SAR Interferometry opportunitieswith the European Space Agency
ERS-1, ERS-2, Envisat, Sentinel-1A /-1B
ESA 3rd Party Missions (ALOS)
Prepared by ESA teams and ESA supporting companies
Special thanks to S. Schmuck, A. Vollrath, N. Miranda and ARESYS
For the last 20 years, ESA has been constantly supporting the SAR
Interferometry (InSAR) communities with:
the provision of relevant InSAR data, through:
the development and operations of SAR satellites (ERS-1, ERS-2, Envisat)
a precise satellite orbital maintenance including InSAR tandem campaigns (ERS-1/ERS-2 tandem, ERS-2/Envisat tandem, Envisat 2010+)
the development of a large and consistent InSAR data archive
a constant effort in facilitating access to SAR data
the development of InSAR science and InSAR applications,
bringing together the InSAR communities through the Fringe workshop.
ESA and SAR Interferometry
20 years of ERS-1/2 SAR data in the archive
The most complete and consistent SAR archive
ERS-1 and ERS-2 missions
20 years of ERS-1/2 SAR data in the archive
ERS-1 and ERS-2 missions
InSAR measurement of surface displacement of the Parkfield section of the San Andreas Fault over the decade before the last Mw 6.0 Parkfield earthquake (28 September 2004).
from M. de Michele et al., 'Spatiotemporal evolution of surface creep in the Parkfield region of the San Andreas Fault (1993–2004) from SAR', June 2011, Earth and Planetary Science Letters
Based on a set of 51 ERS1-2 images combined to calculate 341 differential interferograms with a perpendicular baseline of less than 250 meters.
Parkfield section of San Andreas FaultCalifornia (USA)
2007 2008 2009 2010 2011 2012 2013 2014
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30 m < baseline < 100 m
100 m < baseline < 200 mERS SAR Tandem data allowed identifying the acceleration of Greenland glaciers flow (Rignot, 2006)
ERS SAR 1-day tandem:
a unique dataset !
ERS-1 / ERS-2 SAR 1-day tandem
ERS-2 reached 16 years of operations ERS-2 was designed for 3 years nominal lifetime ! no gyroscopes since 2001: gyro-less operations
gyro-less data was Doppler screened removing the attitude uncertainty
the SAR instrument worked satisfactorily until its last day of operations on 4 July 2011
ERS-2 mission
ERS-2 : a veteran just retired
The decision to terminate the ERS-2 satellite operations is motivated by: no more synergy with Envisat (i.e. different orbits), end of operations budget, need to de-orbit the satellite (space debris mitigation)
Rome, 4 July 2011
DOSTAG meeting 2nd February 2011
Space debris is becoming a major issue in the altitude range 700-900 km
Two collisions of space objects have contributed to increase the overall collision risk:
Space Debris evolution (1)
Iridium / Cosmos 2251 collision in Feb.
2009
Chinese anti-missile test in Jan. 2007
0
10
20
30
40
50
60
2002 2003 2004 2005 2006 2007 2008 2009 2010
DOSTAG meeting 2nd February 2011
Space Debris evolution (2)
==> old satellites shall be moved out the crowded orbit before losing them (when technically feasible) !
==> hence the de-orbitation of ERS-2 after 16 years of operations (ERS-2 altitude has been lowered from 800 km to 570 km, allowing the satellite to re-enter and burn in the atmosphere well within the required maximum of 25 years)
Yearly number of Envisat collision warnings
Envisat collision avoidance manoeuvres
2 1
2
4
Example of increased risk of collisions with Envisat
The most complete and consistent SAR archive
ERS-2 Ice Phase
Fringe’09 recommendation: consider moving ERS-2 to a 3-day repeat orbit for tracking grounding lines – a unique opportunity to assess advance and retreat of ice sheets.
