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ASA_XCH_AX: ASAR External characterization data
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ASA_WS__BP: ASAR Wide Swath Browse Image
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ASA_GM__BP: ASAR Global Monitoring Mode Browse Image
ASA_AP__BP: ASAR Alternating Polarization Browse Image
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ASA_WV__0P: ASAR Wave Mode Level 0
ASA_WS__0P: ASAR Wide Swath Mode Level 0
ASA_MS__0P: ASAR Level 0 Module Stepping Mode
ASA_IM__0P: ASAR Image Mode Level 0
ASA_GM__0P: ASAR Global Monitoring Mode Level 0
ASA_EC__0P: ASAR Level 0 External Characterization
ASA_APV_0P: ASAR Alternating Polarization Level 0 (Cross polar V)
ASA_APH_0P: ASAR Alternating Polarization Level 0 (Cross polar H)
ASA_APC_0P: ASAR Alternating Polarization Level 0 (Copolar)
Level 1 Products
ASA_IMS_1P: ASAR Image Mode Single Look Complex
ASA_IMP_1P: ASAR Image Mode Precision Image
ASA_IMM_1P: ASAR Image Mode Medium Resolution Image
ASA_IMG_1P: ASAR Image Mode Ellipsoid Geocoded Image
ASA_GM1_1P: ASAR Global Monitoring Mode Image
ASA_APS_1P: ASAR Alternating Polarization Mode Single Look Complex
ASA_APP_1P: ASAR Alternating Polarization Mode Precision Image
ASA_APM_1P: ASAR Alternating Polarization Medium Resolution Image product
ASA_WSS_1P: Wide Swath Mode SLC Image
ASA_WVS_1P: ASAR Wave Mode Imagette Cross Spectra
ASA_WSM_1P: ASAR Wide Swath Medium Resolution Image
ASA_APG_1P: ASAR Alternating Polarization Ellipsoid Geocoded Image
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2.9.3 Common Auxiliary Data Sets

The common auxiliary files used in ASAR processing, that have not already been discussed in previous sections, are provided in this section.

2.9.3.1 FOS Orbit State Vectors

The instrument ground processing software uses the CFI orbit propagator software module and an orbit state vector as input to calculate the satellite position all along the orbit. The following describes the product structure of the "Flight Operations Segment" (FOS) instrument's predicted and restituted orbit state vector files. These are used during ground processing and are updated once per day.
FOS Predicted: (AUX_FPO_AX)
One MDSR per orbit, file contains MPH, SPH and MDS and covers 6 days .
FOS Restituted: (AUX_FRO_AX)
One MDSR per minute, file contains MPH, SPH and MDS and covers 1 day, with approximately a 60 minute overlap.
Format

The MPH and SPH of these files will follow the standard MPH, SPH structure of all ENVISAT auxiliary data. The SPH contains a single DSD of type M pointing to the MDS. The file will consist of a single MDS containing several MDSRs. Each MDSR is of the format shown below.

NOTE THAT ORBIT STATE VECTOR MDSRs DO NOT FOLLOW STANDARD ENVISAT-PDS FORMAT. The MDSR is in ASCII format and, although common to all ENVISAT instruments, is given here for convenient reference.

Table 2.70 Format of MDSR for orbit State vectors
N MDSR Contents
Units
Byte Length
DataType
Dim.
1 UTC of Orbit State Vector
UTC
27
uc
27
2 ASCII blank space character
-
1
uc
1
3 Delta UT1 = UT1-UTC
s
8
Ado06
1
4 ASCII blank space character
-
1
uc
1
5 Absolute Orbit number
-
6
As
1
6 ASCII blank space character
-
1
uc
1
7 X position in Earth fixed reference frame
m
12
Ado73
1
8 ASCII blank space character
-
1
uc
1
9 Y position in Earth fixed reference frame
m
12
Ado73
1
10 ASCII blank space character
-
1
uc
1
11 Z position in Earth fixed reference frame
m
12
Ado73
1
12 ASCII blank space character
-
1
uc
1
13 X velocity relative to Earth fixed reference frame
m/s
12
Ado46
1
14 ASCII blank space character
-
1
uc
1
15 Y velocity relative to Earth fixed reference frame
m/s
12
Ado46
1
16 ASCII blank space character
-
1
uc
1
17 Z velocity relative to Earth fixed reference frame
m/s
12
Ado46
1
18 ASCII blank space character
-
1
uc
1
19 Quality Flags (TBD by ESA)
-
6
uc
6
20 ASCII newline character
terminator
1
uc
1
TOTAL
129

2.9.3.2 DORIS Preliminary Orbit State Vectors

The preliminary orbit reconstruction is the first orbit estimate produced from the "Doppler Orbitography and Radiopositioning Integrated by Satellite" (DORIS) instrument Doppler shift data. It is produced off-line systematically for all DORIS data received, and is intended as an orbit estimate of higher quality than that of the Navigator product. The file is used during ground processing and is updated once per day.

