1 asar meris aatsr products - european space...

ASAR Training Course, Hanoi , 25 February – 7 March 2008

ASAR, MERIS and AATSR products

Francesco Sarti and Steffen Dransfeld ESA/ESRIN

25 February 2008


ENVISATENVISATLaunched in 2002. Sun-synchronous polar orbit (SSO): Nominal reference orbit of mean altitude 800 km, 35 days repeat cycle, 10:00 AM mean local solar time (MLST) descending node, 98.55 deg. inclination.

http://envisat.esa.int/

Dimensions:- Launch configuration: length 10.5m

- In-Orbit Configuration: 26m x 10m x 5m

Mass:- Total satellite 8140 Kg

(including 319 Kg hydrazine) - Payload 2050 Kg

Solar Array power: 6.5 kW (EOL)

Average Power demand: Sun Eclipse(watts) (watts)

Payload 1700 1750Satellite 3275 2870

Launch vehicle: Ariane 5 (single launch)


Advanced Synthetic Aperture RADAR (ASAR)

TECHNICAL CHARACTERISTICS:

Sensor Type:Sensor Type: Imaging microwave radarsImaging microwave radars

Accuracy:Accuracy: Radiometric resolution in range: 1.5Radiometric resolution in range: 1.5--3.5 dB3.5 dB

Spatial Resolution:Spatial Resolution: Image, Wave and Alternating Polarisation modes: approx 30m x 30mImage, Wave and Alternating Polarisation modes: approx 30m x 30m. Wide . Wide Swath mode: approx 150m x 150mSwath mode: approx 150m x 150m. Global Monitoring mode: approx 1000m x . Global Monitoring mode: approx 1000m x 1000m. 1000m.

Swath Width:Swath Width: Image and alternating polarisation modes: 56Image and alternating polarisation modes: 56--106km (depending on incidence 106km (depending on incidence angle: 15angle: 15--45 degrees), Wave mode: 5km, Wide swath and global monitoring 45 degrees), Wave mode: 5km, Wide swath and global monitoring modes: 400km or more modes: 400km or more

Waveband:Waveband: Microwave: CMicrowave: C--band, with choice of 5 polarisation modes (VV, HH, VV/HH, band, with choice of 5 polarisation modes (VV, HH, VV/HH, HV/HH, or VH/VV) HV/HH, or VH/VV)

Applications:Applications: Ocean and Coast (Ocean Currents and Topography) Land (Landscape Ocean and Coast (Ocean Currents and Topography) Land (Landscape Topography) Snow and Ice (Snow and Ice)Topography) Snow and Ice (Snow and Ice)


Wide Swath & Global Monitoring Mode

• 5 ScanSAR beams

• VV or HH polarisation

• Swath width: ~ 400 Km

Image Mode

• 7 beams: 15 - 45 deg. inc. angle


• Swath width: 56 Km – 106 Km

Alternating Polarisation Mode

• 7 beams: 15 - 45 deg. inc. angle

• VV/HH, VV/VH and HH/HV polarisation

• Swath width: 56 Km – 106 Km

• 7 beams: 15 - 45 deg. inc. angle + 2

alternate beams capability


• 1 imagette every 100 Km

Wave Mode

IM AP WS GM WVAbout ASARAbout ASAR


ASAR Image Mode Swaths

ASAR provides dual-channel data: in Alternating Polarization Mode, it provides one of three different channel combinations:

• VV and HH

• HH and HV

• VV and VHTx Rx Tx Rx


ASAR acquisition modesAsar Image mode (IM)

• VV or HH polarization images from any of 7 selectable swaths.

• Swath width between approximately 56 Km (swath 7) and 100 Km (swath 1) across-track.

• Spatial resolution of approximately 30m (for precision product)

ASAR Alternating polarization mode (AP)

• Two co-registered images per acquisition, from any of 7 selectable swaths.

