CU-Boulder Satellite Instrument to Provide New Details on Ozone

Just after 3 a.m. on July 10, University of Colorado at Boulder researcher John Gille expects to watch a new NASA satellite blast into orbit from the dark California coastline on a mission to study Earth's protective ozone layer, climate and air quality changes with unprecedented detail.

Gille, principal investigator on the satellite's High Resolution Dynamics Limb Sounder (HIRDLS) instrument, said he and his sleep-deprived colleagues will probably only get to watch the rocket for a few moments before it disappears into a thick deck of clouds that typically settles over the area this time of year.

The irony isn't lost on Gille, who's been at work on the instrument since 1988. "Writing about clouds in a meteorological journal, a scientist once said, 'There's no way to deal with these troublesome objects,' " he laughed.

Surface ozone pollution and air quality deterioration -- byproducts of agricultural burning, deforestation, urban activity and industry -- are increasing worldwide. Questions remain about the recovery of the protective ozone layer and the role of chemistry in climate change. HIRDLS and three other instruments on NASA's AURA satellite are designed to address these questions in detail.

HIRDLS is an international collaboration between scientists and engineers in the U.S. and Britain. Gille is HIRDLS U.S. principal investigator, and along with his Oxford University counterpart he is responsible for the overall success of the instrument, including design, testing, collection and use of data for scientific purposes.

At CU-Boulder, Gille is an adjoint professor in the Program in Atmospheric and Oceanic Sciences and senior research associate at the Center for Limb Atmospheric Sounding. "Limb" is the astronomical term for the edge of a planet and its atmosphere.

"Unlike the satellite images you see during TV weather forecasts, which are looking straight down at the Earth, our instrument is looking off toward the horizon," Gille said. "We look at the horizon from orbit, scanning up and down for a profile view."

The profile gives scientists insight into radiation, temperature and distribution of gases at different levels in the atmosphere. The data is then used to study the ozone layer, climate change and interaction between layers of the atmosphere.

HIRDLS will scan the mid- to upper-troposphere and the tropopause, the boundary region between the troposphere and the stratosphere. The troposphere extends upward from the Earth's surface to about 10 miles high at the equator and five miles high at the North and South poles. The stratosphere, which contains trace gases as well as the radiation-absorbing ozone layer, lies on top of the troposphere.

HIRDLS is expected to present a much clearer picture of whether the ozone layer is recovering, as well as the distribution of greenhouse gases that influence climate.

"HIRDLS has much finer horizontal resolution than we've ever had before," Gille said. "We can send commands to the satellite to zoom in and get readings with resolutions as fine as 30 to 60 miles, and a vertical resolution of 1,500 feet. Also, the HIRDLS detectors are up to 10 times more sensitive than similar instruments that have flown in the past."

The instrument is designed to last much longer in orbit than its predecessors, too. Thanks to an onboard mechanical refrigerator built by Ball Aerospace and Technologies Corp. of Boulder, scientists expect it will last longer than five years. It's hoped that longer-term trends can be predicted with the volume of data that will be collected.

The HIRDLS project began in 1988. Since that time, Gille and his research team at the university have led a collaborative effort to design and build the instrument with scientists and engineers at Oxford University in the United Kingdom, the National Center for Atmospheric Research in Boulder, the University of Washington and Lockheed Martin in Palo Alto, Calif.

Gille expects many of those who have worked on HIRDLS during the past 16 years to make the trip to Vandenburg Air Force Base, north of Santa Barbara, Calif., for the July 10 AURA launch at 3:01 a.m. Pacific Daylight Time.

Watching Space Rocks: Live Chat With NASA's Asteroid Trackers

This view of asteroid Ida and its moon Dactyl, to the right, was taken by the Galileo spacecraft.

March 23, 2009

A live videocast and chat from NASA's Jet Propulsion Laboratory, Pasadena, Calif., offers a unique opportunity for viewers to ask questions of scientists with NASA's Near-Earth Object Program Office about how NASA discovers and tracks asteroids.

The live event will air on the "NASAJPL" channel available on Ustream TV at: on March 25 at 4:30 p.m. PDT (7:30 p.m. EDT and 23:30 UTC).

NASA detects and tracks asteroids and comets passing close to Earth. The Near-Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet.

Participants include:
-- Don Yeomans, manager, NASA's Near-Earth Object Office at JPL
-- Steve Chesley, scientist, NASA's Near-Earth Object Office at JPL
-- Paul Chodas, scientist, NASA's Near-Earth Object Office at JPL

If you are unable to take part in the live chat, you can submit questions in advance to chatquestion@jpl.nasa.gov and watch the archived video at a later time.

