NASA's efforts to demonstrate the USA's commitment to the worldwide effort to monitor the Earth's environment are under threat.
Tim Furniss/GREENBELT, MARYLAND
SINCE 1992, NASA'S EARTH Observing System (EOS) programme has had its $16 billion budget to the year 2000 cut by 50%. A further $2.7 billion may now be axed, leaving it with $5.3 billion. Some observers find this is a strange situation, given worldwide concern about global climate change - highlighted by holes in the ozone layer.
The US National Research Council (NRC) warns that more cuts, constraints and changes to EOS missions will have a severe long-term effect, resulting in the elimination of key spacecraft instruments, delays, loss of data and stalling of the introduction of new technology as the 15-year programme develops.
One component of the international effort to monitor and understand the Earth's environment is the US Global Change Research Programme. A major part of this programme is NASA's Mission to Planet Earth (MTPE), of which the EOS is a major component.
"The programme is about producing 24 essential global-change measurements over 15 years," says John Dalton, deputy associate director of data and information systems at NASA's Goddard Space Flight Center, Greenbelt, Maryland. The EOS programme, introduced formally in 1990, has already been "restructured", then "rescoped", and now "constrained", firstly to focus the science objectives more narrowly on the most important elements of global change and, secondly, to increase the resilience and flexibility of the programme.
This will be achieved by flying fewer instruments on multiple platforms, rather than the series of much larger spacecraft envisaged originally by the agency. "The use of smaller craft is the right way to go," says Dalton.
Seven small-, medium- and intermediate-class EOS spacecraft will be launched by 2002 (see box). Some of the instruments on the first EOS craft have already been changed, to accommodate altered priorities in climate monitoring. One spacecraft series, the EOS-Aero, to gather long-term trend measurements of aerosolos, ozone, water vapour and clouds in the troposphere, has been replaced by a series of flights of its Stratospheric Aerosol and Gas Experiment (SAGE) instrument on a Russian Meteor spacecraft and aboard the Alpha International Space Station. More changes are likely, particularly the introduction of smaller satellites.
ENVIRONMENTAL DATABASE
Twelve or more spacecraft are due to be launched by 2013. With support from ground and data systems, their findings will be used to develop a 15-year environmental database, at a total cost of about $13-20 billion less than estimated originally.
While the EOS is being prepared, Phase 1 MTPE missions have already been flown, including the Upper Atmosphere Research Satellite, deployed from the Space Shuttle STS48 in 1991, and three Atmospheric Laboratory for Applications and Science missions aboard Space Shuttles STS45, STS56 and STS66 in 1992-5. The Space Radar Laboratories and a laser radar experiment to study atmospheric chemistry have also been flown on the Shuttle.
Further Shuttle-based and other US spacecraft are part of the Phase 1 MTPE programme. These include the routine National Oceanic Atmospheric Administration spacecraft, Shuttle Solar Backscatter Ultraviolet Experiment, and the Total Ozone Mapping Spectrometer (TOMS) Earth Probe. The TOMS instrument has already been flown aboard the Russian Meteor 3 weather satellite. Other craft include the Sea-Viewing Wide Field of View Sensor, to be launched on a Pegasus booster.
The Landsat 7 satellite has been adopted into the MTPE programme. It will be flown in 1988 and will carry a single instrument, the Enhanced Thematic Mapper Plus. Advanced Landsat-type instruments will be developed by NASA in a series of Earth-observation missions under the New Millennium programme, the first of which may be flown in 1998 and which may eventually lead to them being flown operationally on future EOS spacecraft. NASA expects to earmark about $25 million of the New Millennium budget on the development of EOS instruments and hopes that the infusion of New Millennium technology into the EOS will also reduce programme costs.
Japan's National Space Development Agency, the Canadian Space Agency and the European Space Agency (ESA) are planning, or have flown, similar missions, complementing the international global-change initiative. These include Canada's Radarsat, Japan's Advanced Earth Observing Satellite (which also carries a NASA TOMS instrument) and the European Remote Sensing (ERS) satellite series.
The ERS 2 carries an instrument to produce routine maps of global ozone and nitrogen dioxide in the atmosphere. These ESA craft will be followed by the Envisat and Metop polar platforms, although the Metop is also threatened by budget constraints. Many of these craft also carry an array of international experiments and include the US-Japanese Tropical Rainfall Mapping Mission, to be launched on an H2 booster.
DATA SYSTEM
To process, archive and distribute data from the Phase 1 MTPE and EOS spacecraft, NASA has established an EOS data and information system (EOSDIS) at the Goddard Space Flight Center. The EOSDIS is being developed by Hughes Information and Technology under a contract worth $2 billion.
EOS craft will provide 460 gigabytes/day of raw data, and other NASA and international missions will provide 28 gigabytes/day of raw data to the EOSDIS, which will then provide 1,600 gigabytes/day of processed data to the user community, through distributed active archive centres (DAACs), including those at other NASA centres, the US Geological Survey, and the US Department of Energy. Data from the DAACs will be made available to all relevant researchers, including 28 EOS interdisciplinary investigation teams.
"The priority of EOSDIS is to service the Earth science community," says Dalton, "but there is a large community out there - education, legal, commercial applications and so on, and we need to find a way of getting the data to these people at a nominal rate." This feeling is echoed by the NRC, which has criticised the EOSDIS as being too institutionalised.
To get the user community more involved in data processing, it has been determined that the EOSDIS should be transformed, to enable it to transfer data rapidly into the real user market. A competitively selected group of organisations will be made responsible for data products and information dissemination to the educational, public and private sectors, made possible by the growth of Internet-related on-line services.
Source: Flight International
