SP-4312 Dreams, Hopes, Realities

 

Chapter 5:

Exploring the Earth

 


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This image of Earth was created using data from four different satellites. It shows fires  burning on land areas (red dots) and a large aerosol cloud over the Atlantic ocean formed by the burning biomass in Africa. It also indicates dust and cloud cover around the globe. Satellite data and images such as this one are beginning to give us a more comprehensive view of the Earth's interrelated systems and climate.

This image of Earth was created using data from four different satellites. It shows fires burning on land areas (red dots) and a large aerosol cloud over the Atlantic ocean formed by the burning biomass in Africa. It also indicates dust and cloud cover around the globe. Satellite data and images such as this one are beginning to give us a more comprehensive view of the Earth's interrelated systems and climate.

 

[131] When scientists first began using rockets for research, their eyes were focused upward, on the mysteries that lay beyond our atmosphere and our planet. But it wasn't long before they realized that this new technology could also give them a unique vantage point from which to look back at Earth.

Scientists working with V-2 and early sounding rockets for the Naval Research Laboratory (NRL) made the first steps in this direction almost ten years before Goddard was formed. The scientists put aircraft gun cameras on several rockets in an attempt to determine which way the rockets were pointing. When the film from one of these rockets was developed, it had recorded images of a huge tropical storm over Brownsville, Texas. Because the rocket....

 


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Otto Berg's montage photo, taken from a gun camera on board an early research rocket, was perhaps the first weather photo ever taken from space. Note the storm clouds in the upper portion of the image.

Otto Berg's montage photo, taken from a gun camera on board an early research rocket, was perhaps the first weather photo ever taken from space. Note the storm clouds in the upper portion of the image.

 

....was spinning, the image wasn't a neat, complete picture, but Otto Berg, the scientist who had modified the camera to take the photo, took the separate images home and pasted them together on a flat board. He then took the collage to Life magazine, which published what was arguably one of the earliest weather photos ever taken from space.1

Space also offered unique possibilities for communication that were recognized by industry and the military several years before NASA was organized. Project RAND2 had published several reports in the early 1950s outlining the potential benefits of satellite-based communication relays, and both AT&T and Hughes had conducted internal company studies on the commercial viability of communication satellites by 1959.3

These rudimentary seeds, already sown by the time Goddard opened its doors, grew into an amazing variety of communication, weather, and other remote-sensing satellite projects at the Center that have revolutionized many aspects of our lives. They have also taught us significant and surprising things about the planet we inhabit. Our awareness of large-scale crop and forest conditions, ozone depletion, greenhouse warming, and El Nino weather patterns has increased dramatically because of our ability to look back on Earth from space. Satellites have allowed us to measure the shape of the Earth more accurately, track the movement of tectonic plates, and analyze portions of the atmosphere and areas of the world that are hard to reach from the ground.

In addition, the "big picture" perspective satellites offer has allowed scientists to begin investigating the dynamics between different individual processes and the development and behavior of global patterns and systems. Ironically, it seems we have had to develop the ability to leave our planet before we could begin to fully understand it.

 

Geodesy

 

From the very earliest days of the space program, scientists realized that satellites could offer an important side-benefit to researchers interested in mapping the gravity field and shape of the Earth, and Goddard played an important role in this effort. The field of geodesy, or the study of the gravitational field of the Earth and its relationship to the solid structure of the planet, dates back to the third century B.C., when the Greek astronomer Eratosthenes combined astronomical observation with land measurement to try to prove that the Earth was, in fact, round. Later astronomers and scientists had used other methods of triangulation to try to estimate the exact size of the Earth. [133] Astronomers also had used the Moon, or stars with established locations, to try to map the shape of the Earth and exact distances between points more precisely. But satellites offered a new twist to this methodology.

For one thing, the Earth's shape and gravity field affected the orbit of satellites. So at the beginning of the space age, Goddard's tracking and characterizing the orbit of the first satellites was in and of itself a scientific endeavor. From that orbital data, scientists could infer information about the Earth's gravity field, which is affected by the distribution of its mass. The Earth, as it turns out, is not perfectly round, and its mass is not perfectly distributed. There are places where land or ocean topography results in denser or less dense mass accumulation. The centrifugal force of the Earth's rotation combines with gravity and these mass concentrations to create bulges and depressions in the planet. In fact, although we think of the Earth as round, Goddard's research showed us that it is really slightly pear-shaped.

Successive Goddard satellites enabled scientists to gather much more precise information about the Earth's shape as well as exact positions of points on the planet. In fact, within 10 years, scientists had learned as much again about global positioning, the size and shape of the Earth, and its gravity field as their predecessors had learned in the previous 200 years.

Laser reflectors on Goddard satellites launched in 1965, 1968, and 1976, for example, allowed scientists to make much more precise measurements between points, which enabled them to determine the exact location or movement of objects. The laser reflectors developed for Goddard's LAGEOS satellite, launched in 1976, could determine movement or position within a few centimeters, which allowed scientists to track and analyze tectonic plate movement and continental drift. Among other things, the satellite data told scientists that the continents seem to be inherently rigid bodies, even if they contain divisive bodies of water, such as the Mississippi River, and that continental plate movement appears to occur at a constant rate over time. Plate movement information provided by satellites has also helped geologists track the dynamics that lead up to Earthquakes, which is an important step in predicting these potentially catastrophic events.

The satellite positioning technique used for this plate tectonic research was the precursor to the Global Positioning System (GPS) technology that now uses a...

 


A technician working on reflectors for one of Goddard's laser geodynamic satellites.

A technician working on reflectors for one of Goddard's laser geodynamic satellites.

 

[134] ...constellation of satellites to provide precise three-dimensional navigation for aircraft and other vehicles. Yet although a viable commercial market is developing for GPS technology today, the greatest commercial application of space has remained the field of communication satellites.4

 

Communication Satellites

 

For all the talk about the commercial possibilities of space, the only area that has proven substantially profitable since 1959 is communication satellites, and Goddard played an important role in developing the early versions of these spacecraft. The industry managers who were conducting research studies and contemplating investment in this field in 1959 could not have predicted the staggering explosion of demand for communications that has accompanied the so-called "Information Age." But they saw how dramatically demand for telephone service had increased since World War II, and they saw potential in other communications technology markets, such as better or broader transmission for television and radio signals. As a result, several companies were even willing to invest their own money, if necessary, to develop communication satellites.

The Department of Defense (DoD) actually had been working on communication satellite technology for a number of years, and it wanted to keep control of what it considered a critical technology. So when NASA was organized, responsibility for communication satellite technology development was split between the new space agency and the DoD. The DoD would continue responsibility for "active" communication satellites, which added power to incoming signals and actively transmitted the signals back to ground stations. NASA's role was initially limited to "passive" communication satellites, which relied on simply reflecting signals off the satellite to send them back to Earth.5

 

Echo

 

NASA's first communication satellite, consequently, was a passive spacecraft called "Echo." It was based on a balloon design by an engineer at NASA's Langley Research Center and developed by Langley, Goddard, JPL and AT&T. Echo was, in essence, a giant mylar balloon, 100 feet in diameter, that could "bounce" a radio signal back down to another ground station a long distance away from the first one.

Echo I, the world's first communication satellite, was successfully put into orbit on 12 August 1960. Soon after launch, it reflected a pre-taped message from President Dwight Eisenhower across....

 


The world's first communications satellite was an inflatable mylar sphere called <<Echo>> that simply reflected transmissions back to Earth. The spacecraft was readily visible to the eye. (NASA Photo G-63-3202)

The world's first communications satellite was an inflatable mylar sphere called "Echo" that simply reflected transmissions back to Earth. The spacecraft was readily visible to the eye. (NASA Photo G-63-3202)

 

[135].....the country and other radio messages to Europe, demonstrating the potential of global radio communications via satellite. It also generated a lot of public interest, because the sphere was so large that it could be seen from the ground with the naked eye as it passed by overhead.

Echo I had some problems, however. The sphere seemed to buckle somewhat, hampering its signal-reflecting ability. So in 1964, a larger and stronger passive satellite, Echo II, was put into orbit. Echo II was made of a material 20 times more resistant to buckling than Echo I and was almost 40 feet wider in diameter.

Echo II also experienced some difficulties with buckling. But the main reason the Echo satellites were not pursued any further was not that the concept wouldn't work. It was simply that it was eclipsed by much better technology - active communication satellites.6

 

Syncom, Telstar, and Relay

 

By 1960, Hughes, RCA, and AT&T were all advocating the development of active communication satellites. They differed in the kind of satellite they recommended, however. Hughes felt strongly that the best system would be based on geosynchronous satellites. Geosynchronous satellites are in very high orbits - 22,300 miles above the ground. This high orbit allows their orbital speed to match the rotation speed of the Earth, which means they can remain essentially stable over one spot, providing a broad range of coverage 24 hours a day. Three of these satellites, for example, can provide coverage of the entire world, with the exception of the poles.

