envisat post-launch...

Doc: PO-MO-ESA-GS-1005Issue: 5 - ASARPage: 1August 2002

ENVISAT Post-Launch ProductsASAR

1. Product SummaryThe following table describes all the ASAR products included in the package. The list is divided in twogroups: The first part describes the Level 1b products processed from different acquisitions taken duringthe first months of operation of the ASAR instrument operation. They try to reflect all the innovativemodes in which the instrument can function. Following, the auxiliary files used to process the data areplaced.

Filename PDS Name Product Name

L1b Products

ASA_IMS_1PXPDE20020730_095910_000000142008_00108_02166_0010.N1 ASA_IMS_1PImage Single LookComplex

ASA_IMP_1PXPDE20020730_095910_000000162008_00108_02166_0020.N1 ASA_IMP_1PImage Mode PrecisionImage

ASA_IMG_1PXPDE20020730_095910_000000162008_00108_02166_0007.N1 ASA_IMG_1PImage Mode EllipsoidGeocoded Image

ASA_IMM_1PXPDE20020730_095830_000001002008_00108_02166_0066.N1 ASA_IMM_1PImage Mode MediumResolution Image

ASA_IM__BPXPDE20020730_095830_000001002008_00108_02166_0065.N1 ASA_IM__BP Image Mode Browse

ASA_APS_1PXPDE20020819_093043_000000072008_00394_02452_0000.N1 ASA_APS_1PAlternating PolarizationMode Complex Image

ASA_APP_1PXPDE20020819_093043_000000152008_00394_02452_0004.N1 ASA_APP_1PAlternating PolarizationMode Precision Image

ASA_APG_1PXPDE20020819_093043_000000152008_00394_02452_0000.N1 ASA_APG_1PAlternating PolarizationMode EllipsoidGeocoded Image

ASA_APM_1PXPDE20020819_093008_000000622008_00394_02452_0009.N1 ASA_APM_1PAlternating PolarizationMedium ResolutionImage

ASA_AP__BPXPDE20020819_093008_000000622008_00394_02452_0009.N1 ASA_AP__BPAlternating PolarizationBrowse

ASA_WSM_1PXPDE20020714_100425_000001202007_00380_01937_0053.N1 ASA_WSM_1PWide Swath StandardImage

ASA_WS__BPXPDE20020714_100425_000001202007_00380_01937_0053.N1 ASA_WS__BP Wide Swath Browse

ASA_GM1_1PXPDE20020317_170454_000001501002_02644_00238_0009.N1 ASA_GM1_1PGlobal MonitoringMode Image

ASA_GM__BPXPDE20020317_170454_000001501002_02644_00238_0009.N1 ASA_GM__BPGlobal MonitoringMode Browse

ASA_WVI_1PXPDE20020503_033815_000003592005_00347_00902_0042.N1 ASA_WVI_1PWave Mode SLCImagette and ImagetteCross Spectra


ASA_WVS_1PXPDE20020503_033815_000003592005_00347_00902_0042.N1 ASA_WVS_1PWave Mode ImagetteCross Spectra

L2 Products

ASA_WVW_2PXPDE20020503_033815_000003592005_00347_00902_0042.N1 ASA_WVW_2PWave Mode OceanWave Spectra

Auxiliary files

ASA_CON_AXVIEC20020308_105002_20020301_000000_20021231_000000 ASA_CON_AXProcessor ConfigurationFile

ASA_INS_AXVIEC20020425_093155_20020413_000000_20021231_000000 ASA_INS_AXInstrumentCharacterization File

ASA_XCA_AXVIEC20020813_080042_20020413_000000_20021231_000000 ASA_XCA_AXExternal CalibrationData

ASA_XCH_AXVIEC20020308_113032_20020301_000000_20021231_000000 ASA_XCH_AXExternalCharacterization data

1.1 Product Summary

The Advanced Synthetic Aperture Radar is a high resolution imaging radar. It can be operated in 5 distinctMeasurement Modes, Image Mode (IM), Alternating Polarization Mode (AP), Wide Swath Mode (WS),Global Monitoring Mode (GM), and Wave Mode (WV). Within each mode, several different image swathsmay be used. IM, AP, and WS modes are designated as High Rate (HR) modes and have a downlink rate of100 Mbps. GM and WV are Low Rate (LR) modes and have a data generation of 0.9 Mbps.

In addition, ASAR supports 2 Auxiliary Modes (Test Mode, and Module Stepping Mode)and one Calibration Mode (External Characterization Mode) which are used for testing,calibration and instrument monitoring. Finally, one of five possible on-board dataquantization methods may be used for each mode, though each has a default choicewhich will be used in most cases.

