Argos DCS (Data Collection System)
Argos is a global spaceborne data collection and location system (DCS) dedicated to studying and protecting Earth's environment. The objective of the Argos DCS is to locate in the ground segment fixed and mobile platforms and collect environmental data from them. The system consists of in-situ data collection platforms in the ground segment equipped with sensors and transmitters and the Argos DCS instrument aboard polar orbiting weather satellites. What makes the DCS unique is the fact that a moving satellite platform allows for locating an in-situ platform using Doppler shift calculations. This positioning capability permits applications such as monitoring drifting ocean buoys and studying wildlife migration paths.
The system was developed under a cooperative program between CNES, the French Space Agency, NASA (National Aeronautics and Space Administration), USA, and NOAA (National Oceanic and Atmospheric Administration), USA. The purpose is to provide an operational service for the entire duration of the POES (Polar-orbiting Operational Environmental Satellites) program of NOAA (TIROS-N series), that is well beyond year 2000. 1) 2) 3) 4)
The cooperative Argos program of CNES, NASA and NOAA started in 1974 for the purpose of long-term continued global satellite data collection services (in particular environmental data) from fixed and mobile platforms located anywhere in the world. The Argos system package has been flown on all TIROS-N family satellite of NOAA since 1978. The space segment comprises the NOAA POES satellites and more recently the ADEOS-II spacecraft of JAXA, and the EUMETSAT MetOp spacecraft in orbit.
The Argos/DCS supports NOAA in its overall environmental mission objectives, collecting (ground and space) truthing data. The concept uses many ground segment platforms (fixed and moving), i.e. buoys, free-floating balloons, wildlife, and remote weather stations, and equips them with a PTT (Platform Transmitter Terminal) package. These PTTs collect and process relevant environmental data and transmit them to the NOAA-POES satellites. The on-board Argos DCS receives the incoming signal and measures both the frequency and relative time of occurrence of each transmission.
The S/C retransmits these data via the CDA (Command and Data Acquisition) stations (one at Wallops Island VA, the other at Fairbanks, AK; there is in addition a downlink station at Svalbard Norway), to a central NOAA processing facility in Suitland, Maryland, USA. The DCS information is decommutated and sent to the Argos processing centers in Toulouse France and Largo (Landover) Maryland USA, where it is processed, distributed to the user community, and stored on magnetic tape for archival purposes. 5) 6)
The processing and distribution service is provided commercially by CLS (Collecte Localisation Satellites - created in 1986), a CNES and IFREMER subsidiary in Toulouse, France, and by Service Argos Inc. of Largo, MD, USA (a CLS subsidiary). Service to the user community has been continuously provided since fall 1978.
The Argos system concept involves three interactive elements or subsystems:
1) PTTs (Platform Transmitter Terminals) of the various clients in the ground segment, equipped with sensors to measure environmental parameters. The PTTs are the Argos user platforms, fixed or mobile, deployed at sea, on land or in the air and transmitting independently.
2) The space segment DCS payload of the service provider. A desired complement of two operational NOAA spacecraft and two in backup in simultaneous orbit, with instrument packages that receive PTT messages on a random access basis, then separate, time-code, format and retransmit the data to ground stations,
3) The ground segment of the service provider. The ground stations and two Global Processing Centers (GPCs) in Toulouse, France and Landover, MD, USA, where data are retrieved, processed, and distributed to users. Each centre can take on the full operational workload if the other fails.
Flying the Argos DCS system aboard NOAA polar-orbiting satellites provides worldwide coverage. Additionally, incorporating the Argos instrument on a moving satellite allows for locating an in-situ platform using Doppler shift calculations. This positioning capability permits applications such as monitoring drifting ocean buoys and studying wildlife migration paths. Argos DCS can track platforms anywhere in the world, supplying positions to users around the globe. Platforms can be attached to practically any type of physical object, for example: an ocean buoy, a stream gauge, a bear, a bird, or a fishing vessel. Argos platforms are located by using the Doppler Effect, which gives an accuracy of up to 150 m. Doppler locations are good for compact, low-power transmitters and in difficult radio environments. The satellites receive the signals sent even in extreme conditions such as a platform transmitting from a dense rainforest or from transmitters on the polar ice caps.
