ASAR Documentation



Table of Contents


ISRO ASAR Documents

ISRO ASAR Product Documentation
ISRO ASAR Product Description V1.2.B
ISRO ASAR HDF Data Format Document V1

ASAR Naming Conventions


File Naming Convention

The ASAR file names hosted by JPL conform to the following naming convention:

ASAR_Mode_Pol_SiteID_LINExx_RUNxx_DOA_Level_FileType_Version.Ext
ASAR_L_JOINT_FP_ID1702N_LINE03_RUN02_051219_LEVEL1_RSLC_V1.2.B.h5 (example)

Field Name Field Description
ASAR Instrument/Campaign
Mode Imaging Mode: S, L, L_S_JOINT
Pol Polarization: CP, FP, QQP, HH_HV, VV_VH
SiteID Application Site ID
LINExx Line Number
RUNxx Run Number
DOA Date of Acquisition in DDMMYY format
Level Product level: LEVEL1 products are in slant range, LEVEL2 products are geocoded into ground range
FileType Type of type: RSLC (NISAR HDF5 format), INC_MAP, GRID, BAND_META, PRODUCT (xml). When the file type is the backscatter image, this field consists of two characters indicating the processed polarization (HH, HV, VH, VV).
Version Product version number. Tied to changes in the ISRO processsor version. See Version section below for more information.
Ext File extension

Mode_Pol_SiteID_LINExx_RUNxx_DOA is the ISRO Product_ID from the ASAR Product Documentation.

 

Product and Archive Webpage Naming Convention

The ASAR product listings on the Data Search and Data Archive pages conform to the following naming convention:

Sitename_LineID_FlightID_DT_Date
Rosamd_1702N_A1902_003_191205 (example)

Field Name Characters Field Description
Sitename 6 Abbreviated name for the target site
LineID 5 ID that describes a unique track, where the first 3 digit aircraft heading is followed by a 2 character incremental counter.
FlightID 5 UAVSAR Flight ID describing the unique flight the line is flown in, where the first character is A indicating ASAR, the first two digits are the last two digits of the year, and the next two digits are the flight number counted sequentially from the first flight of the year.
DT 3 Data take counter indicating which acquisition during the flight this data was from, counted sequentially from the beginning of the flight and starting from zero.
Date 6 Acquisition date in YYMMDD format indicating the year, month, and day the data was collected in UTC time.

 

Versions


Version ISRO Processor Version
 Notes
1.3.B 1.3_14092021 Version 1.3.B Updates
1.3 1.3_14092021 Version 1.3 Updates
1.2.B 1.2_19022021 Version 1.2.B Updates
1.2.A 1.2 Outdated version
1.1 1.1 Outdated version
1.0 1.0 Early test data, not meant for release.

 

Version 1.3.B Updates

  1. Corrects timing information in Phase 2 & 3 RSLC data that lead to large along-track geolocation errors
  2. Fixes non-uniform spacing in the orbit time and invalid frequency list in the RSLCs

 

Version 1.3 Updates

  1. Usage of Copernicus 30m DEM in processing instead of operational SRTM-90
  2. Common Doppler filtering after mosaicking of blocks
  3. Improvement in geolocation accuracy (using hardware delay estimates)
  4. Usage of Noise is improved. Negative sigma0 % has been reduced.
  5. Usage of attitude to refine Doppler centroid estimates. It results in consistent resolution across full image. Additionally, it solves unfilled data problems in the images.
  6. Refined antenna pattern pointing using CR RCS in L-Band and S-Band. This results in good improvement in radiometry.
  7. Processing failure cases are handled

 

Version 1.2.B Updates


Processing updates include radiometric calibration, GeoTIFF format, and HDF5 format updates described in sections 2-4 of ISRO ASAR Product Description V1.2.B.

 

Frequently Asked Questions


  1. What are Phase 1 and Phase 2/3 ASAR data?

    Phase 1 ASAR data are collected in December 2019. Phase 2/3 ASAR data are collected in June and July 2021.

  2. What are the differences between v1.3 and v1.3.B ASAR products? What data sets are impacted?

    v1.3.B ASAR products are modifications of v1.3 products with the following issues corrected:
    • timing information issues that lead to large along-track geolocation errors
    • non-uniform spacing in the orbit time field of RSLCs
    • invalid frequency in the RSLCs
    Only Phase 2/3 data had the timing information/along-track geolocation issue and have v1.3.B products.

  3. Can I use Phase 1 v1.3 products to conduct polarimetric analysis and compare to Phase 2/3 v1.3.B products?

    Yes, Phase 1 v1.3 data did not contain timing information/along-track geolocation issues, and can be compared to Phase 2/3 v1.3.B products directly.

  4. Can I use ASAR data for repeat-pass InSAR analysis?

    Unfortunately, ASAR is not meant for repeat-pass InSAR because the antennas are not electronically steerable and the beam width is small, so repeat observations may not have sufficent beam overlaps (i.e. coherence) for InSAR

  5. Which data takes do not have S-band data?