NASA/SP–2014-619

Earth Radiation Budget Research 

at the NASA Langley Research Center 

G. Louis Smith and Edwin F. Harrison 

Science Systems Applications, Inc., Hampton, Virginia 

Gary G. Gibson 

Langley Research Center, Hampton, Virginia 

 

May 2014
Cover: The image on the cover of this publication 

shows the Earth Radiation Budget Satellite on 

 Remote Manipulator Arm of Space Shuttle 

 Challenger prior to release into orbit. 

NASA photograph STS41G-49-019
NASA/SP–2014-619

Earth Radiation Budget Research 

at the NASA Langley Research Center 

G. Louis Smith and Edwin F. Harrison 

Science Systems Applications, Inc., Hampton, Virginia 

Gary G. Gibson 

Langley Research Center, Hampton, Virginia 

 

May 2014
Acknowledgments 

The authors are grateful to the Science Directorate for supporting the writing of this history. 

They are also indebted to the following friends and colleagues for their contributions: John E. 

Cooper (management issues); Shashi Gupta, Roberta DiPasquale and Paul Stackhouse (surface 

radiation budget); and Wenying Su (surface and atmospheric radiation budget). We also thank 

Gail Langevin, Historian of Langley Research Center, for reviewing this paper and making many 

suggestions to improve the text, and Teresa Hornbuckle of the LaRC Photo Archives for locating 

several photos for this history. 

Available from: 

 NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

This report is also available in electronic format at http://ntrs.nasa.gov 

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration.
Foreword

In the 1970s research studies concentrating on satellite measurements of Earth’s 

radiation budget started at the NASA Langley Research Center. Since that 

beginning, considerable effort has been devoted to developing measurement 

techniques, data analysis methods, and time-space sampling strategies to meet the 

radiation budget science requirements for climate studies. Implementation and 

success of the Earth Radiation Budget Experiment (ERBE) and the Clouds and 

the Earth’s Radiant Energy System (CERES) was due to the remarkable 

teamwork of many engineers, scientists, and data analysts. Data from ERBE have 

provided a new understanding of the effects of clouds, aerosols, and El Nino/La 

Nina oscillation on the Earth’s radiation. CERES spacecraft instruments have 

extended the time coverage with high quality climate data records for over a 

decade. Using ERBE and CERES measurements these teams have created 

information about radiation at the top of the atmosphere, at the surface, and 

throughout the atmosphere for a better understanding of our climate. They have 

also generated surface radiation products for designers of solar power plants and 

buildings and numerous other applications.

iii

1 

Introduction 

In the beginning of space exploration in the early 1960s several research divisions at the 

NASA Langley Research Center (LaRC) were involved in studying materials in space, 

instrumented rocket payloads, satellite experiments, and reentry vehicles. These research 

space flight programs made important contributions to the design of the Apollo heat 

shield, the lunar orbital rendezvous concept, and lunar landing simulations. Other major 

space projects in which Langley played a major role in the late 1960s and 1970s included 

the Viking mission to Mars. Beyond managing a major portion of the Viking project 

from Earth lift-off to landing on Mars, Langley researchers performed interplanetary 

trajectory analyses, designed and tested the Mars entry and landing vehicle as well as 

provided support for instruments, electronics, and systems engineering. The experiences 

gained in these projects were valuable later in the development of the Earth radiation 

budget projects at the NASA Langley Research Center. In the mid-1960s the Apollo 

Program was moving forward; man would set foot on the Moon before the end of the 

decade. Within LaRC research was being done to send a human to Mars and return to 

Earth. Research was being done for the design of the heat shield that would protect 

humans returning from Mars. There were teams in two different organizations of LaRC 

studying the heating problem. After the successful missions to the Moon, public interest 

in space exploration waned. In the early 1970s the Nation’s interest turned inward and the 

demand became Relevance and Societal Benefit. At this time, public concern about the 

environment began to grow. The teams studying reentry from planetary return began 

looking for ways in which their capabilities could be used to address problems on Earth. 

In the late 1950s and early1960s engineers at NASA Langley were concentrating on 

various unmanned Earth-orbiting satellites. Engineers under the leadership of William 

O’Sullivan in the Pilotless Aircraft Research Division (PARD) developed the technology 

to place balloons in orbit and inflate them there. The first balloon had a 100-foot diameter 

(figure 1) and was used to bounce a message from President Eisenhower from Earth to 

the balloon and back to Earth. This balloon was named Echo and was the first 

communication satellite. A second balloon with twice the area (140-foot diameter), 

dubbed Echo II was flown next. 

The orbits of these two balloons were perturbed by the thin air through which they flew 

and by the pressure of sunlight. At that time, little was known about the density of air at 

spacecraft altitudes, so orbit lifetime estimates had large uncertainties. The perturbations 

of the orbits of the Echo balloons demonstrated that balloons could be used to investigate 

the density of air at high altitudes. LaRC engineers had also demonstrated the ability to 

put a balloon in space and inflate it. A 12-foot balloon (Explorer IX) was placed into a 

low orbit by a Scout launch vehicle. The Scout was a four stage solid rocket developed at 

LaRC as an inexpensive booster for placing small satellites into space. Explorer IX was 

the first payload placed in orbit by Scout, with a perigee of 635 km. and apogee of 2600 

km. In 1963 another balloon named Explorer XIX was placed in orbit. The two spacecraft 

together provided much new additional information about air density at these altitudes. 
2 

Figure 1: The Echo I balloon in a hanger for development tests, 

together with the project team. 
3 

The Beginning of Earth Radiation Budget Research at Langley 

One of the researchers on the team that 

worked with the Explorer IX and XIX, 

George E. Sweet (figure 2), pondered what 

other ways these balloons could be used. 

The engineers at LaRC knew that the 

temperature of a balloon depended on the 

sunlight and Earth-emitted radiation and 

the color of the balloon’s surface. George 

Sweet reasoned: Let’s put three balloons 

together with three different color coatings 

and measure their temperatures. From this 

we can measure the direct sunlight, the 

sunlight reflected from the Earth and the 

earth-emitted radiation. This approach 

applied the concept used by Verner Suomi 

(figure 3) for the first Earth radiation 

budget experiment, which was flown on 

the Explorer VII in 1959 (figure 4). 

Dr. Verner Suomi of the University of Wisconsin 

had designed an instrument that consisted of two 

pairs of hemispheres that were mounted on 

opposite sides of the spinning Explorer IV 

spacecraft. (Folklore claimed that he used ping 

pong balls cut in half.) One pair was painted 

black, the other pair white. The black pair 

absorbed sunlight, both direct and that reflected 

from the Earth, and Earth-emitted radiation. The 

white pair reflected sunlight but absorbed Earthemitted radiation. Researchers used the 

temperatures of these hemispheres along with 

thermal balance equations to calculate the amount 

of sunlight and Earth-emitted radiation on the 

device. This experiment provided the first crude 

measurements of the Earth’s radiation balance. 

For his many contributions, Prof. Suomi is 

regarded as the father of satellite meteorology. 

Figure 2: George Sweet, initiator of 

radiation budget research at the 

Langley Research Center. Photo 

Cedit of Mrs. Nancy Sweet. 

