## 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      |