Done
Before its “retirement”, ERS-2 was moved on a 3-days repeat cycle orbit
[March to June 2011]
Same orbital parameters as for ERS-1 Ice Phase in 1992 and 1994
Targets: Antarctica, Greenland, glaciers and some tectonic areas
Archive: more than 5200 segments
Kangerdlugssuaq Ice Stream (East Greenland)
ERS-2 Ice-Phase• 3-day repeat cycle (March - June 2011)• animation over 1.5. months using 13 scenes between 11 March and 1st May
Calving front advances ~1.8km
Ice Stream Tracking with SAR
ERS-2 Ice Phase
2007 2008 2009 2010 2011 2012 2013
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2002
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1991 2000
Extension
2002
Envisat 1stTa
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2ndTa
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Three ERS-2 / Envisat SAR tandem campaigns, exploiting the synergy between the 2 missions (30 min. time interval on the same orbit) until Envisat orbital change at end 2010.
Ice phase
Extension
ERS-2 / Envisat SAR Tandem 2 Feb. 2008, Bperp : 2210 m
Mohave (USA)
ERS-2 / Envisat SAR 30-min. tandemFringe’09 recommendation: More ERS-Envisat cross-InSAR campaigns needed, repeats observations would minimise topographic effects. Done
3rdTa
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South / Northhemisphere
60 to 81 deg South Latitude, descending arc (only within O’Higgins station mask)
Archive: 129 interferometric pairs
Antarctic Tandem Campaign
ERS-2 / Envisat SAR 30-min. tandem
14 Feb 2010 to 26 April 2010
ERS-2 / Envisat SAR 30-min. tandem
06 July 2010 to 22 Oct 2010
Last Tandem Campaign
North hemisphere
Envisat has reached 9.5 years of operations:
Envisat was designed for 5 years nominal lifetime
Satellite:
good overall status will platform and payload ASAR instrument works satisfactorily
Ground segment:
about 270 min. of ASAR (high rate) data acquired every day, equivalent to 270 ScanSAR products or 1080 stripmap products per day
Envisat mission
A large archive dedicated to InSAR
ASAR archive: Image Mode, Swath 2, VV (i.e. ERS-like)
Envisat data archive
Envisat data archiveE. Sansosti et al., Geophysical Research Letters, 2010, “Space-borne radar interferometry techniques for the generation of deformation time series: An advanced tool for Earth's surface displacement analysis"
Envisat archive compatible
with ERS archive
A large archive dedicated to InSAR
Image Mode, Swath 2, HH Image Mode, Swath 6, VV
Wide Swath Mode, HHWide Swath Mode, VV
Envisat data archive
ASAR Wide Swath Mode data used together with Image Mode data to analyse the Lazufre volcanic system (Central Andes)
Jan Anderssohn et al. (GFZ), in Remote Sensing of Environment , Volume 113, Issue 10, October 2009
Envisat data archive
73 ASAR Image Mode IS6 , HH ascending segments
Greenland Campaign [08 Dec 2009 to 30 Jan 2010]
Envisat data archive
2007 2008 2009 2010 2011 2012 2013 2014
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Envisat
2006
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2000Funding to
be confirmed
Envisat mission extension
• Altitude change: -17.4 km • Repeat cycle: 30 days / 431 orbits• Orbit control: only altitude, inclination drift• Mean Local Solar Time variation: +/- 10 min.
The Envisat operations extension requested a modification of the orbital parameters in 2010.
The new orbital parameters allow: 1. to extend the mission well beyond 2010, for about 3.5 years2. to operate all Envisat instruments with no degradation of their measurements, and
minor impact on data quality, excepted for InSAR
Envisat Nominal Phase35 days cycle, nominal control
Envisat Extension Phase 30 days cycle, inclination drift
799.8 Km
782.4 Km
Altitude
22:00
22:07
Mean Local Solar Time
Orbit inclination
21:50
mid 2
014
22 Oc
t 201
0
May 2
012
-17.4 Km
26 Oc
t 201
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no inclination control
altitude control
inclination control
altitude control
Envisat mission extensionhow does it work ?
