CHAPTER 1 SECTIONS > Background | Mission Objectives | System Capabilities
The Landsat 7 Handbook is out of date. A revised
version to bring the information up to date will be developed and posted
when complete. Please see the USGS Landsat site at
https://lta.cr.usgs.gov/LETMP for current information on Landsat 7 ETM+
data and data products.
1.1 Background to the Landsat Program
The Landsat Program has provided over 38 years of calibrated high spatial
resolution data of the Earth's surface to a broad and varied user community,
including agribusiness, global change researchers, academia, state and
local governments, commercial users, military, and the international
Landsat images provide information meeting the broad and diverse needs
of business, science, education, government, and national security.
The mission of the Landsat Program is to provide repetitive acquisition
of high resolution multispectral data of the Earth's surface on a global
basis. Landsat represents the only source of global, calibrated, high
spatial resolution measurements of the Earth's surface that can be compared
to previous data records. The data from the Landsat spacecraft constitute
the longest record of the Earth's continental surfaces as seen from space.
It is a record unmatched in quality, detail, coverage, and value.
The Landsat platforms carry multiple remote sensor systems and data relay
systems along with attitude-control and orbit-adjust subsystems, power
supply, receivers for ground station commands and transmitters to send
the data to ground receiving stations.
The most recent Landsat mission, Landsat 7, offers these features:
- Data Continuity: Landsat 7 is the latest in a continuous series
of land remote sensing satellites spanning 38 years.
- Global Survey Mission: Landsat 7 data will be acquired systematically
to build and periodically refresh a global archive of sun-lit, substantially
cloud-free images of the Earth's landmass.
- Affordable Data Products: Landsat 7 data products will be available
through the EROS Data Center at the cost of fulfilling user requests
- Enhanced Calibration: Data from the ETM+ will be calibrated
to better than 5% absolute, providing an on-orbit standard for other
- Responsive Delivery: Automated request processing systems will
provide products electronically within 48 hours of order.
The continuation of the Landsat Program is an integral component of the
U.S. Global Change Research Program. Landsat 7 is part of a global research
program known as NASA's Earth Sciences Enterprise, a long-term program
that is studying changes in Earth's global environment. The goal of Earth
Sciences Enterprise is to provide a better understanding of natural and
man-made environmental changes. In the Landsat Program tradition, Landsat
7 will continue to provide critical information to those who characterize,
monitor, manage, explore, and observe the land surfaces of the Earth over
Landsat satellites have been providing multispectral images of the
Earth continuously since the early 1970's. A unique 38-year data record
Earth's land surface now exists. This unique retrospective portrait of
the Earth's surface has been used across disciplines to achieve improved
understanding of the Earth's land surfaces and the impact of humans on
the environment. Landsat data have been utilized in a variety of government,
public, private, and national security applications. Examples include
land and water management, global change research, oil and mineral exploration,
agricultural yield forecasting, pollution monitoring, land surface change
detection, and cartographic mapping.
Landsat 7 is the latest satellite in this series. The first was launched
in 1972 with two Earth-viewing imagers - a return beam vidicon and an
80 meter multispectral scanner (MSS). Landsat 2 and 3, launched in 1975
and 1978 respectively, were configured similarly. In 1984, Landsat 4 was
launched with the MSS and a new instrument called the Thematic Mapper (TM).
Instrument upgrades included improved ground resolution (30 meters) and
3 new channels or bands. In addition to using an updated instrument, Landsat
4 made use of the multimission modular spacecraft (MMS) which replaced
the Nimbus based spacecraft design employed for Landsats 1-3. Landsat
5, a duplicate of 4, was launched in 1984 and even today after
26 years - 21 years beyond its 5 year design life - is still returning
useful data. Landsat 6, equipped with a 15 meter panchromatic band, was
lost immediately after launch in 1993.
Table 1.1 lists key mission characteristics of the Landsat Program while
Table 1.2 compares the sensors carried aboard these satellites. A detailed
Program Chronology is also available.
|Table 1.1 Landsat Mission Characteristics
|Table 1.2 Landsat Satellites and Sensors
In the mid 1980's, U.S. Government agencies, including NASA and NOAA,
were directed to attain their commercial space objectives without the
use of direct federal funding by entering into appropriate cooperative
agreements with private sector corporate entities to encourage and advance
private sector basic research, development, and operations.