The nominal characteristics of the various ASAR measurement modes are summarized in the followingtable:

ASAR Image ModeVV or HH polarization images from any of 7 selectable swaths. Swath width between approximately56 km (swath 7) and 100 km (swath 1) across track. Spatial resolution of approximately 30 m (forPrecision product).ASAR Alternating Polarization ModeTwo co-registered images per acquisition, from any of 7 selectable swaths. HH/VV HH/HV or VV/VHpolarization pairs possible. Spatial resolution of approximately 30 m (for Precision product).


ASAR Wide Swath Mode400 km by 400 km wide swath image. Spatial resolution of approximately 150 m by 150 m for nominalproduct. VV or HH polarization.ASAR Global Monitoring ModeSpatial resolution of approximately 1000 m in azimuth by 1000 m in range for nominal product. Up toa full orbit of coverage. HH or VV polarization.ASAR Wave ModeA small imagette (dimensions range between 10 km by 5 km to 5km by 5km) is acquired at regularintervals of 100 km along track. The imagette can be positioned anywhere in an image mode swath. Upto two positions in a single swath or in different swaths may be specified, with acquisitions alternatingbetween one and the other (successive imagettes will hence have a separation of 200 km betweenacquisitions at a given position). HH or VV polarization may be chosen. Imagettes are converted towave spectra for ocean monitoring.

Table 3-1Nominal ASAR characteristics

3.1.1. ASAR IMAGE PRODUCTSASAR Image Products can be grouped into those produced as stand-alone products, and those produced asstripline products. All ASAR Image Products are stored in time-increasing order, except the geocodedproducts which are oriented such that the first pixel of the first line is the most north-west pixel.

3.1.1.1. Stand-alone (non-stripline) Image ProductsStand-alone image products are produced by request only and are created directly from the Level 0 data.They are ordered as a scene. The scene size is 100 km along track by the swath width for the swath fromwhich the data is acquired (between 56 and 100 km wide). All of these products share a common formatwhich is described in the following subsections.

Image Mode Single Look ComplexThis is a Single Look, Complex (SLC), phase preserved, slant range image generated from the Level 0Image Mode product using the Range/Doppler algorithm. It may be in either HH or VV polarization. TheSLC product is generated upon request and is intended for use in SAR quality assessment, calibration, andinterferometric applications. A minimum number of corrections and interpolations are performed on thedata. Absolute calibration parameters (when available) shall be provided in the product annotation.

PRODUCT ID ASA_IMS_1PNAME ASAR image single look complexDESCRIPTION This is a single-look, complex, slant-range, digital image generated

from Level 0 ASAR data collected when the instrument is in imagemode (7 possible swaths HH or VV polarisation).It is primarily intended for use in SAR quality assessment andcalibration, and can be used to derive higher level products.

COVERAGE 100 km along track * 56- 100 km across trackGEOMETRIC RESOLUTION Approximately 6 m in azimuth, programmed chirp bandwidth

dependant in slant range (up to 16 MHz).RADIOMETRIC RESOLUTION 1 look in azimuth, 1 look in rangePIXEL SPACING Natural spacing in both Slant range and AzimuthSIZE 741 MbytesDATASET Each product containing the following:

(1) headers MPH + SPH (2) max 27 000 data records(TBC) (3) max 6850 samples/record (depending on imaging swath) (4) 4 bytes/sample (2bytes I/ 2bytes Q)

AUXILIARY DATA Orbit state vector. Time correlation parameters. Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, Geolocation Grid ADS, SQ ADS

INTERNAL CALIBRATION For the purpose of calibration1. Data I/Q correction2. Replica construction


3. Calibration pulse processing4. Elevation gain function calculation5. Noise power estimation

NOTES 1. Azimuth pixel spacing depends on Earth-Satellite relativevelocity and actual PRF.

2. Slant range pixel spacing is given by ASAR sampling frequency(19.208 Mhz)


Image Mode Precision ImageThis is a multi-look, ground range, digital image generated from the Level 0 Image Mode Product using theRange/Doppler algorithm. May be in either HH or VV polarization. The processing uses up to date (at timeof processing) auxiliary parameters and corrects for antenna elevation gain, and range spreading loss. Theproduct is generated upon request and is intended for users wishing to perform applications orientedanalysis, as well as for multi-temporal imaging and to derive backscatter coefficients. Absolute calibrationparameters (when available) shall be provided in the product annotation.

PRODUCT ID ASA_IMP_1PNAME ASAR image mode Precision ImageDESCRIPTION This is a multi-look, ground range, digital image. Generated from

Level 0 data collected when the instrument is in image mode (7possible swaths HH or VV polarisation).The product includes slant range to ground range correction as perdefinition. It is for users wishing to perform applications-orientedanalysis.It is intended for multi-temporal imaging and to derive backscatteringcoefficients.