More information about NASA's Near-Earth Object Program Office is available at:

NASA's Jet Propulsion Laboratory, managed by the California Institute of Technology, Pasadena, manages the Near-Earth Object Program Office for NASA's Science Mission Directorate, Washington.

Brainstorms Build Bridges Brainstorms Build Bridges

Brainstorms Build Bridges

The Keck Institute for Space Studies brings together the expertise of JPL and the Caltech Campus to address high-return concepts for space mission science and technology.

The Jet Propulsion Laboratory and the California Institute of Technology are collaborating to address the science and technology needs of future space missions. The W.M. Keck Institute for Space Studies, or KISS, brings together study leads from each organization to identify key challenges for missions and instrumentation and then funds the initial technical development research toward breaking those barriers.

The W.M. Keck Foundation awarded an eight-year grant to Caltech in 2008 to develop a “think and do tank” for new planetary, Earth and astrophysics approaches that will impact future space missions. KISS began operations in October, 2008 and is funded at $3 million per year to foster collaborations between Caltech and JPL researchers that will lead to revolutionary space mission concepts and technologies. JPL expects to provide additional discretionary funding, to support its participation in the Institute, through the Research & Technology Development (R&TD) program.

Institute director Tom Prince, who served previously as Chief Scientist at JPL, says the nature of the award is significant. “As far as I know, this represents the first time that a private foundation has invested its money for the benefit of the U.S. space program,” he says. Private funding allows KISS to pursue research that is high-risk, but with correspondingly higher payoffs. “We’re looking for ideas with potentially huge returns, and we’re willing to accept a certain amount of risk for those returns,” says Michele Judd, the Institute’s managing director.

Caltech manages JPL for NASA, but the two Pasadena institutions maintain distinctive personalities and cultures. Both realized there was an enormous underdeveloped potential for collaboration between them.

What grew out of this recognition is an organization that is not just a traditional think tank, in which a diverse group of people comes together for intensive interactions that generate new ideas. The KISS “think and do” charge is to follow up the brainstorming with targeted seed funding of groundbreaking technical work.

KISS awards funding for large, one-year study programs that, with sufficient progress, may lead to two-year technology development follow-up work. In addition, the institute’s short-duration mini-studies allow researchers to quickly target novel concepts and pressing challenges that can serve as incubators for future large studies. Academic programs, including postdoctoral and graduate fellowships, as well as public outreach programs, are also part of the Institute’s ambitious agenda.

Collaboration in KISS studies gives participants leverage in pursuing additional funding sources for their work, as they take with them a vote of confidence by the Institute and funding to immediately begin addressing their technical concerns. Receiving a seed award from KISS makes it easier to apply for larger awards to take their ideas to the next level.

KISS opened its virtual doors in late 2008, and will establish a physical location on the Caltech campus in mid-2009. The space will provide offices for 24 program participants, plus conference and seminar rooms. “It’s important that a KISS program is not just another workshop or symposium,” Prince says. “We want to create the physical environment in which technical discussions take place and bring together people who wouldn’t necessarily talk and work in concert.”

The initial challenge for KISS is to figure out how to enmesh the many institutional cultures, policies and roles of the two organizations. “There are a huge number of different cultures within JPL, and equally many on the Caltech campus, and each culture knows that theirs is the one that everybody should adopt,” jokes Prince. “So part of the challenge is to do the social experiment of merging these different cultures. The Institute is, to some extent, what we choose to make it.”

Cassini Provides Virtual Flyover of Saturn's Moon Titan

Cassini's radar mapper has obtained stereo views of close to 2 percent of Titan's surface during 19 flybys over the last five years. Image credit: NASA/JPL/USGS
›

March 24, 2009

PASADENA, Calif. -- "Fly me to the moon"-to Saturn's moon Titan, that is. New Titan movies and images are providing a bird's-eye view of the moon's Earth-like landscapes.

The new flyover maps show, for the first time, the 3-D topography and height of the 1,200-meter (4,000-foot) mountain tops, the north polar lake country, the vast dunes more than 100 meters (300 feet) high that crisscross the moon, and the thick flows that may have oozed from possible ice volcanoes.

