance of the glider- location of land base - small-ship access to part of gliders tracks for comparison measurements

- speed- descent/ascent angle- max depth - sampling intensity- time spent at surface- two-way communication options

- UW glider

- Scripps glider

- Webb Res. Powered Glider

TASK 5100 : Months 1- 6study ofthe optimal type application capabilities / mission parameters

Slocum Thermal, Webb Research Corp. (WRC) Spray, Scripps Institute of Oceanography (SIO)

Seaglider, University of Washington (UW)Slocum Littoral, Webb Research Corp. (WRC)

Operating Gliders

Weight: 52 KgVehicle Length: 1.5 metersShape: Cylindrical to LaminarDepth Range: 75 – 1000 metersSpeed: 0.25 - 0.45 m/sec horizontalEnergy: Alkaline BatteriesNominal Payload: 4 KgEndurance: Weeks to MonthsRange: 1000 - 7000 kmNavigation: GPS, Attitude Sensor, Pressure, AltimeterCommunications: RF modem, Iridium, ARGOS, Acoustic modemSteering & Attitude: Mass shift, Control surfaces

Legacy Glider Specifications :

Extended capacities Electric glider1000 m depth

Based on the WRC coastal version

- “Training period” at Webb Res., Falmouth, US, Oct. 2003- Observational Meeting at ENEA, Santa Teresa, Italy, Oct. 2003- Glider ready for tests in may 2004

YO Sampling

surface

Waypoint (Lat, Lon)

Starting Point

1) Waypoint (lat, lon) – distance to waypoint2) Angle of ascent/descent3) Max depth4) Nb of YOs between sat. comm.

1000 m

4 - 10 km

GPS, Iridium

z

20-40 cm/skeep its course towards waypoint

GPS, Iridium

YO Sampling

1) Way point (lat, lon) – distance to waypoint2) Angle of ascent/descent3) Max depth4) Nb of YOs between sat. comm.

Way Point (Lat, Lon)

Starting Point

GPS, Iridium

distance to waypoint is reached

(internally estimated) =

end of mission, wait for new instructions

No oceanic currentsx

y

YO Sampling

Mean current along glider YO

1) Way point2) Angle of ascent/descent3) Max depth4) Nb of YOs between sat. comm.


Starting PointGPS,

Iridium GPS, Iridium GPS,

Iridium

GPS, Iridium

x

y

YO Sampling

Mean current along glider YO

1) Way point2) Angle of ascent/descent3) Max depth4) Nb of YOs between sat. comm.


Starting Point

GPS, Iridium GPS,

Iridium

GPS, Iridium

option to take into account previously measured currents to target the

waypoint

x

y

A

VOS XBT network


Endurance of several months : only expected numbers ! By now, maximum proven endurance for coastal glider without batteries change = 22 days (< 80 days needed)

WPT1

WPT2

List of waypoints

VOS XBT network


Similar endurance for coastal and deep gliders By now, we can expect to achieve a section

< 300 km + 300 kmMaintenance operations every ~ 30 days near Messina

(a lot of ship time even with small boats)

New track ?

800 km

Gliders are still “teenagers”

To reach the goals of the project :increase significantly the endurance/range…

Solution : upgrade alkaline to lithium batteries

Other Solutions :

1) sampling optimization

2) use of our knowledge of the currents

3) vertical velocity control, compensators

ADCPAcoustic ModemAltimeterBathyphotometer (bioluminescence)Optical BackscatterOptical AttenuationOxygenConductivity, Temperature, DepthFluorometerHydrophone & Towed ArraysOxygenPAR sensorSpectrophotometer (red tide detection)

Sampling - Present and Planned Sensor Packages:

multidisciplinarity

Lowest energy cost

fewer levels for data transmission in near real time via Iridium

(10 min for sat. comm.)

- Log files

- Data files

- Short data files

The glider records 3 kinds of files

Storage and download during recovery/maintenance cruises onlysampling rate 6 s ~ 1 m along vertical

save satellite communication time (energy) and avoid collisions with boats, nets, biofouling

Sampling - Data transmission in NRT

700 m

surface

~ 6 km, 4-8 hours

Short data filesmissions 2 GPS fixes

> 100 levels of T and S1.5 min GPS8 min Iridium1.5 min GPS

11 minutes

z

angle of ascent/descent = 25 º (minimum energy cost)

25ºLevantine Waters

MED-GLIDERS experiment

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