Product Details

Learn more about the different data products Hydrosat provides.

Level-1 Imagery

The Level-1A data product is the least processed of the available imagery. It includes processing applied onboard the instrument, such as time delay integration and non-uniformity corrections, as well as co-registration of sensor bands and georegistration. The full swath data is provided to users in image space with no resampling. Level-1A pixel values represent top-of-atmosphere (TOA) radiance [W/m²/sr/μm].

The Level-1B product includes converting the radiance values to TOA reflectance (VIRI) or brightness temperature (LIRI), clipping the VIRI data to the extent of the LIRI swath, generation of a cloud mask, and orthorectification.

L1 Product Granule Size	L1A VIRI: 122 km x 70 km L1A LIRI: 70 km x 70 km L1B: Combined 70 km x 70 km
L1 Pixel Size	L1A VIRI: 29.9 m L1A LIRI: 68.8 m L1B: 30 m
Resampling Method	Bilinear (L1B only)
Bit Depth	16-bit
Map Projection	L1A VIRI & LIRI: EPSG 4326 (RPCs included in metadata) L1B: Universal Transverse Mercator (UTM)
No Data Value	0
Scaling Factor	L1A VIRI: 0.01 L1A LIRI: 0.001 L1B VIRI: 0.0001 L1B LIRI: 0.01
Conversion Factors	Coefficients for conversion between radiance and TOA reflectance or BT provided in companion metadata file

Level-1 Assets

Each STAC item includes several assets representing the individual data and metadata files associated with the scene. Items from different collections contain a different set of assets, as defined below.

vz-viri-l1a

Asset	Description	Center Wavelength (nm)	File Type
BLUE	Blue radiance	490.5	COG
GREEN	Green radiance	560.5	COG
RED	Red radiance	665	COG
REDEDGE1	Red edge 1 radiance	705.5	COG
REDEDGE2	Red edge 2 radiance	740.5	COG
REDEDGE3	Red edge 3 radiance	783	COG
NIR	NIR radiance	842.5	COG
QUALITY_ASSURANCE	Radiometric saturation mask		COG
PREVIEW	Full-resolution RGB preview image		COG
THUMBNAIL	Low-resolution RGB thumbnail		PNG
METADATA	Ancillary metadata file		JSON

vz-liri-l1a

Asset	Description	Center Wavelength (µm)	File Type
LWIR1	LWIR 1 radiance	10.895	COG
LWIR2	LWIR 2 radiance	12.005	COG
QUALITY_ASSURANCE	Radiometric saturation mask		COG
PREVIEW_LWIR	Full-resolution LWIR preview image		COG
THUMBNAIL	Low-resolution thumbnail		PNG
METADATA	Ancillary metadata file		JSON

vz-l1b

Asset	Description	File Type
BLUE	Blue TOA reflectance	COG
GREEN	Green TOA reflectance	COG
NIR	NIR TOA reflectance	COG
RED	Red TOA reflectance	COG
REDEDGE1	Red edge 1 TOA reflectance	COG
REDEDGE2	Red edge 2 TOA reflectance	COG
REDEDGE3	Red edge 3 TOA reflectance	COG
LWIR1	LWIR 1 brightness temperature	COG
LWIR2	LWIR 2 brightness temperature	COG
QUALITY_ASSURANCE	Radiometric saturation mask	COG
CLOUD_MASK	Mask indicating cloud, cloud shadow, and snow or ice	COG
PREVIEW	Full-resolution RGB preview image	COG
PREVIEW_LWIR	Full-resolution LWIR preview image	COG
THUMBNAIL	Low-resolution RGB thumbnail	PNG
METADATA	Ancillary metadata file	JSON

Conversions

Level-1A VIRI

L1A VIRI TOA radiance values can be converted to TOA reflectance by applying the per-band LEVEL1_REFLECTANCE_SCALING coefficient in the companion L1A metadata (MTA) file.

Level-1A LIRI

L1A LIRI TOA radiance values can be converted to brightness temperature using the following equation:

BT = K2 / ln(K1 / L + 1)

where K₁ and K₂ are per-band LEVEL1_THERMAL_CONSTANTS from the L1A MTA file, and L represents scaled radiance.

Level-1B VIRI

L1B VIRI reflectance data can be converted back to TOA radiance by applying the per-band LEVEL1_RADIANCE_SCALING coefficient in the companion L1B MTA file.

Level-1B LIRI

L1B LIRI BT values can be converted back to TOA radiance using the following equation:

L = K1 / (e(K2 / BT) - 1)

where K₁ and K₂ are per-band LEVEL1_BT_TO_RADIANCE_CONSTANTS from the L1B MTA file.

Level-2 Imagery

The Level-2 product includes radiometric terrain corrections and conversion to surface reflectance (SR) and land surface temperature (LST).

L2 Product Granule Size	70 km x 70 km
L2 Pixel Size	30 m
Map Projection	UTM
Bit Depth	16-bit
No Data Value	0
Scaling Factor	LST, LST uncertainty: 0.01 SR, emissivity: 0.0001

Level-2 Assets

Level-2 assets include per-band SR and LST COGs (and more).

vz-l2

Asset	Description	File Type
BLUE_SR	Blue band surface reflectance	COG
GREEN_SR	Green band surface reflectance	COG
NIR_SR	NIR band surface reflectance	COG
RED_SR	Red band surface reflectance	COG
REDEDGE1_SR	Red edge 1 band surface reflectance	COG
REDEDGE2_SR	Red edge 2 band surface reflectance	COG
REDEDGE3_SR	Red edge 3 band surface reflectance	COG
LWIR1_EMIS	LWIR 1 band emissivity	COG
LWIR2_EMIS	LWIR 2 band emissivity	COG
LST	Land surface temperature	COG
LST_UNCERTAINTY	Land surface temperature uncertainty	COG
QUALITY_ASSURANCE	Radiometric saturation mask	COG
CLOUD_MASK	Mask indicating cloud, cloud shadow, and snow or ice	COG
PREVIEW	Full-resolution RGB preview image	COG
PREVIEW_LST	Full-resolution LST preview image	COG
THUMBNAIL	Low-resolution RGB thumbnail	PNG
THUMBNAIL_LST	Low-resolution LST thumbnail	PNG
METADATA	Ancillary metadata file	JSON