RISAT-1

Long name Radar Imaging Satellite 1 (RISAT-1)
Short name RI1
Sensor type Synthetic-aperture radar (SAR)
Platform RISAT-1
Frequency 5.35 GHz
Band (wavelength) C (5.3 cm)
Polarization HH, HV, VH, VV, RH, RV (Fully polarimetric and compact polarimetric)
Key file name (use to open data set) BAND_META.txt
Supported file extensions *.txt, *.tif, *.dat
Data distributor Indian Space Research Organization (ISRO)
Sections

Data product name and description
Distribution disk files
Returned data for supported format
References

Data product name and description

RISAT-1 has five acquisition modes. Each is described in the proceeding tables.

Note: The information provided herein is based on the RISAT-1 reference documentation cited under References.
Mode Swath width (km) Resolution (range x azimuth, m)* Polarization Description/notes
High Resolution Spotlight [HRS] 10 0.67 x 1.0

Single (HH or HV or VV or VH)
Dual (HH+HV   or  VV+VH)
Circular (RV + RH)

In the sliding-spotlight mode, the antenna beam is oriented continuously to illuminate a particular 10-by-100 kilometer sliding spot on the ground, which can be imaged at a resolution of 1 meter.
Fine Resolution Stripmap [FRS-1] 25 2.2 x 3.3

Single (HH or HV or VV or VH)
Dual (HH+HV   or  VV+VH)
Circular (RV + RH)

Based on conventional mode of SAR Stripmap imaging.
Fine Resolution Alternate Polarization Stripmap [FRS-2] 25

4.0 x 3.0 (circular)
4.7 x 10.0 (quad)

Circular (RV + RH)
Quad (HH+HV+VH+VV)

This mode is a hybrid of Stripmap and ScanSAR.
Medium Resolution ScanSAR [MRS] 115 8.8 x 24.0

Circular (RV + RH)
Quad (HH+HV+VH+VV)

Six-beam ScanSAR mode.
Coarse Resolution ScanSAR [CRS] 220 8.8 x 48.0

Single (HH or HV or VV or VH)
Dual (HH+HV or VV+VH)
Circular (RV + RH)

Twelve-beam ScanSAR mode.

* Resolution is always single-look complex (SLC) unless noted otherwise.

Processing level Acquisition mode Description/notes
Raw Not supported N/A

1
Single-look complex (SLC)

[FRS-1]
[FRS-2]
[MRS]

CEOS format.
Geometry: Slant range

1
Ground-range detected (GRD)

[FRS-1]
[MRS]
[CRS]

CEOS format.
Geometry: Ground range

2
Terrain georeferenced

[FRS-1]
[MRS]
[CRS]

CEOS and GeoTIff formats.
Geometry: Ground range

2
Enhanced terrain georeferenced

[FRS-1]
[MRS]
[CRS]

CEOS and GeoTIff formats.
Geometry: Ground range

Distribution disk files

RISAT-1 data products are distributed in CEOS and GeoTIFF formats, both of which are supported in CATALYST Professional.

Warning: Data sets for this sensor are organized in a specific folder structure on disk. GDB uses this structure and the file names to identify the data product type. Do not alter the folder structure or any file names prior to data ingestion to ensure the image data and auxiliary information are imported correctly.
Table 1. CEOS
File name Format Required Contents/details
BAND_META.txt ASCII Yes Key file name. Contains metadata that applies to the data set.
*_grid.txt ASCII Yes Table of ground control points (GCP), slant-range distance, and incidence angles. One grid file per polarization.
dat_01.001 Product-specific binary Yes SAR image data. One file per polarization.
Table 2. GeoTIFF
File name Format Required Contents/details
BAND_META.txt ASCII Yes Key file name. Contains metadata that applies to the data set.
*_grid.txt ASCII Yes Table of ground control points (GCP), slant-range distance, and incidence angles. One grid file per polarization.
*.tif GeoTIFF Yes Image data. One GeoTIFF file per polarization.

Returned data for supported format

RISAT-1 data can be opened directly in its raw vendor format or imported into a PCIDSK (*.pix) file using the key file (BAND_META.txt). For optimal processing, use the PCIDSK format.

In the following table, the data structure after it is imported into a PCIDSK file is described.

Data product Data returned Details

Level 1
Single-look complex (SLC), single polarization
[FRS-1]

1 x [C32R] Raster channel

1x [GCP] GCPs from grid file
1 x [ORB] Orbit segment
1 x [ARR] Incidence angle array

Data calibrated in sigma nought.

Level 1
Single-look complex (SLC), dual and circular polarization
[FRS-1]
[FRS-2]

2 x [C32R] Raster channels

1x [GCP] GCPs from grid file
1 x [ORB] Orbit segment
1 x [ARR] Incidence angle array

Data calibrated in sigma nought.

Level 1
Single-look complex (SLC), quad polarization
[FRS-2]

4 x [C32R] Raster channels

1x [GCP] GCPs from grid file
1 x [ORB] Orbit segment
1 x [ARR] Incidence angle array

Data calibrated in sigma nought.

Level 1
Ground-range detected (GRD), single polarization
[FRS-1]
[MRS]
[CRS]

1 x [32R] Raster channels

1x [GCP] GCPs from grid file
1 x [ORB] Orbit segment
1 x [ARR] Incidence angle array

Data calibrated in sigma nought.

Level 1
Ground-range detected (GRD), dual and circular polarization
[FRS-1]
[MRS]
[CRS]

1 x [32R] Raster channels

1x [GCP] GCPs from grid file
1 x [ORB] Orbit segment
1 x [ARR] Incidence angle array

Data calibrated in sigma nought.

Level 2
Terrain georeferenced

1 x [32R] Raster channels

1x [GCP] GCPs from grid file

Data calibrated in sigma nought.

Level 2A
Enhanced terrain georeferenced, single polarization
[FRS-1]
[MRS]
[CRS]

1 x [32R] Raster channels

1x [GCP] GCPs from grid file

Data calibrated in sigma nought.

Level 2
Terrain georeferenced, dual and circular polarization

2 x [32R] Raster channels

1x [GCP] GCPs from grid file

Data calibrated in sigma nought.

Level 2A
Enhanced terrain georeferenced, dual and circular polarization

2 x [32R] Raster channels

1x [GCP] GCPs from grid file

Data calibrated in sigma nought.

References

RISAT-1 Data Products Format V1.4 (September 2015). SAC/ISRO. 66 pages.

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