Argos DCS is used with great success in the following applications:
- Studying oceans and atmospheric conditions (oceanography, meteorology)
- Preserving and monitoring wildlife
- Monitoring volcanoes
- Monitoring fishing fleets
- Monitoring shipments of dangerous goods
- Humanitarian applications
- Managing water resources
- Operation of automatic weather stations in remote areas such as in Antarctica
The majority of Argos DCS users are government/non-profit agencies and researchers. At the start of the 21st century, Argos DCS customers are engaged in over 1000 programs operating approximate ly 15,000 data collection platforms in 72 counties.
Argos space segment:
Each Argos payload is equipped with a DCLS (Data Collection and Location System), also referred to simply as DCS, which receives all transmissions from the platforms in view during a pass. Functionally a DCLS is comprised of the following subsystems:
• Housekeeping equipment, power supply and DCLS command interface
• Receive assembly (receiver and search unit, both with full redundancy)
• Signal processing assembly (four identical Data Recovery Units (DRUs). All data are tape recorded on board the spacecraft.
Figure 1: Illustration of a NOAA POES spacecraft with Argos/DCS instrumentation (image credit: NOAA)
Figure 2: The Argos system concept within the early NOAA POES/TIROS family
Argos ground segment:
A set of user platforms, fixed or mobile, deployed at sea, on land, or in the air. All platforms reporting to the Argos system must carry a certified PTT (Platform Transmitter Terminal) package for satellite uplink communication. Each PTT outputs a short message (of 0.36 to 0.92 seconds duration, or of 32 bits to 256 bits maximum length) modulating a carrier frequency. Message transmission intervals range from 90 - 300 s, depending on the application.
Figure 3: Artist's view of some ground segment elements in the Argos DCS system (image credit: Service Argos Inc.)
The ground segment of the service provider consists of two NOAA/NESDIS CDA (Command and Data Acquisition) stations, one at Wallops Island VA, the other at Fairbanks, AK. In addition there is a downlink station at CMS (Centre de Météorologie Spatiale) Lannion, France. All these stations also provide real-time data during the pass. Argos provides two GPCs (Global Processing Centers), one in Largo, MD, the other in Toulouse, France. Each GPC receives data from all platforms but processes only the data that belong to “its” users. Both centers will, however, immediately process all data in case of necessity, thereby ensuring full redundancy. 7)
As of 2002, the Argos ground segment provides five processing centers (the two global processing centers in Toulouse and Largo continue to process data sets from all receiving stations; the regional centers are: Melbourne, Tokyo, and Lima):
• Toulouse, France
• Largo, MD, USA
• Melbourne, Australia
• Tokyo, Japan
• Lima, Peru
Figure 4: The Argos Processing Centers (image credit: Service Argos Inc.)
Figure 5: The Argos ground segment in the timeframe 2000 (image credit: CLS, Ref. 7)
Collection Uplink: Argos provides a total of four (eight in next series) parallel receiving channels for data collection, each at a rate of 400 bit/s. Each PTT in the ground segment transmits encoded messages at regular intervals (fixed platforms at 45 - 200 seconds, drifting or mobile platforms in the order of 90 - 150 seconds).
Note: the search unit is a spectrum analyzer that scans a 24 kHz band centered at 401.650 MHz. The next series of DCS will have 80 kHz of bandwidth (100 kHz allocated, two safeguard bands of 10 kHz at each end). Time tagging and frequency measurements are made by the DRUs and processed on the ground for location determination.
Table 1: Characteristics of a PTT
Figure 6: Link access method of a PTT in the ground segment by a S/C (image credit: Service Argos Inc.)
