Continued from Part I...
by Hartley Lesser and a cast of dozens of subject-specific experts
Thanks for returning for Part II of the satellite imagery article. Let’s take a look at what, and who, is taking a look... in this edition, and in Part III, we’ll present the leading, commercial satellite imagery firms. In Part II, we present Digital Globe and GeoEye. Please keep in mind that companies arrange the technical specifications for their satellites in various ways. The information contained on each satellite in the “specifications” sections was drawn directly from each company’s satellite spec sheets. Some companies took the time to forward to us additional information for the article, and we are most grateful for their support. For more inclusive information, we recommend you visit each firm’s website and access additional details in their satellite and product information pages.
Digital Globe
This company operates a constellation of sub-meter, commercial imaging satellites. With a complete library of earth imagery, customers include commercial, defense as well as intelligence and civil government users. Through their programs, more than 1 million km2 of imagery is collected each day, with the results available through online platforms. Their satellite-based products include Basic, Standard, Orthorectified, CitySphere, and Basic Stereo Pair.
The online access is via the company’s ImageAtlas. This app is easy to use, as the user does not have to be a sophisticated GIS or mapping specialist to realize benefits from the service. This is afforded users via a subscription service, and the products’ tools allow you to pan, zoom, and overlay street names directly onto the image. Other tools include ImageBuilder for creating base maps and other image layers for integration and display in various applications and devices. ImageConnect is a GIS extension that brings georeferenced photos into your own GIS project from the company’s online library. ImageConnect WMS (Web Mapping Service) gives users instant online access to updated global imagery without any plug-in requirements. In addition, PhotoMapper offers image and mapping solutions using a proprietary data compression format for quick pans, zooms and annotation of imagery markets. Full information on the DigitalGlobe product line is available at the company’s website.
QuickBird
The QuickBird satellite was manufactured by Ball Aerospace and launched in October of 2001 from Vandenberg Air Force Base in California, aboard a Boeing Delta II rocket for DigitalGlobe. QuickBird is still on-orbit performing its mission today at an orbit inclination of 97.2°, SSO, at a distance of 450-km (1,476,378 feet), with a 93.5 minute orbit cycle. QuickBird can revisit target areas in the span of from one to 3.5 days, depending upon the latitude at 70-cm resolution. Its onboard storage can accommodate approximately 57 single area images, and there’s enough fuel onboard to last for seven years.
This satellite is based on the Ball Aerospace Global Imaging System 2000 (BGIS 2000). QuickBird can collect 61-centimeter class panchromatic, and 2.5-meter multispectral stereoscopic data, over a large field, and is capable of rapid target selection.
The Camera 60 on board the QuickBird can image a strip of the Earth’s surface between 14 and 34 kilometers in width. A unique aspect of QuickBird was the ability of DigitalGlobe to alter the satellite’s orbit, thereby increasing the panchromatic resolution from one meter to 61 centimeters, and also increasing multispectral from four- to 2.5-meter resolution. This translates to QuickBird being capable of capturing images that are as small as two-feet in size. Each year, QuickBird can acquire more than 75 million square kilometers of imagery.
Based on 61-cm resolution, at nadir, and 11-bit collected information depth, the QuickBird panchromatic sensor, known as BGIS 200, collects data at the visible and near-infrared wavelengths, and possesses a bandwidth of 7250-nm. Basic imagery products are delivered at the GSD in which the data were collected (ranging from 61-cm at nadir to 1.14-m at 45° off nadir).
WorldView-1
On September 18th of 2007, WorldView-1 was launched from Vandenberg Air Force Base in California aboard a Delta II 7290 launch vehicle. Ball Aerospace built the bus, as well as the camera, known as the Worldview 60.
WorldView-1 is a commercial satellite offering half-meter resolution. Each day, this satellite is able to collect as much as 200,000 square miles of half-meter imagery. At an orbit of 450 km, WorldView-1 is able to revisit collection areas frequently, enabling customers to obtain updated image acquisitions more often on a daily basis. WorldView-1 also boasts Control Movement Gyroscopes (CMGs), which enable the craft to capture in-track stereo imagery, and to engage in rapid targeting of sites. WorldView-1 has a mission life of 7.25 years.
