> For the complete documentation index, see [llms.txt](https://satdocs.hydrosat.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://satdocs.hydrosat.com/product-details.md).

# 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.

<table data-header-hidden><thead><tr><th width="221">Item</th><th valign="top">Details</th></tr></thead><tbody><tr><td><strong>L1 Product Granule Size</strong></td><td valign="top"><p>L1A VIRI: 122 km x 70 km</p><p>L1A LIRI: 70 km x 70 km</p><p>L1B: Combined 70 km x 70 km</p></td></tr><tr><td><strong>L1 Pixel Size</strong></td><td valign="top"><p>L1A VIRI: 29.9 m</p><p>L1A LIRI: 68.8 m</p><p>L1B: 30 m</p></td></tr><tr><td><strong>Resampling Method</strong></td><td valign="top">Bilinear (L1B only)</td></tr><tr><td><strong>Bit Depth</strong></td><td valign="top">16-bit</td></tr><tr><td><strong>Map Projection</strong></td><td valign="top"><p>L1A VIRI &#x26; LIRI: EPSG 4326 (RPCs included in metadata)</p><p>L1B: Universal Transverse Mercator (UTM)</p></td></tr><tr><td><strong>No Data Value</strong></td><td valign="top">0</td></tr><tr><td><strong>Scaling Factor</strong></td><td valign="top">L1A VIRI: 0.01<br>L1A LIRI: 0.001<br>L1B VIRI: 0.0001<br>L1B LIRI: 0.01</td></tr><tr><td><strong>Conversion Factors</strong></td><td valign="top">Coefficients for conversion between radiance and TOA reflectance or BT provided in companion metadata file</td></tr></tbody></table>

### 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>

<table><thead><tr><th width="214">Asset</th><th width="392">Description</th><th data-type="number">Center Wavelength (nm)</th><th>File Type</th></tr></thead><tbody><tr><td>BLUE</td><td>Blue radiance</td><td>490.5</td><td>COG</td></tr><tr><td>GREEN</td><td>Green radiance</td><td>560.5</td><td>COG</td></tr><tr><td>RED</td><td>Red radiance</td><td>665</td><td>COG</td></tr><tr><td>REDEDGE1</td><td>Red edge 1 radiance</td><td>705.5</td><td>COG</td></tr><tr><td>REDEDGE2</td><td>Red edge 2 radiance</td><td>740.5</td><td>COG</td></tr><tr><td>REDEDGE3</td><td>Red edge 3 radiance</td><td>783</td><td>COG</td></tr><tr><td>NIR</td><td>NIR radiance</td><td>842.5</td><td>COG</td></tr><tr><td>QUALITY_ASSURANCE</td><td>Radiometric saturation mask</td><td>null</td><td>COG</td></tr><tr><td>PREVIEW</td><td>Full-resolution RGB preview image</td><td>null</td><td>COG</td></tr><tr><td>THUMBNAIL</td><td>Low-resolution RGB thumbnail </td><td>null</td><td>PNG</td></tr><tr><td>METADATA</td><td>Ancillary metadata file</td><td>null</td><td>JSON</td></tr></tbody></table>

</details>

<details>

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

<table><thead><tr><th width="214">Asset</th><th width="392">Description</th><th data-type="number">Center Wavelength (µm)</th><th>File Type</th></tr></thead><tbody><tr><td>LWIR1</td><td>LWIR 1 radiance</td><td>10.895</td><td>COG</td></tr><tr><td>LWIR2</td><td>LWIR 2 radiance</td><td>12.005</td><td>COG</td></tr><tr><td>QUALITY_ASSURANCE</td><td>Radiometric saturation mask</td><td>null</td><td>COG</td></tr><tr><td>PREVIEW_LWIR</td><td>Full-resolution LWIR preview image</td><td>null</td><td>COG</td></tr><tr><td>THUMBNAIL</td><td>Low-resolution thumbnail </td><td>null</td><td>PNG</td></tr><tr><td>METADATA</td><td>Ancillary metadata file</td><td>null</td><td>JSON</td></tr></tbody></table>

