Prodigious Mapping Capabilities, Spatial Resolution and Geo-location Ability

GeoEye’s Next-Generation Imaging Satellite

In the coming months, insurance companies will have access to commercial satellite images precise enough to determine whether an insured homeowner living in a fire-prone area like southern California should thin the brush in his backyard to prevent the spread of a forest fire. Defense and intelligence communities will have access to imagery that is an ideal tool for broad area mapping. Oil and gas companies will have access to color imagery to help them manage and map facilities and infrastructure on the ground. These sorts of uses are mere snapshots of what commercial imagery provider GeoEye (Dulles, Va.) envisions for its next-generation GeoEye-1 Earth-imaging satellite, slated for launch later this year.

In 1900, in the magazine Ladies Home Journal, an article making predictions for the next century said, “Flying machines will carry powerful telescopes that beam back to Earth photographs as distinct and large as if taken from across the street.”

In the coming months, insurance companies will have access to commercial satellite images precise enough to determine whether an insured homeowner living in a fire-prone area like southern California should thin the brush in his backyard to prevent the spread of a forest fire. Defense and intelligence communities will have access to imagery that is an ideal tool for broad area mapping. Oil and gas companies will have access to color imagery to help them manage and map facilities and infrastructure on the ground. These sorts of uses are mere snapshots of what commercial imagery provider GeoEye (Dulles, Va.) envisions for its next-generation GeoEye-1 Earth-imaging satellite, slated for launch later this year.

Accuracy

Funded 50 percent by GeoEye and about 50 percent by the U.S. Department of Defense, the satellite will set new and unprecedented standards for the performance and capabilities of commercial remote sensing systems.

The 684 kilometer, sun-synchronous, polar orbiting satellite with its ITT Corporation (White Plains, NY) sensor will be able to discern objects on the ground 0.41 meter in size and, just as important, map an object that size to within three meters of its true location on the surface of the Earth. This level of accuracy has never been possible before with civi­lian space-based imagery and will be done without the use of ground control points from outside sources.

In practice, GeoEye-1 imagery will be able to ‘see’ an object the size of home plate on a baseball diamond in both color and black and white. Maximum spatial resolution for color images will be 1.65 meters, a factor of two better than existing commercial satellites with four-band multispectral imaging capabilities, including GeoEye’s IKONOS Earth-imaging satellite. Launched in 1999, IKONOS has a maximum resolution of 0.82 meters (black and white).

ITT, developer of GeoEye-1’s camera and telescope assembly, says the satellite will be capable of collecting on a daily basis up to 700,000 square kilometers of panchromatic data, an area about the size of Texas, or 350,000 square kilometers of pan-sharpened multispectral imagery, the equivalent of photographing and mapping the entire state of New Mexico. Given its altitude, sun-synchronous orbit, field of view and superior

1-meter simulated resolution from aerial imagery of Colorado Capital and Downtown Denver.

0.5 meter simulated resolution from aerial imagery of Pepsi Center, Denver, Colorado.

Prodigious

The satellite’s prodigious mapping capabilities, spatial resolution and geo-location ability are the result of a technological symbiosis between the satellite bus, built by General Dynamics Advanced Information Systems (Gilbert, Ariz.) and ITT’s optical telescope, detectors, focal plane assemblies and high-speed digital processing electronics capable of processing millions of pixels per second. ITT provided similar previous generation equipment for IKONOS and built the imaging sensor for another satellite, DigitalGlobe’s WorldView-1 panchromatic sensor, which was launched in September 2007.

Though it stands two stories high and weighs more than two tons, GeoEye-1 is designed to deftly train the ITT camera on multiple targets during a single orbital pass, able to rotate or swivel forward, backward or side-to-side with robotic precision. These capabilities allow the satellite to image easily east to west even as it moves from north to south around the Earth at a speed of 7 km per second. GeoEye-1 will be able to collect several images of the same area taken at different orbital positions, resulting in the ability to create stereo imagery which can be processed into advanced geospatial products.