• HH/VV, HH/HV or VV/VH polarization pairs possible.

• Spatial resolution of approximately 30m (for precision products)


ASAR Wide Swath Mode (WS)

• 400 Km by 400 Km wide swath image.

• Spatial resolution of approximately 150m by 150m for nominal product.

• VV or HH polarization

ASAR Global Monitoring Mode (GM)

• Spatial resolution of approximately 1Km in azimuth by 1Km in range for nominal product.

• Swath 400 Km

• Up to a full orbit of coverage,

• HH or VV polarization

ASAR acquisition mode


ENVISAT Product Levels

Envisat’s data products are divided into three categories – Level 0, 1 or 2 –depending on the amount of processing needed to transform raw satellite data.

Level 0: raw satellite data

http://earth.esa.int/ Data products Radar Imagery


Product Level 0 (raw satellite data)


Product Level 1 f1

f1 To be extended to the case of ALOS PalSAR. Remark: level 1.1 is phase-preserving (for polarimetric processing with POLSARPRO), level 1.5 is not fsarti, 03/03/2008

ASAR Training Course, Hanoi , 25 February – 7 March 2008Product description

For details see the ASAR Handbook available at http://envisat.esa.int/handbooks/asar/


Acquistion: 12-Mar-2003

This ASAR WSM image is the first transmitted via the satellite ARTEMIS.

The variation in grey tone within the Usangu wetlands indicates a spatial variability in soil moisture. As can be seen over the lakes, water is like a mirror for signal radar, reflecting specularly away from the antenna the energy backscattered. As a result, wet areas generate dark grey tones within the image.


Example of surface water mapping using Envisat ASAR WSM imagery. June 2007

Poyang Lake, China.

10 June 2007


This ASAR APP image shows an area covering the country of Guinea

The brown yellow colour that dominates the image results from the sparse vegetation (savannah) that covers the area (medium-low HV and HH backscattering, but HV backscattering higher than HH). The capital, Conakry is seen in cyan tones as it is densely populated (dominant HH backscattering). From the city of Conakry to northeast is seen a bright fringe in yellow colour due to the increasing of vegetation and human settlements (high HH and HV backscattering). Coastal plains of Guinea are plenty of swamps, seen in blue tones in the image corresponding to wet areas (low HH and HV backscattering and HV lower than HH)

The image is a colour composite where:

Red: HV polarised image

Green: HH polarised image

Blue: Ratio between the amplitude in HH and HV.


Bam (Iran) earthquake (26 Dec. 2003)

35 days apart

Envisat ASAR Interferogram

Bam

Landers (USA) earthquake (1993)

ERS-1 SAR Interferogram

Blind faultrevealed by ASAR

Visible fault


Techniques: SAR Interferometry (InSAR)Radar interferometry is based on the quantitative comparison (phase difference) between paired complex SAR images (taken at different times, ENVISAT/ERS, or simultaneously, SRTM)

T

R

φi

φf

T

R

φi‘

φf ‘

interferometric phase

φr - φr’ = Δφ

Acquisition at time 1

Acquisition at time 2

Δφ = ΔφDISP + ΔφTOPO + ΔφATMO + ΔφNOISE

Interferogram of the Vajont landslide

Different techniques exist to separate the phase contribution due to ground displacements (case of non simultaneous acquisitions)


1’ acquisition 2’ acquisition

R1

Δ r

T0 T0+ΔtTempo tempo

R1= R2

Permits to assess ground deformationswith centimetric accuracy

LaionLandslide

Techniques: SAR interferometry

Δφ = ΔφDISP + ΔφTOPO + ΔφATMO + ΔφNOISE


Techniques: Differential interferometry (DInSAR)

• Detection of ground movements occurred in the time span between twoacquisitions with an accuracy of a small fraction of wavelength

• Satellite: Acquisitions from different positions (baseline >0)Df = DfTOPO + DfMOV

