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  • Data - Data Description

    Data - Data Description

    ERS-1/2 ATSR Averaged Surface Temperature [AT1/AT2_AR__2P]

    The Averaged Surface Temperature Product (AST) contains averaged geophysical data at two different resolutions, and with respect to two different averaging schemes: measurement data sets at resolutions of 0.5 by 0.5 degrees and 10 by 10 arcmin with respect to a latitude/longitude grid; other data sets contain data averaged over equal area cells of 50 by 50 km and 17 by 17 km aligned with the satellite ground track. Both top-of-atmosphere and surface data sets are provided. The surface temperature data sets provide, for sea cells, nadir and dual view sea surface temperatures, and for land cells, land surface temperature (currently 11 micron BT) and NDVI. Cloud data is also included. No ADS are included in the AST product; auxiliary data is contained within the MDS. The data sets of the AST product are arranged by surface type and resolution. The 3rd reprocessing of ATSR data was performed in 2013; the processing updates that have been put in place and the scientific improvements are outlined in full in the User Summary Note for the Third ERS ATSR Reprocessing.

  • Data - Data Description

    Data - Data Description

    ERS PRARE Precise Orbit Product (ERS.ORB.POD/ERS.ORB/PRC)

    The precise orbit results from a data reduction process in which all available tracking data (Single-Lens Reflex, radar altimeter crossovers, PRARE range and Doppler data) and most accurate correction, transformation and dynamical models are taken into account and in which high level numerical procedures are applied. These orbits are "optimal" achievable representations of the real orbital motion under the circumstances of tracking situation and the "state of the art" model situation. The precise orbit product for the ERS satellites are the satellite ephemeris (position and velocity vector) including time tag, given in a well-defined reference frame, together with the nominal satellite attitude information and a radial orbit correction. Several orbit solutions are currently distributed: A new set of ORB POD (Precise Orbit Determination - REAPER v2) computed with the most updated model standards for the complete ERS-1 and ERS-2 mission. A previous set of ORB POD (REAPER v1) data already available on the ESA dissemination site since 2014, covering the ERS-1 full mission and the ERS-2 mission up to July 2003. ORB PRC which is the original Precise Orbit dataset computed during the ERS mission operations for ERS-1 and ERS-2. In the new POD dataset (REAPER v2) for the ERS-1 and ERS-2 missions, two different orbit solutions are provided together with the combined solution to be used for processing of the radar altimeter measurements and the determination of geodetic/geophysical products: those computed by DEOS (Delft Institute of Earth Observation and Space Systems), and those generated by ESOC (European Space Operations Centre) using different software (GEODYN and NAPEOS respectively). Careful evaluation of the various solutions of REAPER v2 has shown that the DEOS solution for both ERS-1 and ERS-2 has the best performance and is recommended to be used as reference. See the ERS Orbit Validation Report. For the previous version of the POD data set (REAPER v1), with ERS-2 mission data only up to 2003, three different orbit solutions together with the combined solution are available. These precise orbits for ERS-1 and ERS-2 have been computed at DEOS, ESOC, and GFZ (Deutschen GeoForschungsZentrums) using different software and different altimeter databases. Combined solutions have been created using three individual solutions for each satellite. All orbits were derived using consistent models in the same LPOD2005 terrestrial reference frame. These new orbit solutions show notable improvement with respect to DGME04 orbits (Scharroo and Visser, 1998). Thus, RMS crossover differences of new orbits improved by 4-9 mm. Careful evaluation of the various solutions has shown that the combined solution for both ERS-1 and ERS-2 has the best performance. All POD orbit files (REAPER v1/v2) are available in SP3c format.

  • Campaign

    Campaign

    TerraSAR SIM

    The current mission design envisages flying two separate radars on separate platforms

  • News - Events and Proceedings

    News - Events and Proceedings

    VH-RODA: Very High-resolution Radar & Optical Data Assessment workshop

    The workshop, hosted by ESA/ESRIN, will provide an open forum for the presentation and discussion of the current status and future deve...

  • News - Data Release news

    News - Data Release news

    New reprocessing of datasets celebrates 30 years of ERS

    For each surface, the experts will use our current knowledge acquired over 30 years of experience, to improve the ERS altimetric and ra...

