Article October 1999.

Another High-resolution Space Imagery Provider.

West Indian Space Takes Up the Challenge.

art1.jpg (19812 bytes)West Indian Space (WIS) is the somewhat improbable sounding title for a consortium that aims to mount a serious challenge to the three main American companies - Space Imaging (IKONOS), EarthWatch (QuickBird) and OrbImage (OrbView) - that are planning to operate commercial high-resolution satellites. In fact, it is the name being given to the joint venture company that is registered in the Cayman Islands in the West Indies and is acting as the front organisation for the international group of companies that hope to provide this challenge.

By Professor Gordon Petrie

 

Two of the main companies that are participating in this venture are from Israel. These are Israel Aircraft Industries (IAI), the well-known manufacturer of aircraft, satellites and electronic systems and Electro-Optics Industries (El-Op), a company that supplies advanced military and commercial electro-optical systems. The third main shareholder in West Indian Space is Core Software Technology (CST), an American company that supplies software and services to handle large databases of geospatial information. Also forming part of the venture - though not as direct shareholders in WIS - are a number of organisations that operate ground receiving stations around the world. They will act as partners providing the data reception facilities and the supply of the high-resolution panchromatic imagery to be acquired by a new family of satellites. 

 

IAI and El-Op

Besides its military aircraft manufacturing and upgrading activities, IAI has a division devoted to space systems. As well as building communication satellites, this division has also developed the Ofeq series of agile, lightweight observation satellites that have been used to monitor the activities of Israel's often unfriendly neighbours. In addition to the actual satellites, IAI has also constructed the Shavit series of launchers that have been used to place the Ofeq satellites into a low Earth orbit (LEO). Furthermore it has also produced and operates the ground control, tracking and receiving stations that are used in conjunction with the Ofeq satellites. Its partner, El-Op, has been responsible for the supply of the sensors used in the Ofeq satellites. So the new consortium does have considerable experience in the construction and operation of space imaging systems.

 

CST

CST is best known for its TerraSoar software which is a Web-based system used to manage, search, pre-view and disseminate geospatial data (including aerial and space imagery, video and textual data and digital cartographic data) using popular Web browsers. The company also operates ImageNet which offers an on-line electronically indexed browsing and distribution service for geospatial data involving the parallel search of networked databases on a World-wide basis. Interestingly CST also has quite close commercial relations with some of the rival American satellite imaging companies. Thus Lockheed Martin is a re-seller of the TerraSoar product and has also integrated the software into Space Imaging's Carterra Analyst software. OrbImage is also using TerraSoar as the basis for the search, pre-viewing and ordering of its OrbView Cities high-resolution imagery. At the present time, this is derived from aerial photography, but this will be supplemented by the high-resolution space imagery that will be acquired from its OrbView-3 and -4 satellites. Furthermore, looking still further into CST's space connections, it is worth noting that its ImageNet service providers currently include Eurimage, Sovinformsputnik and the American Image Links and Scan Systems companies. Other CST links are with Datron (who are major suppliers of ground receiving stations), Autometric (who are prominent in the supply of digital mapping, remote sensing and photogrammetric systems) and StorageTek (who are the leaders in the provision of network storage facilities).

 

EROS-A Satellites

The high-resolution satellites that are being built for the new WIS venture carry the name EROS (Earth Remote Observation System). They comprise two quite different series of satellites, called EROS-A and EROS-B, which are currently being constructed and tested with IAI and El-Op as the prime contractors. The first series (EROS-A) comprises a lightweight (260kg) satellite which is planned to orbit at an altitude of 480km. The original EROS-A satellite (also called Ofeq-4!) was launched on a Shavit rocket in January 1998, but unfortunately it was destroyed when the launcher's second stage failed - only a few days after the failure of EarthWatch's EarlyBird satellite. The two follow-on EROS-A+ satellites are planned to be launched from Russia's Svobodny Cosmodrome in Eastern Siberia using Russian-built Start-1 rockets in December of this year (EROS-A1) and in September 2000 (EROS-A2) respectively. These EROS-A satellites will be placed in a near-polar Sun-synchronous orbit. The EROS-A sensor will have a linear array of 7,000 CCD detectors operating in a pushbroom mode and will provide monochrome (black and white) panchromatic imagery with a swath width of 12.6km; a 1.8m ground pixel size and a 11-bit (2,048) grey level range.

 

EROS-B Satellites

The EROS-B series of satellites will also be placed in near-polar Sun-synchronous orbits. However they will also have some rather different characteristics. In particular, they will be heavier (350kg) and more capable (through having a heavier fuel load available) and will be placed in a much higher orbit (600km). Moreover the CCD linear arrays will produce 20,000 pixels per line providing a swath width of 16.4km with a ground pixel size of just under 1m. To cope with the much greater amount of data that this sensor will generate, the data transmission rate for the EROS-B satellites will be 280 Mbits per sec. using the X-band frequency, as against the 70 Mbits per sec. rate to be used with the EROS-A satellites. Six satellites in the EROS-B series are planned, with launches every nine months or so from the middle of year 2001 onwards. Some of the later satellites in the series may also feature a multi-spectral capability.