Downlink: The data received by the Argos DCLS is multiplexed on-board by the TIP processor and transmitted to the ground via three paths:
• Real-time: the TIP output (8.32 kbit/s, see Figure 2) directly modulates a VHF beacon which transmits continuously.
• Real-time: the TIP output is multiplexed on-board the satellite with HRPT data and transmitted in S-band
• Delayed Transfer: the TIP output is also recorded by a tape recorder, and each time the satellite passes over one of the ground stations, the recorded data is dumped via S-band telemetry.
The Argos communication capability is limited to the function of data collection from the PTTs. The concept does not offer a remote configuration control capability of the data collection platforms in the ground segment.
Figure 7: Argos DCS services in various application fields (image credit: Service Argos Inc.)
The on-board DCLS receiver picks up messages from the transmitting platforms in its area of visibility. The receiving system can discriminate between message arrival times and between frequency shift due to the Doppler effect. Up to four (eight in next series) messages may be processed simultaneously.
The Argos access scheme employs `pure (i.e. unslotted) ALOHA.' Messages from the PTTs are received on-board on a random access basis. The Argos Doppler system provides a position fix for drifter (or mobile) platforms. This setup requires between three and five successful transmissions, which must occur within one pass (footprint).
Within an average footprint of 10 minute duration, each platform in the ground segment usually has a number of attempts to make contact with the DCLS in the space segment.
• Fixed platforms: the number of transmission attempts of fixed platforms is three at a repetition rate of 200 seconds (average = 3).
• Drifting (mobile) platforms: the repetition rate is 90 - 150 seconds, hence the maximum number of transmission attempts possible within a footprint is 5 - 6 (average = 5). [About 80% of the possible position fixes are actually achieved by the system; 20% are rejected during ground processing for various reasons, mainly geometrical configuration: number of messages, pass duration, distance to the track, etc., according to CLS Argos].
The nature of random access very much degrades data collection performance by the space segment. The scheme of pure ALOHA permits under normalized offered channel traffic a maximum channel throughput rate of 18%. Any two signals overlapping in time and frequency may interfere, with the loss of both. The principal parameter that affects the performance of the Argos data relay system is “interference”: it occurs when the demand for service exceeds the system's capability. The result is loss of data from system `blockage'. The maximum number of platforms that a single Argos DCLS can actually service within a footprint is in the order of 650. In this number, there is a certain mix of fixed (collection service only) platforms and drifting (collection and location services) platforms, a further assumption is a certain message length.8) 9) 10)
The probability of good message reception is 67% with a traffic density of 2.6 Erlang, and 8.3 Erlang for the next improved DCLS series which is scheduled to be launched starting in 1998 with NOAA-K.
The total number of platforms registered as active in the Argos system globally is around 4000, out of which around 2300 are transmitting every day. The remaining platforms transmit once every two or three days, or less. This information was provided by CLS Argos (6/1993), the service provider of the system.
Argos-2 DCS, the next generation instrument package:
Argos-2 represents an enhanced instrument package over the old Argos system - in response to user-identified priorities. The new performance spectrum includes: 11)
• Implementation of eight DRUs (Data Recovery Units) instead of four on the previous Argos generation. Hence, the Argos-2 generation spacecraft are able to process eight messages simultaneously.
• The uplink bandwidth was increased from 24 to 80 kHz. This permitted a better distribution of PTT transmitter frequencies and a better discrimination of signal reception at the spacecraft. Hence, for a given platform population more messages can be received intact. The increased onboard capacity - wider receiver bandwidth, and more flexible management of transmitter repetition periods - offers more PPT sensor data transmissions.
Figure 8: Message handling scheme of the Argos-2 version (image credit: NOAA)
• Argos-2 offers greater sensitivity to low-power signals (receiver with sensitivity of -131 dB). The impacts of the higher sensitivity (from -128 to -131 dB) are broad in scope in that the general population of Argos transmitters will require less power.