 


The Syncom satellite proved that high-altitude, geosynchronous satellites could still be used effectively for communications.(NASA Photo G-63-3266)

The Syncom satellite proved that high-altitude, geosynchronous satellites could still be used effectively for communications.(NASA Photo G-63-3266)

 

The disadvantage of using geosynchronous satellites for communications is that sending a signal up 22,300 miles and back causes a time-delay of approximately a quarter second in the signal. Arguing that this delay would be too annoying for telephone subscribers, both RCA and AT&T supported a bigger constellation of satellites in medium Earth orbit, only a few hundred miles above the Earth.7

The Department of Defense had been working on its own geosynchronous communication satellite, but the project was running into significant development problems and delays. NASA had been given permission by 1960 to pursue active communication satellite technology as well as passive systems, so the DoD approached NASA about giving Hughes a sole-source contract to develop an experimental geosynchronous satellite. The result was Syncom, a geosynchronous [136] satellite design built by Hughes under contract to Goddard.

Hughes already had begun investing its own money and effort in the technology, so Syncom I was ready for Goddard to launch in February 1963 - only 17 months after the contract was awarded. Syncom I stopped sending signals a few seconds before it was inserted into its final orbit, but Syncom II was launched successfully five months later, demonstrating the viability of the system. The third Syncom satellite, launched in August 1964, transmitted live television coverage of the Olympic Games in Tokyo, Japan to stations in North America and Europe.

Although the military favored the geosynchronous concept, it was not the only technology being developed. In 1961, Goddard began working with RCA on the "Relay" satellite, which was launched 13 December 1962. Relay was designed to demonstrate the feasibility of medium-orbit, wide-band communications satellite technology and to help develop the ground....

 


The Relay satellite, which Goddard helped RCA build and launch, was a medium-altitude orbit satellite design. (NASA Photo G-63-3970)

The Relay satellite, which Goddard helped RCA build and launch, was a medium-altitude orbit satellite design. (NASA Photo G-63-3970)

 

....station operations necessary for such a system. It was a very successful project, transmitting even color television signals across wide distances.

AT&T, meanwhile, had run into political problems with NASA and government officials who were concerned that the big telecommunications conglomerate would end up monopolizing what was recognized as potentially powerful technology. But when NASA chose to fund RCA's Relay satellite instead of AT&T's design, AT&T decided to simply use its own money to develop a medium orbit communications satellite, which it called Telstar. NASA would launch the satellite, but AT&T would reimburse NASA for the costs involved. Telstar 1 was launched on 10 July 1962, and a second Telstar satellite followed less than a year later. Both satellites were very successful, and Telstar 2 demonstrated that it could even transmit both color and black and white television signals between the United States and Europe.

In some senses, Relay and Telstar were competitors. But RCA and AT&T, who were both working with managers at Goddard, reportedly cooperated very well with each other. Each of the efforts was seen as helping to advance the technology necessary for this new satellite industry to become viable, and both companies saw the potential profit of that in the long run.

By 1962, it was clear that satellite communications technology worked, and there was going to be money made in its use. Fearful of the powerful monopoly satellites could offer a single company, Congress passed the Satellite Communications Act, setting up a [137] consortium of existing communications carriers to run the satellite communications industry. Individual companies could bid to sell satellites to the consortium, but no single company would own the system. NASA would launch the satellites for Comsat, as the consortium was called, but Comsat would run the operations.

In 1964, the Comsat consortium was expanded further with the formation of the International Telecommunications Satellite Organization, commonly known as "Intelsat," to establish a framework for international use of communication satellites. These organizations had the responsibility for choosing the type of satellite technology the system would use. The work of RCA, AT&T and Hughes had proven that either medium-altitude or geosynchronous satellites could work. But in 1965, the consortiums finally decided to base the international system on geosynchronous satellites similar to the Syncom design.8

 

Applications Technology Satellites

 

Having helped to develop the prototype satellites, Goddard stepped back from operational communication satellites and focused its efforts on developing advanced technology for future systems. Between 1966 and 1974, Goddard launched a total of six Applications Technology Satellites (ATS) to research advanced technology for communications and meteorological spacecraft. The ATS spacecraft were all put into geosynchronous orbits and investigated microwave and millimeter wavelengths for.....

 


Goddard's sixth Applications Technology Satellites undergoes final prelaunch testing at Cape Canaveral in Florida. (NASA Photo G-74-7446)

Goddard's sixth Applications Technology Satellites undergoes final prelaunch testing at Cape Canaveral in Florida. (NASA Photo G-74-7446)

 

....communication transmissions, methods for aircraft and marine navigation and communications, and various control technologies to improve geosynchronous satellites.

Four of the spacecraft were highly successful and provided valuable data for improving future communication satellites. The sixth ATS spacecraft, launched 30 May 1974, even experimented with transmitting health and education television to small, low-cost ground stations in remote areas. It also tested a geosynchronous satellite's ability to provide tracking and data transmission services for other satellites. Goddard's research in this area, and the expertise the Center developed in the process, made it possible for NASA to develop the Tracking and Data Relay Satellite System (TDRSS) the agency still uses today.9

After ATS-6, NASA transferred responsibility for future communication [138] satellite research to the Lewis Research Center. Goddard, however, maintained responsibility for developing and operating the TDRSS tracking and data satellite system.10

 

Meteorological Satellites

 

Statistically, the United States has the world's most violent weather. In a typical year, the U.S. will endure some 10,000 violent thunderstorms, 5,000 floods, 1,000 tornadoes, and several hurricanes.11 Improving weather prediction, therefore, has been a high priority of meteorologists here for a very long time.

The early sounding rocket flights began to indicate some of the possibilities space flight might offer in terms of understanding and forecasting the weather, and they prompted the military to pursue development of a meteorological satellite. The Advanced Research Projects Agency (ARPA)12 had a group of scientists and engineers working on this project at the U.S. Army Signal Engineering Laboratories in Ft. Monmouth, New Jersey when NASA was first organized. Recognizing the country's history of providing weather services to the public through a civilian agency, the military agreed to transfer the research group to NASA. These scientists and engineers became one of the founding units of Goddard in 1958.

 

Television and Infrared Observation Satellites

 

These Goddard researchers were working on a project called the Television and Infrared Observation Satellite (TIROS). When it was launched on 1 April 1960, it became the world's first meteorological satellite, returning thousands of images of cloud cover and spiralling storm systems. Goddard's Explorer VI satellite had recorded some crude cloud cover images before TIROS I was launched, but the TIROS satellite was the first spacecraft dedicated to meteorological data gathering and transmitted the first really good cloud cover photographs. 13

Clearly, there was a lot of potential in this new technology, and other meteorological satellites soon followed the first TIROS spacecraft. Despite its name, the first TIROS carried only television cameras. The second TIROS satellite, launched in November 1960, also included an infrared instrument, which gave it the ability to detect cloud cover even at night.

The TIROS capabilities were limited, but the satellites still provided a tremendous service in terms of weather forecasting. One of the biggest obstacles meteorologists faced was the local, "spotty" nature of the data...

 


Dr. Joanne Simpson, who is pictured here with two male colleagues, is a pioneer in the study of clouds, typhoons and other tropical storms and, in fact, has flown through six hurricanes to gather meteorological data. Currently, she is chief scientist for meteorology at Goddard.

Dr. Joanne Simpson, who is pictured here with two male colleagues, is a pioneer in the study of clouds, typhoons and other tropical storms and, in fact, has flown through six hurricanes to gather meteorological data. Currently, she is chief scientist for meteorology at Goddard [Note: This photo caption was obtained from Goddard's 40th anniversary cd-rom. Chris Gamble, html editor].

 

[139] ...they could obtain. Weather balloons and ocean buoys could only collect data in their immediate area. Huge sections of the globe, especially over the oceans, were dark areas where little meteorological information was available. This made forecasting a difficult task, especially for coastal areas.

Sounding rockets offered the ability to take measurements at all altitudes of the atmosphere, which helped provide temperature, density and water vapor information. But sounding rockets, too, were limited in the scope of their coverage. Satellites offered the first chance to get a "big picture" perspective on weather patterns and storm systems as they travelled around the globe.

Because weather forecasting was an operational task that usually fell under the management of the Weather Bureau, there was some disagreement about who should have responsibility for designing and operating this new class of satellite. Some people at Goddard felt that NASA should take the lead, because the new technology was satellite-based. The Weather Bureau, on the other hand, was going to be paying for the satellites and wanted control over the type of spacecraft and instruments they were funding. When the dust settled, it was decided that NASA would conduct research on advanced meteorological satellite technology and would manage the building, launching and testing of operational weather satellites. The Weather Bureau would have final say over operational satellite design, however, and would take over management of spacecraft operations after the initial test phase was completed.14

The TIROS satellites continued to improve throughout the early 1960s.

