Chapter 10: data telemetry

A: data telemetry to shore

Low Earth Orbit Satellites:Low Earth Orbit Satellites:• ArgosArgos• IridiumIridium• OrbcommOrbcomm• Global StarGlobal Star

FleetBroadBand and C-bandFleetBroadBand and C-band

Cellular and freewave modemsCellular and freewave modems

Need to compare:Need to compare:• CoverageCoverage• Cost of service/equipmentCost of service/equipment• Data rateData rate• Power requirementsPower requirements

Satellite data path

1.1. Transmitters send data to satellitesTransmitters send data to satellites

2.2. Satellites collect the data, store it and relay it in real-time Satellites collect the data, store it and relay it in real-time back to earthback to earth

3.3. Ground antennas relay data from satellites to processing Ground antennas relay data from satellites to processing centerscenters

4.4. Processing centers collect the incoming data, process it and Processing centers collect the incoming data, process it and distribute as necessarydistribute as necessary

5.5. Users get the dataUsers get the data

Argos - satellites

Global coverageGlobal coverage Polar orbiting environmentalPolar orbiting environmental

satellites (at least 2 at all satellites (at least 2 at all times; can get extra service times; can get extra service which gives more satellites which gives more satellites at one time)at one time)

850 km above earth with a 850 km above earth with a 5000 km footprint5000 km footprint

Duration of satellite pass is 10 minutes on averageDuration of satellite pass is 10 minutes on average ~ 100 minute orbit~ 100 minute orbit Depending on latitude 20-50 passes per dayDepending on latitude 20-50 passes per day 40 ground receiving stations40 ground receiving stations

Argos platforms (transmitters)

Transmit frequency of 401.650 MHz Transmit frequency of 401.650 MHz ± 30 kHz± 30 kHz

Repetition rate depends on application, but every 45-90 seconds Repetition rate depends on application, but every 45-90 seconds is common for oceanography instruments at the surfaceis common for oceanography instruments at the surface

Usually one 32byte message every 45-90 secUsually one 32byte message every 45-90 sectotal is less than 10kb per day total is less than 10kb per day

Have to transmit for hours since time of satellite pass unknownHave to transmit for hours since time of satellite pass unknown

(high power consumption)(high power consumption)

Message includes:Message includes:

• Statement of message lengthStatement of message length

• Transmitter ID numberTransmitter ID number

• Sensor data from 32 to 256 bitsSensor data from 32 to 256 bits

Used by Argo, DBCP (drifting buoys), SOOP, moorings, ice buoysUsed by Argo, DBCP (drifting buoys), SOOP, moorings, ice buoys

Argos extra/added-value services Processing centers process data, offer many dissemination routes Processing centers process data, offer many dissemination routes

(web, email, fax, telnet, etc), and archive data for up to 6 months(web, email, fax, telnet, etc), and archive data for up to 6 months

Gives a position for platform based on measured Doppler shift; Gives a position for platform based on measured Doppler shift; accuracy ranges from better than 150 m to more than 1000 maccuracy ranges from better than 150 m to more than 1000 m

Can put data onto the Global Telecommunication System (GTS) & Can put data onto the Global Telecommunication System (GTS) & make it publicly availablemake it publicly available

Will soon be (may have already started) offering Argos 3 with the Will soon be (may have already started) offering Argos 3 with the following upgrades:following upgrades:• Two-way communicationTwo-way communication• Faster data rate – 4.8 Kbytes/secondFaster data rate – 4.8 Kbytes/second• Greater data volume transmission (up to 10x current capacity)Greater data volume transmission (up to 10x current capacity)• Confirmation when message has been received error-freeConfirmation when message has been received error-free• Calculate time and date of satellite pass (can surface at that Calculate time and date of satellite pass (can surface at that

time)time)

Argos costs Basic ServiceBasic Service

• BuoysBuoys $5.60 per PTT-day unit$5.60 per PTT-day unit• FloatsFloats $8.40 per PTT-day unit$8.40 per PTT-day unit

A day unit is ¼ of a day or a 6 hour periodA day unit is ¼ of a day or a 6 hour period Additional feesAdditional fees