Cycle nCycle n+1
Equator
Cycle nCycle n+1
Cycle nCycle n+1
Lat. 38 N
Since November 2010, Envisat orbit inclination is not maintained, i.e. there are no more out-of-plane manoeuvres (high saving of hydrazine) the orbit inclination is drifting slowly no impact on Envisat data quality, except for ASAR data:
orbit baselines become loo large for allowing SAR Interferometry (InSAR) applications, except where the orbits cross (for the same track)
Trick for limiting the impact on InSAR applications:“Naturally” orbits of the same track would cross at Equator, however Equator is not the most interesting geographical area for InSAR applications.
The crossing node was moved to 38 deg. latitude, allowing covering the most interesting geographical areas for tectonics (and volcanology)• crossing at latitude 38 deg. North on descending pass
• crossing at latitude 38 deg. South on ascending pass
Envisat new orbit and SAR Interferometry
6 November/ 6 December 2010Bperp 120m
Envisat new orbit and SAR Interferometry
F. Guglielmino & G. Puglisi, INGV
E. Fielding, NASA/JPL
San FranciscoEtna
Baselines suitable only between 2
consecutive cycles
Baselines suitable only between 2
consecutive cycles
38 deg NDescending pass
38 deg SAscending pass
South Italy
Greece Turkey
San Francisco
North Iran
Baselines suitable only between 2
consecutive cycles
+/- 4 deg.for beam 6 desc. pass
Baselines suitable for differential interferometry from 2011 to 2013
+/- 4 deg.for beam 6 asc. pass
Baselines suitable for differential interferometry from 2011 to 2013
A new ASAR background data acquisition scheme was put in place with the new Envisat orbit, including coverage of tectonic/volcanic areas around 38 deg. latitude for InSAR.
Envisat new orbit and SAR Interferometry
As a consequence, there was an excellent and recent archive of ASAR data over Japan at time of the major earthquake of 11 March 2011.
Co-seismic (30 days) displacement
Courtesy JPL/Caltech
Colour cycle = 50 cm
Thanks to the background data acquisitions (pre- seismic acquisitions in February 2011), it was possible to generate a mosaic derived from many Envisat ASAR interferograms (combining with post-seismic acquisitions in March 2011).
The mosaic provides a detailed estimation of the terrain movement on a very large scale.Courtesy
INGV
Displacement map
(line of sight)
Japan earthquake (March 2011)
Importance of providing scientists with easy access not only to EO datasets but also to in-situ datasets:
GeoHazard Supersites initiative
NorthGround motion in three directions derived from integration of Envisat data with GPS data. Both types of data are available through GeoHazard Supersites.Courtesy INGV (S. Stramondo et al.) See GeoHazard Supersites for more details.
Japan earthquake (March 2011)
Envisat new orbit and SAR Interferometry
Fringe’09 recommendation: The post-2010 Envisat acquisition mode should be IS6 to increase the geographical extent of the zone where InSAR can be done.
Done
Fringe’09 recommendation: ESA should redefine a background mission to ensure systematic acquisitions over sensitive regions (Tibet, California, Mediterranean, South America etc…). This will allow incremental time series construction and coverage in the case of a major seismic event.
Done
Since Oct. 2010, Envisat orbit inclination is no more maintained:
InSAR baselines gradually increase with respect to their initial values, except around 38 deg. latitude
some opportunities of better baseline values between consecutive acquisitions during (boreal) spring
Envisat new orbit and SAR Interferometry
1-cycle-step (30-days) normal baseline evolution since Nov. 2010
Nor
mal
bas
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) Latitude
38 deg.Equator
80 deg.