 


Early  meteorology satellite and violent storms pioneer.

Early meteorology satellite and violent storms pioneer. [Note: no photo caption in the book. Chris Gamble, html editor]


 

Although the spacecraft were officially research satellites, they also provided the Weather Bureau with a semi-operational weather satellite system from 1961 to 1965. TIROS III, launched in July 1961, detected numerous hurricanes, tropical storms, and weather fronts around the world that conventional ground networks missed or would not have seen for several more days.15 TIROS IX, launched in January 1965, was the first of the series launched into a polar orbit, rotating around the Earth in a north-south direction. This orientation allowed the satellite to cross the equator at the same time each day and provided coverage of the entire globe, including the higher latitudes and polar regions, as its orbit precessed around the Earth.

The later TIROS satellites also improved their coverage by changing the location of the spacecraft's camera. The TIROS satellites were designed like a wheel of cheese. The wheel spun around but, like a toy top or gyroscope, the axis of the wheel kept pointing in the same direction as the satellite orbited the Earth. The cameras were placed on the satellite's axis, which allowed them to take continuous pictures of the Earth when that surface was actually facing the planet. Like dancers doing a do-si-do, however, the surface with the cameras would be pointing parallel to or away from the Earth for more than half of the satellite's orbit. TIROS IX (and the operational TIROS satellites), put the camera on the rotating section of the wheel, which was kept [140] facing perpendicular to the Earth throughout its orbit. This made the satellite operate more like a dancer twirling around while circling her partner. While the camera could only take pictures every few seconds, when the section of the wheel holding the camera rotated past the Earth, it could continue taking photographs throughout the satellite's entire orbit.

 

NIMBUS/ESSA/NOAA

 

In 1964, Goddard took another step in developing more advanced weather satellites when it launched the first NIMBUS spacecraft. NASA had originally envisioned the larger and more sophisticated NIMBUS as the design for the Weather Bureau's operational satellites. The Weather Bureau decided that the....

 


Goddard test and evaluation personnel conduct vibration testing of a Nimbus research weather satellite. (NASA photo G-67-2656).

Goddard test and evaluation personnel conduct vibration testing of a Nimbus research weather satellite. (NASA photo G-67-2656).

 

....NIMBUS spacecraft were too large and expensive, however, and opted to stay with the simpler TIROS design for the operational system. So the NIMBUS satellites were used as research vehicles to develop advanced instruments and technology for future weather satellites. Between 1964 and 1978, Goddard developed and launched a total of seven Nimbus research satellites.

In 1965, the Weather Bureau was absorbed into a new agency called the Environmental Science Services Administration (ESSA). The next year, NASA launched the first satellite in ESSA's operational weather system. The satellite was designed like the TIROS IX spacecraft and was designated "ESSA 1." As per NASA's agreement, Goddard continued to manage the building, launching and testing of ESSA's operational spacecraft, even as the Center's scientists and engineers worked to develop more advanced technology with separate research satellites.

The ESSA satellites were divided into two types. One took visual images of the Earth with an an Automatic Picture Transmission (APT) camera system and transmitted them in real time to stations around the globe. The other recorded images that were recorded and then transmitted to a central ground station for global analysis. These first ESSA satellites were deployed in pairs in "Sun-synchronous" polar orbits around the Earth, crossing the same point at approximately the same time each day.

In 1970, Goddard launched an improved operational spacecraft for ESSA [141] using "second generation" weather satellite technology. The Improved TIROS Operational System (ITOS), as the design was initially called, combined the functions of the previous pairs of ESSA satellites into a single spacecraft and added a day and night scanning radiometer. This improvement meant that meteorologists could get global cloud cover information every 12 hours instead of every 24 hours.

Soon after ITOS 1 was launched, ESSA evolved into the National Oceanic and Atmospheric Administration (NOAA), and successive ITOS satellites were redesignated as NOAA 1, 2, 3, etc. This designation system for NOAA's polar-orbiting satellites continues to this day.

In 1978, NASA launched the first of what was called the "third generation" of polar orbiting satellites. The TIROS-N design was a much bigger, three-axis-stabilized spacecraft that incorporated much more advanced equipment. The TIROS-N series of instruments, used aboard operational NOAA satellites today, provided much more accurate sea-surface temperature information, which is necessary to predict a phenomenon like an El Nino weather pattern. They also could identify snow and sea ice and could provide much better temperature profiles for different altitudes in the atmosphere.

But while the lower-altitude polar satellites can observe some phenomena in more detail because they are relatively close to the Earth, they can't provide the continuous "big picture" information a geosynchronous satellite can offer. So for the past 25 years, NOAA has operated two weather satellite systems - the TIROS series of polar orbiting satellites at lower altitudes, and two geosynchronous satellites more than 22,300 miles above the Earth.16

 


Satellite imagery showing snow and sea ice cover at the north and south poles of the Earth.

Satellite imagery showing snow and sea ice cover at the north and south poles of the Earth.


 


The polar-orbiting ITOS satellites were an improved version of the original TIROS weather satellites.

The polar-orbiting ITOS satellites were an improved version of the original TIROS weather satellites.

 

ATS/SMS/GOES

 

While polar-orbiting satellites were an improvement over the more equatorial-orbiting TIROS satellites, scientists realized that they could get a much better perspective on weather systems from a geosynchronous spacecraft. Goddard's research teams started investigating this technology with the launch of the first Applications Technology Satellite (ATS-1) in 1966. Because the ATS had a geosynchronous orbit that kept it "parked" above one spot, meteorologists could get progressive photographs of the same area over a period of time as often as every 30 minutes. The "satellite photos" showing changes in cloud cover that we now almost take for granted during nightly newscasts are made possible by geosynchronous weather satellites. Those cloud movement images also allowed meteorologists to infer wind currents and speeds. This information is particularly useful in [142] determining weather patterns over areas of the world such as oceans or the tropics, where conventional aircraft and balloon methods can't easily gather data.

Goddard's ATS III satellite, launched in 1967, included a multi-color scanner that could provide images in color, as well. Shortly after its launch, ATS III took the first color image of the entire Earth, a photo made possible by the satellite's 22,300 mile high orbit.17

In 1974, Goddard followed its ATS work with a dedicated geosynchronous weather satellite called the Synchronous Meteorological Satellite (SMS). Both SMS -1 and SMS-2 were research prototypes, but they still provided meteorologists with practical information as they tested out new technology. In addition to providing continuous coverage of a broad area, the SMS satellites collected and relayed weather data from 10,000 automatic ground stations in six hours, giving forecasters more timely and detailed data than they had ever had before.

 


The Synchronous Meteorological Satellite was the first geosynchronous weather satellite. This design evolved into the GOES series of spacecraft.

The Synchronous Meteorological Satellite was the first geosynchronous weather satellite. This design evolved into the GOES series of spacecraft.

 

Goddard launched NOAA's first operational geostationary18 satellite, designated the Geostationary Operational Environmental Satellite (GOES) in October 1975. That satellite has led to a whole family of GOES spacecraft. As with previous operational satellites, Goddard managed the building, launching and testing of the GOES spacecraft.

The first seven GOES spacecraft, while geostationary, were still "spinning" designs like NOAA's earlier operational ESSA satellites. In the early 1980s, however, NOAA decided that it wanted the new series of geostationary GOES spacecraft to be three-axis stabilized, as well, and to incorporate significantly more advanced instruments. In addition, NOAA decided to award a single contract directly with an industry manufacturer for the spacecraft and instruments, instead of working separate instrument and spacecraft contracts through Goddard.

Goddard typically developed new instruments and technology on research satellites before putting them onto an operational spacecraft for NOAA. The plan for GOES 8,19 however, called for incorporating new technology instruments directly into a spacecraft that was itself a new design and also had an operational mission. Meteorologists across the country were going to rely on the new instruments for accurate weather forecasting information, which put a tremendous amount of added pressure on the designers. But the contractor selected to build the instruments underestimated the cost and complexity of developing the [143] GOES 8 instruments. In addition, Goddard's traditional "Phase B" design study, which would have generated more concrete estimates of the time and cost involved in the instrument development, was eliminated on the GOES 8 project. The study was skipped in an attempt to save time, because NOAA was facing a potential crisis with its geostationary satellite system.

NOAA wanted to have two geostationary satellites up at any given point in order to adequately cover both coasts of the country. But the GOES 5 satellite failed in 1984, leaving only one geostationary satellite, GOES 6, in operation. The early demise of GOES 4 and GOES 5 left NOAA uneasy about how long GOES 6 would last, prompting the "streamlining" efforts on the GOES 8 spacecraft design. The problem became even more serious in 1986 when the launch vehicle for the GOES G spacecraft, which would have become GOES 7, failed after launch. Another GOES satellite was successfully launched in 1987, but the GOES 6 spacecraft failed in January 1989, leaving the United States once again with only one operational geostationary weather satellite.