The topographic maps were made from stereo pairs of radar images. They are available at: and

Cassini radar team member Randy Kirk with the Astrogeology Science Center at the U.S. Geological Survey in Flagstaff, Ariz., created the maps. He used some of the 20 or so areas where two or more overlapping radar measurements were obtained during 19 Titan flybys. These stereo overlaps cover close to two percent of Titan's surface. The process of making topographic maps from them is just beginning, but the results already reveal some of the diversity of Titan's geologic features.

"These flyovers let you take in the bird's-eye sweeping views of Titan, the next best thing to being there," said Kirk. "We've mapped many kinds of features, and some of them remind me of Earth. Big seas, small lakes, rivers, dry river channels, mountains and sand dunes with hills poking out of them, lava flows."

Kirk will present these results today at the Lunar and Planetary Science Conference in The Woodlands, Texas.

High and low features are shown in unprecedented detail at about 2.4-kilometer (1.5-mile) resolution. The maps show some features that may be volcanic flows. These flows meander across a shallow basin in the mountains. One area suspected to be an ice volcano, Ganesa Macula, does not appear to be a volcanic dome. It may still have originated as a volcano, but it's too soon to know for sure. "It could be a volcanic feature, a crater, or something else that has just been heavily eroded," added Kirk.

The stereo coverage includes a large portion of Titan's north polar lakes of liquid ethane and methane. Based on these topographical models, scientists are better able to determine the depth of lakes. The highest areas surrounding the lakes are some 1,200 meters (about 4,000 feet) above the shoreline. By comparing terrain around Earth to the Titan lakes, scientists estimate their depth is likely about 100 meters (300 feet) or less.

More 3-D mapping of these lakes will help refine these depth estimates and determine the volume of liquid hydrocarbons that exist on Titan. This information is important because these liquids evaporate and create Titan's atmosphere. Understanding this methane cycle can provide clues to Titan's weather and climate.

Launched in 1997, Cassini completed its primary four-year mission in 2008 and is now in extended mission operations, which run through September 2010. Over the course of the mission, Cassini plans to map more than three percent of Titan's surface in 3-D. About 38 percent of Titan's surface has been mapped with radar so far. On March 27, Cassini will complete its 52nd targeted flyby of Titan.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

CASSINI MISSION TO SATURN

CASSINI MISSION TO SATURN

Cassini Image Poll - Best of 2008

The spectacular view of Saturn's geologically active moon Enceladus, A Tectonic Feast, proved to be the most popular in the photo contest. See how the others stacked up.

More info | Cassini site

SOLAR SYSTEM EXPLORATION

Featured Planet: Surprising Saturn

This month's International Year of Astronomy feature explores how Saturn has been a consistent source of surprises for 400 years.

Read more | Solar System Exploration site

MARS EXPLORATION

Get the latest updates on the Mars rovers and the orbiters circling the red planet.

Solar System Missions

Cassini-Huygens to Saturn
Studying Saturn and its rings and moons.

Dawn
Dawn, the first spacecraft ever planned to orbit two different bodies after leaving Earth, will orbit Vesta and Ceres, two of the largest asteroids in the solar system.

Epoxi
The Epoxi mission recycles the already "in flight" Deep Impact spacecraft to investigate two distinct celestial targets of opportunity.

Mars Exploration Rovers
Spirit and Opportunity have been exploring Mars since January 2004. Clues found in some rocks indicate liquid water once covered the ground.

Mars Reconnaissance Orbiter
This orbiter has the most powerful telescopic camera ever to another planet, plus five other scientific instruments.

Mars Odyssey
This orbiter studies Mars' surface composition and radiation environment and has instruments to detect water and shallow buried ice.

Microwave Instrument
on Rosetta Orbiter
This JPL instrument will study gases given off by a comet as the European Space Agency's Rosetta spacecraft orbits the comet. Rendezvous with the comet is scheduled for 2014.
› Rosetta home page

Stardust-NExT
The Stardust-NExT mission recycles the already "in flight" Stardust spacecraft to flyby and investigate comet Tempel 1 in Feb. 2011.

Voyager
Voyager 1 and 2 flew past Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 1 is now approaching interstellar space.

Ulysses
Orbits sun around the north and south poles.

The Space Hunt Is On -- for Carbon Dioxide

Music open..

Narrator: The space hunt is on--for carbon dioxide.
I'm jane platt with NASA's Jet Propulsion Laboratory in Pasadena, California. Carbon dioxide---a very high-profile chemical right now. Scientists say it's a major contributor to global warming. The Orbiting Carbon Observatory is NASA's first spacecraft dedicated to studying carbon dioxide in Earth's atmosphere--from space.