Aboard WorldView-1 is the half-meter imaging sensor developed by ITT which offers sub-meter resolution images that are used by the National Geospatial-Intelligence Agency (NGA) to fill their geospatial and imagery needs for a variety of ongoing operations. These activities involve the military, intelligence, foreign policy, homeland security as well as for civil use. In October of 2007, the company released the three initial images shown on the previous page, captured by this advanced sensor system.
WorldView-2
When launched in mid-2009 aboard a Delta 7920 launch vehicle with 9-strap-ons from Vandenberg AFB, the new WorldView-2 bird will offer increased flexibility when it comes to target area selection. The resolution will be half meter. WorldView-2 will have 8 bands and the resolution in the multispectal mode is 1.8-meters (panchromatic at half-meter). The bus is the Ball Commercial Platform (BCP) 5000 and offers increased data storage, more power, enhanced stability, and great agility. WorldView-2 will bring into play high spatial resolution and multispectral imagery. This will be of great use for defense, intelligence, disaster response, and exploration for land mapping and for government use.
As is the case with WorldView-1, this new satellite will also offer CMGs. Another plus for WorldView-2 is an instrument vibration isolation system that will reduce the jitter of the spacecraft, critical in the capture of crisper images. Additionally, global customers will find they will be able to task the spacecraft to deliver data directly to their ground stations, simply by uploading their individual imaging profiles to the satellite. The mission life of WorldView-2 is 7.25 years.
The satellite will have on-board a world-class telescope with high contrast (MTF) and signal-to-noise ratio. Both panchromatic and multispectral bands will offer selectable TDI with 11-bit range. The imaging payload will be the second system of this type engineered and manufactured by ITT Space Systems Division for DigitalGlobe. ITT is responsible for the electro-optical assembly of the camera and telescope, the detectors and focal plane assembly, as well as high-speed digital processing electronics.
Rob Mitrevski, vice president and director, commercial and space sciences, ITT Space Systems Division, adds, “The WorldView-2 imaging payload is the most advanced to date and will supply unprecedented detail and geospatial accuracy, further expanding the applications for satellite imagery in both commercial and government markets.”
GeoEye
Possessing a wide variety of owned satellites, as well as access to satellites belonging to their customers, GeoEye brings into the market advanced image processing and photogrammetry. Any geospatial application could find GeoEye imagery suited to their needs, from digital elevation models to fused images to land-use classification maps and more. Their imagery is used in such environments as mapping, national security, environmental monitoring, urban planning, resource management, homeland defense, commercial fishing, and emergency preparedness.
IKONOS
This satellite was launched in 1999 and collects 1-m panchromatic and 4-m multispectral data, at a rate of more than 2,000 square kilometers per minute, orbiting the earth every 98 minutes at an altitude of about 680 km (423 miles). This was the world’s first one-meter commercial satellite. To date, IKONOS has gathered more than 275 million square kilometers of imager, all available in the company’s digital archive. There are more than a dozen ground stations situated around the globe for this satellite’s downlinks.
OrbView-2
This satellite is used in studies of the world’s carbon balance and global warming, providing 2,800 km wide swaths for broad area coverage. The satellite collects color imagery of all of the Earth’s land and ocean surface. Under a program called SeaStar, commercial fishing vessels use maps that include imagery from OrbView-2 for detecting oceanographic conditions favorable for fishing. There are eight channels of data that provide color information from the visible to near-IR spectrum, and accessibility is via direct downlink or the web. This satellite has a life expectancy of around 12 years. MJ Harden, a well-known firm providing aerial imagery for the Oil & Gas industry, was acquired by GeoEye in March of 2007 and added their aerial imagery expertise to the GeoEye mix.