By 1991, when the GOES 8 project could not predict a realistic launch date, because working instruments for the spacecraft still hadn't been developed, Congress began to investigate the issue. The GOES 7 spacecraft was aging, and managers and elected officials realized that it was entirely possible that the country might soon find itself without any geostationary satellite coverage at all.

 


A computer-generated image of Hurricane Fran, using data from the GOES weather satellites.(NASA Photo PAO H96_01.JPG)

A computer-generated image of Hurricane Fran, using data from the GOES weather satellites.(NASA Photo PAO H96_01.JPG)

 

To buy the time necessary to fix the GOES 8 project and alleviate concerns about coverage, NASA arranged with the Europeans to "borrow" one of their Eumetsat geostationary satellites. The satellite was allowed to "drift" further west so it sat closer to the North American coast, allowing NOAA to move the GOES 7 satellite further west.

Meanwhile, Goddard began to take a more active role in the GOES 8 project. A bigger GOES 8 project office was established at the Center and Goddard brought in some of its best instrument experts to work on the project, both at Goddard and at the contractor's facilities. Goddard, after all, had some of the best meteorological instrument-building expertise in the country. But because Goddard was not directly in charge of the instrument sub-contract, the Center had been handicapped [144] in making that knowledge and experience available to the beleaguered contractor.

The project was a sobering reminder of the difficulties that could ensue when, in an effort to save time and money, designers attempted to streamline a development project or combine research and operational functions into a single spacecraft. But in 1994, the GOES 8 spacecraft was finally successfully launched, and the results have been impressive. Its advanced instruments performed as advertised, improving the spacecraft's focusing and atmospheric sounding abilities and significantly reducing the amount of time the satellite needed to scan any particular area. 20

 

Earth Resources Satellites

 

As meteorological satellite technology developed and improved, Goddard scientists realized that the same instruments used for obtaining weather information could be used for other purposes, as well. Meteorologists could look at radiation that travelled back up from the Earth's surface to determine things like water vapor content and temperature profiles at different altitudes in the atmosphere. But those same emissions could reveal potentially valuable information about the Earth's surface, as well.

Objects at a temperature above absolute zero emit radiation, many of them at precise and unique wavelengths in the electromagnetic spectrum. So by analyzing the emissions of any object, from a star or comet to a particular section of forest or farmland, scientists can learn important things about its chemical composition. Instruments on the Nimbus spacecraft had the ability to look at reflected solar radiation from the Earth in several different wavelengths. As early as 1964, scientists began discussing the possibilities of experimenting with this technology to see what it might be able to show us about not only the atmosphere, but also resources on the Earth.

The result was the Earth Resources Technology Satellite (ERTS), launched in 1972 and later given the more popular name "Landsat 1." The spacecraft was based on a Nimbus satellite,with a multi-channel radiometer to look at different wavelength bands where the reflected energy from surfaces such as forests, water, or different crops would fall. The satellite instruments also had much better resolution than the Nimbus instruments. Each swath of the Earth covered by the Nimbus scanner was 1500 miles wide, with each pixel in the picture representing five miles. The polar-orbiting ERTS satellite instrument could focus in on a swath only 115 miles wide, with each pixel representing 80 meters. This resolution allowed scientists to view a small enough section of land, in enough detail, to conduct a worthwhile analysis of what it contained.

Images from the ERTS/Landsat satellite, for example, showed scientists a 25-mile wide geological feature near Reno, Nevada that appeared to be a previously undiscovered meteor crater. Other images collected by the satellite were useful in discovering water-bearing rocks in Nebraska, Illinois and New York and determining that water pollution drifted off the Atlantic [145] coast as a cohesive unit, instead of dissipating in the ocean currents.

The success of the ERTS satellite prompted scientists to want to explore this use of satellite technology further. They began working on instruments that could get pixel resolutions as high as five meters, but were told to discontinue that research because of national security concerns. If a civilian satellite provided data that detailed, it might allow foreign countries to find out critical information about military installations or other important targets in the U.S. This example illustrates one of the ongoing difficulties with Earth resource satellite research. The fact that the same information can be used for both scientific and practical purposes often creates complications with not only who should be responsible for the work, but how and where the information will be used.

In any event, the follow-on satellite, "Landsat-2," was limited to the same levels of resolution. More recent Landsat spacecraft, however, have been able to improve instrument resolution further.21

Landsat 2 was launched in January 1975 and looked at land areas for an even greater number of variables than its ERTS predecessor, integrating information from ground stations with data obtained by the satellite's instruments. Because wet land and green crops reflect solar energy at different wavelengths than dry soil or brown plants, Landsat imagery enabled researchers to look at soil moisture levels and crop health over wide areas, as well as soil temperature, stream flows, and snow depth. Its data was used by the U.S. Department of Agriculture, the U.S. Forest Service, the Department of Commerce, the Army Corps of Engineers, the Environmental Protection Agency and the Department of Interior, as well as agencies from foreign countries.22

 


A Landsat image of the Muir glacier in southeastern Alaska taken in September 1986. The red color indicates areas of vegetation.

A Landsat image of the Muir glacier in southeastern Alaska taken in September 1986. The red color indicates areas of vegetation.


 

The Landsat program clearly was a success, particularly from a scientific perspective. It proved that satellite technology could determine valuable information about precious natural resources, agricultural activity, and environmental hazards. The question was who should operate the satellites. Once the instruments were developed, the Landsat spacecraft were going to be collecting the same data, over and over, instead of exploring new areas and technology. One could argue that by examining [146] the evolution of land resources over time, scientists were still exploring new processes and gathering new scientific information about the Earth. But that same information was being used predominantly for practical purposes of natural resource management, agricultural and urban planning, and monitoring environmental hazards. NASA had never seen its role as providing ongoing, practical information, but there was no other agency with the expertise or charter to operate land resource satellites.

As a result, NASA continued to manage the building, launch, and space operation of the Landsat satellites until 1984. Processing and distribution of the satellite's data was managed by the Department of Interior, through an Earth Resources Observation System (EROS) Data Center that was built by the U.S. Geological Survey in Sioux Falls, South Dakota in 1972.

 


A Landsat image of Salt Lake City and a portion of the Great Salt Lake in Utah.

A Landsat image of Salt Lake City and a portion of the Great Salt Lake in Utah.

 

In 1979, the Carter Administration developed a new policy in which the Landsat program would be managed by NOAA and eventually turned over to the private sector. In 1984, the first Reagan Administration put that policy into effect, soliciting commercial bids for operating the system, which at that point consisted of two operational satellites. Landsat 4 had been launched in 1982 and Landsat 5 was launched in 1984. Ownership and operation of the system was officially turned over to the EOSAT Company in 1985, which sold the images to anyone who wanted them, including the government. At the same time, responsibility for overseeing the program was transferred from NASA to NOAA. Under the new program guidelines, the next spacecraft in the Landsat program, Landsat 6, would also be constructed independently by industry.

There were two big drawbacks with this move, however, as everyone soon found out. The first was that although there was something of a market for Landsat images, it was nothing like that surrounding the communication satellite industry. The EOSAT company found itself struggling to stay afloat. Prices for images jumped from the couple of hundred dollars per image that EROS had charged to $4,000 per shot, and EOSAT still found itself bordering on insolvency.

Being a private company, EOSAT also was concerned with making a profit, not archiving data for the good of science or the government. Government budgets wouldn't allow for purchasing thousands of archival images at $4,000 a piece, so the EROS Data Center only bought a few [147] selected images each year. As a result, many of the the scientific or archival benefits the system could have created were lost.

In 1992, the Land Remote Sensing Policy Act reversed the 1984 decision to commercialize the Landsat system, noting the scientific, national security, economic, and social utility of the Landsat images. Landsat 6 was launched the following year, but the spacecraft failed to reach orbit and ended up in the Indian Ocean.

This launch failure was discouraging, but planning for the next Landsat satellite was already underway. Goddard had agreed to manage design of a new data ground station for the satellite, and NASA and the Department of Defense initially agreed to divide responsibility for managing the satellite development. But the Air Force subsequently pulled out of the project and, in May 1994, management of the Landsat system was turned over to NASA, the U.S. Geological Survey (USGS), and NOAA. At the same time, Goddard assumed sole management responsibility for developing Landsat 7.

The only U.S. land resource satellites in operation at the moment are still Landsat 4 and 5, which are both degrading in capability. Landsat 5, in fact, is the only satellite still able to transmit images. The redesigned Landsat 7 satellite is scheduled for launch by mid-1999, and its data will once again be made available though the upgraded EROS facilities in Sioux Falls, South Dakota. Until then, scientists, farmers and other users of land resource information have to rely on Landsat 5 images through EOSAT, or they have to turn to foreign companies for the information.