• Monthly active PTT feeMonthly active PTT fee $13.90 per PTT/month$13.90 per PTT/month• Unused ID numbers Unused ID numbers $4.50 per PTT/month$4.50 per PTT/month• Email or file transferEmail or file transfer $0.12 per kilobyte$0.12 per kilobyte

Example calculationExample calculation• PTT cost/month = A + [B * # of PTT-day units]PTT cost/month = A + [B * # of PTT-day units]• A is monthly active PTT fee; B is PTT-day rate depending on PTT A is monthly active PTT fee; B is PTT-day rate depending on PTT Bird carrying a PTT designed to transmit every day in a month, but Bird carrying a PTT designed to transmit every day in a month, but

only 8 hours a day. Usually heard from in 2 daily time slots only 8 hours a day. Usually heard from in 2 daily time slots (sometimes 3). (sometimes 3).

• PTT cost/month = $13.90 + [$8.40 x .5(30 PTT day units)] = PTT cost/month = $13.90 + [$8.40 x .5(30 PTT day units)] = $139.90$139.90

Discounts for large programs on B coefficientDiscounts for large programs on B coefficient

Cost is independent of data volume, only depends on number Cost is independent of data volume, only depends on number of active daysof active days

Iridium

Commerical global satellite voice and data systemCommerical global satellite voice and data system

66 low-earth orbiting satellites (plus 6 in-orbit backups)66 low-earth orbiting satellites (plus 6 in-orbit backups)

Cross-linked to 4 other satellitesCross-linked to 4 other satellites

100 minute orbit100 minute orbit

780 km above Earth780 km above Earth

40 ground stations40 ground stations

2 way communication2 way communication

Iridium

Short Burst Data (SBD) – email messagesShort Burst Data (SBD) – email messages allows short data transactions at about 2 Kbits/secondallows short data transactions at about 2 Kbits/second

Dial-up Data – works like a modem with a 2.4 Kbits/second rate,Dial-up Data – works like a modem with a 2.4 Kbits/second rate,in practice 1600bits/secin practice 1600bits/sec

new RUDICS service, TCP/IP like internet connection, new RUDICS service, TCP/IP like internet connection, nominally 4800baud, in reality 2500-3000baud or 250by/secondnominally 4800baud, in reality 2500-3000baud or 250by/second

Used by some Argo floats, all gliders, some mooringsUsed by some Argo floats, all gliders, some moorings

Possible decreased battery usage as compared to Argos where Possible decreased battery usage as compared to Argos where instrument must transmit for longer time periodsinstrument must transmit for longer time periods

Decreased surface time = reduced risk of damage done to Decreased surface time = reduced risk of damage done to instrument at surfaceinstrument at surface

Iridium cost

Iridium charges by the byte & a small monthly charge of ~ $15Iridium charges by the byte & a small monthly charge of ~ $15

Can buy from value added reseller (VAR) or a providerCan buy from value added reseller (VAR) or a provider

VAR sends data by email or you set up a dedicated server for a direct IP VAR sends data by email or you set up a dedicated server for a direct IP connectionconnection

Provider links to Iridium for you and emails the data (optionally archives Provider links to Iridium for you and emails the data (optionally archives the data and creates a website for you to access the data)the data and creates a website for you to access the data)

SBD charge: $1.50/kbyte, provider with archiving ~ $3.00/kbyteSBD charge: $1.50/kbyte, provider with archiving ~ $3.00/kbyte

Dial-up at 1600bit/sec and $0.80/minute (iridium to iridium) to Dial-up at 1600bit/sec and $0.80/minute (iridium to iridium) to $1.50/minute (lridium to landline) means $0.07-$0.15/kbyte$1.50/minute (lridium to landline) means $0.07-$0.15/kbytei.e. 10-20 times cheaper than SBD/email servicei.e. 10-20 times cheaper than SBD/email service

RUDICS service: 3000bit/sec (=250by/second) at $0.67/min, i.e. $50/MB. RUDICS service: 3000bit/sec (=250by/second) at $0.67/min, i.e. $50/MB. But high start-up charge of $750 for first SIM card, and $40/monthBut high start-up charge of $750 for first SIM card, and $40/month