Figure 3: Prof. Verner Suomi. Photo 

Credit: University Communications, 

University of Wisconsin-Madison. 
4 

Figure 4: Explorer VII Satellite, with spherical radiometers for measuring radiation from 

the Earth. Suomi, V. E., 1958: “The radiation balance of the Earth from a satellite,” 

Annals of the IGY, 6, 331-340. 

Dr. Suomi was appointed as Director of the Weather Bureau, where he advocated the 

development of satellite instruments and the application of these measurements to 

weather forecasting. Dr. Suomi later led the design of the spin-scan instruments and their 

use on the Geostationary Operational Environmental Satellites (GOES) for continuously 

observing the weather over the U.S, and the camera that was used on the Viking Lander 

to give pictures of the surface of Mars in 1976. He returned to the University of 

Wisconsin, where he founded the Space Science and Engineering Center. As a dominant 

figure in satellite meteorology, his support for any project to measure Earth radiation 

budget was vital. 

In the early 1970s a team of LaRC engineers from various divisions (Applied Materials 

and Physics, Aero-Physics, Electronics, and Engineering) was willingly recruited by 

George Sweet to help develop his concept of using balloons to measure Earth radiation 

budget. First, the hardware must be designed to achieve the goals of accuracy and 

longevity. Charles V. Woerner and John (Jack) B. Cooper had also worked on the air 

density balloon projects and led this effort. Next, methods had to be developed to analyze 

the data to produce scientifically useful results. George Sweet concentrated on learning 

the needs of scientists for information about the Earth’s radiation balance. How accurate 

must the data be? How frequently are measurements needed, daily or monthly? What is 

the required spatial scale of the measurements, that is, for areas of thousands of 

kilometers across or only a few kilometers? 
5 

While the rest of the Langley Team was working to complete the concept for the 

experiment, George Sweet began to develop the scientific rationale for measuring Earth 

Radiation Budget and the requirements for the measurements. George Sweet recruited G. 

Louis Smith, another engineer in the Applied Materials and Physics Division, and the two 

visited a number of researchers at the National Center for Atmospheric Research, 

Colorado State University, University of Wisconsin, and University of Maryland. Their 

questions were: what would be done with the data when it became available, that is, what 

scientific questions would it answer, and what were the accuracy and time and space 

scales required? 

What is the radiation budget and why do we need to measure it? 

The first question: Why is Earth radiation balance important? The Sun’s radiation heats 

the Earth, making the Tropics hotter than the higher latitudes. These temperature 

differences cause the atmosphere and oceans to circulate, carrying heat to the cooler 

regions. The Earth emits heat as radiation, so that the outgoing longwave radiation 

balances the Sun’s radiation. This is illustrated in figure 5. This balance of incoming and 

outgoing radiation governs our climate. By measuring the terms that balance the budget 

of radiation over the Earth, we can learn about the climate and the processes that 

determine the climate. These data would also provide insight into interannual changes of 

weather and climate, and perhaps lead to the ability to forecast the changes from the 

average a season in advance. These forecasts would not be specific for a given day, but 

would apply to the average for the season or month. The measurement of the terms of the 

radiation budget of the Earth has been an important task in climate research since the 

earliest days of the Space Age and continues to be so today. 

Figure 5: Showing Sun heating Earth, and heat being emitted by Earth. 
6 

In the early 1970s, William Bandeen, one of the key people in the early days of Goddard 

Space Flight Center, brought in Dr. Thomas Vonder Haar, a student of Dr. Suomi, and 

Dr. Ehrhardt Raschke from the University of Cologne to work with himself and Musa 

Pasternack, also of GSFC, with data from the Medium Resolution Infrared Radiometer, 

which had flown aboard the Nimbus-3 research satellite. The Nimbus satellite series, of 

which there were seven, was a very successful NASA program for developing and 

demonstrating instruments for observing the Earth, its atmosphere, oceans and ice/snow 

cover. The work by Bandeen’s group demonstrated the ability of satellite instruments to 

measure the radiation balance of the Earth and the application of this information to 

studies of the Earth’s climate. 

At that time, climate models were in their infancy. The prevailing viewpoint was that 

radiation was important only for time scales of a month or longer. For time scales for 

weather, the effects of radiation were unimportant and the flow of the atmosphere was 

dominated by its dynamics. This belief had come about largely because the computer 

power until then was too limited to include radiative heating and cooling of the 

atmosphere and the surface. Models of the atmospheric circulation had been developed 

which excluded radiation and provided reasonable results. The requirement for the 

resolution of radiation budget data was established as 1 month. Corresponding to the 1-

month time scale, the spatial scale was also large. The requirement for the spatial scale 

for the Langley experiment was taken to be 10-degree zonal averages. The results of the 

three-balloon design would provide information with zonal resolution, that is, for 

latitudinal bands, and would operate for a long time because it had no moving parts to 

fail. For this reason, the concept was named the Long-term Zonal Earth Energy Budget 

Experiment (LZEEBE; see figure 6). 

Figure 6: Proposed Long-term Zonal Earth Energy Budget Experiment (LZEEBE). 
7 

In order to get a new project start, the LZEBEE concept had to have the backing of the 

Meteorological Program Office (MPO). This office was a headquarters function, but was 

located at Goddard Space Flight Center. Funding for NASA, university and industry 

studies and instrument development came through this Office. The MPO Head was Harry 

Press, who had come from LaRC where he had worked on the Thunderstorm Project in 

the late 1940s. Later he moved to GSFC, and served as head of the Nimbus Project. As 

head of MPO, Harry made certain that if there was a new start for an Earth radiation 

budget project, it would succeed. The Langley team would periodically go to MPO and 

present their work. Harry Press would provide his critique and point out the direction in 

which the team should proceed. He provided the Langley group with a sparring partner to 

assure that there were no major unresolved problem areas. 

Competition Begins 

Interest in Earth Radiation Budget was increasing. Professor Verner Suomi had followed 

his Explorer VII radiation budget measurements with similar radiometers in the ESSA-7 

spacecraft. These two spacecraft were also spin-stabilized, with their spin axes 

perpendicular to their orbits. Professor Suomi proposed to repeat this experiment, but 

with faster radiometers which would make measurements as they rotated to be horizontal, 

thus providing a better measurement of flux. Because there were no mechanisms with 

moving parts to fail, this instrument would operate reliably and provide a long data 

record. As founder and head of the Space Science and Engineering Center at the 

University of Wisconsin, he submitted a proposal to NASA to further develop his 

concept. 

Dr. Thomas P. Vonder Haar, at this time at Colorado State University, submitted a 

proposal to NASA to develop a scanning radiometer to measure Earth’s radiation budget. 

This proposal included participation by Ball Brothers Space Division to develop the 

engineering aspects of the instrument. 

Charlie Woerner and Jack Cooper realized that in order to improve the chances of an 

eventual radiation budget project, the Suomi and Vonder Haar proposals should proceed 

through concept definition along with LZEEBE. They subsequently obtained funding 

through the Meteorology Program Office, which assigned the management of these 

grants to Langley Research Center. By managing these grants, the Langley team became 

familiar with each concept and its advantages and disadvantages. 

