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6.6.5 ASAR external characterization data
The ASAR instrument has an External Characterisation
Mode which is operated overflying a receiver
setup for H or V polarisation located in the
ground. During the mode, the ASAR transmits a
sequence of pulses from each antenna row in turn.
These pulses are received and digitized on the
ground and the data recorded for off-line analysis.
Simultaneously during the mode the calibration loop in
the instrument is used to couple transmit pulses
which are then sampled within a calibration
widow
in order to provide comparative
values. The External Characterisation
Data file is provided as the output of the
external characterisation analysis and is used
for internal calibration
processing correction. It is updated nominally
every 6 months.
SIZE: MPH(1247 bytes) + SPH (378 bytes) + GADS
(596 bytes)
The MPH and SPH of these files will
follow the standard MPH, SPH structure of all ENVISAT -1 auxiliary data. There is one
Data Set Descriptor
(DSD) in the SPH, known as the
ASA_XCH_AX_GADS, and its format is given below:
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Table 6.41 ASAR external characterization data
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Contains ASAR external
characterization data
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#
|
Description
|
Units
|
Count
|
Type
|
Size
|
|
Data Record
|
|
0
|
dsr_time
Time of characterisation |
MJD |
1 |
mjd |
12 byte(s) |
|
1
|
dsr_length
Length of this DSR
in bytes |
bytes |
1 |
ul |
4 byte(s) |
|
2
|
complex_loop_factors
Complex loop
paths characterisation factors
relative to free space (from
External Characterisation data).
gnp where n is the index
of the row (1 to 32) and p
is the index of the
polarisation (H or V).
Arranged H: 1 to 32, V:
1-32). Values are
complex (I,Q) pairs.
|
- |
128 |
fl |
128*4 byte(s) |
|
3
|
pointing_error
Antenna pointing
error (from External
Characterisation data)
This is used to calculate
the elevation angle:
elevation angle = reference
elevation angle
|
deg |
1 |
fl |
4 byte(s) |
|
4
|
spare_1
Spare |
- |
1 |
SpareField |
64 byte(s) |
DS_NAME : Contains ASAR external
characterization data
Format Version 114.0
Note: relating to field# 4 within this table :
As a mathematical expression, the antenna
pointing error is given
elevation angle = reference elevation
angle
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Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,
atmospheric chemistry
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EO Data Access
