This is Part 2 of a series on the origins of civilian satellite imaging programs. Part 1 discussed was an overview and history of these systems while Part 2 provides more in depth information on the payload and applications of each imaging satellite especially the constellations of Landsat, DigitalGlobe, Spot and GeoEye.
Earth Observation Landsat program
Landsat is the longest running satellite program for acquisition of earth observation imagery. The Earth Resources Technology Satellite launched in July 1972 was renamed Landsat in 1975. . The most recent, Landsat 7, was in fact launched in April 1999 and has 8 separate spectral bands with spatial resolutions ranging from 15-60 m, and a temporal resolution of 16 days .
The key Landsat Sensor the MultiSpectral Scanner (MSS) were designed in 1969 and deployed as early as the autumn of 1970. In 1979, President Carter transferred Landsat operations from NASA to NOAA, recommending development of a long term operational system with 4 further satellites beyond Landsat 3, and all important transition to the private sector, which took place in 1985. The Earth Observation Satellite Company (EOSAT) then operated Landsat under a 10 year contract, operating Landsats 4 and 5, with exclusive rights to market Landsat data, and to build Landsats 6 and 7.
However, in 1989, NOAA's funding for Landsat was running out (NOAA hadn’t requested funding, and Congress had only 6 months funding for the financial year). NOAA directed Landsat 4 and 5 to be shut down. Vice President Quayle head of the newly inaugurated National Space Council arranged emergency funding so that the Landsat program could continue. In 1990 and 1991, Congress again provided only half of the required annual funding to NOAA, requesting agencies that sale of Landsat data provide the funding for the other 6 months of the year. In 1992, efforts were made to procure funding for follow on Landsats and continued operations, but by the end of the year EOSAT ceased processing Landsat data completely.
However, Landsat 6 was launched October 5, 1993, but was lost during launch. This could have been the end of Landsat, which would have held back progress on development of civil imaging capabilities, but processing of Landsat 4 and 5 data was resumed by EOSAT in 1994 and NASA finally launched Landsat 7 in April 1999. This drama might have been avoided if the Land Remote Sensing Policy Act (Public Law 102-555) authorizing procurement of Landsat 7 and assuring continued Landsat digital data and image availability, at low cost, to all users of the data passed by the US Congress in October 1992 had actually been fully supported at the time.
From the late 1970’s the French were developing SPOT (Système Pour l’Observation de la Terre) ( "System for Earth Observation") a high-resolution, optical imaging Earth observation satellite system operating from space, run by Spot Image based in Toulouse, France. It was initiated by the CNES (Centre national d'études spatiales — the French space agency) in the 1970s and designed to improve the knowledge and management of the earth by exploring its resources, detecting and forecasting phenomena such as climatology and oceanography, and monitoring human activities and natural phenomena. SPOT includes a series of satellites and ground control resources for control and programming, image production, and distribution. Satellites were launched by the European Space Agency (ESA) rocket launchers: Ariane 2, 3, and 4. The company SPOT Image markets high-resolution images, which SPOT satellites acquire globally, with the latest, SPOT 5, launched May 2002 having 2.5, 5, and 10 m capability respectively.
The SPOT orbit was designed to be polar, circular, and sun-synchronous. The inclination of the orbital plane combined with the earth’s rotation around the polar axis allows a satellite to fly over any terrestrial point every 26 days with orbit at an altitude of 832 km, and an inclination of 98.7°.
SPOT 1, 2, and 3
Since 1986 SPOT satellites have orbited earth and taken more than 10 million high quality images. SPOT 1 was launched by Ariane 2 in February 1986. Two days later, the 1800 kg SPOT 1 transmitted its first image with a resolution of 10-20 meters. SPOT 2 also entered orbit in January 1990 and SPOT 3 followed in September 1993. Satellite loads were identical, including 2 High Resolution Visible (HRV) imaging instruments able to operate in 2 modes, either simultaneously or individually. The two spectral modes used are panchromatic and multispectral.
The panchromatic band has a resolution of 10 m, and the 3 multispectral bands (G\R\NIR) have resolutions of 20 m with a scene size of 3600 km2 and a revisit interval of 1-4 days, depending on latitude. Panchromatic imagery sensors generally refer to a single band system which spans the visible and Near IR (NIR) part of the electromagnetic spectrum, and are usually represented black and white, although false colour representation is possible. Multispectral imagery can also be acquired by sensors that measure energy in several specific bands simultaneously, usually 3 to 7, although increasingly hyper spectral systems, with potentially up to hundreds of bands, are now being developed for deployment.
Because the SPOT 1 orbit was reduced in 2003, it gradually lost altitude and broke up in the atmosphere. A controlled deorbit of Spot 2 commenced mid-July 2009 over two weeks, with a final burn before reentry burn up on 29 July 2009. SPOT 3 has also ceased operations, due to problems with stabilization.
