Jason-3 Altimetry Mission
Jason-3 is the follow-on altimetry mission of Jason-2 / OSTM (launch June 20, 2008) led by the operational agencies: NOAA, EUMETSAT, and CNES. The objective of the Jason-3 Mission is to provide continuity to the unique accuracy and coverage of the TOPEX/Poseidon, Jason-1 and OSTM/Jason-2 missions in support of operational applications related to extreme weather events and operational oceanography and climate applications and forecasting. 1) 2) 3)
In early February 2010, the EUMETSAT Member States approved the Jason-3 transatlantic program - thus ensuring a continuation of the series of measurements made by the Jason-2 satellite and its predecessors in support of meteorology, operational oceanography and in particular the monitoring of the sea level trend, a key indicator of climate change. The MOU (Memorandum of Understanding) was signed in July 2010. 4) 5) 6) 7)
The partnership responsibilities/activities of Jason-3 are distributed in the following way: 8)
• NOAA and EUMETSAT — the operational agencies — are taking the lead
• CNES, the French Space Agency, is making a significant in-kind contribution to the program and will act at the technical level as the system coordinator. This in-kind contribution includes making available the Jason-3 Proteus satellite platform, its facilities and associated human resources.
• NASA, in conjunction with the three other partners (NOAA, EUMETSAT, CNES), will support science team activities. The US contribution to Jason-3 includes the satellite launch, provision of instruments and support to operations.
• Overall, responsibilities sharing has changed, but activities sharing remains almost the same as for Jason-2/OSTM.
Planning for the Jason-CS (Jason-Continuity of Service) mission started in the timeframe 2009/10: The Jason-CS program is the follow-on Reference Mission of Jason-3 spanning the timeframe 2015-2020.
The mission objectives are:
1) Provide continuity of high precision ocean topography measurements beyond TOPEX/Poseidon , JASON-1 and JASON-2
2) Provide an operational mission to enable the continuation of multi-decadal ocean topography measurements
3) The science requirements call for a global sea surface height to an accuracy of < 4 cm every 10 days for determining days, ocean circulation, climate change and sea level rise.
Figure 1: Overview of mission responsibilities (Ref. 7)
Figure 2: Artist's rendition of the TOPEX/Poseidon and Jason altimetry missions (image credit: NASA/JPL)
While the Jason-3 mission will continue the core satellite altimetry measurements for physical oceanography - the plans call in addition for the transitioning from research to operational applications of this valuable measurement. Jason-3 builds upon the heritage of the foundational and transitional missions such as SEASAT (1978), GEOSAT (1985), TOPEX/Poseidon (T/P, 1992), Jason-1 (2001) and Jason-2 / OSTM (2008), which have led to the understanding and development of a wide range of oceanographic applications of satellite altimetry. 9)
Fulfilling the goals of moving satellite altimetry onto routine operations will require a close cooperation and coordination of international, multi-agency mission managers, designers, engineers, scientists and operational systems developers.
NOAA and EUMETSAT gained already experience in operating the Jason-2 / OSTM mission. The Jason-3 mission is fully lead by the operational agencies, NOAA and EUMETSAT, with CNES and NASA in supporting roles. 10)
• Ocean-monitoring data exchange between Europe and China: On August 30, 2012, EUMETSAT signed an agreement with NSOAS (National Satellite Ocean Application Service) of China to exchange data from their ocean-monitoring satellites. For EUMETSAT, this applies to data from the missions: Jason-2 and Jason-3 as well as from the MetOp series satellite (ASCAT data). In return, NSOAS will provide EUMETSAT with similar scatterometer and altimetry data from the Chinese HY-1 and HY-2 ocean-color satellites. 11)
Figure 3: Artist's rendition of the deployed Jason-3 spacecraft (image credit: CNES)
Mission architecture: With a recurring development methodology in mind, the overall mission architecture for Jason-3 is planned to be the same as for Jason-2 / OSTM, taking into account areas of updates due to obsolescence or unavailability.