COVERAGE 100 km along track * 56- 100 km across trackGEOMETRIC RESOLUTION approximately 30 m ground range (except IS1) X 30m azimuthRADIOMETRIC RESOLUTION Product ENL > 3PIXEL SPACING 12.5 m * 12.5 mSIZE up to 134 MbytesDATASET each product containing the following:

(1) header MPH + SPH (2) 8000 data records (3) 8350 samples/record (size for IS1 swath) (4) 2 bytes/sample

AUXILIARY DATA Orbit state vector . Time correlation parameters. Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, SR/GR ADS, Geolocation Grid ADS, SQADS

INTERNAL CALIBRATION For the purpose of calibration:1. Data I/Q correction2. Replica construction3. Calibration pulse processing4. Elevation gain function calculation5. Noise power estimation

NOTES 1. Product size in the range direction will vary function of imagingswath.

2. Corrections: antenna elevation pattern, range spreading loss.


Image Mode Ellipsoid Geocoded ImageThe Image Mode Geocoded SAR image is generated from the Level 0 Image Mode product using theRange/Doppler algorithm with the best available instrument corrections, and is systematically located andresampled on to a map projection. Product is generated upon request, and is intended for mappingapplications and other uses requiring map projection images. Absolute calibration parameters (whenavailable) shall be provided in the product annotation. All processing information in the geocoded productcorresponds to the intermediate product created during processing. Only the Geolocation Grid ADS andMap Projection ADS are updated to reflect the map projection information.

PRODUCT ID ASA_IMG_1PNAME ASAR image mode ellipsoid geocoded imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in image mode. It is the geocoded version of the PRI product.The product is resampled to a map projection and its orientation isnorth up.

COVERAGE 100km * 100 km (corresponding to the input data)RADIOMETRIC RESOLUTION Product ENL > 3GEOMETRIC RESOLUTION approximately 30 m ground range (except IS1) * 30m azimuthPIXEL SPACING 12.5 m * 12.5 m (grid easting and northing)SIZE up to 282 MbytesDATASET each product containing the following:

(1) header MPH + SPH(2) max 11850 records(3) max 11850 samples/record(4) 2 bytes / sample

AUXILIARY DATA Orbit state vector, Time correlation parameters, Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, SR/GR ADS, Geolocation Grid ADS, SQADS

INTERNAL CALIBRATION For the purpose of calibration: 1. Data I/Q correction 2. Replica construction 3. Calibration pulse processing 4. Elevation gain function calculation 5. Noise power estimation

NOTES (1) Product size will vary function of imaging swath position.(2) The absolute calibration of the GEC product shall be the same

as for the corresponding non-geocoded PRI product.


Alternating Polarization Mode Single Look ComplexThis is a complex, slant range image generated upon request from the Level 0 AP Product using the RangeDoppler and the most up to date processing parameters available at the time of processing. The productcontains two co-registered images corresponding to one of the three possible polarization combinations(HH & VV, HH & HV, VV & VH). This product is intended for use in quality assessment, calibration, andinterferometric applications. Absolute calibration parameters (when available) shall be provided in theproduct annotation.

PRODUCT ID ASA_APS_1PNAME ASAR Alternating Polarisation mode complex imageDESCRIPTION This is a complex, slant-range, digital image generated from Level 0

ASAR data collected when the instrument is in AlternatingPolarisation mode (7 possible swaths). It is primarily intended for use in SAR quality assessment andcalibration, and can be used to derive higher level products.If allowed by the instrument acquisition, this product shall be suitablefor interferometric applications.The product contains two images corresponding to one of the threepolarisation combination sub-modes (HH & VV, HH & HV, VV &VH)

COVERAGE 100 km along track, 56- 100 km across trackGEOMETRIC RESOLUTION approximately 9m in slant range, 12 m in azimuthRADIOMETRIC RESOLUTION 1 look in azimuth, 1 look in rangePIXEL SPACING natural spacing in both Slant range and AzimuthSIZE max 1480 MbytesDATASET each product containing the following

(1) headers MPH + SPH and respectively for each polarisation (2) max 27 000 data records (3) 6850 samples/record (depending on imaging swath) (4) 4 bytes/sample (2bytes I / 2bytes Q)

AUXILIARY DATA Orbit state vector, Time correlation parameters, Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, Geolocation Grid ADS, SQ ADS

INTERNAL CALIBRATION For the purpose of calibration 1. Data I/Q correction 2. Replica construction 3. Calibration pulse processing 4. Elevation gain function calculation 5. Noise power estimation

NOTES 1. Product size will vary function of imaging swath, satellitevelocity and actual PRF

2. The images from the two polarisation channels are coregistered.


Alternating Polarization Mode Precision ImageThis is a multi-look, ground range, digital image generated upon request from the Level 0 AP productusing the SPECAN algorithm and the most up to date auxiliary information available at the time ofprocessing. Engineering corrections and relative calibration (antenna elevation gain, range spreading loss)are applied. The product contains two co-registered images corresponding to one of the three possiblepolarization combinations (HH & VV, HH & HV, VV& VH). Absolute calibration parameters (whenavailable) shall be provided in the product annotation.

