Abstract:
Mission Objective:
Please see the relevant SIR-C/X-SAR Mission description contained in the
references and as Supplementary Information for "sensor"(X-SAR).
There were two Missions with the following time frame:
- Space Shuttle Mission STS-59:
Start_Date: 1994-04-09
Stop_Date: 1994-04-20
- Space
... Shuttle Mission STS-68:
Start_Date: 1994-09-30
Stop_Date: 1994-10-11
Worldwide coverage and map prints are available on World Wide Web (see below).
Data Set Content:
The MGD data set contains range and azimuth compressed SAR image data which
are detected and projected on the earth ellipsoid. The number of range
and azimuth looks are variable, depending on the mission parameters
selected. These are in particular the incidence angle, the PRF and the
coarse or fine resolution mode. The image pixels are detected and their
amplitudes are quantized with 16 bits per sample. Information regarding
instrument and platform as well as processing, calibration and image
quality is appended.
The product is presented in range-line order. Range lines are
deskewed to zero Doppler lines and organised in ascending time
reference. The data set contains a scene of 100 km in sensor flight
direction and a maximum of 62.5 km across track. The actual swath
width, which can be smaller, is dependent on the chosen mission
parameters like the incidence angle.
Intended Use:
This is the standard bulk product of the German and Italian PAF for
X-SAR. It is compatible with the standard detected ground range
image produced by JPL for the SRL L- and C-band and can be used for all
applications which require no geocoded or complex data.
Input Data:
- X-SAR raw data and ancillary data from HDDC
- Orbit data from the PATH tape
Processing Algorithm:
Signal processing is performed by two-dimensional matched filtering in
range and azimuth direction. Windowing is applied to meet the specified
PSLR and ISLR values. Doppler parameters are calculated from orbit
data and the SAR raw data itself, during a preprocessing step. The
azimuth processing bandwidth is selected according to the used PRF in
order to guarantee the specified 'Signal to Azimuth Ambiguity Ratio'
SAAR.
The effective number of looks in range and azimuth are chosen to
maintain a spatial resolution of 25 m by 25 m. In case the inherent
spatial resolution is higher, the number of looks will be increased.
Hence, it is the processing strategy to fix the spatial resolution and
to vary the radiometric resolution by the number of looks used in range
and azimuth direction. (Those users who are interested in full spatial
resolution may use the 'X-SAR.SAR.SSC' product.) The look processing is
either performed in the frequency domain or by a weighted time domain
pixel averaging.
The projection to ground range is done by a one-dimensional
interpolation. Resampling and detection is performed to achieve a
12.5 m by 12.5 m pixel spacing.
Due to the nonlinear nature of the Slant-to-Ground range projection the
ground range resolution in the MGD product will vary slightly over
range. The specified value for the spatial resolution is therefore only
applicable for mid-swath.
Calibration:
The MGD product is fully calibrated.
Product Parameter:
Equivalent number of looks
in azimuth 1.5 - 2.5
in range 1 - 3
Geometric representation ground range
ellipsoid used GEM6
Data representation detected, amplitude
pixel quantization 16 bit, signed integer
Ground area covered
azimuth >= 100 km
range <= 62.5 km
Product orientation zero Doppler coordinates
ISLR (1-D) > 14 dB
PSLR (1-D) > 17 dB
SAAR >= 17 dB for PRF <=1440 Hz
>= 20 dB for PRF >=1488 Hz
Spatial Resolution
azimuth 25 m at mid swath
range 25 m at mid swath
Absolute location error azimuth: 3.0 km
gr. range: < 3.9 km
Pixel spacing azimuth 12.5 m
Pixel spacing range 12.5 m
Number of pixels
azimuth >= 8000
range <= 5000
Image data volume up to 80 MBytes
Access to the data:
On-line access to data and information as well to digital quicklook DQL
or browse data is provided by the Intelligent Satellite Data Information
System (ISIS), developed by DLR as a client / server configuration.
It represents the interface of DLR-DFD to users, providing easy access to
catalogue-, inventory-, browse- and general textual information.
ISIS can be accessed with World Wide Web by URL:
http://www.dfd.dlr.de
and clicking on `Information Services (ISIS)` or `Accessing ISIS` (telnet).
ISIS can also be accessed by telnet directly:
input: telnet isis.dfd.dlr.de
user: dlrpid
password: -
Other procedures (modem or X-25) to access ISIS are described as 'Supplemen-
tary Information' for data centers (keyword 'ISIS'. Access presumes the in-
stallation of the client software (available free of charge) which can be
easily done by users (supplied by DLR/DFD).
Digital and photographic products may be ordered at DFD - Help Desk,see Data
Center Contact.
There is also available on CD-ROM and on Web a set of image sample products
as well as general and specific information about the X-SAR missions. This
'user-kit' can be accessed via Web with URL:
http://eoweb.dlr.de:8080/index.html