# Product Details

## 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/m<sup>2</sup>/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.

| Item                          | Details                                                                                                                                     |
|-------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------|
| **L1 Product Granule Size**   | L1A VIRI: 122 km x 70 km \n L1A LIRI: 70 km x 70 km \n L1B: Combined 70 km x 70 km                                                          |
| **L1 Pixel Size**             | L1A VIRI: 29.9 m \n L1A LIRI: 68.8 m \n L1B: 30 m                                                                                       |
| **Resampling Method**         | Bilinear (L1B only)                                                                                                                       |
| **Bit Depth**                 | 16-bit                                                                                                                                     |
| **Map Projection**            | L1A VIRI &#x26; LIRI: EPSG 4326 (RPCs included in metadata) \n L1B: Universal Transverse Mercator (UTM)                                 |
| **No Data Value**             | 0                                                                                                                                           |
| **Scaling Factor**            | L1A VIRI: 0.01 \n L1A LIRI: 0.001 \n L1B VIRI: 0.0001 \n 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.

<details>

<summary>vz-viri-l1a</summary>

| 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        | null                   | COG       |
| PREVIEW         | Full-resolution RGB preview image | null                   | COG       |
| THUMBNAIL       | Low-resolution RGB thumbnail      | null                   | PNG       |
| METADATA        | Ancillary metadata file           | null                   | JSON      |

</details>

<details>

<summary>vz-liri-l1a</summary>

| 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        | null                   | COG       |
| PREVIEW_LWIR    | Full-resolution LWIR preview image | null                   | COG       |
| THUMBNAIL       | Low-resolution thumbnail           | null                   | PNG       |
| METADATA        | Ancillary metadata file            | null                   | JSON      |

</details>

<details>

<summary>vz-l1b</summary>

| 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, shadow,     | COG       |
|                  | and snow or ice                   |           |
| 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      |

</details>

### 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 K<sub>1</sub> and K<sub>2</sub> 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 K<sub>1</sub> and K<sub>2</sub> 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).

| Item                          | Details                                 |
|-------------------------------|-----------------------------------------|
| **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 \n SR, emissivity: 0.0001 |

### Level-2 Assets

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

<details>

<summary>vz-l2</summary>

| 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, shadow,    | COG       |
|                  | and snow or ice                   |           |
| 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      |

</details>