SPOT 4 and SPOT 5
In March 1998 the SPOT 4 satellite added further capabilities to the SPOT series. SPOT 4 has the same geometric imaging characteristics (a swath of 60 km per instrument and oblique viewing capability of 27° on either side of the vertical) as the earlier SPOT satellites. However, its performance has been increased by adding a new Short Wave IR spectral band (SWIR). SPOT 5 was launched in May 2002 and ensures continuity of services for customers with improved quality of data and images. SPOT 5 has 2 High Resolution Geometrical (HRG) instruments offering a higher resolution of 2.5-5 m in panchromatic mode (on the edge of that needed for dwelling sized human rights assessment) and 10 m in multispectral mode (20 m in SWIR 1.58-1.75 μm). SPOT 5 also features an imaging instrument operating in panchromatic mode, pointing forward and backward of the satellite so it can take stereo pair images near simultaneously to provide mapping relief.
SPOT 6 and SPOT 7
SPOT 6 and SPOT 7 launches are scheduled for launch in 2012 and 2013, respectively to form a constellation of earth-imaging satellites to provide continuity of high-resolution, wide-swath data up to 2023 with image resolution: Panchromatic: 1.5 m color merged products: 1.5 m Multispectral: 8 m, of a resolution able to benefit disaster management and mitigation. Spectral bands, with simultaneous panchromatic and multispectral acquisitions: Panchromatic (450 – 745), Blue (450 – 525), Green (530 – 590), Red (625 – 695), NIR (760 – 890) nm respectively, and footprint: 60 km x 60 km, operates to provide a capacity able to acquire up to 3 M km2 daily. The Indian Space Research Organization (ISRO) launched SPOT-6 on a Polar Satellite Launch Vehicle on September 8th 2012, along with a 15-kg Japanese microsatellite.
GEOEYE- Ikonos and OrbView
GeoEye operates a growing constellation of high-resolution earth-imaging satellites collecting millions of square kilometers of map-accurate imagery every month, imagery which is then archived for future use. In 1997 Virginia-based GeoEye launched OrbView-2, by modern standards a low-resolution satellite, capturing broad-area colour imagery of land and ocean surfaces for science research, agricultural and ocean monitoring. OrbView-2 was an extremely successive satellite mission, collecting imagery of earth with a ground resolution of 1 km, and is still in use today. GeoEye Inc. (formerly Orbital Imaging Corporation or ORBIMAGE) is a commercial satellite imagery company based in Herndon, Virginia and is the world's largest space imaging corporation . The company was founded 1992 as a division of Orbital Sciences Corporation in the wake of the 1992 Land Remote Sensing Policy Act permitting private companies to enter the satellite imaging business. It changed its name to GeoEye in 2006 after acquiring Colorado-based Space Imaging for $58 million and runs Ikonos and the OrbView satellites.
GeoEye provides 253 Million km2 of satellite map images to Microsoft and Yahoo! search engines with Google having exclusive online mapping access from the new GeoEye-1 satellite and is a major supplier to the National Geospatial-Intelligence Agency. GeoEye's primary competitors are DigitalGlobe and Spot Image. GeoEye operates a fleet of earth observation satellites, providing visible and NIR images of land and sea at resolutions below 1 m.
Ikonos is a commercial earth observation satellite, the first to collect publicly available high-resolution imagery at both 1 m and 4 m resolution. It offers multispectral (MS) and panchromatic (PAN) imagery from January 1st 2000, and derives its name from the Greek eikōn for image. IKONOS originated under the Lockheed Martin Corporation as the Commercial Remote Sensing System (CRSS) satellite. In April 1994 Lockheed Martin was granted one of the first licenses for commercial satellite high-resolution imagery. In October 1995 partner company Space Imaging received a license to transmit telemetry from the satellite in the 8 GHz Earth Exploration Satellite Services band. Prior to launch, Space Imaging changed the satellite name to IKONOS. Two satellites were originally planned but the 1999 launch of IKONOS-1 failed when the payload fairing of the Athena rocket failed to separate, (a not uncommon launch problem), preventing the satellite reaching orbit. IKONOS-2 was planned for launch later in 2000, but was renamed IKONOS and launched in September 1999 from Vandenberg Air Force Base (AFB), California. The satellite has a polar, circular, sun-synchronous 681-km orbit and both sensors provide a swath width of 11 km.
IKONOS has a primary mirror aperture of 0.7 m, and a folded optical focal length of 10 m using an array of 5 mirrors. The main mirror features a honeycomb design to reduce overall launch mass. The detectors at the focal plane include a panchromatic sensor with 13500 pixels and a multispectral sensor with 3375 pixels and an instrument mass of 171 kg, drawing only 350 watts of power. Spectral bands allow simultaneous panchromatic and multispectral acquisition: 1-m Panchromatic (Blue, Green, Red, and NIR 0.45–0.90 μm), 4-m and 1-m Pan Sharpened (Blue 0.445–0.516 μm), (Green 0.506–0.595 μm), (Red 0.632–0.698 μm), and (NIR 0.757–0.853 μm). The revisit rate for IKONOS is 3-5 days off-nadir and 144 days for true-nadir, with a swath width of 11 km × 11 km (single scene). IKONOS orbits earth every 98 minutes at an altitude of about 680 km, travelling in a sun-synchronous orbit.