Iridium Flares: http://www.heavens-above.com

SIO pier has 32.8662 N117.2541W

Orbcomm

Commercial global satellite system for machine to machine Commercial global satellite system for machine to machine (M2M) communications(M2M) communications

30 low earth orbit satellites 30 low earth orbit satellites

~ 100 minute orbit~ 100 minute orbit

757 km above Earth757 km above Earth

13 ground stations13 ground stations

2 way communication2 way communication

Orbcomm data rates & cost

Data uplink rate: 2.4 Kbytes/secondData uplink rate: 2.4 Kbytes/second

Data downlink rate: 4.8 Kbytes/secondData downlink rate: 4.8 Kbytes/second

Services sold through VARServices sold through VAR

Byte charge: $5/1000 bytesByte charge: $5/1000 bytes

Basic modem: $275Basic modem: $275

Antenna with GPS: $100Antenna with GPS: $100

Globalstar

40 low earth orbit satellites40 low earth orbit satellites

1500 km above Earth1500 km above Earth

Not global, but covers coastal regions & North Atlantic fairly Not global, but covers coastal regions & North Atlantic fairly wellwell

Several satellites pick up one call and simultaneously transmit Several satellites pick up one call and simultaneously transmit data to back to grounddata to back to ground

Can send data at 9.6 Kbytes/second for uncompressed data Can send data at 9.6 Kbytes/second for uncompressed data and up to 38.6 Kbytes/second for express data serviceand up to 38.6 Kbytes/second for express data service

Globalstar CoverageGlobalstar Coverage

Globalstar cost

Similar to Iridium – sold through VAR or a provider for roughly Similar to Iridium – sold through VAR or a provider for roughly the same price per Kbyte & monthly service feethe same price per Kbyte & monthly service fee

Equipment needed is less expensive than IridiumEquipment needed is less expensive than Iridium

Used in coastal lagrangian driftersUsed in coastal lagrangian drifters

LEO Satellite system comparisons Argos:Argos:

• Created for scientists, reliableCreated for scientists, reliable• Gives a position without GPSGives a position without GPS• Extras are helpful – archiving, GTS, etcExtras are helpful – archiving, GTS, etc• Slow data rateSlow data rate• Current system doesn’t offer 2-way communication, but Argos 3 should (very Current system doesn’t offer 2-way communication, but Argos 3 should (very

soon)soon)• Floats must be at the surface for a longer period of time to ensure complete Floats must be at the surface for a longer period of time to ensure complete

message transfermessage transfer Iridium & Orbcomm:Iridium & Orbcomm:

• 2-way communication2-way communication• Faster and service can be cheaper than ArgosFaster and service can be cheaper than Argos• Floats/gliders need be at surface for minutes instead of hours to send data Floats/gliders need be at surface for minutes instead of hours to send data • Confirmation that message was receivedConfirmation that message was received

Globalstar: Globalstar: • Much cheaper and faster than other systemsMuch cheaper and faster than other systems• Only in coastal areas for the most partOnly in coastal areas for the most part• One or two way communicationOne or two way communication

All systems need several watts (1-3W Argos, 5W others) so energy All systems need several watts (1-3W Argos, 5W others) so energy need depends on length of transmission/data ratesneed depends on length of transmission/data rates

C-band, Ku-Band, Ka-BandC-band, Ku-Band, Ka-Band

Refers to the microwave range of frequencies from 4 to 8 GHzRefers to the microwave range of frequencies from 4 to 8 GHz

Used with geostationary satellites Used with geostationary satellites

Require big directional antennas (0.6-2.4 m), i.e. need to track Require big directional antennas (0.6-2.4 m), i.e. need to track satellite on moving platforms !!! satellite on moving platforms !!!

