WorldView-1 By Michael Jones

Abstract  The WorldView-1 satellite is one part of what is to be a three satellite constellation. The group includes QuickBird, WorldView-1 and WorldView-2 (to be launched in later 2008). The ultimate goal is to have all three systems working together to provide global visual coverage commercially at the highest resolution possible as quickly as possible. Additionally, WorldView-1 will be providing imagery to the NGS (National Geospatial- Intelligence Agency).  The WorldView-1 satellite was launched on September 18, 2007 from Vandenberg AFB, and carries a panchromatic only instrument that provides black and white imagery to commercial and government sources. At nadir it can achieve a 0.5 meter resolution along with the capability to image a swath of 17.6 km at a time. This has led to stunningly detailed imagery that only the government has had access to previously.

Introduction  Visual imagery provides a “bird’s eye view” of objects and locations as seen by the human eye. It has many uses including…  Visual Assessments (Construction progress, damages, etc…)  Cartography  Observing Glacial Retreat  Observing Weather Patterns  Military Applications

Key Concepts  Sensor band: panchromatic  Sensitive to all visible light but produces a grayscale image –In depth explanation In depth explanationIn depth explanation  Ground Sample Distance (GSD)  Pixel size expressed in ground units  GSD of 0.5 m represents pixel size of 0.5 m X 0.5 m  Swath Width  The horizontal viewing limit of the Earth’s surface in ground units taken in a single pass  Viewing Angle  Degrees off center of the ground track  Slew  Movement of imager horizontally perpendicular to the ground track

Panchromatic  Unlike traditional black and white images, panchromatic images are sensitive to all wavelengths allowing for correct color values in varying shades of gray.  Click here for more information Click here Click here

Panchromatic Sensor The estimated spectral radiance response, expressed as output counts per unit radiance as a function of wavelength, normalized to unity at the peak response wavelength is shown in figure 1. SourceSource Remember: Visible light: 400 – 700 nm

 Multispectral (Left Image): Has different sensors for different colors. Usually lower spatial resolution (~30 m for Landsat 7)  Panchromatic (Right Image) sensors take in all light from the visible spectrum and usually display it as a monochromatic (grayscale) image. Spatial resolution is usually better (~15 m for Landsat 7)

Multispectral Data can be merged with higher resolution panchromatic luminosity data to produce a “hybrid” color image with high resolution. This process is called “Pan- Sharpening” Multispectral Data can be merged with higher resolution panchromatic luminosity data to produce a “hybrid” color image with high resolution. This process is called “Pan- Sharpening”

Multispectral image from Landsat 7 Pan-Sharpened image from Landsat 7

Key Terms Visualized 48 Inch (122 cm) GSD 24 Inch (61 cm) GSD 6 Inch (15 cm) GSD Example swath diagram. WorldView-1 has a maximum viewing angle of +/- 45° off nadir to yield a maximum 1,036 km swath. Soviet Mig-29 at varying resolutions

Dimensions  3.6 m tall and 2.5 m across  3.2 kW solar array (7.1 m across)  2500 kg

Orbit  WorldView-1 has the following orbit characteristics: –Type: Sun Synchronous –Altitude:496 km –Period:94.6 minutes –Revisit:5.4 days at 59 cm GSD or less 1.7 days at 1 m GSD –Lifespan:7.25 years

Imaging Capabilities  Resolution of 50 cm at nadir –59 cm GSD at 25° off nadir  Retargeting rate of 4.5° per second –Acceleration of 2.5° per second²  Slew time of 10.5 seconds for 300 km

Results  The results of the WorldView-1 satellite system have been astonishing.  In the following slides you will see 50 cm to 59 cm GSD imagery for –Huston, TX –Yokohama, Japan –Ababa, Ethiopia

As you can see, visual imagery has come a very long way…  Most Corona satellites ( ) had a 7.5 m resolution, while one satellite at a lower altitude could achieve 1.8 m resolution. Recovery of a Corona return capsule Fuzhou Airbase, Fuji

Early 1980’s Reconnaissance Imagery

The Future  WorldView-2 –Set for launch late –Will have 46 cm resolution (Resized to 50 cm for non U.S. government customers) –Panchromatic and Multispectral –Faster Targeting and more frequent revisit

To View More Visible Imagery The Global Land Cover Facility has a large collection of panchromatic, multispectral and pan-sharpened imagery of various locations available to download free from their website: The Global Land Cover Facility has a large collection of panchromatic, multispectral and pan-sharpened imagery of various locations available to download free from their website:

Sources Chevron: Remote Sensing Instruments - Panchromatic. Retrieved April 15, 2008 from Franklin, Rod. “WorldView-1 Launch, Half Meter Imagery Coming Mid-October.” Imaging Notes 22.3 (2007) Retrieved April 15, 2008 from “Goofing Around With Pan-Sharpening.” Free Geography Tools. Retrieved April 19, 2008 from sharpening sharpeninghttp://freegeographytools.com/2007/goofing-around-with-pan- sharpening Spectral Response for DigitalGlobe WorldView 1 and WorldView 2 Earth Imaging Instruments. Retrieved April 11, 2008 from WorldView-1 Data Sheet. Retrieved April 10, 2008 from WorldView-1 First Images. Retrieved April 8, 2008 from

Questions?  WorldView-1 launch aboard a Delta II rocket from Vandenberg AFB WorldView-1 launch aboard a Delta II rocket from Vandenberg AFB WorldView-1 launch aboard a Delta II rocket from Vandenberg AFB