5.6. WorldView-1

WorldView-1, was launched on September 18, 2007 by DigitalGlobe, providing the panchromatic images at 0.5 m resolution. It has an average revisit time of 1.7 days, and is capable of collecting in-track stereo. Operating at an altitude of 496 km, WorldView-1 can cover up to 750,000 km2 per day.

WorldView-1 is a satellite launched specifically for high-resolution imaging of the Earth's surface. Its panchromatic images have a resolution of 0.5 meters, which means it can capture fine details from the Earth. For comparison, a standard football field is about 100 meters long, so at a distance, the satellite can discern objects as small as 0.5 meters. It operates around 496 kilometers above the Earth, and due to its advanced technology, it can capture images of a vast area of 750,000 square kilometers each day. Its ability to revisit the same area every 1.7 days ensures that it can monitor changes effectively.

Imagine you are a photographer who can take very detailed photos of a city every few days. If a new building goes up or a park changes shape, you could capture these changes quickly and accurately, much like what WorldView-1 does as it orbits the Earth.

WorldView-2 was successfully launched on October 8, 2009, collecting up to 975,000 km2 of imagery per day. WorldView-2 was the first very high resolution satellite to offer 8-band multispectral imagery with sub-metre resolution, along with increased agility, accuracy and stereo capability.

WorldView-2 improved upon its predecessor by collecting images with 8 different spectral bands. This means it can capture data across multiple wavelengths of light, allowing for more detailed analysis of the Earth's surface. By having sub-meter resolution, it offers even finer details than WorldView-1, making it easier to distinguish between types of land use, monitor environmental changes, and assess damage after disasters. Its agility and accuracy further enhance its ability to respond quickly to specific imaging requests.

Consider this like using a camera with different lens filters to see the world in various colors and details. Just as these filters reveal different aspects of a scene—like seeing a sunset or colorful wildlife—WorldView-2's multiple bands provide a comprehensive view, helping researchers see everything from vegetation types to urban development.

WorldView-3 was launched on August 13, 2014, in a Sun-synchronous orbit, at an altitude of 617 km, with orbital period of 97 minutes. It provides 31 cm resolution in panchromatic, 1.24 m resolution in multispectral, 3.7 m resolution in SWIR, and 30 m resolution in CAVIS (Clouds, Aerosols, Vapors, Ice, and Snow). The CAVIS monitors the atmosphere and provides correction data to improve haze, soot, or dust.

WorldView-3 further advanced satellite imaging technology by capturing images at 31 cm resolution, which allows it to distinguish even smaller details on the ground. The satellite operates at a higher altitude compared to its predecessors but still offers incredibly precise imagery across different wavelength bands. The SWIR and CAVIS bands help in identifying elements like water vapor and atmospheric conditions, which are critical for environmental monitoring.

Think of this as being able to zoom in on a photograph taken from a distance. Not only can you see the broad features, but you can also discern the different materials in treetops versus rooftops. It’s like being able to read a street name from a satellite as easily as looking at a sign in person.

WorldView-4 (formerly GeoEye-2) was launched on November 11, 2016 in a Sun-synchronous orbit, at an altitude of 617 km, with 97 minutes’ orbital period. It has an effective revisit time capability of ≤ 3 days. The satellite provides 31 cm resolution in panchromatic at nadir, 0.34 m at 20º off-nadir, 1m at 56º off-nadir, and 3.51 m at 65º off-nadir, as well as 1.24 m resolution in multispectral.

WorldView-4 includes enhanced capabilities that allow it to capture highly detailed images quickly. Depending on the angle from which it's viewing (off-nadir), it can still maintain a resolution that makes it suitable for various mapping and monitoring applications. This satellite’s ability to revisit areas every three days means it can track changes over time, which is essential for urban planning and environmental studies.

It's like having a drone that can take pictures from different angles and distances but still produce clear, usable images. You can spot changes in a neighborhood or track the growth of forests much like a director reviews scenes from multiple camera angles for a film.

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