by Hartley & Pattie Lesser
and a cast of dozens of subject-specific experts
Thanks for returning for Part III of the satellite imagery article. Let’s take a look at what, and who, is taking a look... in Part II, we present ImageSat International. 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.
ImageSat’s EROS system is manufactured by Israel Aircraft Industries (AIA). ImageSat became the first non-U.S. company, to successfully deploy a commercial high-resolution imaging satellite. EROS satellites are light, low earth-orbiting (LEO), high-resolution satellites designed for fast maneuvering between imaged targets. The orbital period of the EROS satellites is 94 to 96 minutes for one revolution around the Earth. The satellite completes approximately 15 revolutions around the Earth every 24 hours, including two daylight passes per day through the footprint of a typical Ground Receiving Station.
ImageSat International offers a Satellite Operating Partner Program (SOP) that enables governments to own exclusive rights for the use, and control, of EROS satellite imaging time over a defined geographical footprint. This service is conducted through a long-term service basis. Customers receive exclusive, local tasking and confidential reception of imagery to their own ground control station. Their Exclusive Pass on Demand (EPOD) program provides special services from a high resolution satellite but at relatively low cost, and the customer is the only one in the loop of satellite tasking and imagery reception. The program includes upgrading the customer’s ground station to allow autonomous tasking of the EROS satellite to directly receive all acquired imagery. Their Priority Acquisition Service Program (PAS) enables ownership at the nearest imaging opportunity for a pre-selected quantity of images, with commitment to a defined footprint… as long as those images do not fall within the exclusive SOP footprint. This is a cost-effective method for imagery acquisition. For full information on ImageSat International’s product offerings, head to this website.
There are currently two operating models in the EROS family of satellites, with a third satellite planned for launch in 2010.
This was the first in a constellation of sun-synchronous, polar-orbiting satellites that ImageSat plans to deploy during this decade. Successfully launched on December 5, 2000, the 260-kg EROS A has been commercially operational since January 1, 2001.
The launch occurred at the Svobodny Launch Complex in the eastern part of Siberia aboard a Russian Start-1 launcher. The satellite’s weight at launch was 250 kg.
EROS A is equipped with a camera whose focal plane of CCD (Charge Coupled Device) detectors produces a standard image resolution of 1.8 meters, with a swath of 14-km at nadir (perpendicular to the surface) at an altitude of ~500 km, and sub-meter resolution using hypersampling techniques. The satellite’s sun-synchronous orbit allows the craft to cross the equator at 9:45 a.m., local time, and imaged targets are always in daylight. The data transmission rate is 70 Mbit/s. The anticipated lifespan of the EROS A satellite is 10 years.
In order to address market demand for higher resolution and faster revisit of EROS satellites, ImageSat launched the 290-kg EROS B satellite, also on a Start 1 launcher from the Cosmodrome in Svobodni.
Slightly larger and similar in appearance to EROS A, this satellite has superior capabilities, including a larger camera of CCD/TDI type (Charge Coupled Device/Time Delay Integration), with standard panchromatic resolution of 0.70 m at an altitude of about 500 km, a larger on-board recorder, improved pointing accuracy and a faster data communication link. The satellite is expected to provide services for 8 to 10 years.
With a scheduled launch set for 2010, Image Sat’s EROS C satellite will have an expected lifespan of 10 years. EROS C’s highest resolution will be 0.7-m and the satellite will offer higher quality resolution and a higher data link rate than either EROS A or B.
Also in the mix will be multispectral imagery capabilities. EROS C will weigh 350-kg at launch and will orbit in a sun synchronous orbit (SSO) at an altitude of about 500-km. The satellite is equipped with a camera with CCD/TDI (Charge Coupled Device/Time Delay Integration) sensors. Produced will be panchromatic imagery at a standard resolution of 0.70-m, and multispectral imagery at a standard resolution of 2.8-m. The swath will be 11-km at nadir. The data transmission rate will be 455 Mbit/s.
All of the EROS satellites offer a Color Fused Image (CFI) using the EROS A or EROS B sensor as the high-resolution panchromatic data source, and a medium resolution multi-spectral sensor as the color data source. ImageSat awarded Apogee the worldwide rights to commercially supply the CFI product.
SPOT 1, 2, 4 + 5
Spot Image offers standard products to value-added geometric products, and has an archive of several million images. With custom programming of satellites, their multiresolution imagery can meet multiscale needs from 2.5 to 20 meters. They publish an online catalog through SIRIUS, where customers can locate images archived since 1986.
The company has also created a web-based service for AmericaView members in which archived SPOT imagery can be purchased at discounted rates. This data includes the North American Archive, USA Select, USA Nationwide Prime and, coming soon—One Country, One Year.