While this work was being done by Langley researchers and through grants and contracts 

with universities and industry, an Earth radiation budget instrument was being flown by 

the National Oceanic and Atmospheric Administration (NOAA). Dr. Jay Winston, head 

of the NOAA Meteorological Satellite Laboratory, insisted that a spatial resolution of 2.5 

degrees was required. This spatial resolution requires a scanning radiometer. He had 

brought Dr. William L. Smith, a recent graduate of the University of Wisconsin and a 

student of Dr. Suomi, into the Meteorological Satellite Laboratory. Dr. William (Bill) 
8 

Smith had developed techniques for using sounding measurements from scanning 

radiometers to compute temperature and humidity profiles in the atmosphere. Now Bill 

was developing the Earth Radiation Budget (ERB) instrument (see figure 7), which 

would fly on the Nimbus-6 and -7 spacecraft. The ERB included a scanning radiometer 

with eight channels and flat plate radiometers. The scanning radiometer scanned in both 

the nadir angle and in azimuth, so as to provide measurements that enabled determination 

of the angular distribution of radiation leaving the Earth’s atmosphere. The flat plate 

radiometers measured solar radiation reflected from the Earth, the radiation emitted by 

the Earth and the radiation directly from the Sun. After the launch of Nimbus 6, Dr. 

Smith went on a sabbatical to Australia where he made ground measurements to validate 

ERB results. Dr. Herbert Jacobowitz, also of the Meteorological Satellite Laboratory, 

took over the ERB instrument. Unfortunately, the scanning radiometer of the ERB aboard 

the Nimbus 6 spacecraft only operated for about a month before a cable failure rendered 

it useless. 

Figure 7: The Earth Radiation Budget instrument. Copies of this instrument flew aboard 

the Nimbus-6 and -7 spacecraft and provided valuable information for researchers. (W. L. 

Smith et al.,1977, Applied Optics, vol. 15) 

However, the wide field-of-view radiometers provided good measurements of the Earth’s 

radiation budget for several years. This early failure of the scanning radiometer added 

weight to Dr. Suomi’s argument that long-term data sets required non-scanning 

radiometers. 
9 

With the Nimbus-7 spacecraft being prepared for launch, NASA began the Science Team 

concept. Previously, a Principal Investigator (PI) had the responsibility of assuring that 

the instrument met its scientific objectives and for using the data for scientific 

investigations. Under the Science Team approach, an Experiment Scientist led a team of 

scientists in these tasks, which greatly expanded the use of the data for research. NASA 

sent out an Announcement of Opportunity for participation on the science team for the 

ERB instrument. The Langley team, headed by Dr. Louis Smith, submitted a proposal for 

participation on the ERB Science Team, which was accepted. Experience in the ERB 

Science Team greatly extended the scientific understanding and capability of Langley’s 

team to carry out a project for measuring the Earth’s radiation budget. 

The Langley team first addressed some key areas for radiation budget measurements 

required by the scientific community. The determination of the Earth’s radiation budget 

requires several steps, the first of which is the measurements. Robert Babcock, of the 

Instrument Research Division, studied various radiometer concepts for making these 

measurements. The measurements are then used to compute the flux “at the top of the 

atmosphere” at the time of measurement, which requires a model of the distribution of 

the radiation in all directions. For reflected solar radiation these models are called 

“bidirectional reflectance distribution functions” because the direction of the incoming 

and outgoing rays must be included in the computation. Data from the ERB project 

would be used to generate these models. Richard Green and Lou Smith explored new 

data analysis techniques. 

Space and time sampling was also a key issue. Edwin F. Harrison, head of the Mission 

Analysis Section of the Space Technology Division and Gary G. Gibson were experts in 

mission analysis, i.e., the design of orbits for specific purposes. The measurements must 

cover the entire Earth in order to establish the balance of radiation into and away from the 

Earth. Finally, the flux must also be known for all times so as to compute the total energy 

during the day, which also requires information about the variation of fluxes during the 

day. Patrick Minnis, who had just completed his MS degree in Atmospheric Sciences at 

Colorado State University, was hired. To get the needed information, Pat went to the 

World Weather Building of NOAA, where he got daily pictures of satellite imagery. He 

spent a week with these pictures on a light table, tracing clouds and making estimates of 

cloud cover as it varied during the day. Although these results could be called subjective, 

these numbers provided the only knowledge of diurnal variation of radiation at that time. 

(At that time, computers were not sufficiently advanced to automate this process, but 

when they progressed to that point, Minnis would use them to do this objectively.) 

Harrison and Gibson performed computer simulations to determine the geographical and 

temporal coverage of various satellite orbits for Earth radiation measurements. A satellite 

must be placed in an orbit that would pass over the Earth at all times of day during a 

“reasonable” length of time in order to learn how the radiation varies with time of day. 

Their results indicated that a three-satellite system, including two sun-synchronous 

satellites along with a mid-inclined orbit satellite, provided the optimal coverage and 

accuracy for measurement of the Earth’s radiation budget. They showed that a satellite 

placed in orbit by the space shuttle would cover the Earth between 57o

N and 57oS 
10 

latitude, precess through all times of day during a 72-day period, and provide the data 

needed to generate the diurnal variation models. To cover the rest of the Earth and to 

provide additional coverage during the day, instruments should be placed on the NOAA9 and -10 spacecraft. Figure 8 shows the coverage provided by this combination of 

instruments. This work placed the Langley team into a position where they understood 

many of the problems of measuring the radiation budget, analyzing it and producing data 

that the scientific community could use to improve our understanding of climate. 

Figure 8: This plot shows the local times when measurements will be made for each 

latitude by a three-satellite system (Harrison and Gibson, 1981). The band between 60 

degrees north and south would be observed by a precessing spacecraft. 

The study grants for the concepts of the University of Wisconsin and Colorado State 

University and the Langley LZEEBE proposal were completed and submitted to NASA 

Headquarters. Dr. Morris Tepper, Program Scientist for meteorology at NASA 

Headquarters, was in a dilemma as to what path to take for Earth radiation budget 

measurements. Professor Suomi, the highly regarded “Father of Satellite Meteorology”, 

insisted that long-term measurements of Earth radiation budget could only be 

accomplished by use of flat plate radiometers, which would give a resolution of 10 

degrees on the Earth. Because Earth radiation budget is a climate topic, it was necessary 

to have the support of NOAA before the project would be approved. The head of the 

Satellite Meteorological Satellite Laboratory, Dr. Jay Winston, insisted on the 

requirement that any Earth radiation budget program must provide monthly mean maps 
11 

with 2.5-degree resolution. This requirement could be met only with a scanning 

radiometer. The Langley team had stepped into this arena of conflicting requirements and 

competing organizations. One of our branch heads opined that the Langley team was 

strong technically but politically inept. 