PRODUCT ID ASA_APP_1PNAME ASAR alternating polarization precision imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in alternating polarization mode (7 possible swaths).The product contains two images corresponding to one of the threepolarisation combination sub-modes (HH & VV, HH & HV, VV &VH)

COVERAGE 100 km along track, 56- 100 km across trackGEOMETRIC RESOLUTION approximately 30 m ground range (except IS1) * 30m azimuthRADIOMETRIC RESOLUTION Product ENL > 1.8PIXEL SPACING 12.5 m * 12.5 mSIZE up to 268 MbytesDATASET each product containing the following:

(1) header MPH + SPH (2) 16,000 data records (8000 for VV polarisation & 8000 for HHpolarisation) (3) 8350 samples/record (depending on imaging swath) (4) 2 bytes/sample



NOTES 1. Product size in the range direction will vary function of imagingswath (56 to 100km)

2. The images from the two polarisation channels are coregistered.3. Corrections: antenna elevation pattern, range spreading loss.


Alternating Polarization Ellipsoid Geocoded ImageThis is a multi-look geocoded SAR image generated upon request from the Level 0 AP Product using theSPECAN algorithm and the most up to date auxiliary information available at the time of processing.Engineering corrections and relative calibration (antenna elevation gain, range spreading loss) are appliedand the image is systematically geolocated and resampled to a map projection. The product contains twoco-registered images corresponding to one of the three possible polarization combinations (HH & VV, HH& HV, VV & VH). Absolute calibration parameters (when available) shall be provided in the productannotation. All processing information in the geocoded product corresponds to the intermediate productcreated during processing. Only the Geolocation Grid ADS and Map Projection ADS are updated to reflectthe map projection information.

PRODUCT ID ASA_APG_1PNAME ASAR Alternating Polarisation mode ellipsoid geocoded imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in alternating polarisation mode. It is the geocodedversion of the PRI product ASA_APP_1P. The product is resampledto a map projection and its orientation is north up. The productcontains two images corresponding to one of the three polarisationcombination sub-modes (HH & VV, HH & HV, VV & VH)

COVERAGE 100km * 100 kmGEOMETRIC RESOLUTION approximately 30 m ground range (except IS1) * 30m azimuthRADIOMETRIC RESOLUTION Product ENL > 1.8PIXEL SPACING 12.5 m * 12.5 m (grid easting and northing)SIZE up to 563 MbytesDATASET (1) each product containing the following

(2) header MPH + SPH(3) max 23 700 records (11850 for VV polarisation & 11850 for HHpolarisation)(4) max 11850 samples/record (depending on imaging swath)(5) 2 bytes / sample


INTERNAL CALIBRATION For the purpose of calibration:1. Data I/Q correction2. Replica construction3. Calibration pulse processing4. Elevation gain function calculation5. Noise power estimation

NOTES 1. Product size will vary function of imaging swath position.2. The absolute calibration of the GEC product shall be the same asfor the corresponding non-geocoded PRI product.3. The images from the two polarisation combination channels arecoregistered


1.1.1.2 Stripline Processed Image ProductsStripline image products contain image data for an entire segment, up to a maximum size of 10 minutes perproduct for IM, AP and WS and up to a full orbit (100 minutes) for GM. The PF-HS concatenates togetherseveral sub-images called “slices” received from PF-ASAR on a data set by data set basis in order to formthe entire stripline image.Each slice produced by PF-ASAR follows the standard “stand-alone” image product format describedpreviously. After concatenation of slices to form the stripline, the structure of the stripline image isidentical to that of the stand-alone image products except the data sets contain data concatenated fromseveral slices in time ordered sequence.

Image Mode Medium Resolution ImageThis ASAR product is generated from the Image Mode Level 0 Product. The product is processed toapproximately 150 m resolution and contains radiometric resolution good enough for ice applications.

PRODUCT ID ASA_IMM_1PNAME ASAR image mode medium resolution imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in image mode.This product has lower resolution but higher radiometric resolutionthan the ASA_IMP The product covers a continuous area along the imaging swath

COVERAGE 100 km in along track direction for a sceneup to 4000 km for a stripe,56-100 km in across track direction

GEOMETRIC RESOLUTION approximately 150 m * 150 mRADIOMETRIC RESOLUTION Product ENL ~ 40PIXEL SPACING 75 m * 75mSIZE 4 Mbytes of data for a scene

152 Mbytes for a stripeDATASET each product scene containing the following:

(1) header MPH + SPH (2) 1400 data records (3) 1400 samples/record (4) 2bytes/sample

AUXILIARY DATA Orbit state vector, time correlation parameters, Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, SR/GR ADS, Geolocation Grid ADS, SQADS


NOTES 1. The products cover a continuous area along the imaging swath.


