Professionals ranging from civil engineers designing flood control channels to geologists conducting mineral exploration surveys and site investigations will soon have at their fingertips a long-awaited treasury of resources. For the first time, high-resolution digital imagery of the Earth will be delivered to their personal computers, complete with immediate access to a library of Earth images that can be tailored to their specific needs.
      All this will happen when EarthWatch's EarlyBird satellite, equipped with a 3-meter sensor, is launched in early 1996. According to Douglas B. Gerull, president of EarthWatch Inc., "Industries concerned with forestry, oil exploration, agriculture, pollution monitoring, wildlife, geology, urban planning and development, emergency services, natural disaster recovery, map making and many others will have access to information previously unavailable. Imagery data of the type EarthWatch will provide is essential to the development of next generation geographic information systems and environmental and multi-media technology initiatives."

How Does an Industry Like This Get Started?
The only satellite images available to users have been those from government-sponsored programs that provided commercial imagery only as a secondary benefit. The poor resolution of these images has forced users to rely on aerial photography for high-resolution images, which has its own limitations (see below).
      In 1992, Congress passed the Land Remote Sensing Policy Act, allowing U.S. commercial companies to enter the remote-sensing market. This opened the door for what is expected to be a multibillion-dollar industry by the year 2000.
      Anticipating the loosening of U.S. government restrictions on this once very highly protected data source, Dr. Walter Scott and other scientists involved in the Space Defense Initiative (SDI) Brilliant Pebbles program at Lawrence Livermore National Laboratory conceived of using a lightweight satellite bus platform and state-of-the-art component technology to build a reliable and cost-effective commercial imaging satellite. Scott, founder, joined by Gerull, co-founder, (former executive vice president heading the Mapping Sciences Division of Intergraph Corp., the world's largest developer and distributor of GIS products and services) formed WorldView Imaging Corp. It was the first company to obtain a commercial license from the U.S. Department of Commerce to build and operate a system to gather very high-resolution digital imagery of the Earth from space. The company quickly went to work designing and building two satellites that would offer 3-meter resolution. (The WorldView team was also selected by NASA for the Small Satellite Technology Initiative and is currently building a payload for the CTA NASA Clark satellite.) Meanwhile, Ball Aerospace and Communications Group obtained a 1-meter license from the U.S. government. In early 1995 Ball Aerospace and Communications Group and WorldView merged to form EarthWatch, Inc.

Capturing More Valuable Images
The 3-meter sensor in the EarlyBird satellite will provide 11x to 100x better resolution than existing commercial satellites. The highest resolution non-DoD imagery currently obtained from space is 10 meters.
      While EarlyBird image resolution will be comparable to that of some aerial photographs, EarlyBird images will be more cost-effective and up-to-date. The satellite will also reach parts of the world that are unavailable to aerial photographers. One user who comes up against this problem on a regular basis is Vincent Campbell, president of Earth Resource Surveys Inc. (ERSI), Vancouver, British Columbia. ERSI customers conduct mineral and engineering site investigations. "Worldwide coverage would be fantastic. We do lots of work in Africa and Asia where we can't get air photos or topographical maps easily," he says.
      Campbell says his engineering clients would be especially eager to see the high-resolution images to study potential dam and power plant sites. EarthWatch's promise to deliver images within days, or even hours if needed, could be another plus. "A lot of clients are dismayed to find out it will take two to three weeks to acquire images and another week or so to process them. Any way to shorten the time is helpful," says Campbell.
      Another advantage over aerial photography offered by EarlyBird is its digital distribution. Aerial photographs must be converted to digital form after imaging if users want to use the imagery in a computer-based application. In addition, EarthWatch plans to provide a global digital archiving system that will be in place at launch time.