A number of reviews were held of the various concepts, culminating in a review by a 

panel of the National Academy of Sciences. A Langley team consisting of George Sweet, 

Louis Smith, Edwin Harrison, Charles Woerner, and Jack Cooper, as well as Robert 

Curran of Goddard made numerous presentations. After hearing the debate of scientific 

requirements, resolution and length of time record, the panel concluded that there were 

two categories of measurements required: one was for a long-term data set that would 

have a resolution of 10 degrees or smaller, and another was for 2.5-degree resolution data 

set. The panel endorsed both sets of requirements. Their conclusion was to fly both 

scanning and flat plate radiometers. In their Special Report of the Atmospheric Sciences 

Panel of the National Academy of Sciences, 1976, the panel further recommended to NASA 

that “Langley be asked to analyze the data for the next Earth radiation budget 

experiments.” The National Academy of Sciences report was a major factor contributing 

to the decision to assign experiment management responsibility for the NASA Earth 

Radiation Budget Satellite System to the Langley Research Center. 

With the direction provided by the National Academy of Sciences, the Langley team 

abandoned the LZEEBE concept and developed a proposal to fly scanning radiometers as 

proposed by CSU and Ball Brothers and also non-scanning radiometer packages. These 

would fly on the NOAA-9 and -10 spacecraft and a dedicated Earth Radiation Budget 

Satellite that would be placed into orbit by the Space Shuttle. Although the LZEEBE 

concept was supplanted by this new approach, it had served the purpose of establishing 

the science requirements and had resulted in a team that would carry the new project to 

fruition. This proposal was forwarded by the Meteorological Program Office with its 

approval to NASA Headquarters. In addition to the National Academy of Sciences 

recommendation that the Langley Team have the responsibility for the Earth Radiation 

budget project, Dr. Paul F. Holloway, LaRC Director for Space, attended key reviews and 

assured NASA Headquarters that the project would have the support of LaRC to make it 

a success. The project was named the Earth Radiation Budget Experiment to show 

continuity with the ERB project, and was included in the NASA budget. Congress funded 

the new ERBE project in the Fiscal Year 1978 budget and also gave NASA the 

responsibility of conducting research in Earth radiation budget. Langley Research Center 

now had the responsibility of carrying out this project. 

How had this team of retreaded engineers developed a winning proposal and carried out 

this project to a very successful conclusion? As engineers they each had a solid 

background in physics and mathematics and the application of these fields. They also 

built on this background to learn the necessary topics as they went into the new areas. 

And most importantly, they worked together as a team to accomplish their goal and they 

were determined to win. Figure 9 shows the Earth Radiation Budget Study Team. 
12 

Figure 9: The Earth Radiation Budget study team. Front row: John T. Suttles, Mary Alice 

Woerner, Lee M. Avis, Richard N. Green. Back Row: Robert Babcock, George Sweet, 

Charlie Woerner, Louis Smith, Jim Kibler and Edwin Harrison. 

The Earth Radiation Budget Experiment (ERBE) Becomes a Project 

Given the FY1978 new start, the ERBE Project would design, build, calibrate, and fly 

scanning and non-scanning instruments on each of three spacecraft, collect and process 

the data, generate data products, and use them for scientific investigations. The Langley 

Research Center was given the responsibility for the instruments and the scientific 

leadership of the project. Goddard Space Flight Center had the responsibility for the 

Earth Radiation Budget Spacecraft on which the ERBE instruments would fly. At LaRC 

the project was now organized with the design and building of the instruments in the 

Projects Directorate and the scientific functions in the Atmospheric and Environmental 

Sciences Division (AESD) of the LaRC Space Directorate. The scientific functions 

included collaborating with the project engineering team to specify details of the 

instrument that affected the measurements and the calibration of the instrument, 

development of software that would be used for the computations required to process the 

measurements from electronic signals to useful scientific products, and the use of these 

products for scientific investigations. Close collaboration was needed between the 

engineering and scientific teams to assure an instrument that would operate to generate 

good science data. For ERBE, the years of working together to win the project had made 

the group a closely-knit, highly collaborative team. 
13 

NASA Headquarters also selected LaRC to carry out the Stratospheric Aerosol and Gas 

Experiment (SAGE). The ERBE/SAGE Project was established within the Projects 

Directorate of LaRC. Calvin Broom was selected as Project Manager. He was completing 

his service as Project Manager for the Viking Project, which had orbited two spacecraft 

around Mars and then sent a craft from each orbiter to land on the Red Planet and make 

the first scientific measurements from the surface of Mars. Charlie Woerner was assigned 

as ERBE/SAGE Deputy Project Manager and Jack Cooper as ERBE Experiment 

Manager. Michael Luther, who had done much of the original work on the LZEEBE 

concept, was assigned to be Instrument Engineer for the non-scanning package, and 

Leonard Kopia of the Flight Instrument Division became Instrument Engineer for the 

scanner. The first task for the engineering team was to write a statement of work, which 

would be the major part of a Request for Proposals, to design, build, test, calibrate, and 

deliver three scanning radiometers and three non-scanning radiometers for flight on the 

Earth Radiation Budget Satellite, NOAA-9 and NOAA-10 spacecraft. Several companies 

responded to this request and the winning bid was by the TRW Space Division, in 

Redondo Beach, California. Figure 10 shows the non-scanning radiometer package and 

the scanning radiometer. 

Figure 10: Photograph of the ERBE instruments. The Non-scanning radiometer package 

is on the left and the scanning radiometer is on the right. 
14 

The Radiation Sciences Branch was formed in AESD and included the in-house 

scientists, with Edwin Harrison as the head. The Data Management Group was formed 

with the responsibility of producing the software required and using it to process the 

measurements from the electronic signals from the spacecraft to generate scientifically 

useful information. James Kibler was selected as head of this group. Kibler had worked 

from the beginning of the formulation of the project to define the requirements for the 

data processing. Unfortunately, George Sweet, who had initiated the Earth radiation 

budget work at Langley died before ERBE got its start. 

The first task in AESD was to select an Experiment Scientist, who would have the 

responsibility for getting the greatest scientific return possible from the project. The 

Experiment Scientist would lead the Science Team, coordinate with the engineering team 

in the design of the instruments, manage the development of the software to process the 

data, and defend the budget for the science work in the Byzantine politics of a major 

project. Dr. Bruce Barkstrom, a professor with George Washington University and an 

expert in radiative transfer theory, was selected for this role. His first task was to work 

with the team in AESD to specify instrument requirements for the Statement of Work 

being prepared by the engineering team. Next, he wrote requirements for the 

Announcement of Opportunity for participation on the ERBE Science Team. An 

international team was selected from the researchers responding to this announcement, 

including scientists from universities and research laboratories across the US and in 

Europe. Table 1 lists these ERBE Science Team and their affiliations. This core team 

along with several other researchers (Figure 11) were involved in preparing the project 

and the application of the data for scientific investigations. 

