UA Scientists Begin New Work with Terra

Lori Stiles
July 18, 2000


This story released Jan. 18, 2000 -

A newly launched satellite called Terra is about to turn on sensors that begin a 15-year program to collect information about Earth that will help scientists unravel the complexities of changing global environment.

NASA calls Terra "the flagship" spacecraft for a new era of comprehensive monitoring of the Earth's atmosphere, oceans and continents from a single space-based platform. NASA hails Terra as its first attempt to gather a continuous and well-calibrated long-term data set on the entire Earth system.

Five instruments on Terra will record global and seasonal changes in the biological output of land and oceans, global and seasonal changes in surface temperatures, cloud cover, water vapor, snow, ice and vegetation land cover.

Scientists will use Terra data, along with other remote-sensing data, to develop computer models that enable them to understand the causes and effects of climate change. They will be able to detect human impacts on the Earth system and climate. They will develop improved technologies for disaster prediction and for reducing risks posed by wildfires, volcanoes, floods and droughts.

Terra, successfully launched one month ago today, is the first of next-generation Earth Observing System (EOS) satellites, which are part of NASA's Earth Science Enterprise (formerly called Mission to Planet Earth).

Scientists across the University of Arizona campus are involved in Terra, EOS and the Earth Science Enterprise. They include:

**Atmospheric sciences Professor Roger Davies , 520-621-6844, davies@atmo.arizona.edu.
Web site -

Davies studies interactions between clouds and solar radiation - one of the largest uncertainties in understanding global climate change. His special expertise is in the remote sensing of cloud properties and in developing climate models. Davies is co-investigator on the Terra science team that designed and will use MISR, the Multi-angle Imaging SpectroRadiometer.

MISR is a totally new instrument. Earlier sensors have measured reflected sunlight, but in only a single direction at a time. MISR uses an array of nine cameras to measure reflected sunlight from several directions during the seven minutes when a point on the Earth is viewed by the orbiting satellite. These measurements will reveal many new details of how sunlight is scattered by the Earth's atmosphere and surface, Davies says. Combined measurements from different directions will create an enhanced stereo effect that will give scientists their first three-dimensional views of clouds and other short-lived targets on a global scale, he adds.
"Climate is affected by the reflection of solar energy from many different surfaces," Davies explains. "Forests, deserts and the various types of land surface cover change slowly. Clouds and the smoke from forest fires change quickly. Snow-and-ice-covered surfaces and the tiny atmospheric particles that we think of as air pollution _ even though many come from natural sources _ are also important and can vary significantly. MISR will measure the global distribution of each of these types of reflectors and monitor any changes in reflectivity on different time scales."

Most of Davies' work on MISR is directed at studies of cloud reflectivity. He has developed many of the theoretical tools and algorithms needed to usefully interpret the measurements from this new type of instrument. This research is centered in the Radiation, Clouds and Climate Laboratory in the UA atmospheric sciences department.


**Optical sciences Assistant Professor Kurtis J. Thome, 520-621-4535,
kurt.thome@opt-sci.arizona.edu
Web site -

Thome, director of the Optical Sciences Center Remote Sensing Group, is a member of two science teams for Terra. He is responsible for the "vicarious" calibration of two sensors -- ASTER, or the Advanced Spaceborne Thermal Emission and Reflection Radiometer, and MODIS, the Moderate-Resolution Imaging Spectroradiometer.
Calibration is the process by which sensor outputs, given in voltages or digital counts, are converted into physical, real-world values, such as watts.

NASA calibrates all sensors in the laboratory before launch. But sensor characteristics change over time. Thome and his group provide vicarious calibration to validate the data reported by sensors once they are in orbit through the end of their operational lifetimes. This calibration is critical if scientists are to have consistent and reliable data . As Thome says, 'If you want to observe how the Earth is changing, you have to understand how your sensors are changing over time."

Vicarious calibration isn't only laboratory work. Thome and his indomitable UA students strap on backpack frames laden with science instruments that measure ground reflectance and carry the equipment over large areas of land at the same time the satellite sensor views their test site from orbit. They process their ground-reflectance data using computer models to predict the amount of energy detected by the satellite-borne sensors.

Thome and his team have been using several test sites to calibrate the Enhanced Thematic Mapper Plus, which was launched on another EOS satellite, Landsat-7, last April. They will use the same tests sites to calibrate ASTER and MODIS on Terra beginning late next month. The test sites are at the White Sands Missile Range near Alamogordo, N.M., Lunar Lake and Railroad Valley Playas in east central Nevada, and Ivanpah Playa on Interstate-15 on the California-Nevada border. For Terra, they will add a test site near Lake Tahoe, Nev.

For both Landsat-7 and Terra calibration, Thome's group now measures ground reflectance at a test site at the Pima County Fairgrounds east of Tucson every 16 days. It is a site they can visit more often than the remote locations.

**Professor Alfredo Huete of the department of soil, water and environmental sciences, 520-621-3228, ahuete@ag.arizona.edu
Web site for prototype MODIS sample images and early image results _


At the UA, Huete heads the Terrestrial Biophysics and Remote Sensing program within the department of soil, water and environmental sciences. The broad program goal is to analyze and understand environmental change over terrestrial landscapes. Huete and his team use satellite data on vegetation, land cover, land surface wetness, drought, soil and plant condition in studying environmental, regional and global change issues.