Spot Image’s satellites perform 14 + 5/26 revolutions per day. The same pattern is “phased”, meaning it is repeated over and over. Both High Visible Resolution (HRV) and High Geometric Resolution (HRG) instruments offer combined field-of-view that is wider than the greatest distance between two adjacent tracks.
Every point on the Earth’s surface, between 81.5° N and 81.5° S, can be collected during the satellites’ 26-day cycle. Collection above 81.5° N, or below 81.5° S, is possible, but is not conducted on a “normal” basis. The revisit frequency depends upon the latitude needed. At the equator, a target area can be imaged 11 times during the orbital cycle, or, an average of 2.4 days.
SPOT satellites transmit their image data in two ways, all depending on whether or not the bird is within range of a ground station: downloaded in real-time if within range of a Direct Receiving Station (DRS); if not within range of a Spot DRS, the image data is stored onto onboard receivers on SPOT 4 + 5. If within range of a main receiving station, the satellite can be programmed to downlink image data in real-time or play back the onboard recorders and transmit the image data that was recorded earlier.
SPOT 4 + 5 satellites pack two, identical optical imaging instruments as well as two tape recorders for image data, plus a payload telemetry package for images’ transmissions to ground stations. On SPOT 2, there is HRV; SPOT 4 offers HRV-IR, and on SPOT 5, HRG is the imaging device. HRV’s offer an oblique viewing capability, with the look angle being steerable through +/- 27°, relative to the vertical. Such produces an incidence angle of +/-31°. This steering capability is handled by the programming system and provides for target capture of regions that are not directly below the satellite’s path. As you’ll note in the specifications, these instruments can be operated in panchromatic or multispectral mode, simultaneously or individually.
SPOT 5’s HRS (High-Resolution Stereoscopic Imaging Instrument) can capture near simultaneous stereo pairs on a swath 120-km across and 600-km long. The images are acquired in panchromatic mode with a 10-m spatial resolution (to be precise, GSD is 5-m along track in the direction of the satellite’s velocity by 10-m cross track) with a telescope-viewing angle of ± 20°.
There’s one sensor forward and one aft, which allows for the near-instantaneous acquisition of stereopairs. The forward telescope acquires ground images at a viewing angle of 20° ahead of the vertical. The aft-looking telescope then acquires the same strip behind the vertical at 20° 1 minute and 30 seconds later.
SPOT 4 and 5 have a vegetation instrument aboard. This is a very wide angle Earth observation instrument with a resolution of 1-km and high radiometric resolution. The swath is actually two, 2500-km-wide captures of BO (blue), B2 (red), B3 (NIR), and B4 (SWIR).
Surrey Satellite Technology Ltd.
Disaster Monitoring Constellation
Surrey Satellite Technology Ltd. (SSTL), recently acquired by EADS Astrium, manufactured five, remote-sensing satellites known as the Disaster Monitoring Constellation. The Disaster Monitoring Constellation (DMC) is the first earth observation constellation of four, low cost, small satellites that provide daily images for applications, including global disaster monitoring. These satellites are managed for the International Charter for Space and Major Disasters by a wholly-owned subsidiary of SSTL, that being DMC International Imaging (DMCII).
The cooperation of an international consortium makes DMC possible. Each partner owns an independent small satellite mission that services national needs. By sharing space and ground assets membership of the DMC consortium confirms the unique benefits of having access to a seamless global monitoring service. DMC was designed as a proof of concept constellation. The satellites are capable of multispectral imaging of any part of the world every day. All satellites have been equally spaced around a sun synchronous orbit (SSO) to provide daily imaging capability.
SSTL continues to own and operate the United Kingdom’s satellite in this constellation. Daily revisit is possible as they image an area of up to 600x600-km. There’s no need for mosaics of images from different seasons. The members of DMC all agree to provide 5 percent of capacity at no charge for imaging disaster areas. Reuters’ AlertNet is the channeling agency for such work, contributing daily imaging capability to fill the existing three to five day response gap. The DMC Imager is a 6-channel, Surrey Linear Imager (SLIM6). When operated from a near polar, SSO and circular orbit at a 686-km nominal altitude, with an orbit inclination of 98°, the design offers a nadir viewing, three-band multispectral scanning camera that’s capable of providing mid-resolution image info. The swath is 600-km wide as it passes over the target area, using the spacecraft’s orbital motion to provide an along-track scan with the pushbroom configuration. The onboard Close Coupled Device (CCD) scan’s 6 channels are stored in a Solid State Data Recorder (SSDR) in a band-interlaced RAW format. Storing data from each bank of the three CCDs is a separate SSDR. There are 2 banks of 3 channels, with the combination of the 2 banks providing the total swath width of 600-km. The SLIM6 imager channel has a solid-state detector at the focal plane, with the spectral filters located in front of each channel lens. AISAT-1
In November of 2002, SSTL’s AISAT-1 was launched aboard a Kosmos launcher from Plesetsk. This microsatellite was part of a technology transfer project for the Centre National des Techniques Spatiales (CNTS) of Algeria and was intended to help that country develop their space infrastructure. The project included the satellite, a mission control station, and hands-on training for Algerian engineers at SSTL’s HQ. This was the first satellite in the Disaster Monitoring Constellation that provides the world with medium-resolution imagery, including daily, worldwide revisits, all coordinated by SSTL. AISAT-1 carried a SSTL-developed imaging payload that provided 32-m ground resolution and a wide swath of more than 640-km. Green, red, and near-IR bands are used, with images stored in a 9 gigabit solid-state data recorder. Scenes as large as 640-x560-km can be imaged. The images are returned via an 8 Mbps S-band downlink.
