Apr 24, 2012

WorldView-3 promises to be a “superspectral satellite”

Estimated Article Reading Time: 3 min.

Jeff Culwell vice president of operations, DigitalGlobe talked about what led up to their anticipated WorldView-3 satellite and the details about it. The satellite is slated for launch in mid-2014. The announcement was made at the 28th Annual National Space Symposium.

Culwell has been with DigitalGlobe for approximately 13 years and before that was at the Jet Propulsion Lab working on the Galileo mission to Jupiter and also the Deep Space 1 mission which was a technology validation mission for 13 advanced technologies.

With this background, Culwell is well situated to discuss the history of DigitalGlobe’s satellites, beginning with the company’s beginning with the QuickBird satellite which entered the market in a leading position with a 60 centimeter resolution. QuickBird launched Oct. 2001 “and then about six years later we launched WorldView-1 and there made a quantum leap forward for the commercial industry in terms of the agility and capacity of a satellite. We put on the control moment gyros to reorient the satellite between imaging as opposed to using the older technology of reaction wheels. “

According to Culwell, control moment gyros (CMGs) offer a way to reorient a satellite, basically reorienting a satellite is using momentum vectors that are created by spinning flywheels. Reaction wheels are fixed to the satellite and have to be spun up in order to create the momentum vector and then spun at different speeds in order to get the aggregate vector to drive the satellite in the right direction.

“In the case of control moment gyros they’re already spinning and it’s just reorienting the position of the spinning flywheel which is a very fast change of the satellite’s orientation,” explained Culwell. “To put it in context, a satellite might be in view of an interesting piece of land for maybe two or three minutes; in the case of reaction wheels, it might take 30-45 seconds to reposition from one image to the next. For control moment gyros, it could be as small as 4-5 seconds. That allows a lot more time to image while in that interesting area than spending time reorienting.”

The innovation in WorldView-2 was the additional four multispectral bands, making that an 8-band satellite, and that created the opportunity to put value into land use and land cover types of applications such as oil and gas, or bathymetry which allowed you to see see about 30 meters into the water.

WorldView-3 builds upon the WorldView-2 and Worldview-1 technology by carrying forward CMGs for orienting the satellite and carrying forward the 8-band multispectrum capability and also creating what they call a “superspectral satellite” by adding the ability to detect eight-band short-wave infrared (SWIR) imagery.

In addition to offering 0.31 meter resolution panchromatic and eight-band multispectral imagery, WorldView-3 was recently licensed by the National Oceanic and Atmospheric Administration (NOAA) to collect this eight-band short-wave infrared (SWIR) imagery. This will make DigitalGlobe the only company with multi-band SWIR capabilities, greatly expanding the range of customer applications enabled by the DigitalGlobe constellation, and the overall value DigitalGlobe can provide to customers.

“This gives us the ability to sense not only the visible spectrum but beyond that, deeper into the infrared spectrum that provides a rich dataset that allows us to be able to identify much more precisely different manmade and natural materials,” said Culwell. “For example, in a mining application with high resolution SWIR bands you will be able to detect different types of minerals on a high enough resolution that the mine operator will have actual data in their hands and is able to better manage the mine.”

The interesting applications this can be used for include land use, land cover feature identification, a wide range of defense and intelligence applications, differentiating between moistures, such as ice, snow and clouds. This can be useful when looking at ice floes in Antarctica where largely in the visible spectrum you’re looking at a white picture but in the short wave infrared spectrum, you’re looking at snow, or cloud, which can be used in environmental monitoring.