  • Tools - Processing

    Tools - Processing

    PolSARpro

    The current version of PolSARpro is 6

  • News - Success Stories

    News - Success Stories

    Heritage data still widely used today

    Current satellite missions collect data with high frequency, with some able to systematically revisit the same location in the same geo...

  • News - Success Stories

    News - Success Stories

    A stroll through Heritage Missions

    In the current digital era, this confirms ESA’s commitment to maintain heritage data and keep information available, in support of envi...

  • News - General News

    News - General News

    Quality Reports Advanced Search Portal takes off

    The system by default will show the reports for the current month, but the user can easily choose a different type of visualisation, on...

  • Instrument - Altimeters

    Instrument - Altimeters

    RA (ERS)

    The Radar Altimeter (RA) was a Ku-band (13.8 GHz) nadir-pointing active microwave sensor, on board ERS-1 and ERS-2 missions, designed to measure echoes from ocean and ice surfaces.

  • Event - Workshop

    Event - Workshop

    SEASAR 2012

    Ocean current retrievals and applications Wave retrievals and applications Sea ice retrievals and applications Oil spill and ship detect...

  • Event - Workshop

    Event - Workshop

    Fringe 2011 Workshop

    Fringe 2011 was the 8th International Workshop on "Advances in the Science and Applications of SAR Interferometry".

  • Event - Meeting

    Event - Meeting

    VH-RODA and CEOS SAR workshop

    The workshop, hosted by ESA/ESRIN, provided an open forum for the presentation and discussion of current status and future developments...

  • Document - General Reference

    Document - General Reference

    SCI-PUB-14-0002-v01-WMO-report-1.0.pdf

    current and anticipated relationship and role of the ERS scatterometers in the Global Climate Observing System. Conclusions and recommendations are provided to further consolidate this relationship

  • Mission - Third Party Missions

    Mission - Third Party Missions

    TerraSAR-X and TanDEM-X

    The TerraSAR-X and TanDEM-X satellites feature a unique geometric accuracy that is unmatched by any other spaceborne sensor.

  • Instrument - Imaging Radars, Scatterometers

    Instrument - Imaging Radars, Scatterometers

    SAR (ERS) Processor Releases

    Processor Releases It should be noted that for SAR, each product ordered is processed directly from the raw data, using the current vers...

  • Activity - Quality

    Activity - Quality

    SCIRoCCo

    The SCIRoCCo project aims are to consolidate current methodologies for scatterometer data processing and calibration

  • Instrument - Scatterometers

    Instrument - Scatterometers

    WS Processor Releases

    The current processor software version for the operational ground segment is ASPS v 10

  • Instrument - Scatterometers

    Instrument - Scatterometers

    WS Quality Control Reports

    Quality Control Reports Products Availability The ERS Scatterometer mission has been reprocessed with the Advanced Scatterometer Processing System (ASPS) facility, providing data with improved radiometric quality and spatial resolution. ERS-2 AMI Wind Scatterometer data set has been reprocessed covering the period from 30 December 1996 to 5 July 2011 (end of mission). Read More Cyclic Reports The cyclic reports include a summary of the daily quality control made within the IDEAS (Instrument Data quality Evaluation and Analysis Service) and various sections describing the results of the investigations related to the Scatterometer. In each section, results are shown from the beginning of the mission in order to see the evolution and to outline possible "seasonal" effects. An explanation for the major events which have impacted the performance since launch is given, and comments about the events which occurred during the cycle are included. Read More ERS-2 Yaw Error Angle Monitoring - Weekly Reportsy The full set of results of the yaw processing is stored in an internal ESA product named HEY (Helpful ESA Yaw). The estimation of the yaw error angle is based on the Doppler shift measured on the received echo (first three plots for the Fore, Mid and Aft antenna) and aims to compute the correct acquisition geometry for the three Scatterometer antenna throughout the entire orbit. The Yaw error angle information is also used in the radar equation to derive the calibrated backscattering from the Earth surface and to select the echo samples associated to each node in the spatial filter. Read More Cyclone Archive The activities of cyclone tracking were interrupted at the end of September 2001. The data used for these cyclone tracking activities are ERS-2 Fast Delivery scatterometer data. Read More Telemetry Data This section provides information related to the acquisition of the instrument telemetry data. The data includes instrument working modes, temperatures, currents and voltages of the transmitter and calibration chain, and finally the antenna temperatures. Read More