The Science Team was organized into four working groups, with responsibilities for the 

instrument, the computation of fluxes at the “top of the atmosphere,” the averaging of the 

fluxes at the times of measurement to produce daily mean fluxes, and finally to define the 

data products needed by the scientists. In-house scientists had been working already in 

the first three areas and continued this work throughout the project. Lee Avis worked on 

many details of the instrument requirements to use in the Statement of Work. Richard 

Green and Lou Smith worked on methods of retrieving the “top of atmosphere” (TOA) 

fluxes from the measurements from the scanning and non-scanning radiometers (Figure 

10). For the scanning radiometer, based on the approach used by Raschke, Vonder Haar 

et al. Green and Smith developed new methods of retrieving TOA fluxes from the nonscanner measurements. Tim Suttles led a team that used data from the ERB instrument 

and radiative transfer theory to create the bidirectional reflectance functions that were 

needed for retrieving the TOA fluxes. Suttles’ work in angular modeling was 

incorporated in his dissertation for his Ph. D. from Old Dominion University. These 

models would be used for the ERBE, the European Scanner for Radiation Budget 

(ScaRaB), and the ERBE follow-on project called CERES (Clouds and the Earth’s 

Radiant Energy System). These angular models were superseded more than two decades 

later by models developed by Dr. Norman Loeb using CERES data. David Brooks and 

Edwin Harrison developed methods for using the instantaneous measurements to 

compute daily-mean fluxes. 
15 

Table 1: ERBE Science Team Principal Investigators. 

Investigator Institution Investigator Institution 

Bruce Barkstrom LaRC Gary Hunt University College 

Andre Berrior CNES Herb Jacobowitz NOAA/NESDIS 

Robert Cess SUNY/Stony Brook Robert Kandel Ecole Polytechnique 

James Coakley, Jr. Oregon State U. Ann Mecherikunnel GSFC 

Charlie Duncan GSFC A. J. Miller NOAA/NMC 

Yves Fouquart U. de Lille V. Ramanathan U. Chicago 

Arnold Gruber NOAA/NESDIS Ehrhard Raschke U. Koeln 

Edwin Harrison LaRC Louis Smith LaRC 

Dennis Hartmann U. Washington W. L. Smith U. Wisconsin 

Fred House Drexel University Tom Vonder Haar Colorado State U. 

Fred Huck LaRC 

Other Science Team Members 

Robert Schiffer NASA/HQ ERBE Program Manager 

Robert Curran GSFC ERBE Project Scientist 

Michael King GSFC ERBE Project Scientist 

Abbreviations in Tables 

LaRC Langley Research Center 

CNES Centre National d’Etudes Spatiales 

SUNY State University of New York 

GSFC Goddard Space Flight Center 

NOAA/NESDIS National Oceanic and Atmospheric Administration/National 

Environmental Satellite Data and Information Service 

NOAA/NMC National Oceanic and Atmospheric Administration/National 

Meteorological Center 

Figure 11: ERBE Science Team at Science Team Meeting at LaRC. 
16 

As the time approached for launching the Earth Radiation Budget Satellite (ERBS) and 

the NOAA-9 spacecraft, Thomas Charlock, Patrick Minnis and Bruce Wielicki were 

brought into the team to provide science expertise. Minnis and Harrison used 

Geostationary Operational Environmental Satellite (GOES) data to establish the half-sine 

shape for the diurnal variation of outgoing longwave radiation. Bruce Wielicki and 

Richard Green developed the scene identification algorithm for selecting the bidirectional 

reflectance distribution functions for retrieving TOA fluxes from the measured radiances. 

Charlock, an expert in climate modeling, focused on making sure that ERBE data 

products addressed the needs of the modeling community. Shortly after the first ERBE 

launch, Robert B. Lee III joined the team to lead the Instrument Working Group. 

ERBE Goes into Orbit 

In order to measure the Earth’s radiation budget for all hours of the day, Edwin Harrison 

and his colleagues had shown that a minimum of three spacecraft would be needed. 

ERBE instruments would fly on two of the Sun-synchronous operational spacecraft that 

NOAA uses to observe and measure the atmosphere and oceans. The third spacecraft 

(ERBS) was built primarily to carry ERBE instruments. It also carried the SAGE as a 

“guest instrument”. Figure 12 is a drawing of the ERBS, showing the ERBE scanning and 

non-scanning instruments, the SAGE instrument and the major parts of the spacecraft. 

The spacecraft was built by Ball Aerospace Systems Division. 

Figure 12: Earth Radiation Budget Satellite configuration in orbit. 
17 

ERBS was boosted into orbit by the Challenger Space Shuttle in October, 1984 and 

deployed by astronaut Dr. Sally Ride, who was Mission Specialist for Flight 41-G. In 

order to deploy the spacecraft it was necessary to grip the spacecraft using the Shuttle 

arm (Remote Manipulator System), release the spacecraft from its cradle in the Shuttle 

bay and move it out into space. The solar cell arrays provided electrical power to all 

systems of the spacecraft and were folded in order to fit into the Shuttle bay. Before 

releasing the spacecraft these arrays must be unfolded and locked into place. Initially, the 

arrays were stuck and would not unfold. If they did not unfold, the mission would be a 

failure. Dr. Ride used the procedures that had been prescribed for this contingency. First 

she shook the spacecraft. No luck. Last chance was to wait until the Shuttle had been in 

the shadow of the night side of Earth and everything cooled down in the darkness of 

space, and when the Shuttle emerged into daylight and the Sun warmed all of the parts, 

shake well. This worked. (Standard practice of any auto mechanic to break loose a 

recalcitrant bolt: heat it then turn it.) The solar arrays opened and locked into place, to the 

relief of all involved. All spacecraft and instrument systems were checked out and 

operated well. ERBS was now ready to fly. 

After this mission, Dr. Ride served at NASA Headquarters on several major tasks, then in 

1989 became a professor of physics at University of California/San Diego and Director of 

the California Space Institute. In 2001 she founded Sally Ride Science, a company to 

motivate girls and young women to pursue science careers. 

Challenger placed the ERBS into a low Earth orbit. ERBS then fired its own rocket motor 

to boost itself into an orbit 620 km above Earth, where it would begin observing the 

Earth’s radiation budget and stratospheric ozone and aerosols. A month was allowed for 

the gases from the rocket engine and any other contaminants from the spacecraft to 

disperse completely, then the contamination covers to the instruments were opened and 

the measurements of the Earth began. The scanning radiometer had been designed with a 

goal of 2 years of operation. It provided measurements for 5 years. The non-scanning 

radiometer measured the Earth’s radiation for 15 years. In October 1999, there was a 

problem in which the detectors did not return to their correct position after a calibration 

check, but stuck in a tilted position. They continued to provide data for another 5 years, 

for a total of 20 years of measurements. 

The Earth Radiation Budget Satellite performed extremely well over the entire period. 

Also, the Flight Operations Team at the Goddard Space Flight Center kept the spacecraft 

operating as desired during this time. They solved problems in real time, such as loss of a 

gyro, so that no data were lost. Their performance over two decades was outstanding. It is 

necessary to leave sufficient spacecraft capacity to maintain control until it is deboosted 

from orbit, to eliminate space debris. In October 2004, the instruments were turned off 

and the spacecraft was idled. 

To provide observations at high latitudes, ERBE scanning and non-scanning packages 

were included in the NOAA-9 and -10 operational meteorological spacecraft. The 
18 

NOAA-9 was launched from Vandenburg Air Force Base in December 1984. The ERBE 

contamination covers were opened in January 1985 and ERBE was now giving global 

coverage of radiation budget data. Its orbit crossed the Equator (north bound) at 1430 

hours initially. Two years later NOAA-10 was placed into orbit, with an orbit crossing 

the Equator at 1930 hours initially. The system of instruments on three spacecraft needed 

for sufficient coverage in time and space was now complete. 

