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.

Way Point (Lat, Lon)

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.

Way Point (Lat, Lon)

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

local support base : CNR-IST (Messina)

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

local support base : CNR-IST (Messina)

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

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

Use of our knowledge of the currents/modification of the section

During the TOP phase :Forecast bulletins > estimations of U and V fields

25º

< 3 km

1000 mx

z

25º1000 m

xz

> 3 km

U

U

The section will certainly not be a straight line…

To pilot the glider help of - MFSTEP forecasts,- Simulations of the glider flightin the model outputs

Estimation of waypoints

rectilinear trajectory

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

Vertical velocity control

25º

~3 km

700 mx

zBuoyancy pump action, now

25º700 m

xz

Buoyancy pump action, projected

+ Use of compensators to approach the compressibility of seawater

VOS XBT network

local support base : CNR-IST (Messina)

- Sequence of tests at Webb Res. facilities- Cruise in June-July 2004 near Messina with R/V Sanzo15 days of final tests

Glider ready (upgraded) for the TOP

VOS XBT network

local support base : CNR-IST (Messina)

1st step of the TOP phase ~1 month

VOS XBT network

local support base : CNR-IST (Messina)

etc…

VOS XBT network

local support base : CNR-IST (Messina)

New track ? Data assimilation needs ? ~ 600 km- Orthogonal to XBT lines ? - Monitoring exchanges between western and eastern basins ?- Territorial waters (12 miles) ?

800 km