2.1.1 Child Products
2.1.1.1 Definition
Child products are the
result of the extraction from existing
Level 0, Level lB or Level 2 parent
products, and they own the same format
and file name principles as any other
ENVISAT Payload Data Segment (PDS)
product (child product does not apply to
future products). Also, there is no child product
extraction from Auxiliary Data.
The child products are generated by
the Archiving Facility (ARF) and they
consist of one segment, or separated
consecutive scenes.
The product structure is
provided in the previous section,
entitled "Products and
Algorithms Introduction"
Each child product contains an integer number
of granules, which is a part of the product
that corresponds to the time window covered
by a Data Set Record (DSR)
of the Location Annotation Data
Set (LADS). The start time of the
granule is the time label of the LADS DSR.
For the Advanced Synthetic
Aperture Radar (ASAR)
instrument, the stop time of the
granule immediately precedes the time
label of the following LADS DSR in the product.
In table 2.2 below, examples are
given for full scenes, relative to the
specific product mode described, and scenes
the size of only one granule.
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Table 2.2 Child product scene sizes
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Products
|
Full Scene Size
|
Granule Size
|
|
100 Km x 100 Km
(10 granules)
|
10% of the full scene
10 Km along-track
|
|
400 Km x 400 Km
(10 granules)
|
10% of the full scene
40 Km along-track
|
|
One imagette for ASAR WV
( one granule )
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One imagette for ASAR WV
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The Extracted Instrument Header (EIH) product
is extracted from a Level 0 product. It
contains a suite of Instrument Source Packet
(ISP) fields for a selected time
interval. Its structure is the following:
-
Main Product
Header (MPH): It is
identical to the MPH of the Level 0
product from which the data
is being extracted, except for the
time and positioning information
which are updated to reflect the
extracted region.
-
Specific Product
Header (SPH): It contains
sensing time information, offset
and length in MDS-DSR of each field
(one or several fields) extracted
from ISP of the parent product.
- The file name also changes to
"C"; that is ASA_IMM_1C.
2.1.1.2 Child Product Extraction Requirements
As was first discussed in the Introduction, the ASAR
child product is extracted from a parent
product already archived in the ARF. However, the ARF does
not archive the child product, and it does
not update the inventory. After completion
of the instruction, the ARF sends back an
instruction report to the Centre
Monitoring and Control (CMC).
The ASAR child products extraction criteria
is defined as follows:
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Table 2.3 ASAR child product extraction criteria
|
Product Level |
Time
|
Location
|
Bands
|
Data Set
|
Extracted
Ins. Header |
Level 0 |
Yes |
Yes |
No |
No |
Yes |
Level 1B and
Level 2 |
Yes |
Yes |
No |
Yes |
N/A |
2.1.1.2.1 Data Set Selection
The ARF shall select the Data Set (DS) of
the parent product based on data set
names in each Data Set Descriptor
(DSD) of the Specific Product
Header (SPH) 2.3.2.3. to extract
child products with a DS extraction
criterion. All Global ADS
(GADS) shall be kept in the child product.
2.1.1.2.2 ISP Subsets Selection (Extracted
Instrument Headers)
The ARF shall extract from
the Level 0 products
the Extracted Instrument
Headers (EIH) , by selection
of one or several sets of selected Instrument Source
Packets (ISPs).
2.1.1.2.3 Common Archiving Facility Requirements
- The external auxiliary data DSD records shall
always be kept in the child product.
- The GADS shall always
be kept in the child product.
- The MPH of the
extracted child product shall be
copied from the parent product,
and then updated with the following
parameters:
- sensing start day and start
time (t0)
- sensing stop day and stop
time (TL)
- duration of the product (t 140)
- processing centre
- processing time
- total size
- size of each DS
- number of DS
- The name of the extracted child
product shall be updated according
to the parameters updated in the MPH.
- The SPH shall be
copied from the parent product.
- Time information.
- Location information of the products
determined by reading the LADS in Level 1B or Level 2
products, if the product has a LADS.
This information contains at least
the four corners of the product area
expressed in latitude and
longitude, including the first and
last sample latitude and longitude
(determined from the LADS).
The following parameters shall be updated
for each DSD describing a data set in
the extracted child product:
- filename: set to "NOT
_USED" if the DS corresponding
to the DSD is empty, when the DS is
not kept during a data set extraction
- data set offset
- total size of data set
- number of DSRs within the
data set
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