Measurement of coseismic deformation by satellite geodesy

Orbits

In working with interferograms for the Izmit earthquake, we found some unmodeled gradients [Feigl et al., 2001]. These appear to be at leas partially due to be caused by using the preliminary ORRM estimates of the ERS orbital trajectories. Indeed, the eastward and northward derivatives of range change are significant. In their preferred joint inversion of GPS, SPOT and ERS data, these authors find values of ()/x = –0.3 ± 0.05  10^–6 and ()/y = 1.73 ± 0.01  10^–6 for these quantities, respectively. They imply roughly one north-striking fringe spread over the 100-km east-west dimension of the interferogram, and over nine east-striking fringes spread over the 150-km north-south dimension of the interferogram. Left uncorrected, the former error could bias the along-strike variation of the slip distribution. Similarly, the latter effect would lead to an overestimate of the total amount of slip across the fault, and thus the moment. Indeed, including the two horizontal gradients as nuisance parameters reduces the moment by 1.1 x 10¹⁹ N.m.

A cleverer approach would be to adjust the orbital parameters using interferometric pairs in which little or no deformation is expected [Kohlhase et al., 2000].

For future missions, the orbital trajectories should be less of a problem because DORIS and GPS receivers aboard the satellites will improve orbital knowledge to better than a decimeter, and perhaps even control the orbits to within tens of meters.

Satellite missions

During the 8 years of GDR INSAR and STRAINSAR between 1997 and 2004, the following SAR missions operated:

ERS-1.

Launched in July 1991, ERS-1 served faithfully for almost 9 years until she finally failed on March 10, 1999.

ERS-2

Launched in 1995. Doppler frequency began to drift in 2000.

JERS-1.

http://www.eorc.jaxa.jp/JERS-1/user_handbook/index.html

SRTM

Shuttle Radar Topographic Mission. Flew in early 2000. [http://www2.jpl.nasa.gov/srtm]

RADARSAT

MDA's Geospatial Services (formerly RADARSAT International) holds the exclusive distribution rights to Canada’s RADARSAT-1 and RADARSAT-2 synthetic aperture radar (SAR) satellites. MDA will operate the RADARSAT-2 satellite following launch [http://www.rsi.ca]

ENVISAT (2001)

Several members of GDR INSAR were approved by the European Space Agency as investigators for the following projects, granting them ENVISAT data free of charge, as described by the announcement of opportunity [ESA, 1997].

More recently, we have obtained ENVISAT data for 25 euros per scene under the Category-I program. http://eopi.esa.int/esa/esa.

Services Provided by GDR INSAR and GDR STRAINSAR

mail list ([e-mail])

The mail list uses a program called "listproc". There are two addresses for two separate functions.

Messages for the entire INSAR working group:

[e-mail] Messages sent to this address will be sent to all members of the GDR INSAR working group, currently about 150 members. So, please be polite enough to re-read your message before sending it!

An automatic secretary to handle the bookkeeping of the address list:

[e-mail] This adddress understands only the following instructions in the body of the message:
help

subscribe insar your_family_name

unsubscribe insa

get insar

review insar
In particular, to subscribe, you should send a message to this address with the instruction:
subscribe insar dupont
where "dupont" is your family name. There is no need to enter your e-mail address because listproc picks that of your message. Note that you can also obtain all the previous messages with the get function.

Catalog of ERS-1 and ERS-2 orbits

Compiled from the ORRM estimates, with gaps filled by Delft and DLR. In “.orb” format for use with Diapason. X,Y,Z,XDOT, YDOT, ZDOT every 30 seconds in ASCII. One file per orbit.

scp insar.omp.obs-mip.fr

Software for selecting interferometrically compatible pairs from ERS-1 and ERS-2 catalog

Telnet to insar.omp.obs-mip.fr

Execute orbiscan.csh and follow the instructions. You will need to have run DESCW beforehand to find a catalog of aquired images.

Software for filtering interferograms

ps_filt2

Solaris executable written by Zhong Lu using a power spectrum algorithm [Goldstein and Werner, 1998]

Figure 6. Example of power-spectral filtering using ps_filt2, showing unfiltered interferogram (left) and filtered interferogram using alpha = 0.8. Courtesy Benoit Legresy.

DTOOLS

This set of shell scripts automates the running DIAPASON/PRISME version 3. Written by Kurt Feigl, is in the public domain and available by request to him.

It reduces data analysis to the following two operations:

Read CD-ROM or DVD

setup_image_slc_envisat

#or

setup_image

then

create_diapason_files

calculate_interferogram
#or

dtool

Future Satellite Missions

RADARSAT-2 (launch 2006)

Co-funded by Canadian Space Agency (CSA) and MacDonald Dettwiler (MDA). Data continuity from RADARSAT-1. All RADARSAT-1 imaging modes supported. Plus many additional capabilities. Launch in 2006. Mission duration: 7 years.

Same orbit as RADARSAT-1: 798 km altitude, sun-synchronous orbit, 6 PM ascending node and 6 AM descending node. Same repeat cycle and ground track as RADARSAT-1: RADARSAT-1 and -2 scenes precisely aligned.

Image location knowledge: < 300 metres at downlink (c.f. RS1 ~ 1.4 km) and < 100 metres post-processed

RADARSAT-2 Innovations and Improvements3-metre Ultra-Fine resolution

highest-resolution SAR commercially available, Routine left-looking and right-looking mode , more frequent revisit, faster response to user requests

Fully-polarimetric imaging modes, polarimetry modes (amplitude and phase information), selective polarization (HH,HV,VH,VV), Choosing between polarizations or using polarimetric parameters increases the information content and its applicability for various applications such as agriculture, target identification, marine monitoring, and mapping/geology

GPS receivers on-board. Real-time position knowledge ± 60 m

Delay between imaging modes < 1 s. Compared to RADARSAT-1 ~14 s. This decrease in the switching rates allows greater flexibility in changing beam positions/modes within adjacent geographic areas.

Higher downlink power. 3-metre minimum size antenna. lower "cost of entry" for new ground stations

Data encryption. encryption for both data downlink and data transfer is critical for military clients. [http://www.radarsat2.info/rs2_satellite/overview.asp].

ALOS (2005)

Members of GDR INSAR have been approved by NASDA in Japan as investigators for the following projects, granting them ALOS data free of charge, as described by the announcement of opportunity.
Amelung et al., Monitoring Hawaiian and other hot-spot volcanoes with ALOS radar interferometry (RA-129)

Amelung et al., Monitoring large earthquakes in SE Asia and Central America with PALSAR and PRISM (RA-91)

Feigl and Massonnet, Waiting for the Big One.

Feigl et al., Djibouti 

Sigmundsson et al., Dynamicsof the Shangbai Shan (Tianchi) caldera, China, from ALOS PALSAR interferometry

Sigmundsson et al., Monitoring of the Mid-Atlantic Ridge in Iceland with ALOS PALSAR interferometry

This list is not yet complete.

The ALOS will be launched by an H-IIA launch vehicle from the Tanegashima Space Center, Japan in summer 2005 [http://www.eorc.jaxa.jp/ALOS/about/2overview.htm]

HABITAT (2005)

Massonnet describes a genuinely innovative concept for a new mission: “Quasi-simultaneous radar images can be produced by a low cost system using a set of passive receivers onboard a constellation in a special orbial configuration. The combination of thes images can improve the final resolution in range and azimuth and systematically produce across-track and along-track inteferometric data” [Massonnet, 2000]. This concept has been incorporated into a proposal called HABITAT submitted to ESA’s Earth Explorer Programme.