</details>

<details>

<summary>vz-l1b</summary>

<table><thead><tr><th width="214">Asset</th><th width="392">Description</th><th>File Type</th></tr></thead><tbody><tr><td>BLUE</td><td>Blue TOA reflectance</td><td>COG</td></tr><tr><td>GREEN</td><td>Green TOA reflectance</td><td>COG</td></tr><tr><td>NIR</td><td>NIR TOA reflectance</td><td>COG</td></tr><tr><td>RED</td><td>Red TOA reflectance</td><td>COG</td></tr><tr><td>REDEDGE1</td><td>Red edge 1 TOA reflectance</td><td>COG</td></tr><tr><td>REDEDGE2</td><td>Red edge 2 TOA reflectance</td><td>COG</td></tr><tr><td>REDEDGE3</td><td>Red edge 3 TOA reflectance</td><td>COG</td></tr><tr><td>LWIR1</td><td>LWIR 1 brightness temperature</td><td>COG</td></tr><tr><td>LWIR2</td><td>LWIR 2 brightness temperature</td><td>COG</td></tr><tr><td>QUALITY_ASSURANCE</td><td>Radiometric saturation mask</td><td>COG</td></tr><tr><td>CLOUD_MASK</td><td>Mask indicating cloud, cloud shadow, and snow or ice</td><td>COG</td></tr><tr><td>PREVIEW</td><td>Full-resolution RGB preview image</td><td>COG</td></tr><tr><td>PREVIEW_LWIR</td><td>Full-resolution LWIR preview image</td><td>COG</td></tr><tr><td>THUMBNAIL</td><td>Low-resolution RGB thumbnail </td><td>PNG</td></tr><tr><td>METADATA</td><td>Ancillary metadata file</td><td>JSON</td></tr></tbody></table>

</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).

<table data-header-hidden><thead><tr><th width="221">Item</th><th valign="top">Details</th></tr></thead><tbody><tr><td><strong>L2 Product Granule Size</strong></td><td valign="top">70 km x 70 km</td></tr><tr><td><strong>L2 Pixel Size</strong></td><td valign="top">30 m</td></tr><tr><td><strong>Map Projection</strong></td><td valign="top">UTM</td></tr><tr><td><strong>Bit Depth</strong></td><td valign="top">16-bit</td></tr><tr><td><strong>No Data Value</strong></td><td valign="top">0</td></tr><tr><td><strong>Scaling Factor</strong></td><td valign="top"><p>LST, LST uncertainty: 0.01</p><p>SR, emissivity: 0.0001</p></td></tr></tbody></table>

### Level-2 Assets

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

<details>

<summary>vz-l2</summary>

<table><thead><tr><th width="214">Asset</th><th width="392">Description</th><th>File Type</th></tr></thead><tbody><tr><td>BLUE_SR</td><td>Blue band surface reflectance</td><td>COG</td></tr><tr><td>GREEN_SR</td><td>Green band surface reflectance</td><td>COG</td></tr><tr><td>NIR_SR</td><td>NIR band surface reflectance</td><td>COG</td></tr><tr><td>RED_SR</td><td>Red band surface reflectance</td><td>COG</td></tr><tr><td>REDEDGE1_SR</td><td>Red edge 1 band surface reflectance</td><td>COG</td></tr><tr><td>REDEDGE2_SR</td><td>Red edge 2 band surface reflectance</td><td>COG</td></tr><tr><td>REDEDGE3_SR</td><td>Red edge 3 band surface reflectance</td><td>COG</td></tr><tr><td>LWIR1_EMIS</td><td>LWIR 1 band emissivity</td><td>COG</td></tr><tr><td>LWIR2_EMIS</td><td>LWIR 2 band emissivity</td><td>COG</td></tr><tr><td>LST</td><td>Land surface temperature</td><td>COG</td></tr><tr><td>LST_UNCERTAINTY</td><td>Land surface temperature uncertainty</td><td>COG</td></tr><tr><td>QUALITY_ASSURANCE</td><td>Radiometric saturation mask</td><td>COG</td></tr><tr><td>CLOUD_MASK</td><td>Mask indicating cloud, cloud shadow, and snow or ice</td><td>COG</td></tr><tr><td>PREVIEW</td><td>Full-resolution RGB preview image</td><td>COG</td></tr><tr><td>PREVIEW_LST</td><td>Full-resolution LST preview image</td><td>COG</td></tr><tr><td>THUMBNAIL</td><td>Low-resolution RGB thumbnail </td><td>PNG</td></tr><tr><td>THUMBNAIL_LST</td><td>Low-resolution LST thumbnail</td><td>PNG</td></tr><tr><td>METADATA</td><td>Ancillary metadata file</td><td>JSON</td></tr></tbody></table>

</details>