The format is identical to that described above for the FOS State vectors. Each file covers 26 hours, with 1 MDSR per minute. Therefore, there are 1560 MDSRs in the MDS.

2.9.3.3 DORIS Precise Orbit State Vectors

The precise orbit reconstruction is the most accurate orbit estimate produced from the DORIS data. It is produced off-line systematically for all DORIS data received, and is intended as an orbit estimate of the highest quality achievable using DORIS. The file is used during ground processing and is updated once per day.

The format is identical to that described above for the FOS State vectors. Each file covers 26 hours, with 1 MDSR per minute. Therefore, there are 1560 MDSRs in the MDS.

2.9.3.4 DORIS Navigator Level 0

The DORIS Navigator Level 0 product is a file containing time ordered AISPs which are output from the on-board DORIS Navigator software. This product provides the first estimate of satellite positioning available from the DORIS sensor,
the accuracy of which is described in the table below. No further processing is applied to the Level 0 Navigator Product. The NRT version of the product is available within 3 hours of data acquisition. The OFL (fully consolidated) version is available
2 weeks after acquisition.

As with all Level 0 products, it has an MPH and an SPH followed by an MDS containing the annotated instrument source packets. These formats are given in Data Formats.(Chapter 6. )

2.9.3.5 UTC/SBT Time Conversion File

The instrument ground processing software uses the CFI time conversion software module and this file to convert from satellite binary time to UTC time. It is used during ground processing, annotated into MPH and is updated once per orbit.

Format:

The MPH and SPH of these files will follow the standard MPH, SPH structure of all ENVISAT auxiliary data. The SPH contains a single DSD of type G pointing to the GADS. The format of the GADS is shown below:

Table 2.71 Format of GADS for SBT/UTC Time Conversion File
N Description Units Byte Length Data Type Dim.
1
Reference UTC time corresponding to SBT time below

(currently defined to be given at the time of the ascending node state vector)

UTC 27 uc 27
2 ASCII blank space character - 1 uc 1
3
Reference Satellite Binary Time (SBT)
- 11 Al 1
4 ASCII blank space character - 1 uc 1
5
SBT clock step in picoseconds
ps 11 Al 1
6 ASCII newline character - 1 uc 1
TOTAL
52

2.9.3.6 ECMWF Data Files

The "European Centre for Medium-range Weather Forecasting" (ECMWF) data files contain Meteo information. They are ingested into the PDS ground segment on a regular basis and are used by various instrument processors during the generation of products.

There are two kinds of ECMWF data: Forecast data (AUX_ECF_AX) and Analysis data (AUX_ECA_AX). Forecast data is used in NRT processing, while Analysis data is used during OFL product generation. Both Forecast data and Analysis data files have the same format. The data from is used in Level 1B processing and L2 processing. The ECMWF files enter the PDS every 6 hours. There are 4 Analysis files and 4 Forecast files, each valid for a 12 hour time period.

ECMWF files enter the PDS every 6 hours. There are 4 Analysis files and 4 Forecast files, each valid for a 12 hour time period.

Format:

The high level breakdown of the file is shown below:

Table 2.72 Schematic Structure of ECMWF Files
MPH
SPH - standard Auxiliary Data SPH with 1 DSD
DSD for the ECMWF GADS
ECMWF GADS

ECMWF data files entering the PDS are encoded in PB-IO format. Upon entry to the PDS, the file is modified to fit the standard ENVISAT PDS file format. This is done by completing the following steps:

  1. Place the PB-IO file (without modifying its structure) into a GADS (the ECMWF GADS);
  2. Add an Auxiliary Data SPH (with one DSD for the GADS);
  3. Add an MPH (fields not relevant set to zero or filled with ASCII blank space characters);
  4. Assign a PDS filename as per the auxiliary data naming convention described earlier in this volume.

ECMWF GADS

The GADS contains information encoded in PB-IO format. No additions or modifications are made from the original format.