  • Instrument - Altimeters

    Instrument - Altimeters

    RA (ERS) Overview

    RA Applications Significant Wave Height Measured by the ERS Radar Altimeter The ERS Radar Altimeter (RA) operated in two modes: ocean mode and ice mode. The RA operated by timing the two-way delay for a short duration radio frequency pulse, transmitted vertically downwards. The required level of range measurement accuracy (better than 10 cm) calls for a pulse compression technique (chirp). The instrument employed frequency modulation and spectrum analysis of the pulse shape. In ocean mode a chirped pulse of 20 micro-s duration was generated with a band width of 330 MHz. For tracking in ice mode an increased dynamic range is used, obtained by reducing the chirp bandwidth by a factor of four to 82.5 MHz, though resulting in a coarser resolution. The Radar Altimeter for ERS-1 and ERS-2 was designed to meet very demanding constraints and had the following major objectives: Precise altitude (ocean surface elevation for the study of ocean currents, the tides and the global geoid) - global measurements of the height of the ocean waves (as significant wave height) - such measurements are extremely important to marine users and scientists wishing to understand the ocean's dynamic behaviour. The Radar Altimeter provided measurements to latitude 82°, north and south, extending to regions which previously had no regular observations - this included the major wave-generation regions in the Southern oceans. Significant wave height (SWH) - measurements of the satellite's height above the local mean sea surface, with an unprecedented precision (equivalent to 1 cm in 100 km) - the applications of this dataset are numerous, for example the operational monitoring of the boundaries of major ocean currents, likely to have significant economic benefits. Ocean surface wind speed - global measurements of wind speed - these can be used to complement the SAR and Scatterometer wind field measurements and also combined with the Radar Altimeter measurements of SWH to distinguish swell from wind-driven waves. Various ice parameters (surface topography, ice types, sea/ice boundaries) - the ability to make measurements over ice with the long term monitoring of the topography of the ice sheets providing a vital warning capability for any substantial shift in the world's climate. Design ERS-2 platform and payload The Radar Altimeter antenna consisted of a reflector, waveguide feed, tripod plus supporting structure, horn feed and the waveguide. In ocean mode a chirped pulse of 20 micro-s duration was generated with a band width of 330 MHz. For tracking in ice mode an increased dynamic range is used, obtained by reducing the chirp bandwidth by a factor of four to 82.5 MHz, though resulting in a coarser resolution. The Frequency Generator units provided the transmit signal at a frequency of 450 MHz to the chirp generator. This generated a chirped output with a bandwidth of 165 MHz (ocean) and 41.25 MHz (ice), gated within a pulse of 20 micro-s. This signal was up-converted and multiplied (using C- and L-band LO signals) to 13.8 GHz, with 330 MHz (ocean) and 82.5 MHz (ice) bandwidths. The required power output level (42 dBm) was generated by the High Power Amplifier (HPA), which was realised as a Travelling Wave Tube and Electronic Power Conditioner (TWT/EPC) combination. A harmonic filter at the TWT output attenuated the harmonics of the RF signal. The transmitter signal was fed to the antenna. The returned signal was routed to the receiver via the Front End Electronics, with an insertion loss of approximately 1.6 dB. The received chirp signal was deramped by mixing it with the LO chirp at a frequency of 15.025 GHz. The deramped output (first IF) was at 1.225 GHz. The signal was then amplified to recover the conversion loss, filtered and mixed with a second LO chirp (1.3 GHz) to provide a second IF of 75 MHz. The second IF signal was filtered, using a surface acoustic wave (SAW) device with a bandwidth of 3.2 MHz and passed via a step attenuator. This provided an overall gain adjustment over a 62 dB range, implemented as two 31 dB step attentuators with a step size of 1 dB. The output was then coherently detected by a quadrature IF mixer to obtain the I- and Q-components of the received signal. The Processor and Data Handling Sub-system (PDHSS) performed tracking and the necessary processing of the radar echoes in order to maintain the echo within the radar range-window. Measurements over Ocean The return pulse shape as a function of time is the convolution of three functions: the average flat surface impulse response, which is a function incorporating the antenna beam weighting and the geometric spreading of the radar pulse along the original