The French and the Indians have both created commercial companies to sell land resource information from their satellites, but both companies are being heavily subsidized by their governments while a market for the images is developed. There is probably a viable commercial market that could be developed in the United States, as well. But it may be that the demand either needs to grow substantially on its own or would need government subsidy before a commercialization effort could succeed. The issue of scientific versus practical access to the information would also still have to be resolved.

No matter how the organization of the system is eventually structured, Landsat imagery has proven itself an extremely valuable tool for not only natural resource management but urban planning and agricultural assistance, as well. Former NASA Administrator James Fletcher even commented in 1975 that if he had one space-age development to save the world, it would be Landsat and its successor satellites.23 Without question, the Landsat technology has enabled us to learn much more about the Earth and its land-based resources. And as the population and industrial production on the planet increase, learning about the Earth and potential dangers to it has become an increasingly important priority for scientists and policy-makers alike.24

 

Atmospheric Research Satellites

 

One of the main elements scientists are trying to learn about the Earth is the [148] composition and behavior of its atmosphere. In fact, Goddard's scientists have been investigating the dynamics of the Earth's atmosphere for scientific, as well as meteorological, purposes since the inception of the Center. Explorers 17, 19, and 32, for example, all researched various aspects of the density, composition, pressure and temperature of the Earth's atmosphere. Explorers 51 and 54, also known as "Atmosphere Explorers," investigated the chemical processes and energy transfer mechanisms that control the atmosphere.

Another goal of Goddard's atmospheric scientists was to understand and measure what was called the "Earth Radiation Budget." Scientists knew that radiation from the Sun enters the Earth's atmosphere. Some of that energy is reflected back into space, but most of it penetrates the atmosphere to warm the surface of the Earth. The Earth, in turn, radiates....

 


The Earth Radiation Budget Satellite was launched in 1984 to investigate the balance of solar radiation in the Earth's atmosphere.

The Earth Radiation Budget Satellite was launched in 1984 to investigate the balance of solar radiation in the Earth's atmosphere.

 

....energy back into space. Scientists knew that the overall radiation received and released was about equal, but they wanted to know more about the dynamics of the process and seasonal or other fluctuations that might exist. Understanding this process is important because the excesses and deficits in this "budget," as well as variations in it over time or at different locations, create the energy to drive our planet's heating and weather patterns.

The first satellite to investigate the dynamics of the Earth Radiation Budget was Explorer VII, launched in 1959. Nimbus 2 provided the first global picture of the radiation budget, showing that the amount of energy reflected by the Earth's atmosphere was lower than scientists had thought. Additional instruments on Nimbus 3, 5, and 6, as well as operational TIROS and ESSA satellites, explored the dynamics of this complex process further. In the early 1980s, researchers developed an Earth Radiation Budget Experiment (ERBE) instrument that could better analyze the short-wavelength energy received from the Sun and the longer-wavelength energy radiated into space from the Earth. This instrument was put on a special Earth Radiation Budget Satellite (ERBS) launched in 1984, as well as the NOAA-9 and NOAA 10 weather satellites.

This instrument has provided scientists with information on how different kinds of clouds affect the amount of energy trapped in the Earth's atmosphere. Lower, thicker clouds, for example, reflect a portion of the Sun's energy back into space, creating a...

 


[
149]

In a single pass across Hurricane Alley, the Tropical Rainfall Measuring Mission provided graphic information: tropical storm Howard and hurricanes Isis, Vearl, and Danielle.

In a single pass across Hurricane Alley, the Tropical Rainfall Measuring Mission provided graphic information: tropical storm Howard and hurricanes Isis, Vearl, and Danielle.

 

....cooling effect on the surface and atmosphere of the Earth. High, thin cirrus clouds, on the other hand, let the Sun's energy in but trap some of the Earth's outgoing infrared radiation, reflecting it back to the ground. As a result, they can have a warming effect on the Earth's atmosphere. This warming effect can, in turn, create more evaporation, leading to more moisture in the air. This moisture can trap even more radiation in the atmosphere, creating a warming cycle that could influence the long-term climate of the Earth.

Because clouds and atmospheric water vapor seem to play a significant role in the radiation budget of the Earth as well as the amount of global warming and climate change that may occur over the next century, scientists are attempting to find out more about the convection cycle that transports water vapor into the atmosphere. In 1997, Goddard launched the Tropical Rainfall Measuring Mission (TRMM) satellite into a near-equatorial orbit to look more closely at the convection cycle in the tropics that powers much of the rest of the world's cloud and weather patterns. The TRMM satellite's Clouds and the Earth's Radiant Energy System (CERES) instrument, built by NASA's Langley Research Center, is an improved version of the earlier ERBE experiment. While the satellite's focus is on convection and rainfall in the lower atmosphere, some of that moisture does get transported into the upper atmosphere, where it can play a role in changing the Earth's radiation budget and overall climate.25

 

[150] Ozone

 

An even greater amount of atmospheric research, however, has been focused on a once little-known chemical compound of three oxygen atoms called ozone. Ozone, as most Americans now know, is a chemical in the upper atmosphere that blocks incoming ultraviolet rays from the Sun, protecting us from skin cancer and other harmful effects caused by ultraviolet radiation.

The ozone layer was first brought into the spotlight in the 1960s, when designers began working on the proposed Supersonic Transport (SST). Some scientists and environmentalists were concerned that the jet's high-altitude emissions might damage the ozone layer, and the federal government funded several research studies to evaluate the risk. The cancellation of the SST in 1971 shelved the issue, at least temporarily, but two years later a much greater potential threat emerged.

In 1973, two researchers at the University of California, Irvine came up with the astounding theory that certain man-made chemicals, called chlorofluorocarbons (CFCs), could damage the atmosphere's ozone layer. These chemicals were widely used in everything from hair spray to air conditioning systems, which meant that the world might have a dangerously serious problem on its hands.

In 1975, Congress directed NASA to develop a "comprehensive program of research, technology and monitoring of phenomena of the upper atmosphere" to evaluate the potential risk of ozone damage further. NASA was already conducting atmospheric research, but the Congressional mandate supported even wider efforts. NASA was not the only organization looking into the problem, either. Researchers around the world began focusing on learning more about the chemistry of the upper atmosphere and the behavior of ozone layer.

Goddard's Nimbus IV research satellite, launched in 1970, already had an instrument on it to analyze ultraviolet rays that were "backscattered," or reflected, from different altitudes in the Earth's atmosphere. Different wavelengths of UV radiation should be absorbed by the ozone at different levels in the atmosphere. So by analyzing how much UV radiation was still present in different wavelengths, researchers could develop a profile of how thick or thin the ozone layer was at different altitudes and locations.

In 1978, Goddard launched the last and most capable of its Nimbus-series satellites. Nimbus 7 carried an improved version of this experiment, called the Solar Backscatter Ultraviolet (SBUV) instrument. It also carried a new sensor called the Total Ozone Mapping Spectrometer (TOMS). As opposed to the SBUV, which provided a vertical profile of ozone in the atmosphere, the TOMS instrument generated a high-density map of the total amount of ozone in the atmosphere.

A similar instrument, called the SBUV-2, has been put on weather satellites since the early 1980s. For a number of years, the Space Shuttle periodically flew a Goddard instrument called the Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment that was used to calibrate the SBUV-2 [151] satellite instruments to insure the readings continued to be accurate. In the last couple of years, however, scientists have developed data-processing methods of calibrating the instruments, eliminating the need for the Shuttle experiments.

Yet it was actually not a NASA satellite that discovered the "hole" that finally developed in the ozone layer. In May 1985, a British researcher in Antarctica published a paper announcing that he had detected an astounding 40% loss in the ozone layer over a Antarctica the previous winter. When Goddard researchers went back and looked at their TOMS data from that time period, they discovered that the data indicated the exact same phenomenon. Indeed, the satellite indicated an area of ozone layer thinning, or "hole,"26 the size of the Continental U.S.

How had researchers missed a development that drastic? Ironically enough, it was because the anomaly was so drastic. The TOMS data analysis software had been programmed to flag grossly anomalous data points, which were assumed to be errors. Nobody had expected the ozone loss to be as great as it was, so the data points over the area where the loss had occurred looked like problems with the instrument or its calibration. .

Once the Nimbus 7 data was verified, Goddard's researchers generated a visual map of the area over Antarctica where the ozone loss had occurred. In fact, the ability to generate visual images of the ozone layer and its "holes" have been among the significant contributions NASA's ozone-related satellites have made to the public debate over the issue. Data points are hard for most people to fully understand. But for non-scientists, a visual image showing a gap in a protective layer over Antarctica or North America makes the problem not only clear, but somehow very real.

The problem then became determining what was causing the loss of ozone. The problem was a particularly sticky one, because it was going to relate directly to legislation and restrictions that would be extremely costly for industry. By 1978, the Environmental Protection Agency (EPA) had already moved to ban....