• So-called PMTs (Platform Messaging Transceivers) are being introduced by the ground segment platforms (PTTs) able to receive and interpret messages sent by the satellite. The new service spectrum permits for example to calibrate platform sensors and to manage duty cycle by switching terminals on and off when needed.
The first NOAA satellite with the Argos-2 system package implemented was NOAA-15 (launch May 13, 1998) with Argos-2 system improvements continued on NOAA-16 (launch Sept. 21, 2000), NOAA-17 (launch June 24, 2002) and NOAA-18 (launch May 20, 2005).
Note: Initially it was planned to provide an enhanced service of a two-way messaging capability for Argos-2. However, this was only accomplished for Argos-Next.
The first Argos-Next (improved Argos-2) implementation has been flown on ADEOS-II (JAXA) with a launch Dec. 4, 2002; Argos-Next service provision tests started on Jan. 29, 2003. Note: end of ADEOS-II mission Oct. 25, 2003, due to spacecraft power failure).
The Argos-Next implementation on ADEOS-II involved also a corresponding ground segment in Japan and integration into the existing CNES/CLS/NOAA Argos network. This new ground segment provides:
• Reception of data from ADEOS-II, extraction of Argos-Next data and transmission of these data to the CLS processing center in Tokyo, Japan (under JAXA responsibility)
• .Processing and distribution of Argos-2 (and Argos-Next) data and exchange of collected data with the processing center in Toulouse, France (under CNES and CLS responsibility).
Background: As early as December 1993, NASDA (Japan) and CNES (France) agreed to fly an enhanced Argos instrument on Japan's ADEOS-II environmental monitoring satellite. Through this agreement, CNES would be able to conduct in-flight validation of Argos enhancements under development and bring NASDA on board as a third partner in what had previously been a bilateral program managed jointly with NOAA (USA).
Figure 9: The Argos-Next ground segment configuration for the timeframe 2010 and beyond (image credit: CLS, Ref. 7)
Argos-3 instrument package with two-way capability onboard:
The Argos-3 instrument package is also referred to as A-DCS (Advanced Data Collection System) as well as ADCS. The main objectives of the Argos-3, or mission are recalled hereunder: 13)
• To insure the continuity of the system with the current Platforms named PTT-A2
• To improve the performance of the Argos system in terms of waiting time and overall data collection capability. The bandwidth of the Argos-3 receiver is now 110 kHz (24 kHz for Argos-1 and 80 kHz for Argos-2)
• To provide users with the downlink message function, validated by the Argos-Next instrument installed on JAXA's ADEOS-II (now out of service), namely a space-to-earth link dedicated to the transmission of messages to the Argos Platforms fitted with appropriate receivers. This downlink will allow:
- To acknowledge their uplink messages and then to increase the capacity of the system
- To transmit broadcasting messages as time or orbit ephemeris in order to activate the platforms emitters only when a satellite is above
- To modulate the length of the messages or the repetition period of the messages according to the user needs.
• To improve the performance of the Argos system in terms of overall data collection capability, through the introduction of a new kind of Platforms: the high data-rate transmitters named PTT-HD or PMT-HD (Platform Messaging Transceivers-High Data rate). Those Platforms are not designed to be autonomously located by Doppler technique. However they may be located using an integral navigation receiver.
• To provide a better sensitivity thanks to a new kind of Argos-3 Platforms, called the new generation Platforms PTT-A3, PTT-ZE, PMT-A3. Those Platforms have the capability of a very low-power consumption.
• To upgrade the data management system for the function ”User Messages to Platforms” under the responsibility of the Downlink Messages Management Center (DMMC) located in Toulouse.