Huete is a member of the MODIS science team. This Terra sensor, the Moderate-Resolution Imaging Spectroradiometer, scans the entire surface of the Earth every one-to-two days, collecting images of daylight-reflected solar radiation and day/night thermal emissions over the entire globe. Although MODIS has a wide field of view _ more than 2,300 kilometers (1,400 miles) _ it will see features as small as a kilometer (six-tenths of a mile) or even a quarter-kilometer across.

Huete's role as a researcher with the MODIS Land Discipline Group has been in developing the "algorithms," or sets of mathematical procedures, needed to usefully interpret MODIS images of land vegetation. These "vegetation indices" will correct raw MODIS images for changing cloud cover, sun angle and other atmospheric conditions, and also for the amount of old or dead, non-photosynthetic plant debris in the background canopy. The MODIS vegetation index will give researchers a consistently accurate picture of how photosynthetically active vegetation covering Earth's land surfaces is changing over space and time.

This will provide "unprecedented opportunities for satellite mapping of deforestation, land degradation, drought, and agriculture, range and forest productivity," Huete said. "My group and the MODIS team are all so excited at this opportunity to document and monitor biospheric health, and measure the sustainability of human life on planet Earth."

**Soroosh Sorooshian, Regents Professor of hydrology and water resources, EOS interdisciplinary science investigator, 520-621-1661, soroosh@hwr.arizona.edu


Sorooshian is principal investigator on an EOS research project to monitor and study the hydrological cycle and climatic processes in arid and semi-arid areas. The UA coordinated effort focuses on the development of computer models that can quantitatively predict the effects of changing climatic inputs on arid and semi-arid hydrologic systems. More about this project can be found at the UA hydrology and water resources department EOS site

As part of that work, Sorooshian and his group will conduct a regional study that will use MODIS data to keep track of seasonal land cover changes in the Southern Colorado Basin. He will study whether seasonal changes in vegetation growth are connected to large climate events like El Nino. Knowing how larger and smaller climate systems are related could help scientists forecast drought events and evaluate forest fire hazards.

**W. James Shuttleworth, professor of hydrology and water resources, EOS interdisciplinary science investigator and co-investigator, 520-621-8787, shuttle@hwr.arizona.edu


Shuttleworth is principal investigator on an EOS research project to develop better methods for interpreting remote sensing data on land cover, surface temperature and surface reflectance. For example, Shuttleworth will use ASTER data to study different climates in the southwestern United States (specifically, the San Pedro Valley of southern Arizona), the Tennessee Valley and two sites in the Amazon rainforest of Brazil. ASTER will measure heat radiating from the ground more accurately than any previous civilian satellite sensor. Knowing the ground temperature can also tell scientists how much water is in the soil, which is important information for farmers, land managers and climatologists.


**Benjamin M. Herman, director of the UA Institute of Atmospheric Physics and head of atmospheric sciences, 520-621-6831, herman@air.atmo.arizona.edu
Web site -

Herman is co-investigator on the SAGE III science team, part of EOS. The SAGE III satellite is tentatively slated for launch on the Russian Meteor 3M-1 spacecraft in summer 2000, on the International Space Station in 2002 and on a still-to-be-determined third platform later. SAGE III will make long-term measurements of atmospheric aerosols, ozone, water vapor and clouds from the middle troposphere through the stratosphere. (The troposophere is the lowest layer or region of the atmosphere, where our weather occurs. The stratosphere, the next layer up, begins at about 48 kilometers, or 29 miles, up.)

Other UA media contacts on global change involved in NASA's EOS program are:

**Victor Baker, head of the department of hydrology and water resources, interdisciplinary science co-investigator, 520-621-7875, baker@hwr.arizona.edu. Research expertise - flood geomorphology and geology of natural hazards, global flooding and policy implications of geology.

**Roger C. Bales, professor of hydrology and water resources, interdisciplinary science co-investigator, 520-621-7113, roger@hwr.arizona.edu. Research expertise - snow and ice, hydrology, polar ice cores, alpine hydrology, biogeochemistry.

**Stuart F. Biggar, associate research professor of optical sciences, member of the ASTER, MODIS and Landsat 7 calibration team, 520-621-8168, stuart.biggar@opt-sci.arizona.edu. Research expertise - radiometry, sensor calibration and characterization calibration of optical sensors, reflectance measurement.

**Katherine Hirschboek, associate professor of climatology in the UA Laboratory of Tree-Ring Research, interdisciplinary science co-investigator, 520-621-6466, katie@ltrr.arizona.edu. Research expertise - flood hydroclimatology, snynoptic dendroclimatology, climate variability and flooding, atmospheric circulation patterns and tree-ring variability.

**E. Philip Krider, professor of atmospheric sciences, 520-621-6836, krider@atmo.arizona.edu. Research expertise - lightning, atmospheric electricity, electrical structure of thunderstorms, physics of lightning.

**Stuart Marsh, professor of arid land studies, member of the MODIS validation team, 520-621-8574, smarsh@ag.arizona.edu. Research expertise - land cover change, remote sensing.

**Robert A. Schowengerdt, professor of electrical and computer engineering, MODIS sensor performance and data processing, 520-621-2706, schowengerdt@ece.arizona.edu. Research expertise - image processing, remote sensing.

*****EDITORS: This press kit and other stories are online at the UA News Services science web site,

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