Alternating Polarization Medium Resolution ImageThis ASAR product is generated from the AP Level 0 Product. The product is processed to approximately150 m resolution using the SPECAN algorithm and contains radiometric resolution good enough for iceapplications. The product contains one image corresponding to one of the 4 possible polarizationcombinations (HH, VV, HV, or VH) when processed systematically in NRT. This product may also begenerated on request with one or both polarizations included in the product.

PRODUCT ID ASA_APM_1PNAME ASAR Alternating Polarization medium resolution imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in alternating polarization mode.The product has lower geometric resolution but higher radiometricresolution than ASA_APP. The product contains one or two images corresponding to one of thethree polarisation combination sub-modes (HH & VV, HH & HV,VV & VH)

COVERAGE 100 km in along track direction for a scene. Up to 4000km for astripe, 56-100 km in across track direction

GEOMETRIC RESOLUTION approximately 150 m * 150 mRADIOMETRIC RESOLUTION Product ENL ~ 50PIXEL SPACING 75m * 75mSIZE 4 Mbytes for a scene with one polarisation combinationDATASET each product containing for each polarisation:

(1) header MPH + SPH (2) 1400 data records (3) 1400 samples/record (4) 2bytes/sample

AUXILIARY DATA Orbit state vector, Time correlation parameters, Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, SR/GR ADS, Geolocation Grid ADS, SQADS


NOTES (1) The products cover a continuous area along the imaging swath(2) (2) The images from the two polarisation channels are

coregistered.


Wide Swath Medium Resolution ImageThis is the standard product for ASAR Wide Swath Mode. It is processed to approximately 150 mresolution using the SPECAN algorithm. The swath width is approximately 400 km.

PRODUCT ID ASA_WSM_1PNAME ASAR wide swath standard imageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in wide swath mode.The product includes slant range to ground range corrections perdefinition.The product covers a continuous area along the imaging swath.

COVERAGE 400 km * 400 km(approximately) for a scene; 400 km * 4000 kmmax for a stripe

GEOMETRIC RESOLUTION approximately 150 m * 150 mRADIOMETRIC RESOLUTION Product ENL > 11.5PIXEL SPACING 75 m * 75 mSIZE 59 Mbytes for a scene

584 Mbytes for a stripeDATASET each product scene containing the following:

(1) header MPH + SPH (2) 5400 data records (3) 5450 samples/record (4) 2 bytes/sample




Global Monitoring Mode Image ProductThis is the standard product for ASAR Global Monitoring Mode. It is processed to approximately 1 kmresolution using the SPECAN algorithm. The swath width is approximately 400 km.

PRODUCT ID ASA_GM1_1PNAME ASAR Global Monitoring Mode ImageDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in global monitoring mode.The product includes slant range to ground range correction.

COVERAGE up to 40000 km(1 orbit) X 400 km (approximately)GEOMETRIC RESOLUTION 1 km * 1 kmRADIOMETRIC RESOLUTION Product ENL ~ 12PIXEL SPACING 500m * 500mSIZE up to 146 Mbytes /orbit ;

extracted scene 2MbytesDATASET each product containing the following:

(1) header MPH + SPH(2) (up to 80000) data records,(3) 850 samples/record (TBC)(4) 2 bytes/sample

AUXILIARY DATA Orbit state vector. Time correlation parameters. Main Processingparameters ADS, Doppler Centroid ADS, Chirp ADS, AntennaElevation Pattern ADS, SR/GR ADS, Geolocation Grid ADS, SQADS

INTERNAL CALIBRATION For the purpose of calibration: 1. Data I/Q correction (bias removal on both I and Q channels, I/Qchannels gain imbalance correction, I/Q non orthogonalitycorrection) 2. Replica construction 3. Calibration pulse processing4. Elevation gain function calculation5. Noise power estimation

NOTES 1. Stripline Processing one product covers a full orbit


1.1.1.3 Browse ProductsBrowse products are a special form of stripline products. Browse products are also created as individualslices and then concatenated together by the PF-HS. However, browse products are intended only as a useraid when ordering data. Thus, many of the ADSs pertaining to detailed processing records may bediscarded by the PF-HS for the browse product. There are 4 browse products as described in the followingsubsections.

Image Mode Browse ImageThis low resolution product will be produced systematically together with the Image Mode MediumResolution Product. The image is intended for browse purposes only (pixel spacing is approximately 225m). This product will be provided via electronic link in near real time.

PRODUCT ID ASA_IM__BPNAME ASAR image mode browseDESCRIPTION ASAR product generated when the instrument is in image mode.

The product is for browse purpose only.The product is generated from ASA_IMM_1P product.

