In: Wagner W„ Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Voi. XXXVIII, Part 7B
2.2 Data Sets
In these days, TSX is one of the most modem SAR satellites
and its data will be evaluated in this study. The satellite has
been launched on June 15 th 2007 from oldest Russia’s space
launch facility, Baikonur Cosmodrome in Kazakhstan. It is built
in German; the lifetime will be at least 5 years on the space. The
mission is a joint project in a public private partnership (PPP)
between the German Ministry of Education and Science
(BMBF), the German Aerospace Center (DLR) and the Astrium
GmbH. Under DLR contract Astrium constructed and built the
satellite while DLR is responsible for the development of the
ground segment, instrument calibration and scientific use of
satellite at its lifetime (URL 1).
TSX is one of the most advanced SAR satellites using
interferometry until this day and offers the highest quality
spatial data that were not available from space before using high
frequency X-band SAR sensor which can be operated in
different imaging and polarization modes. Figure 2 and Table 1
present the system components of the satellite.
As it can be seen from Table 1, TSX uses 3 different operation
modes as Stripmap, Spotlight, and ScanSAR. These modes
provide high resolution images for detailed analysis as well as
width swath data whenever a larger coverage is required and
imaging can be possible in single, dual and quad-polarization.
Besides, TSX data can be used for interferometry by this way
the DSM generation is possible.
Figure 2. System components of TSX
Launch date, Life
15 June 2007, at least 5 years
Launch site
Baikonur, Kazakhstan (Russia)
Carrier
Dnepr-1
Satellite mass
1230 kilogram
Satellite size
5 m height x 2,4 m diameter
Orbit
characteristics
514 km altitute, 11 days repetition,
97.44° inclination
Antenna
4.8 m active array, multi-pol,
steerable in elevation and azimuth
Radar frequency
9.65 GHz
Power consumption
800 W in average
Data reception,
Mission operation
DLR, Neustrelitz,
Oberpfaffenhofen, Weilheim
Bandwidth
150 MHz (300 MHz experimental)
Memory
256 Gbit (end of life)
Downlink
300 Mbit/s
Imaging modes
Stripmap (3m), Spotlight (l-2m),
and ScanSAR (16m)
Table 1. System components of TSX (URL 1)
TSX is capable to operate two types of Spotlight modes. The
first type purely named as Spotlight mode the scenes of interest
area can be obtained for an area of lOkmxlOkm (length and
width) and recorded with 2m resolution. At the second type, the
lengths of the scenes are shorter by 5kmxl0km but offer higher
resolution. This type is named as high resolution Spotlight
mode and the scenes have lm azimuth resolution. Between
these two types of Spotlight mode just the geometric azimuth
resolution is different in order to increase the azimuth scene
coverage of Spotlight mode. During the observation of a
particular ground scene the radar beam is steered like a spotlight
so that the area of interest is illuminated longer and hence the
synthetic aperture becomes larger. The Maximum azimuth
steering angle range is ±0.75° (Roth, 2003).
At the investigation, for the generation of a DSM, two HRS
mode TSX SAR images were used which have lm resolution
and five months time interval. Figure 2 shows these images and
the following Table 2 presents the characteristics of them.
Figure 3. HRS TSX SAR images
Characteristics
HRS TSX Image 1
HRS TSX Image 2
Sensor Id
SAR
SAR
Sensor mode
High resolution
Spotlight
High resolution
Spotlight
Start date
2008-05-
05T15:57:33,98
2008-10-
06T15:57:42,52
End date
2008-05-
05T15:57:34,73
2008-10-
06T15:57:43,26
Polarization
mode
Single polarization
Single polarization
Polarization
channel
HH
HH
Looking
direction
Right looking
Right looking
Pass direction
Ascending pass
Ascending pass
Centre
incidence angle
40.9752891207
41.0898290780
Length and
width of scene
5kmxl0km
5kmxl0km
Table 2. Characteristics of high resolution TSX SL images
For the generation of TSX DSM, interferometric processing
steps of SARScape module of program ENVI Version 4.6 have
been used. Interferometric processing steps of DSM generation
are not as simple as DSM generation with optical imagery. The
operator has to apply several complex steps and assign
threshold application values depending up on quality and
characteristics of the SAR images which are used for DSM
generation (e.g. co-registration settings, best choice of azimuth
and range looks etc.). At the interferometric processing, after
the registration of images, baseline estimation, interferogram
generation along with co-registered single look complex (SLC)
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