ERBE Accomplishments 

The ERBE project archived over five years of ERBS scanner data, two years of scanner 

results from NOAA-9, and over two years of data from NOAA-10. Over 200 peerreviewed journal articles have been written that use ERBE data. These papers included 

the effects of clouds on the balance of Earth’s energy, the effects of a volcanic eruption 

on the climate, the variation of energy absorbed from the Sun and given off by the Earth 

during the day, and the energy given off by the Sun over a 15-year period. Here we 

discuss only a few highlights of the research to date using ERBE data. 

The Importance of Clouds and their Effects: ERBE results demonstrated that the effects 

of clouds on the radiation balance of Earth were the greatest uncertainty in global climate 

models. The most important achievement of the Earth Radiation Budget Experiment was 

the first accurate measurement that proved that clouds cool the Earth. There is no way for 

the Earth to respond to the energy arriving as light from the Sun and absorbed by the 

planet except by reemitting light to the coldness of outer space. Hot surfaces, like the 

Sahara Desert or Death Valley, California, emit a lot of heat. Cold surfaces, like 

Antarctica or a snow field, emit relatively little heat. The Earth's temperature is 

established by balancing the energy absorbed from the Sun against the energy the Earth 

emits back to space. Before ERBE, scientists were not sure whether the increased 

reflection from clouds would offset the effect that clouds have in trapping the emitted 

heat. By increasing the amount of energy reflected back to space, clouds decrease the 

energy absorbed from the Sun. However, clouds also trap the energy emitted by the 

Earth's surface. High clouds are particularly effective at trapping emitted heat. The ERBE 

instruments were able to measure the radiation budget of both clear and cloudy areas. 

Figure 13a shows the longwave radiation emitted by Earth for all sky conditions. Fig. 13b 

shows the longwave radiation flux emit by the Earth when skies are clear. The difference 

is the effect of clouds on longwave radiation, which is called cloud radiative forcing (fig. 

13c). Similar maps can be made of shortwave radiation showing the effects of clouds on 

radiation reflected by the Earth with and without clouds, to get the shortwave cloud 

forcing. The difference between the shortwave and longwave cloud forcing is the total 

cloud radiative forcing and is shown in figure 14. The scientists on the ERBE science 

team were able to show that low clouds reflect more energy than high clouds trap. In 

other words, clouds cool the present climate. 
19 

a. Longwave radiation flux for all-sky condition for July 1985 

b. Longwave radiation flux for clear sky 

c. Cloud forcing of Longwave radiation flux for July 1985. 

Figure 13: Maps of longwave radiation fluxes for July 1985. a) As measured for all sky 

conditions, b) as measured for clear sky, i.e. no clouds and c) difference between the two, 

which is cloud forcing of longwave radiation. 
20 

With ERBE providing quantitative information about the effects of clouds on the solar 

radiation absorbed by the Earth and the radiation emitted by Earth, scientists were able to 

check their circulation models to find how well these numerical models simulated the 

effects seen by ERBE. Figure 15 shows a comparison of ERBE results for net radiative 

forcing of clouds with that computed by a model used by Tom Charlock and V. 

Ramanathan (University of Chicago) and by Bob Cess (SUNY/Stony Brook) and Jerry 

Potter (Lawrence Livermore National Laboratory) for the month of January. While the 

models have the correct overall shape, there are features that indicate areas to be 

improved. 

Figure 14: Net cloud forcing of radiation for July 1985 as determined from ERBE data. 

Figure 15: Comparison of Cloud –Radiative Forcing observed by ERBE (Blue line) with 

general circulation model calculations. Black line: Charlock and Ramanathan (1985); 

Red line: Cess and Potter (1987). 
21 

Cess and Potter collaborated with 19 modeling groups around the world to compare their 

model results with ERBE observations. These groups included the National Center for 

Environmental Prediction NCEP (U. S.), the United Kingdom Meteorological Office 

UKMO, Max Planck Institute MPI (Germany), and the Geophysical Fluid Dynamics 

Laboratory GFDL (U. S.). Figure 16 shows some of their results. The first plot shows the 

biases, or average differences, for the cloud forcings at the TOA between the general 

circulation models and those observed by ERBE. The second part of figure 16 shows the 

biases due to shortwave and longwave separately. The last part of figure 16 shows the 

annual net radiation averaged over the Earth. Without global warming, this number 

should be zero, but is believed to be between 0.5-0.7 W-m-2 due to global warming. 

These results on cloud radiative effects have enabled scientists to improve their models. 

The Daily Cycle of Radiation: The reason for instruments on multiple spacecraft was that 

the variation during the day of outgoing longwave radiation and reflected solar radiation 

was unknown. If there are no clouds, the surface heats up during the day, the outgoing 

longwave radiation (OLR) increases and during evening and night the surface cools and 

the OLR decreases. However, if clouds develop in the afternoon, the cold cloud tops will 

radiate less OLR to space. A study by the team showed the change during the day of 

OLR. Figure 17 shows the variation of OLR during the day in April for a point in South 

America. The dotted line shows the OLR for clear sky and the solid line shows the 

average OLR for all cases. The OLR changes during the day over a range of about 30 Wm-2 for this location. Figure 18 is a map of the ranges of OLR over the Earth. The deserts 

have very large changes of OLR during the day because with little or no vegetation they 

have very large temperature increases during the day and cool to low temperatures at 

night. Vegetated areas have much lower ranges of OLR. For ocean, there is very little 

change in temperature during the day because oceans can store a tremendous amount of 

energy with very small increase of temperature. 

The above discoveries led to the declaration of the role of clouds as the top scientific 

priority of the U.S. Global Change Research Program. 

Effects of Volcanoes on Climate: In addition to this fundamental measurement of the 

impact of clouds, ERBE was able to show the effects of a volcanic eruption on Earth’s 

climate. Mount Pinatubo, in the Philippines, erupted in June 1991 as shown by fig. 19. 

Tiny stratospheric droplets formed from the volcanic cloud of dust and gases sent into the 

stratosphere when the volcano erupted. Sunlight changes the gas to tiny droplets of 

sulfuric acid that we see as the red color of twilight. The droplets grew by absorbing 

water from the stratosphere and then settled into the lower layers of the atmosphere over 

a 2-year period after the eruption. The ERBE instruments measured the increase in 

reflected sunlight as the cloud spread north and south, as shown by figure 20. Figure 21 

shows the reduction of reflected sunlight when averaged over the globe. The average 

reflected sunlight was increased by over 4 W-m-2. The outgoing longwave radiation also 

decreased by over 1 W-m-2 as shown in figure 21. The decrease of OLR reduced the net 

effect of cooling due to the reflected shortwave radiation, so the net result was a cooling 

as shown also by figure 21. 
22 

Figure 16: a. Difference of cloud forcing between each of 19 general circulation models 

and observations from ERBE, averaged over Earth between 60o south and 60o north; b. 

