> 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/thermal-data/satellite-technology.md).

# Satellite Technology

Get to know Hydrosat's on-orbit sensors.

## VanZyl Constellation

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VanZyl-1 (VZ-1) and VanZyl-2 (VZ-2) are Hydrosat's first two satellites. Launched in August 2024 (VZ-1) and June 2025 (VZ-2), the VanZyl satellites pave the way for our forthcoming constellation that will redefine space-based thermal infrared remote sensing by enabling daily continuous monitoring of any location on Earth. 

Both VZ-1 and VZ-2 host two imaging payloads: Hydrosat’s first-generation, proprietary longwave infrared imager (LIRI) along with its visible and near-infrared imager (VIRI). 
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<div align="center"><figure><img src="https://3702723385-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FBgOfOR7RYuK5Fm69JAWF%2Fuploads%2Fh958VKH3aUHBwReSbuzy%2FYAM-7-pose-1.png?alt=media&amp;token=2759cbec-2816-4b78-adf4-2c18be3d2bb2" alt="" width="188"><figcaption><p>Hydrosat's VanZyl-1 satellite.</p></figcaption></figure></div>
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### Spectral Bands

The LIRI sensor acquires thermal infrared imagery at wavelengths between 10.6 and 12.51 micrometers, similar to Landsat TIRS; VIRI has a total of 7 spectral bands ranging from 458 to 900 nanometers.

<div data-with-frame="true"><figure><img src="https://3702723385-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FBgOfOR7RYuK5Fm69JAWF%2Fuploads%2FcRyNetLFCHT3nPntdeVU%2Fbands.png?alt=media&amp;token=25faf14d-0643-4f81-a688-c5fc1223dce9" alt="" width="563"><figcaption><p>Visual representation of the spectral bands for Hydrosat's VanZyl satellites.</p></figcaption></figure></div>

<table data-search="false"><thead><tr><th width="85.16796875">Sensor<select><option value="9gB76nWqO234" label="VIRI" color="blue"></option><option value="o2z3V3dfn5NN" label="LIRI" color="blue"></option></select></th><th width="318.92578125">Band Name</th><th width="215.796875">Wavelength</th><th data-type="number">GSD (m)</th></tr></thead><tbody><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Blue</td><td>458-523 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Green</td><td>543-578 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Red</td><td>650-680 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Red Edge 1</td><td>698-713 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Red Edge 2</td><td>733-748 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Red Edge 3</td><td>773-793 nm</td><td>29.9</td></tr><tr><td><span data-option="9gB76nWqO234">VIRI</span></td><td>Near-Infrared (NIR)</td><td>785-900 nm</td><td>29.9</td></tr><tr><td><span data-option="o2z3V3dfn5NN">LIRI</span></td><td>Longwave Infrared 1 (LWIR 1)</td><td>10.6-11.19 μm</td><td>68.8</td></tr><tr><td><span data-option="o2z3V3dfn5NN">LIRI</span></td><td>Longwave Infrared 2 (LWIR 2)</td><td>11.5-12.51 μm</td><td>68.8</td></tr></tbody></table>

### Other Specifications

VZ-1 and VZ-2 operate in low Earth orbit, collecting imagery at approximately the same local time each orbit. VZ-1's overpass time aligns approximately with that of Landsat, while VZ-2's is similar to VIIRS.

<table><thead><tr><th width="168.6796875">Orbit Type</th><th>Orbit Altitude</th><th>LTDN</th><th>LTAN</th><th>Swath Width</th></tr></thead><tbody><tr><td>Sun-synchronous</td><td>510 km</td><td>10:30 AM (VZ-1)<br>1:00 PM (VZ-2)</td><td>10:30 PM (VZ-1)<br>1:00 AM (VZ-2)</td><td>70.5 km</td></tr></tbody></table>