GeoEye-1, formerly known as OrbView-5, is the next-generation high-resolution imaging mission of GeoEye, Dulles, VA, USA. In January 2006, the commercial imaging company GeoEye Inc. was formed, made up of former Orbimage of Dulles VA, and of former Space Imaging of Thornton, CO (Orbimage acquired Space Imaging in 2005 and gave the merged company the new name of GeoEye). The newly formed GeoEye company is the world's largest commercial satellite imagery provider.
On Sept. 30, 2004, OrbImage was awarded a NextView vendor contract of NGA (National Geospatial-Intelligence Agency). The contract, referred to as NextView OrbImage, provides long-term revenue commitments as well as capital for the development of OrbView-5. NGA's NextView program is designed to give US commercial imaging satellite operators the financing to build their satellites for high-resolution imaging.
GeoEye's principal partners for the development and launch of the GeoEye-1 satellite include General Dynamics (formerly Spectrum Astro), ITT Industries (imager), and Boeing Launch Services. GeoEye's partners for the ground segment include IBM and MDA (MacDonald, Dettwiler and Associates) of Richmond, BC, Canada. 1) 2)
As of January 31, 2013, GeoEye-1 is a satellite of the DigitalGlobe commercial constellation of Longmont, CO, USA (Ref. 10).
Figure 1: Artist's view of the GeoEye-1 spacecraft (image credit: General Dynamics Corp.)
The GeoEye-1 spacecraft is being designed and developed at General Dynamics/C4 Systems of Gilbert, AZ (formerly Spectrum Astro) as prime contractor. The contract was award in Dec. 2004. The spacecraft design is based on the SA-200HP standard modular bus (of Coriolis and SWIFT heritage). The spacecraft is 3-axis stabilized with a sophisticated attitude control system to provide a highly stable, while also highly agile imaging platform.
A body-pointing capability of up to ± 60º is being provided, made possible by enhanced reaction wheels (low jitter). The image geolocation accuracy is ≤ 3 m. The spacecraft mass is 1955 kg (bus mass = 1260 kg), the S/C design is fully redundant with an operational life of 7 years (the expected life is 10 years). 3) 4) 5) 6) 7)
Table 1: Overview of GeoEye-1 spacecraft parameters
Figure 2: Photo of the dual-head star tracker (image credit: GeoEye)
Figure 3: Photo of the Monarch GPS receiver (left) and the SIRU instrument (right), image credit: GeoEye
Figure 4: Accommodation of optical units on the GeoEye-1 spacecraft (image credit: GeoEye, Ref. 16)
Figure 5: Alternate view of the GeoEye-1 spacecraft (image credit: General Dynamics Corp.)
Figure 6: Photo of GeoEye-1 during test and integration phase (image credit: General Dynamics Corp.)
Launch: GeoEye-1 was launched on Sept. 6, 2008 (18:50:57 UTC) on a Delta-2 (7420-10) vehicle from VAFB, CA. The launch provider was ULA (United Launch Alliance). 8)
Orbit: Sun-synchronous circular orbit, altitude = 681 km, inclination = 98º, period = 98 minutes, local equatorial crossing at 10:30 hours, effective revisit time capability ≤ 3 days.
Note: During late summer of 2013 the orbit altitude of the GeoEye-1 Satellite sensor was raised by Digital Globe from 681 km to 770 km. The GeoEye-1 new nadir GSD (Ground Sample Distance) is 46 cm for panchromatic data compared to the previous GSD of 41cm (Ref. 13). Despite this, GeoEye-1 imagery remains a valuable tool for high resolution requirements and is still being used for many applications today.
RF communications: The source data are being stored on solid-state onboard recorders of 1.2 Tbit capacity. The downlink of imagery in X-band at 740 Mbit/s (or at 150 Mbit/s), the TT&C data are in S-band. The S/C is being operated from the command and control facility at GeoEye headquarters in Dulles, VA, along with an imagery acquisition station. Three other acquisition stations will be operated or leased by GeoEye in Barrow, AK, Tromsø, Norway and Troll, Antarctica (the TrollSat station is located at 72º S and 2º E). The latter two stations are being leased from KSAT (Kongsberg Satellite Services) of Tromsø, Norway.
Ground segment: GeoEye has built a fully integrated receiving, processing, and distribution network for delivering high-quality imagery products to customers around the world.
In late 2006, GeoEye purchased high-bandwidth, high-performance computer technology from SGI (Silicon Graphics Inc.). Four SGI Altix systems were installed at the Dulles (VA) ground station for data processing, distribution, and archiving services.
• According to the WMO website, GeoEye-1 of DigitalGlobe is operational in 2016. 9)
• The GeoEye-1 spacecraft of DigitalGlobe and its payload are operating nominally in 2015.
