Level-0 Product Formatting - Sentinel-1 SAR Technical Guide - Sentinel Online
Level-0 Product Formatting
A Level-0 product type is named using the following convention:
Folder Name Convention
The top-level SENTINEL-1 Level-0 product folder name is composed of upper-case alphanumeric characters separated by an underscore (_).
The Mission Identifier (MMM) denotes the satellite and will be either S1A for SENTINEL-1A or S1B for SENTINEL-1B.
The Mode/Beam (BB) identifies the S1-S6 beams for SM products and IW, EW and WV for products from the respective modes. The mode can also identify RF, N1-N6, and EN modes used internally by the PDGS.
Product Type (TTT) for Level-0 will be RAW.
Resolution Class (R) will be an underscore '_' as it is not applicable for Level-0.
The Processing Level (L) will be 0.
The Product Class can be Standard (S), Calibration (C), Noise (N) or Annotation (A). Calibration, noise and annotation products are only used internally by the PDGS and are not distributed.
Polarisation (PP) can be:
- SH (single HH polarisation)
- SV (single VV polarisation)
- DH (dual HH+HV polarisation)
- DV (dual VV+VH polarisation)
The product start and stop date and times are shown as fourteen digits representing the date and time, separated by the character 'T'.
The absolute orbit number at product start time (OOOOOO) will be in the range 000001-999999.
The mission data-take identifier (DDDDDD) will be in the range 000001-FFFFFF.
The product unique identifier (CCCC) is a hexadecimal string generated by computing CRC-16 on the manifest file using CRC-CCITT.
The folder extension is always "SAFE".
Product Type Convention
The product type for Level-0 products is represented as follows:
- BB = instrument mode/type of data, possible values 'SM', 'EW', 'IW', 'WV' (for SAR instrument modes Stripmap, Extra Wide swath, Interferometric Wide swath, Wave respectively) or 'RF', 'AN', 'EN' (for SAR calibration modes RF Characterisation, Elevation Notch and Azimuth Notch modes).
- RAW = 'RAW' fixed string, indicating raw Level-0 products
- R = '_' fixed string, indicating resolution class
- L = '0' fixed string, indicating Level-0 processing level
- F = product class, possible values 'S', 'C', 'N' or 'A' (for SAR Level-0 Standard, SAR Level-0 Calibration, SAR Level-0 Noise and SAR Level-0 Annotations respectively)
SENTINEL-SAFE File Format
SENTINEL data products are distributed using a SENTINEL-specific variation of the Standard Archive Format for Europe (SAFE) format specification. The SAFE format has been designed to act as a common format for archiving and conveying data within ESA Earth Observation archiving facilities.
The SENTINEL-SAFE format wraps a folder containing image data in a binary data format and product metadata in XML. This flexibility allows the format to be scalable enough to represent all levels of SENTINEL products.
A SENTINEL Level-0 product refers to a directory folder that contains a collection of information. It includes:
- a manifest.safe file which holds the general product information in XML
- measurement data components
- index data components
- annotation data components
- a support folder containing representation data components.
The manifest file is an XML file containing the mandatory product metadata common to all SENTINEL-1 products (platform, mission, instrumentation, product history, timing, orbit, etc.).
Measurement data components can be one or two binary files depending on whether it is single or dual polarisation. They contain raw measurement data in the form of a stream of downlinked ISPs. The binary data is stored in big-endian format (i.e. the byte order is from the Most Significant Bit (MSB) to the Least Significant Bit (LSB)). Each ISP contains the complete SAR data acquired in one Pulse Repetition Interval (PRI) (echo, calibration, noise or test data). The ISP content is the same as the ISP downlinked from the spacecraft platform to the receiving ground station.
Index data components can be one or two binary files depending on whether it is single or dual polarisation, with each associated to a measurement data component. Index data contain the description (bytes location, time, size etc.) of the logical blocks of data in which the corresponding measurement data component can be divided. It points to each block start within the data component, enabling efficient data access and sub-setting.
Annotation data components are binary files, each composed of one record for each ISP. Each record contains annotations (related to ISP timing and quality of ISP reconstruction process), partly extracted from the ISP by the Level-0 processor and partly computed by the Demodulator and Front End Processor (DFEP).
Representation data sets found in the support folder contain information about the format or syntax of the measurement and annotated data sets and can be used to validate and exploit these data. Representation data sets are provided as XML schemas.
The file structure of a SENTINEL-1 Level-0 standard product is as follows:
For further details on SENTINEL-1 Level-0 product formatting, please refer to the SENTINEL-1 Level-0 Product Specification document.