surface the probability distribution of surface heights over the sea surface, expressed in terms of delay times the altimeter system point-target response, which is a function of pulse width Over ocean surfaces, the distribution of the heights of reflecting facets is gaussian or near-gaussian, and the echo waveform has a characteristic shape that can be described analytically, as a function of the standard deviation of the distribution which is closely related to the ocean wave height. The resulting return pulse shape is shown in the figure. In general terms the ocean mode encompassed the following echo characteristics time delay with respect to the transmitted pulse - this provides the measure of altitude slope of the echo leading edge, which is related to the width of the height distribution of reflecting facets, and thus to wave height parameters such as SWH the power level of the echo signal, which depends on small scale surface roughness, and thus on surface wind-field parameters over the ocean Real echoes are composed of the sums of signals from many point scatterers, each with individual phase and amplitude. Therefore, the individual echoes have statistical characteristics superimposed on the pulse shape. In order to reduce uncertainties in the determination of pulse characteristics, the altimeter averages pulses together to reduce this statistical effect. When in ocean tracking mode, the mean sea-level point (mid point of the leading edge) on the time axis is maintained in the centre of the range window. The time interval between the transmitted pulse and this point is effectively the classical radar measurement of range. Measurements over Ice From other surfaces the waveform shape does not always conform to the simple Brown Model. The return echo from sea ice appears more specular than that from the ocean and has a peaked trace. The variability of the range measurement is of the same order as that from the ocean and this surface can therefore be tracked using the altimeter ocean tracking mode. The situation is different for continental ice, as the typical return echo has unpredictable shape and more importantly can have a larger variability in surface elevation An altimeter waveform over continental ice where the typical return echo has unpredictable shape and can have a larger variability in surface elevation. In order to maintain track of the surface, the Radar Altimeter, in ice mode, benefited from a wider observation window. The required increase in the size of the observation window was obtained by reducing the pulse bandwidth by a factor of four. This solution did not change the intermediate frequency (IF) bandwidth and was equivalent to enlarging the filter bandwidth without changing the filter bank; therefore it did not introduce major hardware changes into the system. In ice mode, tracking the echo of unpredictable shape was achieved by tracking the centre of gravity of the return pulse rather than the leading edge. This technique was used as the location of the centre of gravity is always unique, whereas there may be more than one leading edge, so avoiding any ambiguities. The main instrument parameters and technical characteristics of the Radar Altimeter are listed below: Mass: <= 96 kg Antenna diameter: 1.2 m DC power: <=134.5 W Data rate: <= 15 kbit/sec Bandwidth: ocean mode: 330 MHz ice mode: 82.5 MHz Pulse repetition frequency: 1020 Hz RF transmit power: 50 W Pulse length: 20 micro-s chirp Altitude measurement: 10 cm (1s, SWH = 16 m) Significant wave height: 0.5 m or 10% (1s) whichever is smaller Backscatter coefficient: 0.7 dB (1s) Echo waveform samples: 64 x 16 bits at 20 Hz Beam width: 1.3° Sea surface elevation: better than 10 cm Spatial Resolution: Footprint is 16 km - 20 km, depending on sea state Waveband: Microwave: Ku-band: 13.8GHz Sensor Modes ERS Radar Altimeter sea level map The ERS Radar Altimeter operated in 2 modes: ocean mode and ice mode. Beam width = 1.3° foot print = 16 - 20 m (depending on sea state). RA-1 operated by timing the two-way delay for a short duration radio frequency pulse, transmitted vertically downwards. The required level of range measurement accuracy (better than 10 cm) calls for a pulse compression technique (chirp). The instrument employs frequency modulation and spectrum analysis of the pulse shape. RA-1 provided measurements leading to the determination of: Precise altitude (ocean surface elevation for the study of ocean currents, the tides and the global geoid) Significant wave height Ocean surface wind speed Various ice parameters (surface topography, ice types, sea/ice boundaries) More details about RA (ERS-2) Sensor Modes are available in an ESA Bulletin Instrument Operations Find out about RA (ERS-2) instrument operations