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Landsat-7 Launch Delayed

Douglas Isbell
Headquarters, Washington, DC                       March 12, 1998
(Phone: 202/358-1753)

Allen Kenitzer/Lynn Chandler
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-8955)

RELEASE:  98-41

LANDSAT-7 LAUNCH DELAYED

     The Landsat-7 Earth science spacecraft will not be launched 
in July 1998 as planned, due to necessary changes in the design 
of the electrical power supply hardware for the spacecraft's main 
instrument.  A new target launch date will be set by NASA 
officials after completion of instrument thermal vacuum tests 
scheduled for this July.

     During a series of instrument-level thermal vacuum tests 
beginning in December 1997, a power supply on the Enhanced 
Thematic Mapper Plus (ETM+) instrument failed twice.  ETM+ is 
Landsat-7's only science instrument.  As a result of the most 
recent failure in January, both internally redundant power 
supplies were returned to their manufacturer.  Completion of 
vacuum testing will be delayed while the power supplies are being 
repaired, which will consequently delay the launch.  

     It is not possible to set a precise new date for the launch 
from Vandenberg Air Force Base, CA, at this time, according to 
project managers.  NASA will now work with its launch contractor, 
Boeing, on moving the Landsat-7 launch to a mutually agreeable date.

     "We're looking at several options in order to minimize the 
impact to the launch schedule," said Phil Sabelhaus, Landsat-7 
project manager at NASA's Goddard Space Flight Center, Greenbelt, 
MD.  "When we understand precisely why the power supply failed 
and how long it will take to fix the problem, we'll be able to 
ascertain the impact to the launch schedule."

     The enhanced thermatic mapper was designed and built by 
Raytheon (formerly Hughes) Santa Barbara Remote Sensing, Santa 
Barbara, CA.  The Landsat-7 spacecraft was built by Lockheed 
Martin Missiles and Space, with integration of the instrument and 
spacecraft conducted at the company's facility in Valley Forge, PA.

     Landsat-7 is the latest installment in a long history of 
land remote-sensing spacecraft, spanning over 25 years of 
multispectral imaging of the Earth's surface, starting with the 
launch of Landsat-1 in 1972.  Landsat-5, launched in March 1984, 
is still transmitting images to several domestic and 
international ground stations worldwide.  

     In particular, the science instrument on Landsat-7 will 
continue a data base of high-resolution Earth imagery begun in 
1982 by the Landsat-4 thematic mapper.  As changes occur on the 
Earth's surface due to natural or human-induced events, 
scientists will be able to study these recent changes with the 
aid of the archive of similar imagery.  Applications include 
agriculture, forestry and urban planning.

     Landsat-7 will add to the global archive of sun-lit, 
substantially cloud-free images of the Earth's land surfaces.  
Approximately one-quarter of the Earth's landmass will be imaged 
every 16 days, with a emphasis on seasonal changes in vegetation.
     
     Landsat-7 contains several technological improvements over 
previous Landsat satellites and their instruments.  These 
improvements include better instrument calibration and a solid 
state data recorder capable of storing 100 individual enhanced 
thematic mapper images of the Earth.  This capability will enable 
Landsat-7 to update a complete global view of Earth's land 
surfaces seasonally, or approximately four times per year.

     NASA also is developing an advanced land imager instrument 
and related small spacecraft technology that will enable future 
follow-on measurements to be made by a sensor that is one-fourth 
the mass of the enhanced thermatic mapper and uses only 20 
percent of the electrical power, while reducing the instrument's 
cost by 75 percent.

     Landsat-7 was authorized by the Land Remote Sensing Policy 
Act of 1992, which established a joint NASA-U.S. Air Force 
program.  This was superseded by a second Presidential Directive 
in 1994, that established a joint program between NASA, the 
National Oceanic and Atmospheric Administration (NOAA) and the 
U.S. Geological Survey (USGS).

     Landsat-7 is part of NASA's Earth Science enterprise, a 
long-term research program designed to study Earth's land, 
oceans, atmosphere, ice and life as a total integrated system.  
Goddard Space Flight Center manages the development of Landsat 
for NASA's Office of Earth Science in Washington, DC.

                          -end-