Same as a, but for shortwave and longwave separated; c. Net radiation over the Earth as 

computed by 19 general circulation models. (G. L. Potter and R. D. Cess, 2004: J. 

Geophys.Res., 109, D02106) 
23 

Figure 17: Change of outgoing longwave radiation during day in April 1985 for region 

3.75o

S, 66.25oS. The dotted line is for clear sky and solid line is the average for all 

conditions. (Harrison et al., Oct. 1988, Bull. American Met. Soc., 69) 

Figure 18: Range of change of Outgoing Longwave Radiation for April 1985. (Harrison 

et al., Oct. 1988, Bull. American Met. Soc., 69) 
24 

Figure 19: Mount Pinatubo erupted in June 1991, sending vast amounts of volcanic 

aerosols into the stratosphere. (USGS, http//pubs.usgs.gov/fs/1997/fs113-97/) 

Figure 20: ERBE showed that the aerosols in the stratosphere from the Mount Pinatubo 

eruption increased the reflected sunlight, thus cooling the Earth. (Minnis et al., Science, 5 

March, 1993, v. 259) 
25 

Figure 21: Changes in reflected shortwave, longwave (emitted) and net radiation from 

both fluxes between 40o

S and 40oN for 1985 through 1989, showing effects of Mount 

Pinatubo eruption. (Minnis, private communication) 

Interannual Variations: Our weather changes from year to year, and at present we have 

only limited ability to predict these changes. However, it would be extremely valuable to 

develop even a small capability for seasonal and yearly forecasts. One area that may pay 

off in this research is a better understanding of the El-Nino/La Nina oscillation. Figure 22 

shows the changes of longwave radiation from average conditions at the Equator across 

the Pacific Ocean. The blue areas correspond to the El Nino events of 1987 and 1992. 

These changes of longwave radiation are due to the movement of large cloud areas in 

response to changing the sea surface temperature. There are many investigations to be 

made using the ERBE data to learn about such interannual variations. 

Measurements of the Sun’s Radiation: The ERBE non-scanner package included a solar 

monitor radiometer, which is a high accuracy instrument for measuring the radiation from 

the Sun. Interestingly, this solar output increases a tiny bit when there are sunspots and 

decreases during periods when there are few sunspots. Because the ERBE solar 

instruments on the Earth Radiation Budget Satellite (ERBS) have lasted over 15 years, 

ERBE has helped reduce the uncertainty about whether the differences between its 

measurements and those of other instruments were caused by the Sun or by instrument 

calibrations. 

 
26 

Figure 22: Longwave anomalies between 5o

 South and 5o North, as measured by the wide 

field-of-view instrument on ERBS spacecraft. (Minnis, private communication) 

External Reviews 

Since the 1980’s, NASA LaRC has frequently had external Peer Review Panels to 

evaluate their atmospheric science research program. One Peer Review panel stated in 

1987 that “The Radiation Sciences Branch achievements are exceptional; demonstrating 

its world-recognized prowess and scientific products in terms of data for the general 

research community and significant publications is remarkable, considering the (small) 

size of the branch.” Another Peer Review noted that “The branch programs’ impact on 

international science has been immense and is truly world class.” A third Panel wrote: 

“The Panel’s overall impression of the Radiation Sciences Branch’s personnel is that they 

constitute an exceptionally harmonious group that is characterized by a high degree of 

interaction among scientists, both internally and externally.” This teamwork was indeed 

an accomplishment in itself, which led to the other accomplishments. 

Questions Raised by ERBE 

The fact that clouds act to cool the current climate does not mean that we understand how 

clouds will respond if the climate changes. For example, if carbon dioxide increases trap 

more emitted heat, climate changes might increase the amount of high clouds and thereby 

enhance the greenhouse effect. Such an enhancement is called a positive feedback. The 

ERBE measurements did not provide enough information to identify how clouds will 

respond to other climate changes. To answer these questions would require long-term, 

accurate measurements of clouds and the Earth's radiant energy system. 
27 

Summary of ERBE Project Accomplishments: 

• Archived over 5 years of scanner data from the Earth Radiation Budget Satellite 

(ERBS), 2 years of NOAA-9 results, and over 2 years of NOAA-10 data. 

• ERBE data answered the longstanding controversy of whether clouds warm or cool the 

Earth. ERBE produced first data confirming clouds have a net radiative cooling effect on 

the planet. 

• Provided the radiation standard for validating and improving General Circulation 

Models for climate sensitivity studies. 

• Derived the first accurate diurnal variations of regional radiative parameters over the 

globe for climate studies. 

• Determined radiative cooling as a result of the 1991 eruption of Mt. Pinatubo that was 

the largest ever recorded. 

• Observed large longwave and shortwave radiative anomalies during the 1987 El Nino as 

well as the El Nino starting in 1990 that continued through 1993, which represents the 

longest El Nino period in the past 50 years. 

• Determined solar irradiance variations and correlated results with Earth's atmospheric 

temperature. 

• Developed a new technique for deriving narrowband albedos from temporally matched 

ERBE scanner and geostationary visible channel data. 

• Devised and applied a new method using a combined ERBE-GOES dataset to develop 

and evaluate new time-space averaging techniques. 

• Used combined ERBE scanner and surface flux data to show that plane-parallel models 

overestimate cloud albedo, models overestimate surface shortwave absorption by 

overestimating surface insolation, the cause is macrophysical rather than microphysical, 

and it is highly unlikely that observational evidence of excess shortwave absorption is 

due to satellite sampling errors. 
28 

The Beginning of CERES 

As the decade of the 1980’s came to a close, the scanning ERBE instruments aboard the 

NOAA-9 and -10 spacecraft had each met the requirement of operating for 2 years and 

stopped. The non-scanning instrument aboard the ERBS continued to perform with no 

problems. The ERBE Data Processing System was now generating data products from 

the measurements and these products were being used by researchers to learn about the 

relationships between radiation and climate. With the value of radiation budget data 

demonstrated, it was time to initiate a project that would become a successor to ERBE. 

In 1987, NASA initiated the Earth Observing System Program, which would fly a 

number of instruments on a set of spacecraft so as to study the Earth, its atmosphere, 

oceans and ice. The first two of these spacecraft would be the Terra and Aqua satellites, 

which would be placed in Sun-synchronous orbits. 

Bruce Barkstrom proposed a project that would put radiation budget instruments on these 

spacecraft. This project would build on the successes of ERBE and go far beyond. For 

this project he selected the name Clouds and the Earth’s Radiant Energy System 

(CERES). This is name of the Roman goddess of agriculture, home, family and stability. 

A gilded statue of Ceres stands atop the commodities market building in Chicago. One of 

the early hopes of radiation budget research was to understand interannual variations of 

climate well enough to make seasonal forecasts that would benefit agriculture. 