COVERAGE Product stripe up to 4000 km;56-100 km in across track direction

PIXEL SPACING 225 m * 225 m (multiple of ASA_IMM pixel spacing)RADIOMETRIC RESOLUTION Product ENL ~ 80SIZE Stripline max 3MbytesDATASET Each scene containing:

(1) header (2) 8889 data records (3) 480 samples/record (4) 1 byte/sample

AUXILIARY DATA Orbit state vector, Time correlation parameters, SQADS, GeolocationGrid ADS

NOTES The products cover a continuous area along the imaging swath.


Alternating Polarization Browse ImageThis low resolution product will be produced systematically together with the AP Medium ResolutionProduct. The image is intended for browse purposes only (pixel spacing is approximately 225 m). Thisproduct will be provided via electronic link in near real time. The product will contain only one of thepolarization options rather than two. The polarization used will be that of the MDS1 of the APM product.This means the polarization may vary depending upon which polarization option is chosen for MDS1 forthe Medium Resolution AP product.

PRODUCT ID ASA_AP__BPNAME ASAR alternating polarization browseDESCRIPTION ASAR product generated when the instrument is in alternating

polarisation mode.The product is for browse purpose only.The product is generated from ASA_APM_1P productIt contains one of the two possible polarisation combinationgenerated in AP mode

COVERAGE product stripe up to 4000 km;56-100 km in across track direction

PIXEL SPACING 225 m * 225 m (multiple of ASA_APM pixel spacing)RADIOMETRIC RESOLUTION Product ENL ~ 75SIZE stripline max 3 MbytesDATASET each scene containing:

(1) header(2) 8889 data records(3) 480 samples/record(4) 1 byte/sample




Wide Swath Browse ImageThis low resolution product will be produced systematically together with the WS Medium ResolutionProduct. The image is intended for browse purposes only (pixel spacing is approximately 900 m). Thisproduct will be provided via electronic link in near real time.

PRODUCT ID ASA_WS__BPNAME ASAR wide swath browseDESCRIPTION ASAR product generated when the instrument is in wide swath

mode.The product is for browse purpose only.

COVERAGE product stripe up to 4000 km ;405 km in across track direction

PIXEL SPACING 900 m * 900 m for WSRADIOMETRIC RESOLUTION Product ENL ~ 57 to 62SIZE stripline max 3 MbytesDATASET each product containing:

(1) header(2) 4445 data records(3) 500 samples/record(4) 1 byte/sample


NOTES (1) The products cover a continuous area along the imaging swath.

Global Monitoring Mode Browse ImageThis low resolution product will be produced systematically together with the GM Image Product fromLevel 0 GM data. The image is intended for browse purposes only (pixel spacing is approximately 1000m). This product will be provided via electronic link in near real time.

PRODUCT ID ASA_GM__BPNAME ASAR Global monitoring mode browseDESCRIPTION ASAR product generated from the ASA_GM1_1P when the

instrument is in Global Monitoring modeThe product is for browse purpose only.

COVERAGE 405 km in across track direction ; product stripe up to 40000 km forGM

PIXEL SPACING 1000 m * 1000 m for GMRADIOMETRIC RESOLUTION Product ENL ~ 18 -21SIZE Stripline max 18 MbytesDATASET each containing:

(1) header (2) 40000 data records (3) 410 samples/record (4) 1 byte/sample




1.1.2 WAVE MODE PRODUCTSWave Mode products are those products produced from data acquired while the ASAR instrument isoperating in Wave Mode. During Wave Mode operation, the ASAR instrument acquires smallmeasurements called wave cells which are approximately 5 km along track by (up to) 10 km in acrosstrack. The wave cells are acquired at 100 km intervals. The cells may have alternating positions in the sameswath or be in alternating swaths. In theory, up to 400 of these wave cells may be acquired per orbit, but inpractice it is anticipated that the average number of acquisitions per orbit will be substantially lower. Eachwave cell is processed into a small SLC image called an imagette. In addition, each imagette is furtherprocessed using the cross-spectra methodology to produce the cross spectra of the imagette.

Wave Mode SLC Imagette and Imagette Cross SpectraThis is the basic Wave Mode product. The product includes up to 20 single look, complex, slant range,imagettes generated from Level 0 data and up to 20 imagette power spectra computed using the cross-spectra methodology. A minimum number of corrections and interpolations are performed. Absolutecalibration parameters (when available) shall be provided in the product annotations.

PRODUCT ID ASA_WVI_1PNAME ASAR Wave Mode SLC imagette and Imagette Cross SpectraDESCRIPTION ASAR product generated from Level 0 data collected when the

instrument is in wave mode.The product is the basic level 1B product of ASAR wave mode.The information is retained in complex form to allow derivation ofCross spectra.Product containing up to 20 imagettes and associated imagettes crossspectra.