 


This series of Total Ozone Mapping Spectrometer maps shows the development of an ozone <<hole>> over Antartica. Red indicates areas of thicker ozone; blues and violets indicate areas of ozone thinning.

This series of Total Ozone Mapping Spectrometer maps shows the development of an ozone "hole" over Antarctica. Red indicates areas of thicker ozone; blues and violets indicate areas of ozone thinning.

 

[152]....the use of CFCs in aerosols. By 1985, the United Nations Environmental Program (UNEP) was calling on nations to take measures to protect the ozone and, in 1987, forty-three nations signed the "Montreal Protocol, agreeing to cut CFC production 50% by the year 2000.

The CFC theory was based on a prediction that chlorofluorocarbons, when they reached the upper atmosphere, released chlorine and flourine. The chlorine, it was suspected, was reacting with the ozone to form chlorine monoxide - a chemical that is able to destroy a large amount of ozone in a very short period of time. Because the issue was the subject of so much debate, NASA launched numerous research efforts to try to validate or disprove the theory. In addition to satellite observations, NASA sent teams of researchers and aircraft to Antarctica to take in situ readings of the ozone layer and the ozone "hole" itself. These findings were then supplemented with the bigger picture perspective the TOMS and SBUV instruments could provide.

The TOMS instrument on Nimbus 7 was not supposed to last more than a couple of years. But the information it was providing was considered so critical to the debate that Goddard researchers undertook an enormous effort to keep the instrument working, even as it aged and began to degrade. The TOMS instrument also hadn't been designed to show long-term trends, so the data processing techniques had to be significantly improved to give researchers that kind of information. In the end, Goddard was able to keep the Nimbus 7 TOMS instrument operating for almost 15 years, which provided ozone monitoring until Goddard was able to launch a replacement TOMS instrument on a Russian satellite in 1991.27

A more comprehensive project to study the upper atmosphere and and the ozone layer was launched in 1991, as well. The satellite, called the Upper Atmosphere Research Satellite (UARS), was one of the results of Congress's 1975 mandate for NASA to pursue additional ozone research. Although its goal is to try to understand the chemistry and dynamics of the upper atmosphere, the focus of UARS is clearly on ozone research. Original plans called for the spacecraft to be launched from the Shuttle in the mid-1980s, but the Challenger explosion back-up delayed its launch until 1991.

Once in orbit, however, the more advanced instruments on board the UARS satellite were able to map chlorine monoxide levels in the stratosphere. Within months, the satellite was able to confirm what the Antarctic....

 


The Upper Atmosphere Research Satellite was launched in 1991 to take an intensive look at components and processes in the Earth's upper atmosphere.

The Upper Atmosphere Research Satellite was launched in 1991 to take an intensive look at components and processes in the Earth's upper atmosphere.

 

[153] ....aircraft expeditions and Nimbus-7 satellite had already reported - that there was a clear and causal link between levels of chlorine, formation of chlorine monoxide, and levels of ozone loss in the upper atmosphere.

Since the launch of UARS, the TOMS instrument has been put on several additional satellites to insure that we have a continuing ability to monitor changes in the ozone layer. A Russian satellite called Meteor 3 took measurements with a TOMS instrument from 1991 until the satellite ceased operating in 1994. The TOMS instrument was also incorporated into a Japanese satellite called the Advanced Earth Observing System (ADEOS) that was launched in 1996. ADEOS, which researchers hoped could provide TOMS coverage until the next scheduled TOMS instrument launch in 1999, failed after less than a year in orbit. But fortunately, Goddard had another TOMS instrument ready for launch on a small NASA satellite called an Earth Probe, which was put into orbit with the Pegasus launch vehicle in 1996. Researchers hope that this instrument will continue to provide coverage and data until the next scheduled TOMS instrument launch.

All of these satellites have given us a much clearer picture of what the ozone layer is, how it interacts with various other chemicals, and what causes it to deteriorate. These pieces of information are essential elements for us to have if we want to figure out how best to protect what is arguably one of our most precious natural resources.

Using the UARS satellite, scientists have been able to track the progress of CFCs up into the stratosphere and have detected the build-up of chlorine monoxide over North America and the Arctic as well as Antarctica. Scientists also have discovered that ozone loss is much greater when the temperature of the stratosphere is cold. In 1997, for example, particularly cold stratospheric temperatures created the first Antarctic-type of ozone hole over North America.

Another factor in ozone loss is the level of aerosols, or particulate matter, in the upper atmosphere. The vast majority of aerosols come from soot, other pollution, or volcanic activity, and Goddard's scientists have been studying the effects of these particles in the atmosphere ever since the launch of the Nimbus I spacecraft in 1964. Goddard's 1984 Earth Radiation Budget Satellite (ERBS), which is still operational, carries a Stratospheric Aerosol and Gas Experiment (SAGE II) that tracks aerosol levels in the lower and upper atmosphere. The Halogen Occultation Experiment (HALOE) instrument on UARS also measures aerosol intensity and distribution.

 


The light green to bold orange colors in this image taken by NASA’s Upper Atmosphere Research Satellite show the increase in sulfur dioxide levels following the June 1991 eruption of Mt. Pinatubo in the Philippines.

The light green to bold orange colors in this image taken by NASA's Upper Atmosphere Research Satellite show the increase in sulfur dioxide levels following the June 1991 eruption of Mt. Pinatubo in the Philippines.


 

[154] In 1991, both UARS and SAGE II were used to track the movement and dispersal of the massive aerosol cloud created by the Mt. Pinatubo volcano eruption in the Philippines. The eruption caused stratospheric aerosol levels to increase to as much as 100 times their pre-eruption levels, creating spectacular Sunsets around the world but causing some other effects, as well. These volcanic clouds appear to help cool the Earth, which could affect global warming trends, but the aerosols in these clouds seem to increase the amount of ozone loss in the stratosphere, as well.

The good news is, the atmosphere seems to be beginning to heal itself. In 1979 there was no ozone hole. Throughout the 1980s, while legislative and policy debates raged over the issue, the hole developed and grew steadily larger. In 1989, most U.S. companies finally ceased production of CFC chemicals and, in 1990, the U.N. strengthened its Montreal Protocol to call for the complete phaseout of CFCs by the year 2000. Nature is slow to react to changes in our behavior but, by 1997, scientists finally began to see a levelling out and even a slight decrease in chlorine monoxide levels and ozone loss in the upper atmosphere.28

Continued public interest in this topic has made ozone research a little more complicated for the scientists involved. Priorities and pressures in the program have changed along with Presidential administrations and Congressional agendas and, as much as scientists can argue that data is simply data, they cannot hope to please everyone in such a politically charged arena. Some environmentalists argue that the problem is much worse than NASA is making it out to be, while more conservative politicians have argued that NASA's scientists are blowing the issue out of proportion.29

But at this point a few things are clearer. The production of CFC chemicals was, in fact, harming a critical component of our planet's atmosphere. It took a variety of ground and space instruments to detect and map the nature and extent of the problem. But the perspective offered by Goddard's satellites allowed scientists and the general public to get a clear overview of the problem and map the progression of events that caused it. This information has had a direct impact on changing the world's industrial practices which, in turn, have begun to slow the damage and allow the planet to heal itself. The practical implications of Earth-oriented satellite data may make life a little more complicated for the scientists involved, but no one can argue the significance or impact of the work. By developing the technology to view and analyze the Earth from space, we have given ourselves an invaluable tool for helping us understand and protect the planet on which we live.

 

Oceanographic Satellites

 

One of the biggest advantages to remote sensing of the Earth from satellites stems from the fact that the majority of the Earth's surface area is extremely difficult to study from the ground. The world's oceans cover 71% of the Earth's [155] surface and comprise 99% of its living area. Atmospheric convective activity over the tropical ocean area is believed to drive a significant amount of the world's weather. Yet until recently, the only way to map or analyze this powerful planetary element was with buoys, ships or aircraft. But these methods could only obtain data from various individual points, and the process was extremely difficult , expensive, and time-consuming.

Satellites, therefore, offered oceanographers a tremendous advantage. A two-minute ocean color satellite image, for example, contains more measurements than a ship travelling 10 knots could make in a decade. This ability has allowed scientists to learn a lot more about the vast open stretches of ocean that influence our weather, our global climate, and our everyday lives.30

Although Goddard's early meteorological satellites were not geared specifically toward analyzing ocean characteristics, some of the instruments could provide information about the ocean as well as the atmosphere. The passive microwave sensors that allowed scientists to "see" through clouds better, for example, also let them map the distribution of sea ice around the world. Changes in sea ice distribution can indicate climate changes and affect sea levels around the world, which makes this an important parameter to monitor. At the same time, this information also has allowed scientists to locate open passageways for ships trying to get through the moving ice floes of the Arctic region.