• Like its predecessor Jason-2, the Jason-3 mission employs the Proteus bus of CNES/TAS (Thales Alenia Space) and a payload module, with Thales Alenia Space as the prime contractor of the spacecraft. The CNES contract with TAS followed the early February 2010 approval by the EUMETSAT governments for the required funding of the spacecraft. Jason-3 is three-axis stabilized and nadir pointing - maintained by reaction wheels and magnetic torque rods. 12)
• NOAA will contribute to Jason-3's payload and will also be responsible for the launch of the spacecraft. The payload will consist of the same core instruments as Jason-2: a Poseidon class Ku/C-band radar altimeter to provide the primary ranging measurement, a nadir–looking three frequency (18.7, 23.8, and 34.0 GHz) microwave radiometer (as flown on Jason-2), along with a POD (Precise Orbit Determination) package consisting of a GPS (Global Positioning System) receiver, DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite), and a LRA (Laser Retroreflector Array), as flown on prior Jason series missions. Two additional instruments (dosimeters from CNES and JAXA) will also be embarked to evaluate the radiation environment. - NOAA has engaged NASA/JPL to act on its behalf to fulfill some of its respective commitments on the flight system development (Ref. 9).
Figure 4: Photo of the Jason-3 Proteus bus (image credit: CNES, TAS)
Integration of the Jason-3 platform has been completed in late 2010 and is stored since December 2010.
Like Jason-2, the Jason-3 spacecraft employs the Proteus bus of CNES/Thales Alenia Sapce and a payload module, with Thales Alenia Space as the prime contractor of the spacecraft. Jason-3 is three-axis stabilized and nadir pointing - maintained by reaction wheels and magnetic torque rods. Power (580 W) is provided by two solar panels. A hydrazine propellant system is being used for orbital maintenance. Jason-3 has a launch mass of about 550 kg; the design life is 5 years.
Table 1: Parameters of the Jason-3 spacecraft
RF communications: Downlink data rate at 838 kbit/s (S-band, QPSK modulation), uplink at 4 kbit/s (S-band). The CCSDS communication protocol standard is used in the forward and return link mode (use of virtual channels). Convolutional coding is also applied to telemetry.
Figure 5: Illustration of the Jason-3 spacecraft (image credit: CNES)
Launch: A launch of the Jason-3 is scheduled for the spring of 2015.
Orbit: Circular non-sun-synchronous orbit; 1336 km altitude (2 hour period), inclination = 66.038º, 9.9 day repeat orbits (127 revolutions), ground track repeatability = ±1 km cross-track at the equator. The drift of the orbital plane with respect to the inertial reference frame is -2º per day.
Sensor complement: (Poseidon-3B, AMR-2, GPSP, DORIS, LRA)
In addition to the sensor complement, 2 experiments will be embarked on Jason-3: Carmen-3 and LPT for radiation effects with the same constraints as for Jason-2 (Ref. 10).
Drift requirements : Specific Seattle OSTST (Ocean Surface Topography Science Team)<recommendation: 14)
• J3-TARG-PROD-147: As a goal, Jason-3 shall measure globally averaged sea level relative to levels established during the cal/val phase with zero bias ±1 mm (standard error) averaged over any one year period.
• J3-TARG-SYST-335: In order to satisfy the stability goal of reaching an uncertainty of less than 1mm/year in mean sea level change, allocations shall be given and enforced to the different components of the JASON-3 system that contribute to this measurement.
• J3-GUID-SYST-336. Tentative allocation for mean sea level change error budget is as follows:
- External geophysical correction: 0.1 mm/yr
- Orbit drift: 0.1 mm/yr
- Microwave radiometer wet troposphere correction: 0.7 mm/yr
- Sigma naught (σο) drift impact on sea state bias through wind speed): 0.1 mm/yr.
Legend to Table 2: (changes compared to Jason-2 are in blue)
(a) Real time DORIS onboard ephemeris
(b) Whichever is greater
(c) Jason-3 shall measure the globally averaged sea level relative to the levels established during the cal/val phase with zero bias ±1 mm (standard error) averaged over any one year period.