Basilio: Well, we stand on the doorstep of a historical moment. The data from the Orbiting Carbon Observatory are going to be able to allow scientists to be able to produce more accurate models of the global carbon cycle. And the models will actually be able to produce results that policymakers here in the United States and throughout the world will be able to use in order to make better-informed decisions on how best to control and even manage carbon dioxide emissions in the future.

Narrator: Ralph Basilio of JPL, deputy project manager for the Orbiting Carbon Observatory. Right now, carbon dioxide monitoring is limited, but this new mission will change all that.

Basilio: We'll collect on the order of about 37,000 measurements every orbit. Now there's 14-1/2 orbits per day, and there's a 16-day repeat cycle. So if you add everything up, we are looking to collect on the order of about eight million pieces of data over a little more than a two-week long period. And we'll do that repeatedly.

Narrator: Scientists want to know more about carbon dioxide sources--where it comes from, and carbon dioxide sinks--where it is stored. Natural sources include volcanoes, brush fires, respiration of plants and animals. The human sources? Here's David Crisp of JPL, principal investigator for the Orbiting Carbon Observatory.

Crisp: About 85 percent of all of the carbon dioxide that humans emit to the atmosphere comes from the burning of things like coal, natural gas, fuel oil, gasoline. The rest comes from such things as land use practices, for example we might burn our crops at the end of a growing season, for example, and that releases carbon dioxide. Other things that release carbon dioxide that we do include things like manufacturing cement, which actually releases a lot of carbon dioxide into the atmosphere. A lot of other manufacturing processes do as well.

Narrator: The carbon dioxide sinks--where it is pulled out of the atmosphere and stored--are the ocean and plants on land. But there is a mystery about the sinks.

Crisp: More than half of the carbon dioxide that we have been putting into our atmosphere since the beginning of the industrial era has been disappearing someplace. Most of that, we think, is being absorbed either by the oceans or by plants on land. And this is something that is fairly well understood, but we don't know where the plants are absorbing carbon dioxide, we don't know what the relative fraction of carbon dioxide being absorbed by the ocean is, versus what's being absorbed on land.

Narrator: Crisp and his colleagues will use the new observatory to learn where the missing carbon dioxide is going, and why the levels fluctuate so wildly.

Crisp: From year to year, the amount of carbon dioxide that's absorbed by the Earth's oceans and land plants varies dramatically. Some years the Earth absorbs almost a hundred percent of the carbon dioxide that humans release. Other years, the Earth absorbs almost none. We don't know why.

Narrator: By helping scientists solve mysteries like that, and policymakers plan for the future, the Orbiting Carbon Observatory, plus satellites like the recently-launched Japanese Gosat, and the Airs instrument on NASA's Aqua spacecraft, may ultimately benefit those of us who reside here on Planet Earth. More info on the Orbiting Carbon Observatory is at www.nasa.gov/oco . Thanks for joining us for a podcast from NASA'a Jet Propulsion Laboratory.

Asteroid to Fly By Earth Wednesday

Orbit of 2009 FH, Mar. 17, 2009.

March 17, 2009

PASADENA, Calif. – A small asteroid will fly past Earth early tomorrow morning (Wed., March 18). The asteroid, 2009 FH, is about 50 feet (15 meters) wide. Its closest approach to Earth will occur at 5:17 a.m. PDT (8:17 a.m. EDT, 12:17 UTC) at an altitude of about 49,000 miles (79,000 kilometers).

"This asteroid flyby will be a good viewing opportunity for both professional and amateur astronomers," said Don Yeomans of the Near-Earth Object Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The asteroid poses no risk of impact to Earth now or for the foreseeable future."

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.

NASA Celebrates Sun-Earth Day With Illuminating Webcast

Left and right composite image of the sun. Image credit: NASA/JPL-Caltech/NRL/GSFC › Full image and caption

March 18, 2009

PASADENA, Calif. – NASA scientists will reveal new information and images about our sun and its influence on Earth and the solar system for Sun-Earth Day, recognized each year in conjunction with the spring equinox. The highlight of this year's celebration is a webcast for students and teachers around the world, beginning at 10 a.m. PDT (1 p.m. EDT), Friday, March 20.

This year's theme, "Our Sun, Yours to Discover," celebrates the International Year of Astronomy and emphasizes daytime astronomy. During the live, interactive event, participants from around the world and NASA scientists will share new discoveries and visualizations about our sun. Participating students will have the opportunity to demonstrate personally designed sundials, while others will be monitoring the sun and preparing their own space weather forecast.