Figure 7: GeoEye-1 satellite imagery of China's Rainbow Mountains, acquired in 2015 (image credit: DigitalGlobe)
Legend to Figure 7: The Rainbow Mountains, a new UNESCO World Heritage Site, are located at the Zhangye Danxia Landform Geological Park in the Gansu Province of northwestern China. Zhangye 's Danxia was formed by the erosion of red sandstone, forming isolated peaks and steep stratified outcrops. Its special geological structure, combined with long-term desert conditions , freeze-thaw peeling, and wind and water erosion gave rise to its present appearance. Geologists believe that Danxia topography was formed by folding of layered oceanic crust. Exposed slanting rock layers have different colors, textures, shapes, sizes, and patterns. The combination of differences in density and erosion create towering peaks, cave holes, and stone halls.
• In 2014, the GeoEye-1 spacecraft of DigitalGlobe and its payload are operating nominally completing 6 years on orbit in Sept. 2014.
• In 2013, the GeoEye-1 spacecraft and its payload are operating "nominally".
• During late summer of 2013 the orbit altitude of the GeoEye-1 Satellite sensor was raised from 681 km to 770 km. GeoEye-1 new nadir GSD (Ground Sample Distance) is 46 cm compared to the previous GSD of 41cm. 13)
• In 2012, the GeoEye-1 spacecraft and its payload are operating "nominally". The satellite imagery is used for a variety of purposes, including but not limited to defense, disaster response, air and marine transportation, oil and gas exploration, mining production and exploration, mapping of remote regions, location-based services, insurance and risk management, agricultural crop management, etc.
Table 3: Geolocation accuracy test results of GeoEye-1
Legend to Table 3:
- RMSE (Root Mean Square Error)
- CE90 (Circular Error of 90%)
- LE90 (Linear Error of 90%)
• GeoEye maintains continuous calibration assessments for the GIS (GeoEye Imaging System) instrument of GeoEye-1 involving the geometric, radiometric and focus parameters to verify the performance quality of the imagery. 16)
Legend to Figure 8: This half-meter resolution satellite image shows the Pearl Harbor Memorial, located about two miles west of the Honolulu Airport in Pearl Harbor on the island of Oahu, Hawaii. GeoEye tasked its GeoEye-1 satellite on Dec. 7, 2011 to commemorate the 70th anniversary of the Pearl Harbor Attack on Dec. 7, 1941. The image specifically shows the USS Missouri (center), a museum ship docked at Battleship Row, and crowds of people standing in formation on the dock. The USS Arizona Memorial (upper right) was built over the remains of the sunken battleship USS Arizona, which can be seen below the white memorial under the water's surface. The Arizona Memorial is managed by the National Park Service and is now a part of the dedicated WWII Valor in the Pacific National Monument Ref. 17).
• In October 2011, an ELR (Enhanced Line Rate) firmware package was uploaded with the objective to increase the overall collection capacity v. the SLR (Standard Line Rate) of the GIS camera. The ELR features are: 18)
- ELR camera slew rate is double that of SLR
- Faster collection of large area targets (25% – 30% increase)
- Point target collection times largely unchanged
- Camera on times decrease up to 40%
- End-to-end capacity increase: 15% – 20%.
Figure 9: GeoEye-1 image of Rome and Vatican City acquired on April 24, 2011. The image depicts a massive group of the faithful attending Easter services at the Vatican City (image credit: GeoEye)
• The GeoEye-1 spacecraft and its payload are operating "nominally" (with a downlink antenna pointing anomaly) in 2011. GeoEye-1 continues to have excellent radiometric performance.
- The geolocation accuracy performance assessment for GeoEye-1 system during 2010 was better than 4 m for mono CE90 and stereo CE90/LE90 (Circular Error of 90%/Linear Error of 90%). The GeoEye-1 system continues produce very good geolocation accuracy performance. 19)
Figure 10: GeoEye-1 image of the Nova Friburgo landslides in Brazil (January 2011), image credit: GeoEye
Legend to Figure 10: This half-meter resolution satellite image shows numerous landslides in Nova Friburgo, which is located north of Rio de Janeiro, Brazil. According to news reports the slides were triggered by deluges in the mountains just north of Rio and are the deadliest natural disaster to hit Brazil since flooding occurred four decades ago. The image was collected by the GeoEye-1 satellite on January 20, 2011 from 681 km in space as it moved from north to south over Brazil. 20)
• The GeoEye-1 spacecraft and its payload are operating "nominally" (with a downlink antenna pointing anomaly) in 2010.