Capturing and Recording Images
There are many subsystems on board the spacecraft crucial to the success of EarlyBird's three-year mission, including two systems that must operate together flawlessly to produce geographic information system (GIS) data: the 3-meter image sensor built by EarthWatch and the 16 Gb high-bandwidth solid-state recorder built by Odetics, Inc., Anaheim, Calif.
      The EarlyBird spacecraft, with its unique pointing system and selected orbit, will revisit any point on Earth in 1.5 to 2.5 days, meaning customers can obtain images of the same region from various angles. EarlyBird will provide "in-track" stereoscopic imaging, which will provide better quality and more reliability.
      EarlyBird's 3-meter panchromatic and 15-meter multispectral sensors will image the Earth's surface with a staring array of charge-coupled devices (CCDs), each of which views 3-meter- or 15-meter-square areas of the Earth and converts the image of that area into a single picture element ("pixel"). These CCDs function as "electronic film" measuring the strength and spectra of light reflected by the imaged features on the Earth's surface. The table below shows general and specific characteristics of the EarthWatch imager.
      Other characteristics of the EarlyBird sensor:
• 30-degree fore-and-aft, and side-to-side pointing capability
• Can expose a matrix of overlapping frames in a single pass over any area of interest, 500-frame capacity per orbit
• 470 km sun-synchronous orbit, store-and-forward operation downlink to EarthWatch ground stations
      EarthWatch is also building a 1-meter resolution panchromatic sensor and a 4-meter resolution multispectral sensor for a satellite called QuickBird, which will be launched in about two years.
      The QuickBird sensor also features a 30-degree fore-and-aft, and side-to-side pointing capability, a 470 km sun-synchronous orbit, store-and-forward operation and downlink to EarthWatch ground stations.

New Solid-State Recorder Technology Developed to Store Images
The solid-state recorder that will record EarlyBird image data and playback the data to the ground-link communications channel represents a major transition from tape to solid-state recorder technology.
      Satellites currently acquiring geographic-information imagery from space include France's SPOT satellites, Japan's JERS, Europe's ERS-1 and the recently launched ERS-2. The imagery acquired by these satellites is 10 meters or greater. All are using tape-based data-storage units built by Odetics.
      The EarlyBird satellite requirements for a small, lightweight, high-data-rate recorder exceeded the capabilities of tape recorders. As the first small satellite engaged in a low Earth orbit, EarlyBird needed high-bandwidth and high-capacity data recording combined with simultaneous playback requirements that could only be met using the latest solid-state recorder technology. The Odetics unit, the first solid-state recorder to function in a fully operational (not experimental) GIS program, weighs less than 12 pounds, provides a data-storage capacity of 16 Gb and records data at a rate of 160 Mb/s. In addition to these critical parameters, the recorder stores and retrieves data using a unique file-based architecture that permits random accessing the data and provides simultaneous record/playback capability. The recorder operating on EarlyBird may also have the distinction of being the first solid-state recorder to have 16 Mb DRAM memory devices (which are the current state-of-the-art memory technology) applied to a fully operational system.
      Like many firms that established themselves as government suppliers in the 1970s and 80s, Odetics is now adding commercial companies, like EarthWatch, to its customer list. One of the challenges for Odetics was to design and build a recorder incorporating new technology, in just six months. The quick turnaround was necessary to meet EarthWatch's three-year design-to-launch schedule. (In contrast, government satellites can take from five to eight years from authorization to launch.) Odetics proudly delivered a fully functioning system on time and is already working on future EarthWatch recorders. According to Jerry Muench, vice president of Odetics "The close cooperation of EarthWatch and Odetics working in parallel helped to produce outstanding results. This was an iterative process unencumbered by contractual red tape and paperwork that often stifles and slows creative progress."
      Odetics is targeting other commercial GIS opportunities for its solid-state recorders. The company believes the operational firmware and command structures incorporated in the EarlyBird recorder and its high bandwidth interface will allow other GIS providers to minimize technical risk, cost and schedule.
      After the first EarlyBird satellite is launched in 1996, EarthWatch will be adding a constellation of satellites in low-Earth orbits that will provide even more high-resolution 3-meter images. The geographic imagery never before seen by scientists and engineers around the world, will no doubt spark new ideas and industries.

About the Author:
Bob Tripp is manager of business development, space data-storage products, Odetics Inc. in Anaheim, Calif.

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