The implementation of this policy required the transfer of government-developed
space technology to the private sector in such a manner as to protect
its commercial value, which included retention of technical data rights
by the private sector. Commercial sector space activities developed under
this mandate were to be supervised or regulated by federal agencies only
to the extent required by law, national security, international obligations
and public safety.
With the passage of Public Law 98-365, the "Land Remote Sensing Commercialization
Act of 1984", NOAA was directed to delegate management of the Landsat
4 and 5 satellites and their data distribution to the private sector.
In addition, NOAA was to pursue procurement of future remote sensing Landsat
products and services from the private sector.
In 1985, NOAA solicited bids to manage the existing Landsat satellites
and to build and operate future systems. The Earth Observation Satellite
Company (EOSAT), a joint venture between RCA and Hughes Aircraft, now
called Space Imaging Corporation, won the competitive bidding process
in August 1984 and took over operation of the Landsat system on September
From 1985 to 1994, EOSAT retained exclusive sales rights to all Landsat
4 and 5 Thematic Mapper (TM) data until July 1994, at which time Landsat
data over ten years old became available from the National
Archive at the EROS Data Center (EDC). This agreement
between Landsat Program management and EOSAT Corporation on cost and reproduction
rights for Landsat 4 and 5 Thematic Mapper data remains in effect and
was last updated in October 1996. EOSAT also won competition to produce
the next satellite in the series, Landsat 6.
By 1992, it had become clear that the high cost of commercially-provided
Landsat data had greatly restricted its use in research and other public
sector applications. In response, the U.S. Congress passed H.R. 6133,
Remote Sensing Policy Act of 1992", into law in September of that
year. This law established a new national land remote sensing policy which:
- Abandoned full commercialization of the Landsat Program.
- Returned management of the Program to the Government.
- Established a data policy of distributing Landsat data at the cost
of fulfilling a user request (COFUR).
- Directed that preliminary work begin on a new Landsat 7.
- Foster development of advanced land remote sensing systems and opportunities
The loss of Landsat 6 in October, 1993
suddenly made the new Landsat 7 mission imperative. A May
5, 1994 Presidential Decision Directive (NSTC-3) defined the new Landsat
7 data policy, program management strategies and implementation guidelines.
Subsequent NASA and NOAA memoranda later that summer brought the current
Landsat 7 mission into existence.
Other, recent legislation relevant to Landsat:
Short title: "Civilian Space Authorization Act, Fiscal Years 1998 and
Short title: "National Oceanic and Atmospheric Administration Authorization
Act of 1997"
Short title: "Commercial Space Act of 1997"
and Pending Legislation Affecting the Landsat Program for detailed
public law information.
The Landsat 7 Program management structure changed repeatedly from
1992 through 1998, from NASA/USAF/USGS to NASA/NOAA/USGS to a bi-agency
NASA/USGS partnership. As
described in the Landsat
7 Management Plan, NASA is responsible for the development and launch
of the Landsat 7 satellite and the development of the ground system.
The Landsat Project at Goddard Space Flight Center manages these responsibilities
with Hughes Santa Barbara Remote Sensing building the sensor and Lockheed
Martin Missiles and Space developing the spacecraft. The USGS is responsible
for operation and maintenance of the satellite and the ground system
for the life of the satellite. In this role the USGS captures,
processes, and distributes the data and is responsible for maintaining
the Landsat 7 data archive. The following web sites should be visited
for additional information:
- NASA Landsat
7 Project developed the Landsat 7 System. Specifically,
it meant designing, developing, and testing the Landsat 7 spacecraft,
ETM+ instrument, and the end-to-end ground system. NASA was also responsible
for the satellite launch and performing a 60 day in-orbit check
before handing operations to the USGS. NASA is still responsible
for verifying data processing integrity and assuring high image
- The USGS Center for Earth
Resources Observation and Science (EROS)
manages the overall Landsat 7 Mission Operations. In this capacity
EDC directs on-orbit flight operations, implements mission policies,
directs acquisition strategy, and interacts with International Ground
Stations. EDC captures Landsat 7 data and performs pre-processing,
archiving, product generation, and distribution functions. EDC also
provides a public interface
into the archive for data search and ordering and handles billing and