Then, in September of 2003 from the same launch site as AISAT-1, BILSAT-1 was placed into orbit via a Kosmos launch vehicle. It was one of three satellites launched simultaneously to complete the Disaster Monitoring Constellation’s first phase. The client was the Turkish Scientific and Technical Research Council (TUBITAK), and the project included the satellite, a mission control station in Turkey, and that all-important, hands-on training for Turkish engineers at SSTL.
The payloads included a high-resolution panchromatic imager with 12-m ground resolution, a four-band, medium-resolution imager with 26-m ground resolution, plus a 9-band hyperspectral imager designed and built by engineers at BILTEN (Information Technologies and Electronics Research Institute of Turkey). Provided by BILTEN was also a DSP image processor that could handle high-speed, multispectral image compression using JPEG2000 algorithms. The spacecraft could slew and capture images anywhere within its ground footprint, due to it employing a zero-bias, three-axis attitude control system. The system used two SSTL star imagers that were supplemented by MEMS gyroscopes. This mission was completed in 2006. Another of these simultaneous satellites launches was...
Launched in September of 2003, this was part of a technology transfer program for the Federal Ministry of Science and Technology (FMST) of Nigeria. During this project, Nigeria formed the National Space Research and Development Agency (NASRDA), which continue to manage the NigeriaSat-1 program. This satellite offered 32-m ground resolution with a swath width of more than 640-km. Also using green, red, and near-IR bands, images are stored on a 1 Gbyte, solid-state data recorder and returned via an 8 Mbps S-band downlink.
Launched with BILSAT-1 and NigeriaSat-1, UK-DMC was developed for the British National Space Centre (BNSC) under a grant from the Microsatellite Applications in Collaboration (MOSAIC) program. UK-DMC is a standard DMC design, with added research and development payloads. It carries an optical imaging payload developed by SSTL to provide 32-m ground resolution with a swath width of over 640 km. The payload uses green, red, and near-IR bands equivalent to Landsat TM+ bands 2, 3 and 4. In comparison with other DMC satellites, UK-DMC features increased on-board data storage, with 1.5 Gbyte capacities. Images are returned to the SSTL mission operations center using the Internet Protocol over an 8-Mbps S-band downlink. UK-DMC also contains a commercial Internet router from Cisco Systems, which builds on the use of the Internet Protocol by the DMC satellites to experiment with Internet packet routing to, and in, space. UK-DMC is also the test bed for a new SSTL concept in remote sensing, GPS reflectometry. This technique, which measures the signals from the GPS navigation system after they are reflected off the sea, could revolutionize oceanographic remote sensing.
October of 2005 saw the launch of Beijing-1, which was developed for Beijing Landview Mapping Information Techology Ltd. (BLMIT). The satellite combines SSTL’s standard DMC multispectral camera with a high-resolution panchromatic imager. Enhancements to the two imagers included a 32-m multispectral imager (also flown on AISAT-1, UK-DMC, and NigeriaSat-1) and a new, 4-m panchromatic imager that was developed under contract to SIRA Electro-Optics Ltd. This satellite is fully supported by SSTL S-band telemetry, telecommand as well as an 8 Mbps data retrieval ground station. Plus, customers furnished X-band data retrieval support for a ground station and reflector subsystem is incorporated into this project.
In the 4th quarter of 2008, the DMC will be enhanced by the addition of two more SSTL satellites: Demios-1 for Spanish customer Deimos Space and SL and UK-DMC-2, funded by SSTL. Both of these satellites will carry an enhanced version of the DMC wide area imaging system. They will provide 600-km wide swaths of the Earth in three spectral bands at a ground resolution of 22-m. Additionally, the new spacecraft will benefit from more than 10 times the capacity for information provision. These significant enhancements reflect SSTL’s evolutionary approach to development that provides state of the art performance with minimal risk. The improved resolution and capacity enable the system to better meet European Global Monitoring for Environment and Security (GMES) program needs, particularly in the areas of forestry and fire.
