Umbra

Long name UMBRA
Short name UMBR
Sensor type Synthetic-aperture radar (SAR)
Platform UMBRA
Frequency 9.8 GHz (nominal)
Band (wavelength) X-band wavelength
Polarization HH, VV
Key file name (use to open data set) *.json
Supported file name extensions *.json, *.tif, *.nitf
Data distributor https://umbra.space/
Sections

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

Data product name and description

Umbra is developing synthetic aperture radar (SAR) microsatellites to deliver sub-meter resolution imagery as a service. Umbra's satellites produce X-band synthetic aperture radar data which can be dissected into two constituent properties: amplitude and phase and can be acquired in either right or left looking configurations. The Umbra SAR sensor are as described in the following tables.
        

Note: The information provided herein is based on the Umbra product documentation cited under References.
Mode Swath width (km) Resolution (range x azimuth, m) Polarization Description/notes

Spotlight

Single Pol

                

4km x 4km

0.25m – 1.0m ground plane IPR
                

Single Pol
HH or VV
                

System Design Life: 5 years
Orbit (IDs below): 517 ± 30 km
Inclination: 97.4°
Repeat Ground Track: ~7 day
Grazing Angle Range: 20° - 70°
Squint Angle Range: 45° - 135°, 225° - 315°
Antenna Type: Center fed parabolic mesh reflector
Center Frequency: 9.8 GHz (nominal)
PRF: less than 10.0 kHz
Chirp Bandwidth: Up to 1200 MHz
Polarization: HH or VV selectable
IPR Width: less than 10% of theoretical
IPR Sidelobes: -25dB
Pulse Dropouts: less than 1%
ADC Values within range: 97.5% (typical)
Absolute Geolocation Accuracy: less than 15 meters (3-sigma)
                

The data products Umbra delivers are listed below. These are published standards adopted by National Geospatial-Intelligence Agency (NGA) of the U.S. government.

Product Processing level Description

CPHD -
Compensated Phase History Data
                

L1

For advanced users with radar science expertise and strong opinions about image formation techniques, CPHD offers a blank slate to start from.
This processing level is not supported currently.
              

SICD -
Sensor Independent Complex Data
                

L1 ~ L1A(SLC)

Phase information is determined by the distance from the satellite to the reflecting surface.
A SICD product contains a single SAR complex image and a set of metadata that describes how the data was collected, how the data was processed, and the parameters needed for exploitation.
SICD data is constituted of two complementary parts inside of a NITF container:A block of complex image pixel data containing the phase history of the SAR data and A metadata description of the data adhering to a strict XML structure.
                

SIDD -
Sensor Independent Derive Data
                

1C (GEC)

SIDD Design provides metadata specifications for common tasks which are designed to support basic exploitation, geographic measurements, exploitation, and proper visual display.
This processing level is not supported currently.
                

GeoTIFF -
Amplitude Data
                

1C (GEC)

The characteristic black-and-white images commonly associated with SAR are amplitude products. Amplitude data can be used for mapping features on the ground, measuring surface roughness, or even basic change detection.
                

Distribution disk files

Umbra SICD data is distributed in NITF format and GEC data distributed in GeoTIFF format.

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.

File name Format Required Contents/details
*.json JavaScript Object Notation Yes Key file name. Main product annotation file.
*.nitf National Imagery Transmission Format Yes For SICD data, includes image data and xml metadata
*.tif GeoTIFF Yes For GEC data

Returned data for supported format

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

In the following table, the data structure after it is imported is described (supported processing levels only).

Data product Data returned Details

SICD
Spotlight - single pol
                  

1 x [C32R] raster channel (calibrated to sigma nought)
1 x [TEX] main product annotation
1 x [BIN] rational function model from state vectors
1 x [ORB] Orbit segment
                

Data can be converted to beta, or gamma nought.

GEC
Spotlight - single pol
                

1 x [8U] raster channel
1 x [TEX] main product annotation
                

 

References

[1] 20230515 UMBRA Product Guide - V1.pdf

[2] NGA.STND.0024-1_1.2.1_SICD_DID_2018_12_13.pdf

[3] NGA.STND.0024-2_1.2.1_SICD_NITF_FFD_2018_12_13.pdf

[4] NGA.STND.0024-3_1.2.1_2018-12-13.pdf

[5] Geotiff specification http://www.alternatiff.com/resources/TIFF6.pdf

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