By 1970, NOAA weather satellites also had instruments that could measure the temperature of the ocean surface in areas where there was no cloud cover, and the Landsat satellites could provide some information on snow and ice distributions. But since the late 1970s, much more sophisticated ocean-sensing satellite technology has emerged.31

The Nimbus 7 satellite, for example, carried an improved microwave instrument that could generate a much more detailed picture of sea ice distribution than either...

 


Goddard’s Nimbus 7 satellite carried a Coastal Zone Color Scanner, which detected the distribution of phytoplankton around the world. Phytoplannkton is a critical component of the global carbon cycle and its distribution has important implications for global climate change predictions.

Goddard's Nimbus 7 satellite carried a Coastal Zone Color Scanner, which detected the distribution of phytoplankton around the world. Phytoplankton is a critical component of the global carbon cycle and its distribution has important implications for global climate change predictions.


 

[156]...the earlier Nimbus or Landsat satellites. Nimbus 7 also carried the first Coastal Zone Color Scanner (CZCS), which allowed scientists to map pollutants and sediment near coastlines. The CZCS also showed the location of ocean phytoplankton around the world. Phytoplankton are tiny, carbon dioxide-absorbing plants that constitute the lowest rung on the ocean food chain. So phytoplankton generally mark spots where larger fish may be found. But because they bloom where nutrient-rich water from the deep ocean comes up near the surface, their presence also gives scientists clues about the ocean's currents and circulation.

Nimbus 7 continued to send back ocean color information until 1984. Scientists at Goddard continued working on ocean color sensor development...

 


This image from the Coastal Zone Color Scanner depicts ocean temperatures in the Atlantic Ocean off North America. Reds are the warmest, and blues and violets are the coolest. Swirls indicate eddies in the Gulf Stream.

This image from the Coastal Zone Color Scanner depicts ocean temperatures in the Atlantic Ocean off North America. Reds are the warmest, and blues and violets are the coolest. Swirls indicate eddies in the Gulf Stream.


 

....throughout the 1980s, and a more advanced coastal zone ocean color instrument was launched on the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite in 1997. In contrast to most scientific satellites, SeaWiFS was funded and launched by a private company instead of by NASA. Most of the ocean color data the satellite provides is purchased by NASA and other research institutions, but the company is selling some data to the fishing industry, as well.32

Since the launch of the Nimbus 7 and Tiros-N satellites in 1978, scientists have also been able to get much better information on global ocean surface temperatures. Sea surface temperatures tell scientists about ocean circulation, because they can use the temperature information to track the movement of warmer and cooler bodies of water. Changes in sea surface temperatures can also indicate the development of phenomena such as El Nino climate patterns. In fact, one of the most marked indications of a developing El Nino condition, which can cause heavy rains in some parts of the world and devastating drought in others, is an unusually warm tongue of water moving eastward from the western equatorial Pacific Ocean.

NOAA weather satellites have carried instruments to measure sea surface temperature since 1981, and NASA's EOS AM-1 satellite, scheduled for launch in 1999, incorporates an instrument that can measure those temperatures with even more precision. The launch of Nimbus 7 also gave researchers the ability to look at surface winds, which help drive ocean circulation. [157] With Nimbus 7, however, scientists had to infer surface winds by looking at slight differentiations in microwave emissions coming from the ocean surface. A scatterometer designed specifically to measure surface winds was not launched until the Europeans launched ERS-1 in 1991. Another scatterometer was launched on the Japanese ADEOS spacecraft in 1996. Because ADEOS failed less than a year after launch, Goddard researchers have begun an intensive effort to launch another scatterometer, called QuickSCAT, on a NASA spacecraft. JPL project managers are being aided in this effort by the Goddard-developed Rapid Spacecraft Procurement Initiative, which will allow them to incorporate the instrument into an existing small spacecraft design.Using this streamlined process, scientists hope to have QuickSCAT in orbit by the end of 1998.33

In the 1970s, researchers at the Wallops Flight Facility also began experimenting with radar altimetry to determine sea surface height, although they were pleased if they could get accuracy within a meter. In 1992, however, a joint satellite project between NASA and the French Centre National d'Etudes Spatiales (CNES) called TOPEX/Poseidon put a much more accurate radar altimeter into orbit. Goddard managed the development of the TOPEX radar altimeter, which can measure sea surface height within a few centimeters. In addition to offering useful information for maritime weather reports, this sea level data tells scientists some important things about ocean movement.

 


The first Earth Observing System satellite under construction. (NASA Photo G98-019-008)

The first Earth Observing System satellite under construction. (NASA Photo G98-019-008)


 

For one thing, sea surface height indicates the build-up of water in one area of the world or another. One of the very first precursors to an El Nino condition, for example, is a rise in ocean levels in the western equatorial Pacific, caused by stronger-than-normal easterly trade winds. Sea level also tells scientists important information about the amount of heat the ocean is storing. If the sea level in a particular area is low, it means that the area of warm, upper-level water is shallow. This means that colder, deeper water can reach the surface there, driving ocean circulation and bringing nutrients up from below, leading to the production of phytoplankton. The upwelling of cold water will also cool down the sea surface temperature, reducing the amount of water that evaporates into the atmosphere.

All of these improvements in satellite capabilities gave oceanographers and scientists an opportunity to integrate on-site surface measurements from buoys or ships with the more global perspective available from space. As a result, we are finally beginning to piece together a more complete picture of our oceans and the role they play in the Earth's biosystems and climate. In fact, one of the most significant results of ocean-oriented satellite research was the realization that ocean and atmospheric processes were intimately linked to each other. To really understand the dynamics of the ocean or the atmosphere, we needed to look at the combined global system they comprised.34

 

El Nino and Global Change

 

The main catalyst that prompted scientists to start looking at the oceans and atmosphere as an integrated system was the El Nino event of 1982-83. The rains and drought associated with the unusual weather pattern caused eight billion dollars of damage, leading to several international research programs to try to understand and predict the phenomenon better. The research efforts included measurements by ships, aircraft, ocean buoys, and satellites, and the work is continuing today. But by 1996, scientists had begun to understand the warning signals and patterns of a strong El Nino event. They also had the technology to track atmospheric wind currents and cloud formation, ocean color, sea surface temperatures, sea surface levels and sea surface winds, which let them accurately predict the heavy rains and severe droughts that occurred at points around the world throughout the 1997-98 winter.

The reason the 1982-83 El Nino prompted a change to a more integrated ocean-atmospheric approach is that the El Nino phenomenon does not exist in the ocean or the atmosphere by itself. It's the coupled interactions between the two elements that cause this periodic weather pattern to occur. The term El Nino, which means "The Child," was coined by fishermen on the Pacific coast of Central America who noticed a warming of their coastal ocean waters, along with a decline in fish population, near the Christ Child's birthday in December. But as scientists have discovered, the sequence of events that causes that warming begins many months earlier, in winds headed the opposite direction.

In a normal year, strong easterly trade winds blowing near the equator drag warmer, upper-level ocean water to the western edge of the Pacific ocean. That build-up of warm water causes convection....

 


This image of the sea surface temperature anomaly during the 1982-1983 El Niño eventwas created from satellite data.

This image of the sea surface temperature anomaly during the 1982-1983 El Niño eventwas created from satellite data.


 

[159] ....up into the tropical atmosphere, leading to rainfall along the Indonesian and Australian coastlines. It also leads to upwelling of colder, nutrient-rich water along the eastern equatorial Pacific coastlines, along Central and South America. In an El Nino year, however, a period of stronger-than-normal trade winds that significantly raises sea levels in the western Pacific is followed by a sharp drop in those winds. The unusually weak trade winds allow the large build-up of warm water in the western tropical Pacific to flow eastward along the equator. That change moves the convection and rainfall off the Indonesian and Australian coasts, causing severe drought in those areas and, as the warm water reaches the eastern edge of the Pacific ocean, much heavier than normal rainfall occurs along the western coastlines of North, Central, and South America. The movement of warm water toward the eastern Pacific also keeps the colder ocean water from coming up to the surface, keeping phytoplankton from growing and reducing the presence of fish further up on the food chain.

In other words, an El Nino is the result of a change in atmospheric winds, which causes a change in ocean currents and sea level distribution, which causes a change in sea surface temperature, which causes a change in water vapor entering the atmosphere, which causes further changes in the wind currents, and so on, creating a cyclical pattern. Scientists still don't know exactly what causes the initial change in atmospheric winds, but they now realize that they need to look at a global system of water, land and air interactions in order to find the answer. And satellites play a critical role in being able to do that.