One of GeoEye’s services is the Ocean Monitoring Service. For use by technicians or scientists, this program provides science quality imagery, or model-based data sets of various geophysical parameters. Another often requested product from OrbView-2 is the Chlorophyll-a. This is the green pigment found in plants and marine phytoplankton, indicators of total plant biomass. Spatial patterns in Chlorophyll-a reveal more detailed definition of the dynamic ocean’s surface structure than is observed from spatial patterns in Sea Surface Temperature (SST). Often used is the SeaWIFS Data Analysis Systems (SeaDAS) image analysis package, which processes, displays, analyzes, and ensures quality control of ocean color data. See the next page for illustrations.
Another product is SeaStar for commercial and sport fishing use as well as for tracking OrbBuoys and vessels. GeoEye creates SeaStar oceanographic maps by integrating oceanographic information that’s collected in near real-time from satellites and other sources. For commercial fishermen, maps are delivered electronically to vessels showing areas of high fish-finding probabilities. Using GeoEye’s OrbMap software, vessel captains combine their own, personal knowledge of an area with the SeaStar map to create customized images where fish are likely to gather. For example, in the map grouping shown on the next page, from left to right the maps show sub-surface temperature (50-m) with contour lines, a SST base map with surface currents overlay, and a regional weather chart showing barometric pressure and wave height. The next map presents OrbBuoy tracking on a sea surface temperature base map with a surface current overlay using the OrbMap software. For information on GeoEye’s OrbBuoy products, check out the asset tracking site here.
GeoEye-1
The company’s nexgen satellite, GeoEye-1, is planned for a launch from Vandenberg Air Force Base soon. The launch vehicle will be a Boeing Delta II rocket. General Dynamics is designing and manufacturing the satellite, while ITT is providing the electro-mechanical camera, optical telescope assembly, the detectors, as well as the focal plane assembly and high-speed digital processing electronics. MacDonald, Dettwiler and Associates and Orbit Logic are involved in upgrading GeoEye’s ground segment to support GeoEye-1’s advanced technologies.
Images will be collected at 0.41-m panchromatic and 1.65-m multispectral resolution and will have the capability of precisely locating an object to within 3-m of its true location anywhere on the surface of the Earth. GeoEye-1 will be able to collect 700,000 square kilometers of panchromatic imagery, and up to 350,000 square kilometers of pan-sharpened multispectral imagery, in one day, storing the data to its 1 terabyte capacity solid-state recorders.
This satellite will complete 12 to 13 orbits per day at an altitude of 684 km (425 miles), with an orbital velocity of about y.5 km/sec (16,800 mph). Due to its SSO, GeoEye-1 will pass over a given area at about 10:30 a.m. local time each day. Additionally, the satellite will possess greater agility, being able to turn and swivel in orbit to point the camera at target locations below it, as well as from side to side and front to back.
An interesting simulation of GeoEye-1’s imaging capabilities may be viewed at this link. A Flash presentation reveals how various target locations would be captured at the various imaging resolutions of the satellite. GeoEye offers various image processing services from a broad range of data sources. These include their satellites as well as QuickBird, Landsat, SPOT and IRS satellite imagery. In example, regional and local governments would use this imagery for public facilities planning.
GeoEye-2
Coming online after GeoEye-1 will be GeoEye-2, with the camera work having already been contracted to ITT. Plans are for this satellite to launch three years after a builder has been contracted for the project. GeoEye-2 will be a 3G remote sensing satellite and should launch in either 2011 or 2012. According to the company, objects as small as 25 centimeters will be discerned on the earth’s surface by GeoEye-2. This satellite will be of the same general class as GeoEye-1. However, there will be significant improvements in the satellite’s capabilities. These will include enhanced direct tasking, and retrieving Earth’s surface imagery at 0.25-m or 9.75-inch ground resolution. GeoEye also operated OrbView-3 which was decommissioned on April 23, 2007. Images from OrbView-3 are available now only through the company’s archive sales process.
To Be Continued...
In the next issue of SatMagazine, we delve into ImageSat International & Spot Image and close the series with a look at Surrey Satellite Technology and RapidEye.
Reference:
QuickBird Characteristics
World View-1 Characteristics
World View-2 Characteristics
Ikonos Characteristics
OrbView-2 Characteristics
GeoEye-1 Characteristics
