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    24-Jul-2014
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Level2 processing
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5.1.2 Product types and structure

5.1.2.1 Types of products by processing level

 

Level 0

The Level0 products are build from the source packets products by GOMOS. Actually, The level 0 product contains Annotated Instrument Source Packets (AISP). These are Instrument Source Packets as received from the instrument, with a small header attached by the Front End Processor (FEP). The packets contain the three band measurements, the photometer data, the SATU and SFA data for one or several occultations. Nominally, there should be one product per orbit (consolidated products) or a mix of two consecutive orbits (NRT products).

Level 1b

The Level1b products are generated from the Level 0 products by the Level 1b processing. There are two types of Level 1b products: the geolocated and calibrated transmission spectra products (Level1b transmission products), containing the full transmission and the covariance spectra needed for the Level2 processing; and the geolocated and calibrated background spectra limb products (Level 1b limb products), containing the background spectra measured by the two external bands of the CCD spectrometers. Each Level 1b product corresponds to one occultation.

Level 2

The Level2 products are generated from the Level 1b products by the Level 2 processing. There are three types of Level 2  products: the Level 2 atmospheric and constituent profile products which are the main outputs of the Level 2 processing; the  Level 2 residual extinction products containing the spectral transmission corrected for scintillation and dilution effects and a result of a forward model of the transmission with the "best fit" values of the parameters; and the Level 2 meteo products containing selected vertical profiles processed in Near Real Time. Each Level 2 product corresponds to one occultation.

 

5.1.2.2 Structure of the products

 

MPH (Main Product Header)

contains information on the main characteristics of the product. Its size and its structure are fixed and are common to all ENVISAT instruments. It is in ASCII format.

SPH (Specific Product Header)

contains information specific to the product itself. This information is described in the DSD of the SPH.  Its size and its structure are fixed for a specific product. It is in ASCII format.

DSD (Data Set Descriptor)

points to and describes the DS contained in the product. There is one DSD per DS. May also provide references to external files relevant to the current product.

DS (Data Set)

composed of one or more DS Records, in an ASCII-binary mixed format. The DS may be MDS or ADS.

GADS (Global Annotation Data Set)

contains auxiliary data relevant to the product (nominal wavelength assignment, reference star spectrum, LUT, …). A GADS is made of only one DS Record.

ADS (Annotation Data Set)

contains auxiliary data applicable to one measurement. Made of one or several DSR.

MDS (Measurement Data Set)

contains measurements and/or processed data. Made of one or several DSR.