COVERAGE One product per 20 imagettes with imagette of 5 kmx5km (min.)every 100 km

GEOMETRIC RESOLUTION Natural spacing slant range and azimuth azimuth.Wavelength range from 20 to 1000m in 24 logarithmic steps direction 0-360 degrees in 10 degree steps (only half real part andimaginary part of spectra in product)

RADIOMETRIC RESOLUTION 1 look in azimuth, 1 look in range for the SLC imagettePIXEL SPACING Natural pixel spacing in range and azimuth. note 1-2-3SIZE Max 120 Mbytes (20 imagettes and spectra)DATASET MPH + SPH

+ Data Set Record A: 20 Polar Spectrum (18 bins in direction x 24bins in wavelengthx2bytes per bin)+ Data Set Record B: 1 imagette max 1350 data records x 1100samples/record x 4bytes/sample(2 bytes I/ 2 bytes Q)

AUXILIARY DATA Orbit state vector . Time correlation parameters. Wave Processingparameters ADS, Wave Geolocation ADS, SQ ADS

NOTES 1 Azimuth pixel spacing depends on Earth-Satellite relative velocityand actual PRF.2 Slant range pixel spacing is given by ASAR sampling frequency(19.208 Mhz)3 N/A for the imagette cross spectra.


Wave Mode Imagette Cross SpectraThis product contains up to 20 cross spectra extracted from the SLC Imagette and Imagette Cross Spectraproduct. It contains only the cross spectra derived using cross spectra methodology.

PRODUCT ID ASA_WVS_1PNAME ASAR Wave Mode Imagette Cross SpectraDESCRIPTION ASAR Cross Spectra extracted from the combined SLC and Cross

Spectra product ASA_WVI_1P generated from data collected whenthe instrument is in wave mode using the Cross Spectramethodology.The Product is for Meteo users.

COVERAGE Up to 20 spectra acquired every 100 km,product coverage 5kmx5km minimum

GEOMETRIC RESOLUTION Wavelength range from 30 to 800 m in 24 logarithmic steps. Direction 0-360 degrees in 10 degree steps (only half real part andimaginary part of spectra in product)

PIXEL SPACING N/ASIZE max 0.2 MbytesDATASET MPH + SPH.

20 Polar Spectrum (18 bins in direction (10deg. steps) x 24 bins inwavelength x 2bytes per bin)


Wave Mode Ocean Wave SpectraThis is the highest level Wave Mode product The product contains up to 20 ocean wave spectra producedfrom the SLC imagette product. This is achieved by inverting the cross spectra computed from the inter-look processing of the SLC imagettes to derive the directional ocean product ocean wave spectra. AuxiliaryADSs included in the product remain the same as for the Cross Spectra product.

PRODUCT ID ASA_WVW_2PNAME ASAR Wave Mode Ocean Wave SpectraDESCRIPTION This is the highest level Wave Mode product. It is produced from the

SLC imagette product. This is achieved by inverting the cross spectracomputed from the inter-look processing of the SLC imagettes toderive the directional ocean product ocean wave spectra. Valuesrepresent energy density. Wind field is also included.The Product is for Meteo users.

COVERAGE Up to 20 spectra acquired every 100 km,product coverage 5kmx5km minimum

GEOMETRIC RESOLUTION Wavelength range from 20 to 1000 m in 24 logarithmic steps. Direction 0-360 degrees in 10 degree steps

PIXEL SPACING N/ASIZE max 0.2 MbytesDATASET MPH + SPH.

20 Polar Spectrum (18 bins in direction (10deg. steps) x 24 bins inwavelength x 2bytes per bin)



1.1.3 AUXILIARY DATA FILESThe following files are used by PF-ASAR to create the ASAR products.

External Characterization DataThe ASAR instrument has an External Characterization Mode which is operated overflying a receiversetup for H or V polarization located in the ground. During the mode, the ASAR transmits a sequence ofpulses from each antenna row in turn. These pulses are received and digitized on the ground and the datarecorded for off-line analysis. Simultaneously during the mode the calibration loop in the instrument isused to couple transmit pulses which are then sampled within a calibration window in order to providecomparative values. The External Characterization Data file is provided as the output of the externalcharacterization analysis.

FILE_ID: ASA_XCH_AXTYPE: AuxiliaryUSE: Used for internal calibration processing correctionUPDATED: nominally every 6 monthsSIZE: MPH(1247 bytes) + SPH (378 bytes) + GADS (596 bytes)

External Calibration DataThe external calibration scaling factor is determined by ESA using three calibrated transponders, and thein-flight elevation pattern estimates are obtained using natural targets with known properties such as therainforest.

FILE_ID: ASA_XCA_AXTYPE: AuxiliaryUSE: Used during image calibrationUPDATED: nominally every 6 monthsSIZE: MPH(1247 bytes) + SPH (378 bytes) + GADS (6752 bytes)

Processor Configuration FileThis file contains static processing parameters used by the PF-ASAR which includes the threshold valuesused for setting PCD flags. This file is available in the inventory so a user may check what the processingconfiguration and threshold values were for the product of interest.