 

Operational Modes

The EROS linear array imaging sensor is rigidly attached to the main structure of the satellite. Thus the pointing of the sensor is carried out by changing the orientation (i.e. tilting) of the satellite towards the area that has to be imaged. In the along-track direction, the satellite actually points backward with an ever increasing tilt angle applied at a constant angular rate to allow the sensor to acquire its images of the ground. This gives a larger dwell time during which more light will reach the CCD sensors and so improve the quality of the image through an increase in its contrast and an improved signal-to-noise ratio. Thus the satellite moves at a greater rate than the rate of imaging being conducted by its sensor. The use of this unusual operating mode also allows the acquisition of stereo-coverage in the along-track direction. For cross-track coverage, again the satellite as a whole has to be tilted to provide an off-nadir orientation with lateral tilts of up to 45 to give an improved re-visit capability of a given area for monitoring purposes.

 

Ground Receiving Stations

A highly unusual feature of the EROS satellites is that they will have no on-board recording and storage capability. Thus the images that will be collected by the satellite sensors need to be transmitted back immediately (i.e. in real time) to a ground receiving station. Furthermore this means that the area that can be covered by an EROS satellite needs to lie within the line of sight of a suitably equipped ground station. This may not have been a difficulty with the Ofeq reconnaissance satellites, where the main area of interest lay within reach of the ground station located in Israel, However the situation is very different if world-wide coverage is required as envisaged with the commercially oriented EROS satellites.

 

Upgrading of Receiving Stations

The solution to these difficulties has been for WIS to offer cooperative partnerships to the operators of existing ground stations receiving SPOT, Landsat and ERS image data which would enable them to become involved in the venture. To this end, WIS invited many of these operators to a meeting held in Tel Aviv at the beginning of March 1999 to explain its proposals for such a cooperation. Under this scheme, WIS offered to supply new hardware and software free-of-charge in the form of kits designed by CST to upgrade the existing ground stations to allow them to receive and process the new imagery. Several receiving stations in the Far East - in Korea, Japan and Taiwan - have already accepted this offer, as has the IPT station located in Sardinia, Italy and the CSIR station at Hartebeesthoek in South Africa.

 

Data Acquisition & Distribution

The main WIS ground control station located in Israel will transmit to each operational EROS satellite the planned imaging programme for the next 12 hours ahead. The ground receiving stations participating in the scheme can then receive the EROS images for its footprint area operating through one or other of three different services. The first of these is the Acquisition, Archiving and Distribution (AAD) programme. This will allow the station operator to receive and process the image data that is acquired within the station's field of view and to store it on a RAID drive in its own local archival system - without any requirement to pay an annual access fee. The ground station and its local distributors can then sell this data or value-added products based on the data to customers lying within the footprint area. The data will also be forwarded to the WIS central archive, which is based on CST's TerraSoar system, with WIS having the exclusive right to sell the data via ImageNet to those customers who are based outside the ground station's home area. Revenues will be shared between the AAD partner and WIS.

 

Priority Acquisition Service

A second alternative is the Priority Acquisition Service (PAS). Those ground receiving stations participating in this service will pay a fixed annual access fee, which will allow them to submit requests to the WIS ground control station for the acquisition of a fixed number (e.g. 100. 300 or 500) of images per year. These requests will have priority in the programming of each satellite. Again the image data will be received, processed and stored by the ground station operator but, in this case, without any obligation to pass the data on to WIS. However, if they so wish, the PAS partners can join and provide images and products under the ImageNet programme.

 

Satellite Operating Partner

The final possibility that is being offered to participating ground stations is that of becoming a Satellite Operating Partner (SOP). This will allow an individual ground station to receive image data from the EROS satellites on an exclusive basis, thus allowing it, in effect, to implement a national space imaging programme. The SOP ground station can generate and transmit an imaging programme to a specific EROS satellite while it is within the operating radius of the station. However it cannot be used for data acquisition outwith the station's footprint area. The service is intended to provide a relatively risk-free and inexpensive alternative to that of developing and operating a national Earth observation satellite programme. Needless to say, the first SOP partner is the Israeli government which, on this basis, has signed up to receive the image data from the first three EROS satellites that can be obtained within the viewing range of its own ground receiving station in Israel. However the SOP programme will still be available to other ground stations operating in other regions.

 

Conclusion

According to press reports, WIS is raising a large part of the funding needed for the joint venture through a bond offering of US$ 250 million that is being arranged and managed by the Merrill Lynch finance house. The remaining funding for the WIS venture will be provided by the three main shareholders - IAI, El-Op and CST. As the above account has described, both the WIS satellite technology and its business plan are unique and quite different to those of its competitors. At the time of writing, the launch of the second IKONOS satellite to replace the failed IKONOS-1 is scheduled for 24th September, while that of QuickBird-1 is planned for 23rd December. These will be followed shortly after by the launches of EROS-A1 and OrbView-3. A very interesting, indeed exciting, time lies ahead for potential users of high-resolution space imagery when many previously unresolved questions are going to be answered!

 

Professor G. Petrie, Department of Geography & Topographic Science, University of Glasgow, G12 8QQ, UK.