General Dynamics provides the satellite’s precision pointing and attitude knowledge -- essential ingredients for GeoEye’s spatial resolution and geo-location performance -- using GPS, gyros and star-tracking sensors. The GPS system and the star trackers are the most sophisticated on the commercial market, having previously been used only for U.S. Government missions. The star trackers were built by Ball Aerospace & Technologies Corp. headquartered in Boulder, Co.

1-meter simulated resolution from aerial imagery of Charles B. Wheeler, Downtown Airport, Kansas City, Missouri.

Telescope

At the heart of ITT’s camera is a five-element modified Cassegrain telescope with a 1.1-meter primary mirror, which is a larger diameter than the primary mirror used in current systems. ITT uses two “fold mirrors” in the optical path to compress the system focal length allowing it to fit within the available envelope. “The telescope is the subassembly that collects photons,” says ITT’s Cliff Olds, project manager for the GeoEye-1 camera. “It’s like a ‘light bucket’.”

Compared to current technology, it’s quite the “bucket.” GeoEye-1’s quantum efficiency, the measure of how well a telescope collects light photons is nearly double that of other systems. “That makes the instrument more affordable, lower in cost and able to collect more data, faster,” says Chris Young, president of ITT Space Systems Division.

After passing through the telescope, the light passes through two parallel slits at the focal plane. Beneath one are the panchromatic charge-coupled device (CCD) detectors; below the other are four rows of multispectral sensors, each filtered to gather light in the correct spectrum – blue, green, red and near infrared. The miniscule size of the individual pixels in each panchromatic sensor CCD are a key reason GeoEye-1’s images will have greater sharpness and ground resolution than existing commercial imaging satellites, says Olds. As a whole, Young says, GeoEye-1's camera and electronics offer five times the power efficiency, 10 times the weight efficiency, and three times the cost efficiency that current high-resolution systems offer.

Once operational, GeoEye-1 will become a key asset in GeoEye’s satellite constellation, which includes IKONOS and the 1,100-meter ground resolution OrbView-2 satellite, launched in 1997. GeoEye-1 will launch on a Boeing Delta II rocket from Vandenberg Air Force Base in California. Because of its sun-synchronous orbit, the satellite will pass over the sunlit portions of the Earth at approximately 10:30 a.m., providing an optimal mix of lighting and shadow for imaging. The satellite is designed to operate for a minimum of seven years and carries enough re-boost fuel to maintain its orbital altitude for more than 10 years.

1-meter simulated resolution from aerial imagery of Coors Field, Denver, Colorado.

0.5-meter simulated resolution from aerial imagery of Coors Field, Denver, Colorado.

Customers

Once data from Geo-Eye-1 begins to flow, after a 45-60 day on-orbit checkout phase, the U.S. Government and other customers will receive access to imagery from the satellite. Panchromatic and multi-spectral data will be downlinked separately and recombined at GeoEye, with multispectral data used to colorize the higher resolution panchroma­tic images.

For commercial sales, GeoEye will resample the images to decrease the maximum spatial resolution to 0.5 meters, a requirement levied by the U.S. government. Mark Brender, vice president of corporate communications and marketing for GeoEye, expects that half-meter resolution imagery will enable the company to provide customers and resellers in the U.S. and overseas with new geospatial products with a superb metric accuracy. For the government customer, GeoEye-1, will provide more eyes in the sky and high-quality unclassified imagery to support intelligence and broad area mapping missions—all on a cost-effective basis.

GeoEye-1 At Lift-off, Vandenberg AFB, California

Awe

Imagination appears to be the only limit as to what users may create with GeoEye-1’s unparalleled views of Earth. Potential markets that would likely increase their use of geospatial technologies to involve satellite imagery include oil and gas, insurance and risk management, real estate, location-based services, and agencies designed to better understand the impact of climate change on the Earth’s surface. Whatever the use, ITT’s Young predicts customers far and wide will have the same impression of GeoEye-1’s imagery: “Awe.”

That one-hundred-year-old prediction from Ladies Home Journal has come true, almost right on time.

John Croft is an aerospace journalist.

For more information, have a look at www.geoeye.com and www.ssd.itt.com.

Thanks to Mark Brender and Adam Konowe.