SPACE.com -- Planet Celebrates Earth Day With Sky Doctor

Terra Scouts Looming Drought

Terra Takes First Peek at Earth

$1.3 Billion Terra Satellite Reaches Final Orbit

Climate Satellite Terra Fixed, Again


	Planet Celebrates Earth Day With Sky Doctor By Maia Weinstock Staff Writer posted: 02:19 pm ET 16 April 2000

On April 22, 1970, millions of Americans observed the first Earth Day in parks and streets across the country. It was the first time that the nations masses would drop everything and convene out of concern for the health and well being of what some consider to be a fragile environment. Yet despite all the celebration, humans still had no way to gauge how Mother Nature was really feeling. Thirty years later, the doctor is finally in.

Currently in orbit around planet Earth, the Terra satellite is the most sophisticated Earth monitoring system in history. A virtual doctor in the sky, Terra is the flagship for NASAs new Earth Observing System, a new program aimed at studying long-term global environmental phenomena including weather, pollution, radiation, and vegetation.

"Earth Day reminds us that humans began an uncontrolled experiment on our planet that may have repercussions for our grandchildren and their grandchildren."

"Terra is the first mission designed to measure global changes on an almost daily basis over land, ocean and atmosphere," said Yoram Kaufman, Terra project scientist at NASAs Goddard Space Flight Center in Greenbelt, Maryland. The satellite will also "begin to differentiate natural changes from human-induced changes," said Kaufman.

Terra is not the first Earth monitoring satellite, but its by far the most comprehensive. Early environmental satellite systems like the Landsats enabled scientists to check one or two aspects of Earths health at a time. Today, Terra has the ability to capture dozens of data types, effectively giving Earth a full physical examination each day.

Originally launched in December 1999, Terra is equipped with five highly specialized science instruments from the United States, Japan, and Canada. Just one month after the satellite opened its eyes to the world, Terra has already given Earth science research an immense boost.

This Terra Earth image is created from four seperate data layers: visible light reflection over land (SeaWiFS), fires over land (AVHRR), aerosol over the oceans (AVHRR) and an infrared cloud image from four geostationary satellites. The large aerosol plume over the Atlantic is from fires and wind blown dust from Africa.

"Given the complexity and sophistication of the mission, its a little surprising for us to be seeing such high-quality images so soon," said Kaufman. "This is an exciting time for us."

Earth Day Every Day

Thirty years ago, the world witnessed the birth of a new environmental age: the age of Earth awareness. This year, Terra marks the beginning yet another environmental age: the age of Earth observation.

"Earth Day reminds us that humans began an uncontrolled experiment on our planet that may have repercussions for our grandchildren and their grandchildren," explained Kaufman. "In the last century, the expansion of the human population, of our Gross National Product, and of our exploitation of the planets natural resources have noticeably impacted the landscape, as well as air and water quality. These impacts are what eventually prompted a call for an Earth Day celebration."

With Terra, scientists will begin an ongoing process of giving the planet a thorough checkup. But instead of checking for heartbeat, vision, breathing, and hearing, Terra will inspect Earths land, ocean, atmosphere, ice reserves, and energy budget. "We will examine at an unprecedented level of detail how [these factors] affect each other, and how they affect the changes in climate that we observe," explained Kaufman.

One example of how Terra is already changing our view of the world can be seen in the sophistication of one the satellites five instruments, the Multiangle Imaging SpectroRadiometer (MISR). MISR is for the first time ever capturing information about Earths clouds, aerosols and land surfaces from nine different angles simultaneously. Images created with data collected by MISR will be used to, among other things, highlight hazardous aerosols and smoke plumes in the atmosphere, and even trace them back to their original sources.

The Future of Earth Observation

Terra is in fact only the first of a series of Earth Observing System (EOS) satellites. The next scheduled EOS satellite is called Aqua, and is slated for launch in December 2000. Aqua will complement Terras data collection with five new environment-observing instruments, two of which are copies of instruments already aboard Terra, and three of which are unique.

"The combination of Terra and Aqua will work out very well," said Aqua project scientist Claire Parkinson at NASAs Goddard Space Flight Center. "Both are supposed to last for five years, so there should be a four year overlap of data."

NASAs ultimate goal is to have indefinite Earth observation with orbiting satellites such as Terra and Aqua. Their aim is to understand not only immediate changes in our atmosphere, land, oceans, but to be able to predict how smaller changes lead to greater ones -- and uncover which changes the human population may be responsible for.

"The Earth system is a product of numerous processes that evolve rapidly and continually and affect each other in myriad ways," said Kaufman. "If we want to distinguish between the effects of human activity and natural trends on climate, worldwide weather patterns, food production, and severe storms, we need to constantly monitor Earth in order to acquire enough of a time series to better understand these processes."