The Argos-3 system design proposes three types of terminals to cover more applications. These terminals use different modulation waveforms: BPSK (Bi-Phase Shift Keying), QPSK (Quadra-Phase Shift Keying) and GMSK (Gaussian Minimum Shift Keying), channel coding, data volumes and bit rates with a good stability oscillator for the Doppler location. 14) 15) 16)
The major improvement of the new system is that it will now be able to send orders to its terminals whereas before they were only capable of receiving data (up to Argos-2 inclusive). There are some 10,000 Argos terminals throughout the world that send back data daily on the state of the oceans (currents, salinity, etc.), the habits and movement of some 3,000 animals, whether they be in the sea, on land, or in the air, as well as the localization and position of adventurers and navigators.
Figure 10: Message handling scheme of the Argos-3 version (image credit: NOAA)
Current Argos-2 buoys are sending data back continuously, even if no satellite is close enough to detect it, which uses up the buoys energy supply. With the new system, it will be possible to send messages to tell terminals to emit their data which will thus prolong their lifespan. The current terminals also send their data several times to assure that it is received; but the new system will be able to send messages letting the terminal know that the data has been collected. As a result, the terminals will not need to repeat themselves; hence, they will conserve their batteries. Engineers have also greatly enhanced the channels used for sending and receiving Argos-3 data; they now have broadband capabilities (4.8 kbit/s), which is ten times the amount of data transmission capability as was possible in the previous Argos generation.
Table 3: Actual and projected launch dates of spacecraft with Argos instruments
• The MetOp-A spacecraft of EUMETSAT (launch Oct. 19, 2006) carries the first Argos-3 instrument demonstrator package (also referred to as A-DCS (Advanced Data Collection System), equipped with a downlink capability of 400 bit/s (low) and the 4.8 kbit/s high data rate channel.
• Uplink: support of 3 types of platforms @ 401 MHz
- Standard: 400 bit/s, basic Argos Service; STD (Standard Service): Argos-1, 2, and 3; Bi-phase-L, no coding
- High sensitivity: 400 bit/s, very low power; NG (High Sensitivity Service): additional 5 dB margin; Mix-QPSK, convolutional coding 7, 1/2
- High data rate (HD): 4.8 kbit/s, 5 W; HD: up to 50 kbit per pass; GMSK, convolutional coding 7, 3/4
• Improvement of system sensitivity for STD beacons (probability of correct processing > 99%)
- Argos 1: C/N0 (Carrier-to-Noise) ratio=43 dB Hz
- Argos 2: C/N0=40 dB Hz
- Argos 3 : C/N0=37 dB Hz (-134 dBm at instrument input)
• Improvement of system sensibility with new types of beacons (probability of correct processing > 99%)
- NG: C/N0=34 dB Hz (-137 dBm)
- HD: C/N0=48 dB Hz (-123 dBm)
Argos-3 downlink: transmits messages @ 466 MHz of variable length (~ 200 bit max) to the platforms fitted with appropriate receivers
• Beacon equipped with a receiver = PMT (466 MHz, 400 bit/s, half or full duplex)
• Main functionalities:
- Acknowledgement of uplink messages [from a designated PMT (Platform Messaging Transceiver)]
- Sending of PMT instructions (all kinds of information sent by the user to his PMT)
- Transmission of satellite ephemeris
- Time broadcasting
Figure 12: Message format layout for the various Argos-3 services
Figure 13: Overview of Argos-2/3 instrumentation (image credit: NOAA)
Figure 14: Comparison of Argos-2/3 system performance (image credit: NOAA)
Argos-3 onboard instrumentation:
The Argos-3 project began in 1997. Delivered in 2002, the instrument received new versions of the management and processing software in 2004 and was tested extensively, at satellite level by Astrium, and in conjunction with the operational ground segment by EUMETSAT. All integration activities and associated tests with the Argos-3 instrument are managed by the CNES Argos team. 20)
Figure 15: Conceptual view of Argos-3 on MetOp providing two-way communications (image credit: CLS)
Figure 16: Exploded view of RPU components (image credit: CNES/CLS)
The Argos-3 onboard instrument is composed of the following components:
• The RPU (Receiver Processor Unit) providing the following functions
- Processing of the received uplink signals
- Downlink management
- Interfaces with the receiver, the TxU and the satellite
• The TxU (Transmitter Unit) sending the emissions (messages) to the PTTs in the ground segment
• The harness for the RPU to TxU connection
The RPU (16 kg, 36 W) and TxU (8kg, 26 W) boxes have a cold internal redundancy that can be activated by TC level. In the same way, the USO (Ultra Stable Oscillator) has a cold redundancy.