An El Nino weather pattern is the biggest short-term "coupled" atmospheric and oceanographic climate signal on the planet after the change in seasons, which is why it prompted researchers to take a more interdisciplinary approach to studying it. But scientists are beginning to realize that many of the Earth's climatic changes or phenomena are really coupled events that require a broader approach in order to understand. In fact, the 1990s have seen the emergence of a new type of scientist who is neither oceanographer or atmospheric specialist, but is an amphibious kind of researcher focusing on the broader issue of climate change.35

 

Global Warming

 

One of the other important topics these researchers are currently trying to assess is the issue of global warming. Back in 1896, a Swedish chemist named Svante Arrhenius predicted that the increasing carbon dioxide emissions from the industrial revolution would eventually cause the Earth to become several degrees warmer. The reason for this warming was due to what has become known as the "greenhouse effect." In essence, carbon dioxide and other "greenhouse gases," such as water vapor, allow the short-wavelength radiation from the Sun to pass through the atmosphere, warming the Earth. But the gases absorb the longer-wavelength energy travelling [160] back from the Earth into space, radiating part of that energy back down to the Earth again. Just as the glass in a greenhouse allows the Sun through but traps the heat inside, these gases end up trapping a certain amount of heat in the Earth's atmosphere, causing the Earth to become warmer.

The effect of this warming could be small or great, depending on how much the temperature actually changes. If it is only a degree or two, the effect would be relatively small. But a larger change in climate could melt polar ice, causing the sea level to rise several feet and wiping out numerous coastal communities and resources. If the warming happened rapidly, vegetation might not have time to adjust to the climate change, which could affect the world's food supply as well as timber and other natural resources.

 


This satellite image shows global water vapor levels, which are an important factor in global warming studies.

This satellite image shows global water vapor levels, which are an important factor in global warming studies.


 

The critical question, then, is how great a danger global warming is. And the answer to that is dependent on numerous factors. One, obviously, is the amount of carbon dioxide and other emissions we put into the air - a concern that has driven efforts to reduce our carbon dioxide-producing fossil fuel consumption. But the amount of carbon dioxide in the air is also dependent on how much can be absorbed again by plant life on Earth - a figure that scientists depend on satellites in order to compute. Landsat images can tell scientists how much deforestation is occurring around the world, and how much healthy plant life remains to absorb CO2. Until recently, however, the amount of CO2 absorbed by the world's oceans was unknown. The ocean color images of SeaWiFS are helping to fill that gap, because the phytoplankton it tracks are a major [161] source of carbon dioxide absorption in the oceans.

Another part of the global warming equation is how much water vapor is in the atmosphere - a factor that is driven by ocean processes, especially in the heat furnace of the tropics. As a result, scientists are trying to learn more about the transfer of heat and water vapor between the ocean and different levels of the atmosphere, using tools such as Goddard's TRMM and UARS satellites.

All of these numbers and factors are fed into atmospheric and global computer models, many of which have been developed at the Goddard Institute for Space Studies (GISS) in New York City. These models then try to predict how our global climate may change based on current emissions, population trends, and known facts about ocean and atmospheric processes.

While these models have been successful in predicting short-term effects, such as the global temperature drop after the Mt. Pinatubo volcano eruption, the problem with trying to predict global change is that it's a very long-term process, with many factors that may change over time. We have only been studying the Earth in bits and pieces, and for only a short number of years. In order to really understand which climate changes are short-term variations and which ones are longer trends of more permanent change, scientists needed to observe and measure the global, integrated climate systems of Planet Earth over a long period of time. This realization was the impetus for NASA's Mission to Planet Earth, or the Earth Science Enterprise.36

 

Earth Science Enterprise

 

In some senses, the origins of what became NASA's "Mission to Planet Earth" (MTPE) began in the late 1970s, when we began studying the overall climate and planetary processes of other planets in our solar system. Scientists began to realize that we had never taken that kind of "big picture" look at our own planet, and that such an effort might yield some important and fascinating results. But an even larger spur to the effort was simply the development of knowledge and technology that gave scientists both the capability and an understanding of the importance of looking at the Earth from a more global, systems perspective.

Discussions along these lines were already underway when the El Nino event of 1982-83 and the discovery of the ozone "hole" in 1985 elevated the level of interest and support for global climate change research to an almost crisis level. Although the "Mission to Planet Earth" was not announced as a formal new NASA program until 1990, work on the satellites to perform the mission was underway before that. In 1991, Goddard's UARS satellite became the first official MTPE spacecraft to be launched.

Although the program has now changed its name to the Earth Science Enterprise, suffered several budget cuts, and refocused its efforts from overall global change to a narrower focus of global climate change (leaving out changes in solid land masses), the basic goal of the program echoes what was initiated in 1990. In essence, the Earth Science Enterprise aims to integrate satellite, [162] aircraft and ground-based instruments to monitor 24 interrelated processes and parameters in the planet's oceans and atmosphere over a 15-year period.

Phase I of the program consisted of integrating information from satellites such as UARS, the TOMS Earth Probe, TRMM, TOPEX/Poseidon, ADEOS and SeaWiFS with Space Shuttle research payloads, research aircraft and ground station observations. Phase II is scheduled to begin in 1999 with the launch of Landsat 7 and the first in a series of Earth Observing System (EOS) satellites. The EOS spacecraft are extremely large research platforms with many different instruments to look at various atmospheric and ocean processes that affect natural resources and the overall global climate. They will be polar-orbiting satellites, with orbital paths that will allow the different satellites to take measurements at different times of the day. EOS AM-1 is scheduled for launch in late 1998. EOS PM-1 is scheduled for launch around the year 2000. The first in an EOS altimetry series of satellites, which will study the role of oceans, ocean winds and ocean-atmosphere interactions in climate systems, will launch in 2000. An EOS CHEM-1 satellite, which will look at the behavior of ozone and greenhouse gases, measure pollution and the effect of aerosols on global climate, is scheduled for launch in 2002. Follow-on missions will continue the work of these initial observation satellites over a 15-year period.

There is still much we don't know about our own planet. Indeed, the first priority of the Earth Science Enterprise satellites is simply to try to fill in the gaps in what we know about the behavior and dynamics of our oceans and our atmosphere. Then scientists can begin to look at how those elements interact, and what impact they have and will have on global climate and climate change. Only then will we really know how great a danger global warming is, or how much our planet can absorb the man-made elements we are creating in greater and greater amounts.37

It's an ambitious task. But until the advent of satellite technology, the job would have been impossible to even imagine undertaking. Satellites have given us the ability to map and study large sections of the planet that would be difficult to cover from the planet's surface. Surface and aircraft measurements also play a critical role in these studies. But satellites were the breakthrough that gave us the unique ability to stand back far enough from the trees to see the complete and complex forest in which we live.

 

Conclusion

 

For centuries, humankind has stared at the stars and dreamed of travelling among them. We imagined ourselves zipping through asteroid fields, transfixed by spectacular sights of meteors, stars, and distant galaxies. Yet when the astronauts first left the planet, they were surprised to find themselves transfixed not by distant stars, but by the awe-inspiring view their spaceship gave them of the place they had just left - a dazzling, mysterious planet they affectionally nicknamed the "Big Blue Marble." As our horizons expanded into the universe, so did our perspective [163] and understanding of the place we call home. As an astronaut on an international Space Shuttle crew put it, "The first day or so we all pointed to our countries. The third or fourth day we were pointing to our continents. By the fifth day we were aware of only one Earth."38

Satellites have given this perspective to all of us, expanding our horizons and deepening our understanding of the planet we inhabit. If the world is suddenly a smaller place, with cellular phones, paging systems, and Internet service connecting friends from distant lands, it's because satellites have advanced our communication abilities far beyond anything Alexander Graham Bell ever imagined. If we have more than a few hours' notice of hurricanes or storm fronts, it's because weather satellites have enabled meteorologists to better understand the dynamics of weather systems and track those systems as they develop around the world. If we can detect and correct damage to our ozone layer or give advance warning of a strong El Nino winter, it's because satellites have helped scientists better understand the changing dynamics of our atmosphere and our oceans.

We now understand that our individual "homes" are affected by events on the far side of the globe. From both a climatic and environmental perspective, we have realized that our home is indeed "one Earth," and we need to look at its entirety in order to understand and protect it. The practical implications of this information sometimes make the scientific pursuit of this understanding more complicated than our explorations into the deeper universe. But no one would argue the inherent worth of the information or the advantages satellites offer.

 


Earthrise, as seen by the Apollo astronauts on the Moon. Ironically, it has only been since we left our planet that we have really begun to understand it.

Earthrise, as seen by the Apollo astronauts on the Moon. Ironically, it has only been since we left our planet that we have really begun to understand it.


 

The satellites developed by Goddard and its many partners have expanded both our capabilities and our understanding of the complex processes within our Earth's atmosphere. Those efforts may be slightly less mind-bending than our search for space-time anomalies or unexplainable black holes, but they are perhaps even more important. After all, there may be millions of galaxies in the universe. But until we find a way to reach them, this planet is the only one we have. And the better we understand it, the better our chances are of preserving it - not only for ourselves, but for the generations to come.


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