The Landsat Blues


  Space News Business

The Landsat Blues


posted: 31 October 2005
01:20 pm ET

I spent this year’s World Space Week in South Africa in the company of several other space professionals from the United States and Europe. We had been invited to present various aspects of space issues to audiences in the population centers of Pretoria and Johannesburg, Durban and Cape Town. Though the audiences came from different disciplines and professions, they shared a common interest in space activities. Their questions showed they all had a strong desire to advance the use of space systems, particularly remote sensing systems, for the benefit of South African development.

As part of the week’s activities, the South African Minister of Science and Technology approved the development and operation of a South African commercially developed optical remote sensing system, ZAsat. ZAsat1, developed and built by SunSpace, Inc., of Stellenbosch, will contain a multispectral sensor, operating with a resolution of 6 meters. ZAsat2, operating at higher resolution, is also in development.

These events captured the imagination of educators, government officials and scientists, and are expected to lay the groundwork for the eventual development of a South African space office or space agency.

South Africa, like Algeria and Nigeria before it, has recognized that one important way to support economic and social development and to enter the league of space-capable nations is to build and operate a small remote sensing satellite capable of providing basic multispectral data in an operational mode.

With the addition of Kenya, these three countries already are planning an innovative, indigenous multisatellite system to support the monitoring and management of Africa’s rich natural resources. With other international partners, the South African small satellite manufacturer SunSpace already is building an engineering model of a remote sensing spacecraft that will carry both multispectral and hyperspectral scanners.

In the meantime, as Africa looks ahead in Earth observations, the continuation of the Landsat system in the United States continues to be mired in indecision even though Landsat data play an important part, some say a critical one, in routinely monitoring the U.S. and global environment.

We now have a 33-year record of Landsat data stored in the archives at the U.S. Geological Survey’s EROS Data Center in Sioux Falls, S.D. Coverage of the data set is spotty because of the up and down record of policymakers with respect to Landsat funding, but for some regions, mostly over the United States, the data set is excellent.

Among other things, these high quality data sets provide local and regional authorities with an important long-term record of environmental change and the basis for predictive modeling of urban growth patterns, environmental degradation and regeneration. Such broad-area, high-quality data are extremely difficult to obtain any other way.

The contrast with the optimism of today’s Africa toward operational remote sensing systems is striking. U.S. scientists and resource managers instead express doubt, uncertainty and disappointment about the future provision of broad-area remote sensing for public uses.

The heartrending, disastrous effects of hurricanes Katrina and Rita reminded us that despite billions of dollars spent, we remain woefully unprepared to plan for and cope with the effects of a major natural disaster. The dismal record of planning and response failures spread throughout all levels of government — from local to federal. However, one of the bright spots was and still is the use of remotely sensed data to evaluate the extent of flooding and to assist in the recovery efforts.

The data sets used especially include Landsat data. Although the sensor resolution is too coarse to be used to identify fine detail like housing or most other urban structures, it is perfect for evaluating the extent of flooding over wide areas and for planning evacuations and general relief efforts. Even agencies that use high-resolution commercial data often make use of Landsat data as a backdrop and base data set to gain overall perspective on a region.

Further, environmental scientists focusing on the short- and long-term effects of hurricane damage to coastal marshes and urban structures learn much from studying Landsat images. Such information will prove extremely important as local, state and federal land managers attempt to set policies for managing these fragile land areas.

The Landsat system has a checkered policy history, from the unsuccessful 1980s attempt to transfer the system to private-sector ownership to the 1992 law that brought Landsat 7 back under government operational control.

During this entire time, policymakers have failed to assure that continuity of Landsat data supply, required by that same 1992 law. As a result, we are now left with well-meant but rather feeble attempts to kluge together existing data sets that resemble Landsat data while NASA, other agencies and Congress dither over the future of Landsat data continuity.

Landsat is continually at risk from infighting among the various federal agencies that use the data. All want the data for different purposes, but no one agency is willing to take the lead for funding the system. Because the Landsat series serves a varied set of users in both the scientific and applied communities, it has not had a strong agency champion since the late 1970s.

Two years ago, NASA and the U.S. Geological Survey tried to offer private companies the opportunity to enter into partnership with the government to build and operate a system. When that attempt failed, they proposed putting a variant of the Landsat sensor on the National Polar Orbiting Environmental Satellite System (NPOESS), the Operational Line Imager . NPOESS is the new, improved system of polar-orbiting meteorological satellites developed by NASA, the National Oceanic and Atmospheric Administration and the U.S. Department of Defense in partnership. However, the first of the NPOESS birds now is scheduled for launch only in 2010, which makes a significant gap in data continuity extremely likely.

The NPOESS satellites will fly in a different orbit from Landsat 7, which means that the data will have different geometrical characteristics than Landsat data. Unlike Landsat 7, it would not carry a thermal band. It is not clear that data users will find such changes immediately workable, since even relatively small changes in the data characteristics may require significant changes in their applications algorithms and models. Users of the thermal band will be simply out of luck in the Operational Line Imager era.

Given the funding and technical difficulties NPOESS has encountered recently, the NPOESS solution for Landsat seems less attractive. NASA scientists have been revisiting the notion of a gap-filler satellite for Landsat to assure some small semblance of data continuity. However, given the fact that Landsat 7’s line scan corrector failed in May 2004, and that the satellite already has lived beyond its expected lifetime, there may well be a serious gap in service even with the launch of a “Gapsat .”

Whatever decision they make, U.S. policymakers need to choose a course and stick to it. The Landsat system is a major public resource –for research and for monitoring and managing U.S. and global resources. What is required to assure data continuity for the long-term benefit of the country is the will to make an investment soon in the future by funding not only a replacement for the crippled Landsat 7, but also Landsat capabilities to follow in a fully operational system. Our country deserves no less.

Ray A. Williamson is a research professor of space policy and international affairs in the Space Policy Institute of The George Washington University.