RPU (Receiver Processor Unit). The RPU onboard a spacecraft processes received uplink signals @ 401.6 MHz, measures the incoming frequency, time-tags the message, creates and buffers mission telemetry, manages the downlink and acts as interface between the receiver, the TxU (Transmitter Unit) and the satellite. Featuring fully digital processing, the RPU stores messages and either relays them in real-time to the nearest regional antenna - or in deferred time to a global center (maintained by NOAA, Eumetsat). A backup RPU is included as part of the device. The RPU has dimensions of 195 mm x 280 mm x 365 mm.
Figure 17: Illustration of RPU and TxU devices (image credit: Thales Alenia Space)
The TxU sends signals to platforms in the ground segment equipped with transceivers (PMTs) @ 466 MHz, including error-free message acknowledgement signals. The downlink allows users to send defined PMT instructions (TxU can selectively address one or more PMTs) and system operators to send global messages/commands such as satellite ephemeris or broadcasting time. Downlink software was specially designed for Argos-3. A backup TxU is included. The TxU has dimensions of 100 mm x 280 mm x 310 mm. The RPU and TxU instruments are being manufactured at Thales Alenia Space.
Figure 18: The MetOp-A spacecraft with the Argos-3/A-DCS instrumentation (image credit: CNES/CLS)
Plans are to embark also an Argos-3 instrument on an ISRO (Indian Space Research Organization) platform in the near future. As a result, the Argos system is an operational system exploited by a number of international programs. It is the main transmission channel and processing chain for data gathered by the following major international ocean observation programs:
• DBCP (Data Buoy Cooperation Panel), a network of drifters and moored buoys
• SOOP (Ship of Opportunity Program), XBT (Expendable Bathythermograph) lines
• Argo profiling float project.
In the future, Argos will be an important part of GEOSS (Global Earth Observation System of Systems) - an international initiative approved by over 60 governments and the European Commission (EC) and designed to improve our understanding of the Earth system.
Figure 19: Three generations of Argos implementations on LEO S/C during the last two decades (image credit: Service Argos Inc.)
PMT (Platform Messaging Transceiver) - Argos-3 user platforms
Argos-3 and all future two-way communication satellite instruments are completely compatible with existing transmitters. However, to benefit from the downlink and high data rate uplink unique to Argos-3, user platforms in the ground segment must be equipped with a new generation of Argos-3 compatible terminals called Platform Messaging Transceiver (PMT). The innovative and new PMT is capable of sending and receiving messages to/from satellite, as well as processing commands. Users equipped with a PMT and subscribed to the downlink service will fully benefit from the new communication capabilities made possible with Argos-3.
The first PMT prototypes were developed for the ADEOS-II spacecraft of JAXA (launch Dec. 4, 2002). Since then, smaller prototypes have been developed, capable of transmitting larger volumes of data. Furthermore, PMTs are able to receive and process system information and remote commands from users.
First generation PMTs were available in 2007, a few months after the launch of MetOp-A (launch Oct. 19, 2006, commissioned on May 21, 2007). The first interactive session on May 10, 2007 between METOP-A and PMT worked perfectly well.
PMTs communicate intelligently with the Argos-3 payload.
• Once the PMT receives acknowledgement that a message has been received error-free, it stops sending this message.
• When the PMT receives a user command, it sends acknowledgement to the satellite, then processes the command.
• When the PMT receives system information, it calculates the orbit of the different satellites, thus sending messages efficiently and intelligently, only when a satellite is in sight.