Nigerian customer NASRDA has contracted SSTL for a next generation DMC satellite and will launch NigeriaSat-2 in 2009. The contract includes a training and development program for 25 Nigerian engineers, and the launch of the training satellite, NX, into the DMC alongside NigeriaSat-2.
RapidEye AG (Brandenburg, Germany), a public-private cooperative enterprise, has stated that during 2008, the already delayed launch of five microsatellites will occur. RapidEye controls and partially handles the satellite manufacturing. Subcontractors involved in this constellation effort include MacDonald, Dettwiler and Associates (MDA) in Canada, who received a $170 million CDN contract from RapidEye in June of 2004, and is the prime contractor.
MDA, in turn, awarded a 19.2 million pound contract to Surrey Satellite Technology Ltd. (SSTL) in the United Kingdom to supply the spacecraft platforms, integration, and launch arrangements for the five satellites. The satellites will use SSTL’s advanced microsatellite avionics, a precision attitude orbit and control system with star tracker. The latter will provide 30 degrees roll-offset for accurate image targeting and onboard propulsion for constellation station keeping. SSTL is going to provide the Spacecraft Control Center ground equipment for the mission. The camera subcontractor is Jena Optronik GmbH.
RapidEye will offer a variety of commercial geospatial products and services, with the primary source of their data in their planned constellation of five imaging satellites. The firm will offer data for information solutions, from the integration of multiple geospatial data sets, including their satellite image data and a variety of third-party raster or vector data. This information is delivered directly to clients in the format that best fits their needs. Specific solutions have been developed for the agriculture, cartography, forestry, government, and utility markets.
This unique public-private partnership will find the DLR Space Agency holding the rights for use of the satellites for scientific research, and they will also function as an interface between these sectors. There will be no costs attributed to German scientists working on projects using RapidEye imagery data.
The RapidEye satellites will have a total weight of approximately 150 kilograms, and will be carried aloft together on one rocket. They will orbit at an altitude of 630-km and will have a SOS inclined at 97.8°. Orbits will require 96.7 minutes to complete. The life span is expected to be 7 years.
The RapidEye constellation of Earth observation satellites collects multispectral image data at a high resolution over large areas, with the capability to reach any point on Earth every day. The system will be able to collect more than 4 million square kilometers of data per day. The satellites orbit at an altitude of 630-km and within 3,000-km. Customers will be provided with data of up to a maximum of 1,500-km in length.
Data will be received at a ground station operated by Kongsberg Satellite Services AS in Svalbard, Norway, with the mission control center in Brandenburg controlling the vehicles. The camera system is a multispectral pushbroom imager, which packs an additional red edge channel.
Get The Point...
Futron recently published their 2008 Space Competitiveness Index, which is an analysis of the manner in which countries invest in, and benefit from, the space industry. Part of their report deals with Earth Observation (EO) and offers a benchmark for this dynamic and increasingly commercial, international, and highly competitive industry.
Currently, the U.S., Canada, and Europe have the most well developed, national EO policy, laws, and regulations. However, within the next five to 10 years, Europe is planning significant investments in EO assets and may well overtake the U.S. India’s long-standing investment and organizational capacity continues to build their EO capability. This has launched India into one of the top three countries; however, its weakness is a lack of clear government policy. Assessing China is difficult, due to their lack of transparency. Futron believes this fact is, in and of itself, insightful because that lack of transparency hampers the country’s commercialization and applications development. Today, the largest customers of commercial EO data are governments yet, innovative products such as Google Earth permit public access to integrated remote sensing data, while raising awareness, and increases product value.
Faster, longer and crisper — improvements are a regular occurrence in the satellite realm, making it surely one of today’s most exciting industries.
This closes our look at satellite imagery, with a commercial perspective. Tables for the mentioned satelliets follow... we hope you have found the information useful... we recommend you go directly to any of the mentioned companies’ websites to learn more about their services and the satellites on orbit. Thank you for attending this series!—Hartley & Pattie Lesser
CREDITS and THANKS…
Companies supplying information for this article, and their missions, include…
- Earth Observation Research Center, JAXA
- Lockheed Martin
- Space Foundation
- National Weather Association (NWA) Remote Sensing Committee
- Satellite Imaging Corporation
- ViaSat GeoTechnologies
1The GIS information text and graphics in Part I of this article were excerpted from ww.gis.com and www.esri.com and are the intellectual property of ESRI and are used by permission. Copyright © ESRI. All rights reserved.