"Tremendous strides have been made with satellite and ground-based observations of the sun, which have enabled us to monitor the sun to gain a better understanding of the processes that govern its influence on our solar system," said Eric Christian, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.

Sun-Earth Day is a celebration of the sun and how it affects life on our planet and the space around Earth, known as geospace. For the past nine years, NASA has sponsored and coordinated education and public outreach events for Sun-Earth Day that highlight NASA heliophysics research and discoveries. NASA's goal is to use celestial events to engage the public and students in kindergarten through 12th grade via webcasts, podcasts, space science activities, demonstrations and interactions with space scientists.

"These events also support the spirit of international collaboration," said Lou Mayo, project manager at Goddard for Sun-Earth Day 2009. "We are excited about sharing the latest discoveries about our sun and encourage others to join our quest for a greater understanding of our closest star."

Goddard is producing the Sun-Earth Day webcast. NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the Adler Planetarium in Chicago also are participating in the broadcast. NASA Television and the agency's Web site will broadcast the event live.

NASA Team Finds Riches in Asteroid Treasure Hunt

This space-based view of the Nubian Desert shows altitude in kilometers (in white circles) and meteor locations in red. Image courtesy NASA Ames/SETI/JPL
› Full resolution

March 25, 2009

Scientists are studying recovered meteorites that link directly with a tracked asteroid. NASA's Jet Propulsion Laboratory produced the "treasure map" that gave the recovery team its search grid and specific target area.

GLOBAL CLIMATE CHANGE NASA'S eyes on the Earth

Fuel for Thought

A Caltech researcher hopes to put fuel cells on the fast track.

Read more | Global Climate Change site

EARTH IMAGES from the JPL Photojournal

Carbon Monoxide From the Australian Fires of Feb 2009

In February 2009, the deadliest wildfires in Australia's history left more than 200 dead and more than 1,800 homes destroyed. These large wildfires that displaced more than 7,500 people lofted carbon monoxide high into the atmosphere.

Full image and caption | More Earth images

Earth Observing Missions

Active Cavity Irradiance Monitor Satellite
Monitors total sun energy that reaches Earth.
› Instrument home page

Atmospheric Infrared Sounder on Aqua satellite
Measures air and surface temperature, clouds, humidity.
› Instrument home page

Microwave Limb Sounder on Aura satellite
Improves understanding of ozone and precursors.
› Mission home page

Tropospheric Emission Spectrometer on Aura satellite
Observes ozone and gases in the troposphere, the part of atmosphere where we live.
› Instrument home page

CloudSat
Revealing the inner secrets of clouds.
› Mission home page

Gravity Recovery and Climate Experiment
Measures Earth's gravitational field.
› Mission home page

Ocean Surface Topography Mission/Jason 2
A follow-on to Jason 1, this mission charts sea level, and its data will help improve climate and weather forecasts.
› Mission home page

Jason-1
Measures ocean level changes and El Niño.
› Mission home page

Quick Scatterometer
Measures ocean surface winds.
› Mission home page

Advanced Spaceborne Thermal Emission and Reflection Radiometer on Terra satellite
Takes high-resolution images, global and local.
› Instrument home page

Multi-angle Imaging Spectro-Radiometer on Terra satellite
Images Earth and aerosols from nine angles.
› Instrument home page

Shuttle Radar Topography Mission
Acquired the most complete near global mapping of Earth's topography.
› Mission home page

A History of Scatterometry

A History of Scatterometry

In the past, weather data could be acquired over land, but our knowledge of surface winds over oceans came from infrequent, and sometimes inaccurate, reports from ships and buoys.

Scatterometery has its origin in early radar used in World War II. Early radar measurements over oceans were corrupted by sea clutter (noise) and it was not known at that time that the clutter was the radar response to the winds over the oceans. Radar response was first related to wind in the late 1960's. The first scatterometer flew as part of the Skylab missions in 1973 and 1974, demonstrating that spaceborne scatterometers were indeed feasible. The Seasat-A Satellite Scatterometer (SASS) (http://nasascience.nasa.gov/missions/seasat-1/?searchterm=seasat) operated from June to October 1978 and proved that accurate wind velocity measurements could be made from space. A single-swath scatterometer flew on the European Space Agency's Remote Sensing Satellite-1 (ERS-1) mission.