Figure 20: View of some PMT models on the market in 2007 (image credit: CLS)
2) D. Meldrum, D. Mercer , O. Peppe, “Developments in Satellite Communication Systems, Update Oct. 2001,” URL: http://noaasis.noaa.gov/ARGOS/pdfiles/telecom-review-dec-2001.pdf
4) B. Woodward, “The Argos Data Collection and Location System,” 2004 Satellite Direct Readout Conference, Dec. 6-10, 2004, Miami, FLA, USA, URL: http://directreadout.noaa.gov/miami04/docs/tues/Bill_Woodward.pdf
6) “Guide to Data Collection and Location Services using Service Argos,”, DBCP (Data Buoy Cooperation Panel) Technical Document No. 3, Intergovernmental Oceanographic Commission (of UNESCO), World Meteorological Organization, 1995, URL: http://ioc-unesco.org/components/com_oe/oe.php?task=download&id=10332&version=1.0&lang=1&format=1
7) Philippe Schwab, Claude. Gal, “Argos DCS Ground Segment,” 5th International Symposium on Space Mission Operation and Ground Data Systems (SpaceOps 98), June 1-5, 1998, Tokyo, Japan, URL: http://track.sfo.jaxa.jp/spaceops98/paper98/track2/2c003.pdf
8) Note: the figure of 650 serviceable platforms in a footprint was provided by `CLS Argos' of Toulouse
9) “A Definition Study of an Advanced Data Collection and Location System (ADCLS),” prepared for GSFC by ECOSYSTEMS International Inc., January 1986
10) Christian Ortega, Bill Woodward, “Argos Downlink,” DBCP Technical Workshop, Angra dos Brazil, Oct. 20, 2003, URL: ftp://ftp.wmo.int/Documents/PublicWeb/amp/mmop/documents/dbcp/Dbcp24-Angra-2003/Documents/2_Sesssion_II/2_2_Ortega_Woodward.ppt
12) “Argos Joint Tariff Agreement, Twenty-third Meeting,” Final Report, Angra dos Reis, Brazil, 27-29 October 2003, URL: http://www.jodc.go.jp/info/ioc_doc/JCOMM_Other/jta23_Final_Report.pdf
13) “The Argos-3 (or A-DCS) instruments,” 39 th Argos Operations Committee meeting, Prepared by CNES, June 7th, 2005, URL: http://noaasis.noaa.gov/ARGOS/conf05/E2_Argos3_instrument.pdf
14) E. Bouisson, J.-F. Dutrey, P. Guillemot, J. Delporte, “Post-Processing Solutions to Characterize Data Collection and Location Terminals for the Argos-3 System,” PSIP'2003 - 3rd International Symposium on Physics in Signal and Image Processing., Jan. 29-31, 2003, Grenoble, France
15) Argos-3 - The New Generation, URL: https://www.argos-system.org/html/system/enhancements_en.html
16) “Advanced Data Collection System Instrument Control Document, (A-DCS ICD)” EADS Astrium and MetOp Team, April 2005, URL: http://www.eumetsat.int/idcplg?IdcService=GET_FILE&dDocName=PDF_TEN_EPS-ADCS-ICD&RevisionSelectionMethod=LatestReleased
17) “The Argos-3 (or A-DCS) instruments,” 40th Argos Operations Committee meeting, CNES, May 24, 2005, URL: http://noaasis.noaa.gov/ARGOS/conf06/E-2_Argos3_Instrument_40.pdf
18) Information provided by Christopher O'Connors, NOAA, Suitland, MD, USA
19) “A-DCS Advanced Data Collection System,” ESA, June 26, 2006, URL: http://www.esa.int/esaLP/SEM3JGG23IE_LPmetop_0.html
20) “Argos-3: The New Generation,” CLS (Collecte Localisation Satellites), URL: https://www.argos-system.org/documents/publications/brochures/argos3_metop_en.pdf
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.