• Ground-based: Acquisitions from the same position (baseline =0)Df = DfMOV

SAR Image (ERS) differential interferogram

inte

rfer

omet

ric p

hase


Techniques: Permanent Scatterers

multi-imageprocessing

tem

po

100 Km100 Km

ESA - ERS

35giorni

Dataset of SAR images

pixel by pixel analysis

Processing technique of SAR images which allows to assess deformations with millimetric accuracy on single specific points (PS), coincident with highly reflective elements on the ground surface

Los Angeles


Overflowing

Overtopping

Piping

Sliding inner slope

Plastic horizontal sliding

Nipping ice

BLUE Below Sea level

17000 km of water barriers:– 3565 km primary water

barriers (big rivers, sea, IJsselmeer, Markermeer),

– >14000 km regional water barriers

On the potential of PS-InSAR for monitoring dikes in the NetherlandsCourtesy R. Hanssen Delft Institute of Earth Observation and Space Systems


029

258 487 215180380151

151

423

Landsat background, with PSI-dike results of 9 frames superposed (1992-2005)

On the potential of PS-InSAR for monitoring dikes in the NetherlandsCourtesy Ramon Hanssen, Delft Institute of Earth Observation and Space Systems

dike monitoring


More Information on ASAR Data

ESA webpage containing general information about ASAR http://earth.esa.int/object/index.cfm?fobjectid=3772

Envisat ASAR product handbook: http://envisat.esa.int/pub/ESA_DOC/ENVISAT/ASAR/asar.ProductHandbook.2_2.pdf

Contains all information about different ASAR products, their formats, how they are generated, what they are used for, etc.



Sensor Type:Sensor Type: Imaging Imaging multispectralmultispectral radiometer (radiometer (visvis/NIR)/NIR)

Spatial Resolution:Spatial Resolution: Ocean: 1040m x 1200 m, Land & coast: Ocean: 1040m x 1200 m, Land & coast: 260m x 300m260m x 300m

Swath Width:Swath Width: 1150km, global coverage every 3 days1150km, global coverage every 3 days

Waveband:Waveband: VISVIS--NIR: 15 bands selectable across range: NIR: 15 bands selectable across range: 390 nm to 1040 nm390 nm to 1040 nm (bandwidth programmable (bandwidth programmable between 2.5 and 30 nm)between 2.5 and 30 nm)

Applications:Applications: Ocean and Coast (Ocean Colour/Biology) Ocean and Coast (Ocean Colour/Biology) Land (Vegetation)Land (Vegetation) Atmosphere (Clouds, Atmosphere (Clouds, Precipitation) Precipitation)

Medium Resolution Imaging Spectrometer (MERIS)


1150 km

Pushbroom Imager ( 5 cameras)

Total swath width: 1150 KmFull Resolution: 300 mReduced resolution: 1200 m

VIS-NIR Spectrometer within spectral range: 390 to 1040 Nanometers

15 bands electronically programmable (in width and position)

About MERISAbout MERIS


Processing levels available


Level 1b (geolocated, calibrated TOA radiances) StructureSpectral bands: Radiance measurements at all 15 different wavelengths


This MERIS FR image shows two huge sand dune seas in the Fezzan region of southwestern Libya.

A persistent high-pressure zone centred over Libya keeps the heart of the Sahara completely arid for years at a time, but research has discovered evidence of 'paleolakes' in this region associated with a wetter and more fertile past.

Libya today has no permanent rivers or water bodies, but has various vast fossil aquifers. These natural underground basins hold enormous amounts of fresh water.

Image Acquired: 24 Nov 2004.

Spatial Resolution: 300 m

Swath Width 672 km


MERIS image showing phytoplanktonupwelling, Mauritania



In this MERIS image the contrast can clearly be seen between the desert areas of Senegal in the north to the vegetated coastal plains of Guinea-Bissau, The Gambia and Southern Senegal (shown in red on the image).