Operational Service Specifications : Reference TP4-J0-STB-32-CNES v 1.0
• Data Products requirements : Level2 ocean type products (geolocated and along-track geophysical products)
• NRT (Near-Real Time) products : Operational Geophysical Data Record (OGDR) : produced in near real time (3-5 hours)
- Fast Quality Control & Check : Elementary and automatic controls, product delivered in any case
- Priority given data latency with respect to validation and auxiliary data availability + forecast meteo files used.
• OFL (Off-Line) products : Interim Geophysical Data Record (IGDR) : produced in 1.5 days
- Quality Control & Check : Product not delivered in case of problems detected; Products validated by SALP/Calval activities (Calval chain + verification step); Possible reprocessing in case of quality problems.
- Improvement of : orbit quality (MOE), pole location data, restituted DORIS USO frequency, altimeter/radiometer calibrations, analyzed meteorological fields, dynamic atmospheric corrections applied.
• Geophysical Data Record (GDR) : produced in 60 days
- Quality Control & Check : Products fully validated by experts (CNES and JPL); Possible reprocessing
- Improvement of: orbit quality (POE), more accurate pole location data, more accurate dynamic
Table 3: Jason-3 Level 2 product file allocation (no change compared to Jason-2)
Table 4: Changes and new features of Jason-3 wrt Jason-2
Poseidon-3B is funded by CNES and of Poseidon-2 heritage (built by Thales Alenia Space). The Poseidon-3B dual-frequency (5.3 and 13.6 GHz) nadir-looking radar altimeter continues to be the key instrument in this spaceborne observation program. The objective is to map the topography of the sea surface for calculating ocean surface current velocity and to measure ocean wave height and wind speed. Poseidon-3 has a measurement precision identical to its predecessor Poseidon-2.
Table 5: Poseidon-3B parameters
In addition, Poseidon-3B features an experimental mode to support measurements closer to coastal zones, as well as on lakes and rivers. This will be achieved by an open loop tracker: the satellite to surface distance will be estimated by the altimeter using the real-time orbit position predicted by DIODE (on board navigator based on DORIS receiver) and using the elevation of the surface with respect to the Earth GRIM5 geoid stored in a DEM (Digital Elevation Model) within the altimeter. The instrument's RFU is recurrent from Poseidon-2, while the PCU (Processing & Control Unit) largely reuses electronics from the SIRAL radar altimeter on the CryoSat mission of ESA (European Space Agency).
Figure 6: Illustration of the Poseidon-3 instrument (image credit: Thales Alenia Space)
Figure 7: Photo of the Poseidon-3B antenna (image credit: TAS)
AMR-2 (Advanced Microwave Radiometer-2)
The AMR-2 instrument is provided by NASA/JPL with the objective to measure the altimeter signal path delay due to tropospheric water vapor. 15)
AMR-2 is a passive microwave radiometer measuring the brightness temperatures in the nadir column at 18.7, 23.8, and 34 GHz, providing path delay correction for the altimeter (the brightness temperatures are converted to path-delay information). The 23.8 GHz channel is the primary water vapor sensor, the 34 GHz channel provides a correction for non-raining clouds, and the 18.7 GHz channel provides the correction for effects of wind-induced enhancements in the sea surface background emission. 16)
The AMR-2 consists of two subsystems: ESA (Electronics Structure Assembly) and RSA (Reflector Structure Assembly). The ESA is developed by JPL, while the RSA is developed by ATK Space Systems, San Diego, CA.
Figure 8: The ESA system of AMR-2 (image credit: NASA/JPL)
Figure 9: The calibration target of AMR (image credit: NASA/JPL)
Figure 10: Photo of the RSA (Reflector Structure Assembly) of AMR (image credit: NASA/JPL) 17)
DORIS (Precise Orbit Determination System)
The Doris system uses a ground network of 60 orbitography beacons around the globe, which send signals at two frequencies to a receiver on the satellite. The relative motion of the satellite generates a shift in the signal's frequency (called the Doppler shift) that is measured to derive the satellite's velocity. These data are then assimilated in orbit determination models to keep permanent track of the satellite's precise position (to within three centimeters) on its orbit.
