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Issue 3: Remote Sensing Satellites (page 1)


EROS (Earth Remote Observation System) A1 was launched in December 2000 as the first constellation of eight high-resolution imaging satellites to be launched between year 2001 and 2005. EROS satellites are high performance, low cost, light, and agile and have been designed for low earth orbit (LEO). The satellites are owned and operated by ImageSat International. This Cyprus-based company was established in 1997 by a consortium of leading satellite, sensor and information management companies and information producers around the world.

In February 2001, a couple of months after EROS A1 was launched, ImageSat decided to forgo the production and launch of its planned EROS A2 satellite. The company cited EROS B series' better performance and longer life span as the main reasons. EROS B series will have higher resolution imaging sensors than the company's first satellite. ELOP, the manufacturer of EROS sensors and cameras, has designed EROS B series camera to carry a device that enables synchronous imaging of Earth under weak lighting conditions.

All EROS satellites will go into polar orbit and are sun-synchronous so all images photographed by a given satellite will be taken at the same local time, no matter the day, month, or year. The orbital period (time taken for one revolution around the Earth) of each satellite is 90 minutes or 16 revolutions of the Earth in 24 hours. EROS satellites are unrivaled in their ability to acquire numerous specific images of the ground due to a high-resolution camera aboard the satellite. The camera has a focal plane of CCD (Charge Coupled Device) detectors with 7,800 pixels per line and produces a panchromatic image with a resolution of 1.8-m pixel spacing. EROS remotely sensed data is used by scholars, engineers, land managers, and policy makers worldwide conducting studies on a wide range of natural hazards, global environmental change, land use planning and landscape transformation, and economic development and conservation issues. Spatial resolutions images are used for different applications.

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Launched in December 1999, Terra is the flagship of NASA's Earth Observing System (EOS) series of 10 satellites scheduled for launched over a 10-year period.

EOS is part of NASA's Earth Science Enterprise, a long-term research program dedicated to understanding how human-induced and natural changes affect the global environment.

The satellite was previously known as EOS AM-1, signifying its morning equatorial crossing time. The name Terra was given to the EOS AM-1 spacecraft by a 12th grader from St. Louis, Missouri in a contest that was co-sponsored by NASA and the American Geophysical Union (AGU). The satellite was manufactured by Lockheed Martin Missiles & Space (LMMS) and is managed by NASA's Goddard Space Flight Center.

A multi-national mission, Terra carries a payload of five complementary sensors. The Clouds and the Earth's Radiant Energy System (CERES) and the Moderate-resolution Imaging Spectroradiometer (MODIS) instruments were developed by NASA Field Centers. The Measurements Of Pollution In The Troposphere (MOPITT) instrument was designed by Canadian scientists at the University of Toronto and manufactured by COM DEV International of Cambridge, Ontario. The Multi-angle Imaging SpectroRadiometer (MISR) instrument was built by Jet Propulsion Laboratory, while the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was developed in Japan for the Ministry of Economy Trade and Industry (METI).

Terra emphasizes observations of terrestrial surface features. Each sensor has unique design features that will provide a thorough evaluation of the Earth system. Continents, oceans, and atmosphere, which determine the water and nutrients cycle on Earth, make up the system. The instruments on Terra collect and archive an unprecedented quantity of high-quality multi-spectral data. These remotely sensed images provide a high-resolution multi-faceted view of both seasonal and inter-annual changes in the terrestrial environment.

EOS scientists use TERRA data to meet a wide range of science objectives, mainly to study the interactions among the components of the Earth system and their interactions with solar radiation, interactions essential to understanding global climate change. The instruments will also improve users ability to identify human activity and detect human impacts on the Earth system and climate.

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Aqua, the twin sister satellite to NASA's Terra spacecraft, is the latest sibling in the Earth Observing System (EOS) series of satellites. Launched in May 2002, Aqua represents a multidisciplinary study of the world's global water cycle. Aqua was formerly named EOS PM, signifying its afternoon equatorial crossing time.

Aqua is an international partnership between the United States, Japan and Brazil. The spacecraft and four of Aqua's six scientific instruments are provided by NASA, while NASA's Goddard Space Flight Center provided the Moderate Resolution Imaging Spectroradiometer (MIRS) and the Advanced Microwave Sounding Unit (AMSU-A). Jet Propulsion Laboratory provided the Atmospheric Infrared Sounder (AIRS). NASA's Langley Research Center provided the Clouds and the Earth's Radiant Energy System (CERES) instrument. Japan's National Space Development Agency provided the Advanced Microwave Scanning Radiometer (AMSR-E). The Instituto Nacional de Pesquisas Espaciais (the Brazilian Institute for Space Research) provided the Humidity Sounder for Brazil (HSB).

Instruments aboard Aqua employ the latest remote sensing technologies and take multiple readings of climate-related measurements, such as global precipitation, evaporation and the cycling of water, to maximize the amount of information returned to Earth. Like Terra, Aqua instruments provide coverage on areas of largest uncertainty such as atmospheric humidity, radiative energy fluxes, aerosols, vegetation cover, phytoplankton and dissolved organic matter. Its Atmospheric Infrared Sounder (AIRS) instrument can help scientists to improve weather prediction and to observe changes in the climate. Scientists can better understand how global ecosystems are changing, how to respond to and affect global environmental change. In its first weeks of operation, after the instrument opened its Earth-view door, Aqua MODIS observed significant Earth events occurring all over the globe. MODIS collected and beamed to Earth images of typhoon, floods, and wildfires in 3 different areas in very-near real time. Japan's Advanced Microwave Scanning Radiometer (AMSR-E) produced Aqua's first geophysical product: a global map of sea surface temperatures.

Like Terra, Aqua spacecraft is in a near-polar, sun synchronous orbit with an orbital period of 98.8 minutes. It has 6 years of mission life. Aqua provides direct broadcast services on X-Band. The spacecraft bus is scalable to meet the needs of future remote sensing missions, including Aura that is due to be launched in 2004. Aqua and subsequent EOS spacecraft due to be launched within the next decade will be operated in groups, rather than as single entities. Terra and Aqua are in formation with Landsat 7. This formation takes advantage of the enhanced calibration of Landsat's ETM+ instrument, which serves as an on-orbit standard for cross-calibration of other Earth remote sensing mission.

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Issue No. 3:
Remote Sensing of Earth
via Satellite

Winter 2003

General Editor Introduction

From the Guest Editors

Introduction to Remote Sensing

A Tutorial:
p. 1
, p. 2

Science for Society:
p. 1
, p. 2, p. 3

AmericaView Consortium

Remote Sensing Satellites:
p. 1
, p. 2

Online Resources

Research and Applications

Critical Perspectives

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