Acquistion: 24-Feb-2004

The green colour of the sea around the islands of the Buagos Archipelago is caused by sediment being swept out to sea from the river


One of the first images acquired by Envisat, this MERIS image shows the complex river system inside Casamance with its heavy discharge into the sea. A series of such images are needed to monitor the transport of sediment which arises from inland soil erosion. This scene covers the transition zone between savannah in the north and tropical vegetation in the south. MERIS can also monitor the intensification of land use which leads to increased erosion and soil loss.


Casamance, Senegal


Water Quality in Egypt

5 May 2006 12 May 2006 18 May 2006 24 May 2006

MERIS-based relative water turbidity index

MERIS-based relative water chlorophyll-a index

Examples of MERIS Derived ProductsExamples of MERIS Derived Products


More Information on MERIS Data

ESA webpage containing general information about MERIS http://earth.esa.int/object/index.cfm?fobjectid=1665

Envisat MERIS product handbook: http://envisat.esa.int/handbooks/meris/

Contains all information about different MERIS products, their formats, how they are generated, what they are used for, etc.


MERIS images (not N1. products but full jpeg in the true colour bands) can be found on:

Miravi: http://miravi.eo.esa.int/en/

Earth Watching:http://earth.esa.int/ew/special_events/Meris_FRS_gallery/Mer_FRS_gallery.htm

Image Gallery (nice images taken from "image of the week"):http://earth.esa.int/earthimages/

Background Regional Mission (places where ENVISAT acquires images by default when there are no programming requests, e.g. major cities, areas prone to disaster - like active volcanoes, etc):http://earth.esa.int/object/index.cfm?objectid=4045 (under construction, but hopefully soon ready!)


Advanced Along Track Scanning Radiometer (AATSR)


TypeType Imaging multiImaging multi--spectral radiometers (spectral radiometers (visvis/IR) & Multiple direction/IR) & Multiple direction / polarisation / polarisation radiometersradiometers

AccuracyAccuracy Sea surface temperature: <0.5KSea surface temperature: <0.5K over 0.5 deg x 0.5 deg (lat/long) area with 80% over 0.5 deg x 0.5 deg (lat/long) area with 80% cloud cover. cloud cover. Land surface temperature: 0.1KLand surface temperature: 0.1K (relative)(relative)

Spatial Resolution:Spatial Resolution: IR ocean channels: 1km x 1km, Visible land channels: 1km x 1kmIR ocean channels: 1km x 1km, Visible land channels: 1km x 1km

Swath Width:Swath Width: 500km500km

Waveband:Waveband: VIS VIS -- NIRNIR: 0.555, 0.659, 0.865 micrometers, : 0.555, 0.659, 0.865 micrometers, SWIRSWIR: 1.6 micrometers, : 1.6 micrometers, MWIRMWIR: 3.7 : 3.7 micrometers, micrometers, TIRTIR: 10.85, 12 micrometers: 10.85, 12 micrometers

Applications:Applications: Ocean and Coast (Sea Surface Temperature)Ocean and Coast (Sea Surface Temperature), Atmosphere (Atmospheric , Atmosphere (Atmospheric chemistry (Trace Gases, Clouds), chemistry (Trace Gases, Clouds), LandLand (Vegetation) (Vegetation)


RGB combination of:

Red = 870 micrometer reflectance channel

Green = 670 micrometer reflectance channel

Blue = 550 micrometer reflectance channelAATSR image over Caspian Sea


Derived from 3 AATSR scenes:• 16-AUG-2006• 19-AUG-2006• 24-AUG-2006

Lake surface temperature


More Information on AATSR Data

ESA webpage containing general information about AATSR: http://earth.esa.int/object/index.cfm?fobjectid=3773

Envisat AATSR product handbook: http://envisat.esa.int/handbooks/aatsr/

Contains all information about different AATSR products: their formats, how they are generated, what they are used for, etc.

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