# 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>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://satdocs.hydrosat.com/product-details.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.