This instrument is supplied by CNES with a new generation (DGXX-S) taking into account lessons learned from Jason-2. Improvement in modeling solar panels position will be made. Current model improvements will be integrated: albedo and infrared pressure, ITRF 2008, pole prediction, Hill along-track empirical acceleration, on-board USO frequency prediction, ... allowing a more and more accurate Diode navigation tool. 18)
Figure 11: Photo of the DORIS DGXX-S instrument (image credit: CNES)
GPSP (GPS Payload)
The GPSP uses the Global Positioning System (GPS) to determine the satellite's position by triangulation, in the same way that GPS fixes are obtained on Earth. At least three GPS satellites determine the mobile's exact position at a given instant. Positional data are then integrated into an orbit determination model to track the satellite's trajectory continuously.
Supplied by NASA, it will be a different receiver but with same basic (blackjack) design as on Jason-1 and 2. No changes to data processing or products with expect same or better performance as on Jason-2.
Figure 12: Photo of the GPS electronics unit (image credit: NASA/JPL)
LRA (Laser Retro-reflector Array)
LRA is a JPL instrument of TOPEX/Poseidon heritage, built by ITE Inc. under NASA/GSFC contract. LRA provides a reference target for satellite laser ranging (SLR) measurements, which are necessary to calibrate the POD system and the altimeter throughout the mission. The LRA is placed on the nadir face of the satellite. It is a totally passive unit that consists of nine quartz corner cubes arrayed as a truncated cone with one in the center and the other eight distributed azimuthally around the cone. This arrangement allows laser ranging at FOV (Field-of-View) angles of 360º in azimuth and 60º elevation around the perpendicular. The retroreflectors are optimized for a wavelength of 532 nm (green), offering a FOV of about 120º. The LRA instrument mass is 2.2 kg.
Figure 13: Illustration of LRA (image credit: NASA)
The LRA is a passive instrument that acts as a reference target for laser tracking measurements performed by ground stations. Laser tracking data are analyzed to calculate the satellite's altitude to within a few millimeters. However, the small number of ground stations and the sensitivity of laser beams to weather conditions make it impossible to track the satellite continuously. That is why other onboard location systems are needed.
JRE (CARMEN-3 + LPT)
CARMEN (CARacterization and Modeling of ENvironment) is an instrument concept dedicated to space environment measurement: orbital debris, high and low energy particles. CARMEN-3 is composed of the ICARE-NG module and an additional sensor AMBRE. ICARE-NG is a dedicated instrument to study the influence of space radiation and their effects on electronic components. AMBRE is a type of sensor which is able to detect low level ions and electrons.
CARMEN-3 instrument has particular mission objectives as well as objectives related to the satellite:
• Scientific objectives for ICARE-NG: to allow the measurement of charged particles fluxes and the effects of these particles fluxes on under test electronic components.
• Scientific objectives for AMBRE: to allow the measurement of low energy charged particles fluxes responsible for electrostatic discharges.
• Mission objectives for CARMEN-3 associated with JASON-3: to allow the local radiative environment characterization and the evaluation of the potential drifts of the equipments in particular due to radiation from South Atlantic Anomaly (SAA), and to participate in the data cross calibration with the LPT instrument in the frame of JRE (Joint Radiation Experiment).
Carmen-3 (CNES instrument) is a dosimeter used to improve knowledge of particularly aggressive radiation in Jason's orbit.
LPT (Light Particle Telescope):
LPT is a detection unit of JAXA (Japan Aerospace Exploration Agency), Tokyo, Japan. LPT complements the radiation measurements of Carmen-2. In June 2006, JAXA and CNES signed a MOU (Memorandum of Understanding) with the intent to load the JAXA instrument LPT (Light Particle Telescope) onto the Jason-2 spacecraft of CNES. 19)
LPT consists of two units, which are LPT-E and LPT-S. Figure 14 shows the external views of LPT-E (left) and LPT-S (right). A block diagram of LPT is shown in Figure 15. LPT-E is mounted inside of the satellite and LPT-S is outside.
