Figure 1 - This .5-meter resolution image of SeaWorld in San Diego, California was taken by MJ Harden, a GeoEye company, with its aerial Digital Mapping Camera (DMC) imaging system. The image shows Rocky Point Preserve, part of SeaWorld’s 22-acre marine zoological park. Once GeoEye launches its next-generation satellite GeoEye-1, it will be able to collect images with a ground resolution of 0.41 meters in the panchromatic or black-and-white mode. Photo courtesy of GeoEye.
GeoEye & ITT Team Up
for Out-of-this-World Technology
In 1900, in the magazine Ladies’ Home Journal, the author of an article making predictions for the next century wrote, "Flying machines will carry powerful telescopes that beam back to Earth photographs as distinct and large as if taken from across the street."
By next summer, insurance companies will have access to commercial satellite images precise enough to determine whether an insured homeowner living in a fire-prone area such as southern California should thin the brush in his back yard 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 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 in the coming months.
Funded 50 percent by GeoEye and 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-high (425-mile-high), sun-synchronous, polar-orbiting satellite with its ITT Corporation (White Plains, N.Y.) sensor will be able to discern objects on the ground 0.41 meter (about 16 inches) in size with panchromatic images and, just as important, map an object that size to within three meters (about 10 feet) of its true location on the surface of the Earth. This level of accuracy has never before been possible 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 (5.4 feet), 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 resolution, GeoEye-1 can "revisit" any point on the globe every three days or less, depending upon the required orbital angle.
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, which are capable of processing 700 million 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. WorldView-1 offers .5-meter resolution in panchromatic imagery only. ITT has also delivered the sensor for WorldView-2 and is under contract for GeoEye-2.
Though it stands two stories high and weighs more than two tons, dwarfing the 726 kg (1,600 lb.) IKONOS, GeoEye-1 is designed to deftly train the ITT camera on multiple targets during a single orbital pass, able to rotate or swivel forward, aft 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 17,000 mph. 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.
Figure 2 - Artist rendering of GeoEye-1.
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 will be 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 Corporation (Boulder, Colo.).
At the heart of ITT’s camera is a five-element modified Cassegrain telescope with a 1.1-meter primary mirror, which is a 57 percent larger diameter than the primary mirror used in IKONOS. ITT uses two "fold mirrors" in the optical path to achieve a focal length of 13.3 meters in the physical space of about two meters.
"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 IKONOS, it’s quite the "bucket." GeoEye-1’s quantum efficiency, the measure of how well a telescope collects light photons, is 62 percent, nearly double that of IKONOS. "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 individual pixels in each panchromatic sensor CCD are 8 microns and 32 (TS) microns wide for the multispectral channels; their minuscule size is 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 IKONOS offers.
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 in a few months 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 hydrazine re-boost fuel to maintain its orbital altitude for more than 10 years.
GeoEye will control the satellite from its northern Virginia headquarters and will receive downlink information at its Dulles and Barrow, Alaska, ground stations. The company also is leasing ground stations in Tromso, Norway, and Troll, Antarctica, through Kongsberg Satellite Services. GeoEye’s Denver operational facility has been upgraded to be a back-up ground station for GeoEye-1. This geographically dispersed ground station architecture will enable the satellite to clear the imagery in its memory at least every orbit so that the imagery gets back to the processing facility in Dulles, Virginia, more quickly.
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 multispectral 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 and a superb metric accuracy. For the governmental customer, GeoEye-1 will provide more eyes in the sky and high-quality unclassified imagery to support intelligence and mapping missions—all on a cost-effective basis.
Figure 3 - This .5-meter resolution image of Coors Field, home of the Colorado Rockies professional baseball team in Denver, was collected by an aerial imaging system, representing what GeoEye’s next-generation satellite GeoEye-1 will be capable of producing once operational in 2008. Half-meter resolution means objects on the ground larger than one-half meter in size (16 inches), such as home plate, can be seen. Examples seen in the image are lines and demarcations in the turf on the playing field, light poles, and individual chairs in each row. Photo courtesy of GeoEye.
Since the start of the GeoEye-1 program, the satellite is being delivered on budget without any change orders, which often drive up the cost of such complex systems.
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 more 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, right on time.