80
38
0
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20
2 4 6 8 10 12 14-8
-6
-4
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[km
]
0° N desc20° N desc38° N desc60° N desc80° N desc
Envisat new orbit and SAR Interferometry
Since Oct. 2010, Envisat orbit inclination is no more maintained:
InSAR baselines gradually increase with respect to their initial values, except around 38 deg. latitude
some opportunities of better baseline values between consecutive acquisitions during (boreal) spring cumulative normal baseline
evolution since Nov. 2010
Bold: Actual values
Predicted values
2007 2008 2009 2010 2011 2012 2013 2014
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Envisat
2006
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ESA 3rd party mission: ALOS
ALOS (ESA 3rd party mission)
ALOS mission has ceased its operations due to a satellite malfunction in early 2011 ESA operated the ALOS Data European Node (ADEN) ESA intends to continue providing the archived ALOS data
1stTa
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2ndTa
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S S
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3rdTa
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Ice Flow of the Antarctic Ice SheetE. Rignot et al., Science, September 2011
=> A result of the coordination between SAR satellite operators (CSA, ESA, JAXA)
during the International Polar Year 2007-2008
The coordination with other agencies
2007 2008 2009 2010 2011 2012 2013 2014
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Envisat
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GMES and Sentinel-1 mission
ALOS (ESA 3rd party mission)
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Sentinel-1B
+ national SAR missions (Radarsat, TerraSAR-X, COSMO, …)
GMES Space Component – led by ESA :• Sentinel missions: developed specifically for GMES• Contributing missions: EO missions built for
purposes other than GMES but offering part of their capacity to GMES (EU/ESA Member States, EUMETSAT, commercial, international)
GMES Space Component – led by ESA :• Sentinel missions: developed specifically for GMES• Contributing missions: EO missions built for
purposes other than GMES but offering part of their capacity to GMES (EU/ESA Member States, EUMETSAT, commercial, international)
Sentinel-1A
07 08 09 10 11 12 13 14 15 16 171995
2002
The future ESA missions
Extension
GOCE
Extension
Extension
SMOS
CryoSat
Note: data management (e.g. access, reprocessing) shall be ensured beyond mission active lifetime
ADM-Aeolus
1998
ERS-2
Envisat
Sentinel-1A, -1BSentinel-2A, -2BSentinel-3A, -3B
Sentinel-5P
EarthCARE
SWARM
More information on ESA Earth Observation:
http://www.esa.int/esaEO
Funding requested to ESA Ministerial
Council 2012
ERS and Envisat New ESA data policy [approved in 2010]:• Open and Free datasets (for all data available on Internet)• Some restrictions in case of technical constraints (e.g. SAR instrument tasking, large SAR data production)
Data Policy of individual data providers
Third Party Missions & Contributing Missions (to GMES)
Earth Explorers
Sentinel missions
Earth Observation data policy
Full and open access to all users [Joint Principles for a Sentinel Data Policy, approved by ESA]
Fringe’09 recommendation: ESA should extend the Sentinel data policy to the existing ERS and ENVISAT archive.
Done
A constant objective: ease access to Earth Observation data
Common objective for all missions data handled by ESA:Envisat, ERS, Earth Explorers, and Third Party Missions
New ESA EO data policy
Development of alternative ways to provide data (e.g. processing on demand, toolboxes)
Maintain effort in improving quality of products (algorithms, validation)
Maintain effort in supporting data exploitation by scientists and by value adding industry
Facilitating access to Earth Observation data
see following presentation on GeoHazard Supersites (W. Lengert)
Industrial Sectors• Mining• Oil & Gas• Civil Engineering• Utility operators• Transport• Insurance • CO2 Capture &
Storage (emerging)
Supporting value adding industry Precision Land Motion Services
• Unique, Specialist Service Providers
• Growing commercial Business,
• European leadership in services
Long-Term ESA support (15+ years) from R&D to commercial exploitation
As for the last 20 years, ESA is committed to continue its support to the InSAR user communities:
maintaining the effort in facilitating access to SAR data,
strengthening the exploitation of its large InSAR archive,
developing and operating the Sentinel-1 mission (2 satellites),
seeking reinforced partnerships with other SAR operators.
Conclusions
