The EnviSat RA-2 Instrument Design and Tracking Performance

Roca, M.; Laxon, S. W.; Zelli, C.

doi:10.1109/tgrs.2009.2020793

Cited by 31 publications

(14 citation statements)

References 13 publications

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“…Envisat and Saral used the same nominal orbit and the same return frequency of 35 days. The spacing between measurements within the satellite track is approximately 400 m and 165 m for Envisat and Saral respectively and the distance between neighbouring tracks is about 80 km at the equator (Roca et al, 2009). …”

Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

“…Since the variation in range from the satellite to the surface is much larger than is captured by the echo recording system, it is necessary to track the return echo (Roca et al, 2009). The sensor has to estimate the time needed for the impulse to go forth and back in order to predict the "range window".…”

Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

“…The sensor has to estimate the time needed for the impulse to go forth and back in order to predict the "range window". This is the role of the "tracker", an on-board program that computes the "opening" and "closing" time of the 128 recording gates (Roca et al, 2009). The raw data is recorded in a signal waveform (WF) that covers a time lag representing a distance of about 40 m for SARAL and 60 m for ENVISAT.…”

Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

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An Original Processing Method of Satellite Altimetry for Estimating Water Levels and Volume Fluctuations in a Series of Small Lakes of the Pantanal Wetland Complex in Brazil

Costa¹,

Pereira²,

Maillard³

2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Satellite altimetry is becoming a major tool for measuring water levels in rivers and lakes offering accuracies compatible with many hydrological applications, especially in uninhabited regions of difficult access. The Pantanal is considered the largest tropical wetland in the world and the sparsity of in situ gauging station make remote methods of water level measurements an attractive alternative. This article describes how satellites altimetry data from Envisat and Saral was used to determine water level in two small lakes in the Pantanal. By combining the water level with the water surface area extracted from satellite imagery, water volume fluctuations were also estimated for a few periods. The available algorithms (retrackers) that compute a range solution from the raw waveforms do not always produce reliable measurements in small lakes. This is because the return signal gets often "contaminated" by the surrounding land. To try to solve this, we created a "lake" retracker that rejects waveforms that cannot be attributed to "calm water" and convert them to altitude. Elevation data are stored in a database along with the water surface area to compute the volume fluctuations. Satellite water level time series were also produced and compared with the only nearby in situ gauging station. Although the "lake" retracker worked well with calm water, the presence of waves and other factors was such that the standard "ice1" retracker performed better on the overall. We estimate our water level accuracy to be around 75 cm. Although the return time of both satellites is only 35 days, the next few years promise to bring new altimetry satellite missions that will significantly increase this frequency.

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Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

Section: Background On Satellite Altimetry In Low Resolution Mode (Lrm)mentioning

confidence: 99%

See 1 more Smart Citation

An Original Processing Method of Satellite Altimetry for Estimating Water Levels and Volume Fluctuations in a Series of Small Lakes of the Pantanal Wetland Complex in Brazil

Costa¹,

Pereira²,

Maillard³

2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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“…Satellite altimetry on the other hand provides excellent spatial resolution covering entire areas of the ocean at a time, with accuracy of a few centimetres and homogeneous measurements with 1 measurement per second every 7 km in all weather conditions [2]. This method however, suffers from extremely poor temporal resolution for measuring ocean wave heights in real time, with the return period passes ranging from 10 days to 35 days [2], [3]. Satellite altimetry can be used to track large storm cells as they evolve and move along a storm path since they occur over long time periods, but cannot be used as a real time ocean wave height monitoring tool.…”

Section: Wave Height Quantificationmentioning

confidence: 99%

Wave height quantification using land based seismic data with grammatical evolution

Donne

Nicolau

Bean

et al. 2014

2014 IEEE Congress on Evolutionary Computation (CEC)

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Abstract-Accurate, real time, continuous ocean wave height measurements are required for the initialisation of ocean wave forecast models, model hindcasting, and climate studies. These measurements are usually obtained using in situ ocean buoys or by satellite altimetry, but are sometimes incomplete due to instrument failure or routine network upgrades. In such situations, a reliable gap filling technique is desirable to provide a continuous and accurate ocean wave field record. Recorded on a land based seismic network are continuous seismic signals known as microseisms. These microseisms are generated by the interactions of ocean waves and will be used in the estimation of ocean wave heights. Grammatical Evolution is applied in this study to generate symbolic models that best estimate ocean wave height from terrestrial seismic data, and the best model is validated against an Artificial Neural Network. Both models are tested over a five month period of 2013, and an analysis of the results obtained indicates that the approach is robust and that it is possible to estimate ocean wave heights from land based seismic data.

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“…A detailed description of the RA-2 instrument, innovative functions features with respect to previous altimeters (like ERS and TOPEX), and its configuration is presented in [1]. The EnviSat satellite orbit is a near circular polar orbit, sun-synchronous, with high inclination (95.55 deg) and an altitude of ~800 km.…”

Section: Data Rate (Kbit/sec) 91mentioning

confidence: 99%

EnviSat Altimeter system: Near Real Time long-term monitoring

Pinori¹,

Cotton²,

Louis³

et al. 2012

2012 IEEE International Geoscience and Remote Sensing Symposium

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ESA declared the end of the EnviSat mission on 9 th May 2012, after 10 years of life (doubling the initial expected 5 years of operations). Monitoring of Near Real Time (NRT) data started in 2003to assess the quality of measurement and calibration of the EnviSat Radar Altimeter instrument. Since then, NRT data has been stored to build a comprehensive database of altimeter parameters that can be now used not only to assess the instrument calibration and the processing data quality, but also as a starting point for defining specific performance objectives for NRT data for future altimeter missions.

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The EnviSat RA-2 Instrument Design and Tracking Performance

Cited by 31 publications

References 13 publications

An Original Processing Method of Satellite Altimetry for Estimating Water Levels and Volume Fluctuations in a Series of Small Lakes of the Pantanal Wetland Complex in Brazil

An Original Processing Method of Satellite Altimetry for Estimating Water Levels and Volume Fluctuations in a Series of Small Lakes of the Pantanal Wetland Complex in Brazil

Wave height quantification using land based seismic data with grammatical evolution

EnviSat Altimeter system: Near Real Time long-term monitoring

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