FILE_ID: ASA_CON_AXTYPE: AuxiliaryUSE: Used during image formationUPDATED: infrequently, only if static processing parameters change or PCDthresholds are updated.SIZE: MPH(1247 bytes) + SPH (378 bytes) + GADS (796 bytes)

Instrument Characterization FileThis file contains key parameters which characterize the instrument. This includes look up tables and otherparameters needed in the ground processing. It contains a subset of the data found in the InstrumentCharacterization database.

FILE_ID: ASA_INS_AXTYPE: AuxiliaryUSE: Used during image formationUPDATED: infrequently, only if instrument operating parameters changeSIZE: MPH(1247 bytes) + SPH (378 bytes) + GADS (160664 bytes)

1.2 Data set descriptionThe products included in the package are processed from different acquisitions taken during thecommissioning phase of ASAR instrument. They try to reflect all the innovative modes in which theinstrument can operate. Data has been acquired in all the modes, in different swaths and polarizationcombinations. The products have been processed with the latest version of the operational processorintegrated in the ENVISAT ground segment except for the ASAR Ocean Wave Spectra Level 2 productwhich has been generated using the prototyping software from NORUT following SRD IT650/1-01 version2.2.7 In this last case products are processed from Level 1b WVI products containing ASAR imagettesacquired in Wave Mode.


It is important to note that the ASAR instrument and products are in process of being calibrated andvalidated. Although the quality of the products included in the package is very close to the one in thespecifications, some products are affected by small quality anomalies.

The following list reflects the location of the images contained in the products:

ASA_IMS_1P: ASAR Image acquired over The Netherlands in the IS3 beam VVpolarization from orbit 2166.ASA_IMP_1P: ASAR Image acquired over The Netherlands in the IS3 beam VVpolarization from orbit 2166.ASA_IMG_1P: ASAR Image acquired over The Netherlands in the IS3 beamVV polarization from orbit 2166.ASA_IMM_1P and ASA_IM__BP : ASAR Image acquired over TheNetherlands in the IS3 beam VV polarization from orbit 2166.ASA_APS_1P: ASAR Image acquired over Germany in cross-polarization modeHH-HV from orbit 2452.ASA_APP_1P: ASAR Image acquired over Germany in cross-polarization modeHH-HV from orbit 2452.ASA_APG_1P: ASAR Image acquired over Germany in cross-polarization modeHH-HV from orbit 2452.ASA_APM_1P and ASA_AP__BP: ASAR Image acquired over Germany incross-polarization mode HH-HV from orbit 2452.ASA_WSM_1P and ASA_WS_BP: ASAR Image acquired over the eastern coastof Spain in VV polarization from orbit 2452.ASA_GMM_1P and ASA_GM__BP: ASAR Image acquired over the northerncoast of Canada in VV polarization from orbit 238.ASA_WVI_1P, ASA_WVS_1P and ASA_WVW_2P: Contain 25 waveimagettes over the eastern coast of South America in the IS2 beam from orbit902.

The auxiliary files used to process the level 0 data contained the pre-launchcharacterization data except for the ASA_XCA_AX file which already includes themost up to date antenna patterns measured in-orbit.

1.2.1 Limitations of the different Products

Due to the fact that these products were acquired during the Calibration and Validationphase of the ASAR instrument, where different test are being carried out, some qualityanomalies are affecting the products.

• APS Product size: APS products contain two complex images of 2+2 bytes / pixel.This ends up nominally with product sizes larger than 1 Gbyte for 15 seconds ofacquisition (normal scene size). In order to include an APS example in this release ofsample products in CD-ROM, only 8 seconds of data were processed.

• Scalloping: Due to the fact that the APS product is shorter than the nominal size, theDoppler estimate was not based on the data but on the orbit ephemeris. In this case


the value was not accurate enough causing scalloping (amplitude modulation) on theimage.

• Alternating Polarization defocusing: A slight defocusing of the AP images around theSampling Window Start Time changes can be detected. This effect is currently beingcorrected.

• Calibration: The calibration constant for the PF-ASAR processor has not beencalculated yet for all the ASAR modes and products. In the product annotations thecalibration constant is set to 1.0. The most accurate up to date antenna patterns havebeen used during the processing.

• Quality thresholds: Thresholds to fix the quality parameters in the product headershave not been already tuned to the expected nominal values for ASAR data. As sucha certain number of quality flags are set within the product although its quality isright.

• Global Monitoring Mode preliminary validation: This mode will be the last ASARmode to be validated during the commissioning phase. The example included in thepackage shows one of the earliest acquisitions where a very few updated parameterswhere available to processor. The product has been generated using nominal chirpand not normalization has been done using the ASAR internal calibration pulses. Inthis way the different ScanSAR beams can be distinguished in the image.

envisat post-launch...

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