This satellite (also called SeaStar) was launched 1997 by ORBIMAGE, and collects real colour imagery of earth's land and ocean surfaces on a daily basis. Commercial fishing vessels use OrbView-2 data for detecting oceanographic conditions to create fishing maps. OrbView-2 provides broad-area cover in 2,800 km-wide swaths, routinely used in naval operations, environmental monitoring, and global crop assessments, integrating its optical and NIR multiband SeaWiFs sensor for scientific research (operating 1997-2004). The principal OrbView-2 science objective was to acquire data critical for the study of the role of oceans, and the exchange of critical gases between the atmosphere and ocean, and how these exchanges affect phytoplankton production. It stopped collecting data in December 2010.
Launched in 2003 by ORBIMAGE, OrbView-3 acquired 1 m panchromatic and 4 m multispectral imagery in 8-km-wide swaths.
The satellite collected up to 210,000 km2 of imagery each day revisiting each terrestrial location in less than 3 days. On April 23, 2007, GeoEye, Inc. announced that its OrbView-3 satellite no longer produced usable imagery, and the spacecraft orbit finally decayed in March 2011 via controlled reentry into the Pacific Ocean.
GeoEye-1 (formerly OrbView 5) launched September 6, 2008 and separated successfully from its Delta II launch vehicle 59 minutes after launch. The satellite provides 41 cm panchromatic and 1.65 m multispectral imagery in 15.2 km wide swaths. The spacecraft has a sun-synchronous orbit at an altitude of 684 km and inclination of 98° and can image up to 60° off nadir.
GeoEye-2 has a scheduled launch date in 2013 and a planned resolution of 25 cm. Lockheed Martin was selected to build the satellite platform in preference to General Dynamics and will provide imagery comparable with the best quality aerial imagery of the Cold War era.
DigitalGlobe was founded 1993 under the name WorldView Imaging Corporation, becoming EarthWatch Incorporated in 1995, and lastly DigitalGlobe (2002). In 1993, the US Department of Commerce granted DigitalGlobe the first license for private enterprise to build and operate a satellite system to gather high-resolution digital imagery of earth for commercial sale. In October 2001 DigitalGlobe successfully launched w the world’s highest-resolution commercial satellite, QuickBird, from Vandenberg AFB, California, USA (2 prior attempts from Russia were unsuccessful) with QuickBird still operational today. Following the successful launch of QuickBird, DigitalGlobe built an extensive business serving both governmental and commercial markets. Of note was its agreement to provide high-resolution imagery to the Keyhole Corporation, acquired by Google in 2004, a vital component in the creation and commercial success of Google Earth and beginning the proliferation of online mapping portals. In September 2003, DigitalGlobe won a lucrative $500 million contract from the National Imagery and Mapping Agency (NIMA) through its NextView program to provide imagery from the next generation of commercial high-resolution imaging satellites. DigitalGlobe announced plans to build 2 next generation, high-resolution imagery satellites, WorldView-1 and WorldView-2. In January 2007, DigitalGlobe acquired GlobeXplorer, a leading online imagery provider. DigitalGlobe’s archive and high-resolution, high-capacity satellites combined with GlobeXplorer’s effective online hosting infrastructure, web services, GIS products and services and developer toolkits to provide easy access to world imagery. In September 2007, WorldView-1 was launched on a Boeing Delta II rocket from Vandenberg. Shortly after receiving a downlink signal confirming that the satellite had separated from its launch vehicle and had automatically initialized its onboard processors. Full operating capability began November 2007 and DigitalGlobe became the first company to deliver to the NextView program.
By early 2009, DigitalGlobe announced several other strategic agreements expanding availability of high-resolution imagery to online portal, navigation, and applications: The first extended its service agreement with Google continuing Google and DigitalGlobe’s relationship to pioneer wider global imagery accessibility. A new partnership with Microsoft will provide high-resolution satellite and aerial imagery for its Virtual Earth Platform. Agreement with Oracle, NAVTEQ and Nokia will make imagery in Nokia Location Services available on compatible Nokia devices. Using streamlined technology integration and development of a proprietary format for delivering imagery to Nokia, users will have quick, easy and seamless access to a wide range of global imagery from DigitalGlobe. On October 8, 2009, WorldView-2 was successfully launched from Vandenberg AFB, bringing the total number of sub-meter satellites DigitalGlobe has in orbit to 3, enabling the company to offer a constellation of spacecraft to provide a high collection capacity, some 500M km2 annually, of high-resolution earth imagery to customers world-wide.
Additionally, WorldView-2 is the only commercial high-resolution satellite with 8-band multispectral capability and features advanced agility and accuracy.
Reprint with permission by Chris Lavers, author of “Recent Developments in Remote Sensing for Human Disaster Management and Mitigation- Natural and Man-made 2013 - Spotlight on Africa”