Super high data rate – up to 2 Mbytes/secondSuper high data rate – up to 2 Mbytes/second

Used on ships or large buoys Used on ships or large buoys

Needs kilowatt powerNeeds kilowatt power

C-band – example for ORION

FleetBroadBandFleetBroadBand(new INMARSAT internet service)(new INMARSAT internet service)

1.5-1.6 GHZ

Cellular Modem

Uses the cellular phone network to transmit and receive data, Uses the cellular phone network to transmit and receive data, with enhanced data modes (GPRS, EDGE, 3-G)with enhanced data modes (GPRS, EDGE, 3-G)

Fast data rate – minimum 9.6 Kbit/second up to 56kbaudFast data rate – minimum 9.6 Kbit/second up to 56kbaud Provides direct internet connection, and thus 2-way Provides direct internet connection, and thus 2-way

communication communication Good for coastal applicationsGood for coastal applications Need to be where cellular networks are located Need to be where cellular networks are located Pricing may be reasonable depending on the plan offered. Pricing may be reasonable depending on the plan offered.

Often just a flat rate like $40-70/month, so good if sending lots Often just a flat rate like $40-70/month, so good if sending lots of data frequently.of data frequently.

Uses approx. 4W power while transmitting, less than 1W when Uses approx. 4W power while transmitting, less than 1W when idle, so may want to power down when not in use (but then not idle, so may want to power down when not in use (but then not reachable).reachable).

Freewave Modem

Uses spread spectrum radio signals in the 900 MHz rangeUses spread spectrum radio signals in the 900 MHz range

Spread spectrum radio – uses wide band, noise-like signals. Spread spectrum radio – uses wide band, noise-like signals. Very secure, less prone to jamming and interference.Very secure, less prone to jamming and interference.

Transmits well though glass, wood, plasterTransmits well though glass, wood, plaster

Range of 15 km with 7.5 cm antennaRange of 15 km with 7.5 cm antenna

Speed ranges from 1.2 to 115 Kbytes/secondSpeed ranges from 1.2 to 115 Kbytes/second

Need to set up own/dedicated receiving station for each unitNeed to set up own/dedicated receiving station for each unit

Good for coastal applicationsGood for coastal applications

10W power typically10W power typically

LEO SatellitesLEO Satellites C-bandC-band Cellular & Freewave Cellular & Freewave

ModemsModems

Mostly global and long Mostly global and long

range coverage range coverage

Slow to medium data Slow to medium data rates rates

Small transmittersSmall transmitters

Used mainly on Used mainly on ships ships or large buoys or large buoys

Very fast data ratesVery fast data rates

Allows large files to Allows large files to be transferred easily be transferred easily

ExpensiveExpensive

For coastal For coastal applications applications

Medium to fast data Medium to fast data rates – same or rates – same or better than LEO better than LEO satellites satellites

B: Underwater telemetry

• Acoustic links

• Inductive links

Acoustic modemhere (Teledyne) Benthos

Cost: $9000 ($5000 OEM version)

Baud rate:

Available are 140,300,600,800,1066,1200 bit/sec

Power consumption:

7.5/B amp-seconds/byte   where B is the measured baud rate.

The battery supply is a nominal 21 volts.  The full alkaline battery pack is 28 Amp-hour.

The number of bytes you can send depends upon how long the modem is sitting idle waiting for the other end to ask for data.  The full memory of the modem is 700 Kbytes.

The modem uses 9.6 mWatt when in the low power state.

Approximately one could have a modem idle for a year and still send 700Kbytes at 140 baud. We now have lithium batteries installed, and with the current glider-mooring success rate (over up to 7km range), we expect to have 2-year life and telemeter approx. 2MB

Inductive modem (here Seabird): cost: $500 (SIM)

Speed 9600baud30mA @ 12-25V 1 hour transmission needs 30mAh and gives 4Mby data.So with battery pack similar to Benthos modem could transfer 3-4Gbytes !

Inductive links

Inductive swivel

C: Surface and subsurface (emergency) beacons

Surface beacons validate position and maybe functioning of system (mainly moorings). They transmit regularly on a fixed schedule.They may also act a recovery aid.

Subsurface beacons are used for emergency locator transmitters.They

• alert owner in case of unforeseen surfacing

• allow tracking of surfaced/drifting components until rescue

• allows location of equipment after regular release (may need direction finders)

• triggered by pressure, or conductivity switch, or light (careful near surface, may need red filters etc)

Iridium beacons: have GPS position (better accuracy) and 2-way communication (saves power)

XEOS Sable XEOS Melo