• In mid-December 2009, GeoEye Inc. reported that the GeoEye-1 satellite has developed a glitch in its antenna-pointing system that could affect the operations of the company's overseas partners but will not diminish GeoEye's ability to serve its biggest customer, the U.S. NGA (National Geospatial-Intelligence Agency). 21)
The defect reduces GeoEye-1's ability to take images and simultaneously downlink to ground stations other than the four stations operated by GeoEye itself. For the GeoEye-owned facilities, GeoEye-1's imaging and downlinking functions are not performed simultaneously. 22)
• In early Dec. 2009, GeoEye announced the start of GeoEye-1 commercial operations for its regional affiliate in Saudi Arabia, KACST (King Abdulaziz City for Science and Technology). In addition to directly acquiring GeoEye-1 imagery, KACST will be able to provide other GeoEye-1 imagery and value-added products to its customers. 23)
• However, on May 12, 2009, the GeoEye company disclosed a problem with the GIS camera of GeoEye-1 which leaves small areas of black and white in certain color images collected. The investigation team determined, that the issue is only present in one profile but not in the others. The issue doesn't affect resolution or accuracy. There is little or no impact for GeoEye's Service Level Agreement with NGA. The causes of the problem are still being investigated. 24)
• In February 2009, GeoEye announced the start of commercial operations for its GeoEye-1 spacecraft. On Feb. 22, 2009, the National Geospatial-Intelligence Agency (NGA) notified the Company that imagery from the GeoEye-1 satellite has been certified as meeting their stringent requirements for quality, accuracy and resolution. As a result of the certification, the GeoEye-1 satellite is fully commissioned. The NextView program is designed to ensure that the NGA has access to commercial imagery in support of its mission to provide timely, relevant and accurate geospatial intelligence in support of national security. 25) 26)
• As of Dec. 2008, GeoEye-1 still experienced geolocation problems that prevented the company of selling its imagery.
• On Nov. 11, 2008 GeoEye Inc. reported that the GeoEye-1 spacecraft will not enter commercial service until December due to software glitches on the ADCS (Attitude Determination and Control Subsystem) that went undetected in ground testing. 27)
• On Oct. 8, 2008 GeoEye Inc. released the first, color half-meter ground resolution image taken from its GeoEye-1 satellite (Figure 14). The spacecraft had been undergoing calibration and check-out since it was launched on Sept. 6 from Vandenberg Air Force Base in California. 28)
Sensor complement: (GIS)
The requirements of GeoEye-1 called for panchromatic imagery with a resolution of 0.41 m and multispectral imagery with a resolution of 1.64 m. The imager has been designed and developed by ITT Space Systems Division, formerly Kodak Remote Sensing Systems of Rochester, New York, which built also the sensor for Ikonos-2 (launch April 27, 1999). In January 2007, the GeoEye-1 imager system was delivered to General Dynamics for integration into the spacecraft. 29) 30)
GIS (GeoEye Imaging System):
GIS is a pushbroom imaging system whose basic elements are the optics subsystem (telescope assembly), the focal plane assembly (CCD detector), and the digital electronics subsystem. The optics subsystem employs a TMA (Three Mirror Anastigmatic) telescope design with a primary mirror aperture of 1.1 m in diameter. Three mirrors are used to image and focus the light, and two additional mirrors to direct the image to the FPA (Focal Plane Assembly). The telescope is designed to give a near-perfect (diffraction limited) image to the FPA and to convert the analog pixels into digitized signals.
The FPA consists of an array of CCD detectors with 8 µm pixel size for PAN and 32 µm pixel size for multispectral imagery. ITT has included an outer barrel and door assembly to help protect the telescope and maintain its thermal environment.
Table 4: Parameter specification of the GIS instrument
In orbit, the GIS instrument is providing the highest spatial resolution available in 2008 [GSD (Ground Sample Distance) = 41 cm for Pan and 1.64 m for MS]. The operational support modes of the GIS instrument are: 31)
• Simultaneous panchromatic and multispectral (pan-sharpened) 32)
• Panchromatic only
• Multispectral only
The agile spacecraft is capable to provide also stereo observations in any direction (along-track or cross-track with a continuous stereo area up to 6270 km2 daily). The daily monoscopic collection capacity is:
- Up to 700,000 km2 of panchromatic imagery
- Up to 350,000 km2 of pan-sharpened multispectral imagery
Figure 11: Focal plane electronics of GIS (image credit: ITT)
Figure 12: Schematic view of the GIS optics assembly (image credit: ITT)
As a major customer, NGA will receive priority tasking and a large discount for agreeing to purchase a large volume of imagery. But there will still be a large amount of capacity dedicated to commercial customers and for the company to build a vast archive of imagery in a relatively short period of time.
Figure 13: GeoEye-1 collection modes and advanced agility allow for collection of large areas in any orientation and/or multiple point targets (image credit: Eurimage)
Figure 14: First image captured by GeoEye-1 shows the Kutztown University campus of Kutztown, PA, USA (image credit: GeoEye Inc.)
The color image of Figure 14 was observed on October 7, 2008 from an orbital altitude of 761 km as GeoEye-1 moved down the eastern seaboard of the United States. Although the satellite collects Pan imagery at 0.41m ground resolution, due to U.S. licensing restrictions, commercial customers will only get access to imagery that has been processed to 0.5 m ground resolution.
MDA (MacDonald, Dettwiler and Associates) and Orbit Logic have upgraded elements of GeoEye's ground segment. The receiving antennae are located at the Company's headquarters in Dulles, VA and in Barrow, AK. Kongsberg Satellite Services is providing leased ground terminal services in Tromso, Norway and Troll, Antarctica.
Figure 15: Schematic view of the GeoEye-1 ground system elements (image credit: GeoEye) 33)
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).