The NASA Scatterometer (NSCAT) (http://winds.jpl.nasa.gov/missions/nscat/index.cfm) which launched aboard Japan's ADEOS-Midori Satellite in August, 1996, was the first dual-swath, Ku-band scatterometer to fly since Seasat. From September 1996 when the instrument was first turned on, until premature termination of the mission due to satellite power loss in June 1997, NSCAT performed flawlessly and returned a continuous stream of global sea surface wind vector measurements. Unprecedented for coverage, resolution, and accuracy in the determination of ocean wind speed and direction, NSCAT data has already been applied to a wide variety of scientific and operational problems. These applications include such diverse areas as weather forecasting and the estimation of tropical rain forest reduction. Because of the success of the short-lived NSCAT mission, future Ku-band scatterometer instruments are now greatly anticipated by the ocean winds user community. The NSCAT mission proved so successful, that plans for a follow-on mission were accelerated to minimize the gap in the scatterometer wind database. The QuikSCAT mission (http://winds.jpl.nasa.gov/missions/quikscat/index.cfm) launched SeaWinds in June 1999.

Introduction

What is a Scatterometer?
A scatterometer is a microwave radar sensor used to measure the reflection or scattering effect produced while scanning the surface of the earth from an aircraft or a satellite.

Description of the SeaWinds Scatterometer and How It Works
The SeaWinds scatterometer is a microwave radar designed specifically to measure ocean near-surface wind speed and direction.

The SeaWinds scatterometer consists of three major parts called subsystems. They are the Electronics Subsystem (SES), the Antenna Subsystem (SAS), and the Command and Data Subsystem (CDS).

The Electronics Subsystem is the heart of the scatterometer and it contains a transmitter, receiver and digital signal processor. It generates and sends high radio frequency (RF) waves to the antenna. The antenna transmits the signal to the Earth's surface as energy pulses. When the pulses hit the surface of the ocean it causes a scattering affect referred to as backscatter. A rough ocean surface returns a stronger signal because the waves reflect more of the radar energy back toward the scatterometer antenna. A smooth ocean surface returns a weaker signal because less of the energy is reflected. The echo or backscatter is routed by the antenna to the SES through waveguides (rectangular metal pipes that guide RF energy waves from one point to another). The SES then converts the signals into digital form for data processing.

The CDS is essentially a computer housing the software that allows the instrument to operate. It provides the link between the command center on the ground, the spacecraft and the scatterometer. It controls the overall operation of the instrument, including the timing of each transmitted pulse and collects all the information necessary to transform the received echoes into wind measurements at a specific location on Earth. To locate the precise position on Earth at which the echo was taken, the CDS collects (for each pulse) the antenna rotational position, spacecraft time, and an estimate of the spacecraft position. The CDS also collects instrument temperature, operating voltages and currents, so that the overall health of the instrument can be monitored. It is through the CDS that the other two subsystems receive the commands that control all of their functions.

The SAS consists of a one-meter parabolic reflector antenna mounted to a spin activator assembly, which causes the reflector to rotate at 18 Rpm's (revolutions per minute). The activator assembly provides very accurate spin control and precise position or pointing information to the CDS. Optical encoders, glass disks with small patterns printed on the surface, tell the CDS exactly where the antenna is pointing to about 10/1000 of a degree. The antenna spins at a very precise rate, and emits two beams about 6 degrees apart, each consisting of a continuous stream of pulses. The two beams are necessary to achieve accurate wind direction measurements. The pointing of these beams is precisely calibrated before launch so that the echoes may be accurately located on the ground from space.

Why is Scatterometry Important?
Data derived from ocean scatterometers is vital to scientists in the their studies of air-sea interaction and ocean circulation, and their effects on weather patterns and global climate. These data are also useful in the study of unusual weather phenomena such as El Ni�o, the long-term effects of deforestation on our rain forests, and changes in the sea-ice masses around the polar regions. These all play a central role in regulating global climate.

Computer modeling of global atmospheric dynamics for the purpose of weather forecasting has become an increasingly important tool to meteorologists. Scatterometer data, with wide swath coverage, have been shown to significantly improve the forecast accuracy of these models. By combining scatterometer data of ocean-surface wind speed and direction with measurements from other scientific instruments, scientists gather information to help us better understand the mechanisms of global climate change and weather patterns.

U-Boulder Satellite Instrument to Provide New Details on Ozone

Just after 3 a.m. on July 10, University of Colorado at Boulder researcher John Gille expects to watch a new NASA satellite blast into orbit from the dark California coastline on a mission to study Earth’s protective ozone layer, climate and air quality changes with unprecedented detail.

