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    24-Jul-2014
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2.2.2 Product structure

All products follow the same structure and contain three main fields, the Main Product Header, the Specific Product Header, and the Data Sets.

Main Product Header (MPH):

         The MPH is in ASCII format. Its size and its structure are fixed and are common to all ENVISAT instruments.

It contains information on the main characteristics of the product. Table 2.7 lists some of the records of the MPH. The exhaustive list of these records is given in the document ENVISAT-1 products specifications,  Issue 3, rev. 1, ref. PO-RS-MDA-GS-2009, 2005.

Record

Description

Unit

product

Product File Name

ascii

proc_stage

Processing Stage Flag:

N = Near Real Time, T = test product, V= fully validated (fully consolidated) product, S = special product. Letters between N and V (with the exception of T and S) indicate steps in the consolidation process. If not used, set to X

ascii

acquisition_station

Acquisition Station ID (up to 3 codes). Not used characters are set to blank space characters

ascii

proc_center

Processing Center ID which generated current product. If not used, set to

ascii

proc_time

UTC Time of Processing (product generation time). If not used, set to

UTC

software_ver

Software Version number of processing software

Format: Name of processor (up to 10 characters)/ version number (4 characters) -- left justified (any blanks added at end). If not used, set to

ascii

sensing_start

UTC start time of data sensing (first measurement in first data record) UTC Time format. If not used, set to

UTC

sensing_stop

UTC stop time of data sensing (last measurements last data record) UTC Time format. If not used, set to

UTC

cycle

Cycle number. If not used, set to +000

-

rel_orbit

Start relative orbit number. If not used, set to +00000

-

abs_orbit

Start absolute orbit number. If not used, set to +00000

-

state_vector_time

UTC of ENVISAT state vector. UTC time format. If not used, set to

UTC

utc_sbt_time

UTC time corresponding to SBT below (currently defined to be given at the time of the ascending node state vector). If not used, set to

UTC

sat_binary_time

Satellite Binary Time (SBT) 32bit integer time of satellite clock. Its value is unsigned (=>0). If not used, set to +0000000000

-

Table 2 . 7 : Records of the MPH (non-exhaustive list). See the document ENVISAT-1 products specifications,  Issue 3, rev. 1, ref. PO-RS-MDA-GS-2009, 2005 for a complete description.

Specific Product Header (SPH):

    The SPH is in ASCII format. Its size and its structure are fixed for a specific product.

    It contains information specific to the product itself.

    The SPH contains Data Set Descriptors fields (DSD).

    Those DSD point to and describe the Data Sets (DS) contained in the product. There is one DSD per DS.

    The DSD may also provide references to external files relevant to the current product.

Some DSD of the SPH of the Level 1b products and of the SPH of the Level 2 products are similar. They provide information on the date, the location of the measurements, and the star characteristics of which occultation was measured. These DSD are listed in Table 2.8 . The complete description of the SPH for the different products is given in the IODD.

Field

Description

Unit

START_TIME

Start time of the occultation

UTC

STOP_TIME

Ending time of the occultation

UTC

START_TANGENT_LAT

Latitude of the tangent point at START_TIME

(1e-6) deg (positive = North)

START_TANGENT_LONG

Longitude of the tangent point at START_TIME

(1e-6) deg (positive = East)

STOP_TANGENT_LAT

Latitude of the tangent point at STOP_TIME

(1e-6) deg (positive = North)

STOP_TANGENT_LONG

Longitude of the tangent point at STOP_TIME

(1e-6) deg (positive = East)

STAR_ID

Star identifier in the star catalogue (*)

STAR_MAG

Star visual magnitude

1e-3

STAR_TEMP

Star effective temperature

(1e-1)K

Table 2.8: DSD of the SPH of the Level 1b products (non exhaustive list), also contained in the Level 2 products; see the IODD for a complete description of the SPH. (*) The list of stars selected for use by GOMOS is given in Appendix B.

Data Sets (DS):

    The DS are stored in a mixed ASCII-binary format. Each DS is composed of one or more Data Set Records (DSR).

    The DS may be Measurement Data Set or Annotation Data Set.

   

Global Annotation Data Set (GADS):

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

Annotation Data Set (ADS):

             Each ADSR contains auxiliary data applicable to one measurement. An ADS is made of one or several DSR.

Measurement Data Set (MDS):

             The MDS contains measurements and/or processed data. A MDS is made of one or several DSR.