LPT-E provides functions of the electrical I/F with the Jason-2 satellite system. It receives primary power supply from satellite system and provides sensors and electrical circuits with secondary power. It also receives telecommands and sends telemetry data via the MIL-1553B bus using protocols specified by the PROTEUS standard satellite bus which is used for the Jason-2.
LPT-S consists of four sensors. Specifications of each sensor are shown in Table 6. Each sensor counts number of interesting particles irradiated from inside of the view angle with the specific energy of each channel every one second (time resolution).
Figure 14: Illustration of the LPT device (image credit: JAXA)
Figure 15: Block diagram of the LPT (image credit: JAXA)
Table 6: Specification of the LPT sensors
The LPT-S device has a FOV in the zenith direction; it is accommodated on the outside of the spacecraft. The LPT-E device is installed inside of Jason-2.
LPT-S consists of 4 sensor units; ELA-A, ELS-B for counting electrons, APS-A and APS-B for protons. Each unit includes a set of radiation detectors, their preamplifiers, high voltage supplies, analog and digital board for data processing and analyzing. They measure energies of incident particles and identify particle species by the ΔE x E method. The counts of each particle are accumulated for a second and transmitted to LPT-E. There is an electrical interface between LPT-S and the satellite bus system. LPT-E includes a CPU board for data handling, receiving commands, and transmitting telemetry data in order to control the LPT-S according to a command. LPT-E also supplies LPT-S with power. 20)
Each sensor has 2 measurement modes. The nominal mode is called “count mode”, which obtains count data in energy bins for each particle. Another “list mode” transmits analog-to-digital converted data indicating energy of incident particles. The list mode is used for checking health and gain drift of the detector and electronics while the volume of data to be transferred is limited.
Initial performance check: LPT was initially checked out from June to November 2008 and the LPT was working correctly. The electrical noise was measured for ELS-A, APS-B and APS-A using regular test pulses. The full width of half maximum (FWHM) derived from the test pulses corresponded to 16.3 keV for ELS-A. For APS-A and APS-B, the electrical noise was smaller than a digit of the ADC (Analog–to-Digital Converter) in LPT. Those FWHMs are consistent with the technical requirement.
A world flux map for electrons measured by ELS-A in the 400 – 490 keV energy range is shown in Figure #. The map shows averaged data for 4 months from November 2008 to February 2009. It is easily found that the border of SAA (South Atlantic Anomaly) at that altitude of 1336 km is extended from the middle of Indian Ocean to the western edge of Pacific Ocean. The slot region between the inner radiation belt and the outer radiation belt is also seen clearly.
The observational data of LPT helps to improve the radiation environment knowledge and characterize the local radiation environment to evaluate errors of other mission instruments. An improved LPT device will be also onboard JASON-3 which has the same orbit as JASON-2.
Capability to operate simultaneously JASON-2 and JASON-3 :
• Required the addition of ground stations for the phase of formation flight : Barrow (NOAA) and Usingen2 (EUM, new)
• JASON-2 and JASON-3 operations “merging” considered after the launch.
Figure 16: Overview of the distributed Jason-3 ground segment (image credit: Jason-3 collaboration)
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19) Tatsuto Komiyama, Haruhisa Matsumoto, Tateo Goka, Takahiro Obara, “JAXA/CNES Joint Radiation Experiment onboard Jason-2 Satellite,” Proceedings of the 27th ISTS (International Symposium on Space Technology and Science) , Tsukuba, Japan, July 5-12, 2009, paper: 2009-r-2-24
20) Osamu Okudaira, Haruhisa Matsumoto, Takahiro Obara, Tatsuto Komiyama, “Observation Result of Light Particle Telescope onboard JASON-2 Satellite,” Proceedings of the 28th ISTS (International Symposium on Space Technology and Science), Okinawa, Japan, June 5-12, 2011, paper: 2011-r-57
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.