Gille, principal investigator on the satellite’s High Resolution Dynamics Limb Sounder (HIRDLS) instrument, said he and his sleep-deprived colleagues will probably only get to watch the rocket for a few moments before it disappears into a thick deck of clouds that typically settles over the area this time of year.

The irony isn’t lost on Gille, who’s been at work on the instrument since 1988. “Writing about clouds in a meteorological journal, a scientist once said, ‘There’s no way to deal with these troublesome objects,’ “ he laughed.

Surface ozone pollution and air quality deterioration — byproducts of agricultural burning, deforestation, urban activity and industry — are increasing worldwide. Questions remain about the recovery of the protective ozone layer and the role of chemistry in climate change. HIRDLS and three other instruments on NASA’s AURA satellite are designed to address these questions in detail.

HIRDLS is an international collaboration between scientists and engineers in the U.S. and Britain. Gille is HIRDLS U.S. principal investigator, and along with his Oxford University counterpart he is responsible for the overall success of the instrument, including design, testing, collection and use of data for scientific purposes.

At CU-Boulder, Gille is an adjoint professor in the Program in Atmospheric and Oceanic Sciences and senior research associate at the Center for Limb Atmospheric Sounding. “Limb” is the astronomical term for the edge of a planet and its atmosphere.

“Unlike the satellite images you see during TV weather forecasts, which are looking straight down at the Earth, our instrument is looking off toward the horizon,” Gille said. “We look at the horizon from orbit, scanning up and down for a profile view.”

The profile gives scientists insight into radiation, temperature and distribution of gases at different levels in the atmosphere. The data is then used to study the ozone layer, climate change and interaction between layers of the atmosphere.

HIRDLS will scan the mid- to upper-troposphere and the tropopause, the boundary region between the troposphere and the stratosphere. The troposphere extends upward from the Earth’s surface to about 10 miles high at the equator and five miles high at the North and South poles. The stratosphere, which contains trace gases as well as the radiation-absorbing ozone layer, lies on top of the troposphere.

HIRDLS is expected to present a much clearer picture of whether the ozone layer is recovering, as well as the distribution of greenhouse gases that influence climate.

“HIRDLS has much finer horizontal resolution than we’ve ever had before,” Gille said. “We can send commands to the satellite to zoom in and get readings with resolutions as fine as 30 to 60 miles, and a vertical resolution of 1,500 feet. Also, the HIRDLS detectors are up to 10 times more sensitive than similar instruments that have flown in the past.”

The instrument is designed to last much longer in orbit than its predecessors, too. Thanks to an onboard mechanical refrigerator built by Ball Aerospace and Technologies Corp. of Boulder, scientists expect it will last longer than five years. It’s hoped that longer-term trends can be predicted with the volume of data that will be collected.

The HIRDLS project began in 1988. Since that time, Gille and his research team at the university have led a collaborative effort to design and build the instrument with scientists and engineers at Oxford University in the United Kingdom, the National Center for Atmospheric Research in Boulder, the University of Washington and Lockheed Martin in Palo Alto, Calif.

Gille expects many of those who have worked on HIRDLS during the past 16 years to make the trip to Vandenburg Air Force Base, north of Santa Barbara, Calif., for the July 10 AURA launch at 3:01 a.m. Pacific Daylight Time.

NASA Satellite Instrument Warms Up Global Cooling Theory

Measurements from a NASA Langley Research Center satellite instrument dispute a recent theory that proposes that clouds in the Tropics might cool the Earth and counteract predictions of global warming. The Langley instrument indicates these clouds would instead slightly strengthen the greenhouse effect to warm the Earth.

Scientists at NASA Langley in Hampton, Va., used observations from an instrument called CERES (Clouds and the Earth's Radiant Energy System) on the Tropical Rainfall Measuring Mission (TRMM) satellite to test the Iris effect?the proposed cooling mechanism.

"The Iris effect is a very interesting but controversial idea for how clouds might act to stabilize the climate system. If correct, it would be welcome news for concerns over future climate change," said Bruce Wielicki, CERES principal investigator at NASA Langley. "We tested the Iris hypothesis by looking down at these clouds using the latest generation of satellite data in the Tropics and found the opposite answer. If anything, these clouds appear to slightly destabilize climate."

According to the Iris effect, the climatically important canopy of clouds in the Tropics decreases as climate warms. As its size shrinks, so does the area of ocean and land covered by the canopy. With more of the Earth's surface and atmosphere free from heat-trapping clouds, more emitted thermal energy (or heat) can escape to space and, according to the theory, cool the Earth.

While a smaller cloud canopy could allow more heat to leave the Earth, it also means more sunlight could reach the surface. In the battle between the cooling of escaping heat and the warming of incoming sunlight, cloud properties determine which one will have a stronger effect on climate. CERES provides the most accurate measurements ever of how much heat clouds trap and how much sunlight they reflect.

"We used the cloud observations from CERES, placed them inside the Iris climate model and found a slightly destabilizing effect of these clouds," said Wielicki. "The result is that the Iris effect slightly warms the Earth instead of strongly cooling it."

"A recent study by Dennis Hartmann at the University of Washington has seriously challenged whether the Iris decrease in cloud canopy would occur in a warmer climate," Wielicki adds. "Our study takes the next step and shows that, even if the Iris effect decreases the cloud canopy, the resulting change in the planetary energy balance would not act to stabilize the climate system."

Bing Lin, a NASA Langley researcher and CERES team member, will present the paper on this research during Session 10 of the 13th Symposium on Global Change and Climate Variations at the American Meteorological Society annual meeting on Wednesday, Jan. 16, at 1:45 p.m. The Journal of Climate published this paper in the January 1, 2002, issue.

Designed and managed by NASA Langley, there are CERES instruments aboard the TRMM and Terra satellites. The CERES instruments were built by the TRW Corp., Redondo Beach, Calif.

The Iris hypothesis was published by Richard Lindzen and co-authors in the March 2001 issue of Bulletin of the American Meteorological Society.

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Main

Main

man-made object launched into a temporary or permanent orbit around the Earth. Spacecraft of this type may be either manned or unmanned, the latter being the most common.

The idea of an artificial satellite in orbital flight was first suggested by Sir Isaac Newton in his book Philosophiae Naturalis Principia Mathematica (1687). He pointed out that a cannonball shot at a sufficient velocity from atop a mountain in a direction parallel to the horizon would go all the way around the Earth before falling. Although the object would tend to fall toward the Earth’s surface because of gravitational force, its momentum would cause it to descend along a curved path. Greater velocity would put it into a stable orbit, like that of the Moon, or direct it away from the Earth altogether. On Oct. 4, 1957, nearly three centuries after Newton had proposed his theory, the Soviet Union launched the first Earth satellite, Sputnik I. Sputnik circled the Earth every 96 minutes, and its simple radio signal was heard by scientists and radio operators across the world. The United States orbited its first satellite, Explorer 1, three months later (Jan. 31, 1958). Explorer, though much smaller than Sputnik, was instrumented to detect radiation and discovered the innermost of the two Van Allen radiation belts, a zone of electrically charged solar particles that surrounds the Earth.

Since these initial efforts, more than 5,000 Earth satellites have been orbited by at least 15 different nations. The satellites vary widely in size and design, ranging from a tiny sphere of several pounds equipped with only two radio transmitters to heavily instrumented space laboratories weighing many tons. They are equally diverse in function. Scientific satellites are chiefly used to collect data about the Earth’s surface and atmosphere and to make astronomical observations. Weather satellites transmit photographs of cloud patterns and measurements of other meteorological conditions that aid in weather forecasting, while communications satellites relay telephone calls, radio and television programs, and data communications between distant parts of the world. Navigation satellites enable the crews of oceangoing vessels and airplanes to determine the position of their craft in all kinds of weather. Some satellites have distinctly military applications, such as reconnaissance and surveillance.

Satellites can be placed in any number of different orbits. The particular path selected is largely determined by the function of the spacecraft. Most weather and reconnaissance satellites, for example, are fired into a polar orbit in which the Earth’s polar axis is a line on the orbital plane. Because the Earth rotates under polar-orbiting satellites, they pass over its entire surface within a given time period, providing full global coverage. Communications satellites, on the other hand, are generally placed into an equatorial orbit, which enables them to circle the most densely populated regions of the Earth from west to east. Moreover, communications satellites comprising a network or system are nearly always launched to a distance of 22,300 mi (35,890 km) above the Earth. At this altitude, the motion of a satellite becomes synchronized with the Earth’s rotation, causing the craft to remain fixed over a single location. If properly positioned, three communications satellites travelling in such a synchronous orbit can relay signals between stations around the world. See also spacecraft.