The CERES project would go beyond ERBE in three ways. First, the data record would 

be much more accurate than ERBE. When measuring Earth’s radiation budget there are 

three sources of error in the final data products: the instrument, the retrieval of fluxes 

from the measurements, and the averaging over the day from the limited measurements 

available. CERES would attack all three of these error sources. The new project would 

use knowledge gained from the ERBE instrument to reduce measurement errors by a 

factor of two. Also the field of view would be reduced by a factor of two, thus giving 

more uniform fields for which bidirectional reflectance functions (BDRFs) would be 

used. To reduce the errors in the retrieval of fluxes from the radiance measurements, 

improved BDRFs are required, which in turn required more measurements from which 

models would be developed. The models for ERBE had been developed using 208 days 

of measurements from the ERB instrument aboard the Nimbus-7 spacecraft. The CERES 

project would have one instrument aboard a spacecraft operating in cross-track scan so as 

to map the geographic variation of the radiance and another instrument would rotate in 

azimuth and nadir angle to measure radiation in all directions so that more accurate 

BDRFs could be created. These improved descriptions would reduce the error of the 

fluxes retrieved from the measured radiances. Finally, to reduce the errors in computing 

the daily average radiation fluxes, a pair of instruments would fly on a morning and an 

afternoon spacecraft, and also data from the geostationary meteorological satellites would 

be brought in to define changes in radiation between the times of CERES measurements. 

CERES instruments were selected to fly in pairs on both the Terra and Aqua spacecraft. 
29 

CERES would also expand the objectives of measuring the radiation from the “top of the 

atmosphere” to include the radiation flux from the Earth’s surface and from the 

atmosphere. These new data products required cloud information from on-board imaging 

instruments and geostationary meteorological satellites, and meteorological data. 

The CERES project would require bringing in and processing massive amounts of data, 

which was a foreboding undertaking in 1990. However, Dr. Barkstrom’s avocation was 

computer technology and he foresaw the evolution of computers and the capacity to 

transfer data so that by the time the instrument was in orbit, this work could be done with 

reasonable resources. Without this great evolution in computational and data transfer 

capability, the new objectives of extracting the surface radiation budget and the radiation 

absorbed and emitted by the atmosphere would be impossible. It was a daring move. In 

the late 1980’s and early 1990’s, Dr. Barkstrom was instrumental in formulating and 

promoting the development of an organization for acquiring, processing, and storing the 

massive amounts of data, and then disseminating the data to scientific, educational and 

policy-making communities. This organization is known today as the Langley 

Atmospheric Science Data Center (ASDC). 

A proposal was prepared and submitted by Dr. Barkstrom to NASA HQ to build, 

calibrate and fly six CERES instruments. Concurrently, Edwin Harrison led the strategic 

development of a proposal to use the data for scientific investigations, with Dr. Bruce 

Wielicki as the Principal Investigator. The Langley Team had proven itself, the need for 

radiation budget data had been demonstrated and the new proposal was a major step 

forward. Both proposals were accepted, and CERES was funded for a new start. 

An Announcement of Opportunity was released by NASA HQ and the Science Team was 

selected (see Table 2). Figure 23 shows the CERES Science Team members. The LaRC 

researchers, the Science Team and the support contractors were divided into working 

groups. The Instrument Group (figure 24) was led by Robert B. Lee, III, who had 

previously worked with the ERBE instruments and would direct the development of the 

CERES instruments in regard to scientific issues. Lou Smith would support the 

Instrument Working Group with analyses to address various questions. Also, Professor 

Robert Mahan of Virginia Tech received grants to develop computer models to 

complement this work. Kory Priestley, a doctoral student, would play a key role in this 

work and then join LaRC to continue his involvement in CERES. Richard Green had led 

the Inversion Group for ERBE and would lead this work for CERES. David Young 

assumed leadership of the Temporal Interpolation and Spatial Averaging (TISA) Group. 

Tom Charlock was selected to lead the new Surface and Atmospheric Radiation Budget 

(SARB) working group (figure 25). For the development of the Bidirectional Reflectance 

Distribution Functions (BRDFs), Norman Loeb, a recent Ph.D. from McGill University 

was brought in. To select the correct BRDF, it is necessary to first identify the presence 

of cloud and its type. Pat Minnis had built a team that would develop the cloud 

identification algorithms. The Science part of CERES was in place. 
30 

Table 2: CERES Science Team Members. 

Researcher Institute 

Bruce R. Barkstrom, PI Instrument LaRC 

Robert D. Cess State University of New York/Stony Brook 

James A. Coakley Oregon State University 

Dominique Crommelynck Royal Meteorological Institute of Belgium 

Leonard J. Donner NOAA/Geophysical Fluid Dynamics Lab. 

Robert Kandel Centre National de la Recherche 

Scientifique, France 

Michael D. King Goddard Space Flight Center 

Alvin J. Miller NOAA/National Weather Service 

V. Ramanathan Scripps Institution of Oceanography 

David A. Randall Colorado State University 

Larry L. Stowe NOAA/National Environmental Satellite, 

Data, and Information Service 

Ronald M. Welch University of Alabama/Huntsville 

Bruce A. Wielicki, PI Interdisciplinary LaRC 

Langley Research Center Researchers in CERES 

Bryan A. Baum David P. Kratz Kory J. Priestley 

Donald R. Cahoon Edwin F. Harrison G. Louis Smith 

Lin H. Chambers Robert B. Lee, III Tak-Meng Wong 

Thomas P. Charlock Norman G. Loeb David F. Young 

Richard N. Green Patrick Minnis 

Figure 23: CERES Science Team. Back Row: Lou Smith, Bob Cess, Ed Harrison, Bruce 

Barkstrom, Ron Welch, Larry Stowe, Bob Kandel, Bob Lee. Front Row: Pat Minnis, Jim 

Coakley, Bruce Wielicki, Dave Randall, Wayne Darnell, Tom Charlock, Richard Green. 
31 

Figure 24: Instrument Working Group. From left: Bruce Barkstrom, Lee Avis, Robert 

Lee, Lou Smith, Jack Cooper. 

Figure 25: Surface and Atmospheric Radiation Budget Working Group. Back Row: ShiKeng Yang, John Nealy, Bob Cess, Dave Kratz, Fred Rose. Front Row: Lou Smith, Tom 

Charlock, Dave Randall, Anand Inamdar, Wayne Darnell, Shashi Gupta. 
32 

On the Project side of CERES, which had the responsibility of managing the design and 

development through build, environment testing and calibrating of the instruments and 

having them integrated with the spacecraft, there was also an experienced team from 

ERBE. Charles Woerner had become Deputy Chief of the Projects Division. Jack Cooper 

was selected as Project Manager for CERES. Leonard Kopia was selected to be the 

Instrument Manager. 

A statement of work was prepared and a Request for Proposals was released by LaRC. 

The Space Division of TRW, in Redondo Beach, California, won the competition. A 

major factor in their selection was their including the Radiation Calibration Facility in 

their proposal. Upgrades to the thermal-vacuum tank that had been used for the ERBE 

instruments would be designed and built in parallel with the instrument. Steve Carman, 

who had been TRW’s Lead Calibration Engineer for ERBE, was named as the TRW 

Project Manager for CERES. Tom Evert, a key systems engineer during the ERBE 

development, would be TRW’s Chief Engineer for CERES. The contract called for six 

CERES instruments to be built and calibrated. These were designated the Proto-Flight 

Model and Flight Models 1 through 5. 

CERES in Orbit 

The ERBE scanning radiometer aboard the ERBS spacecraft ceased operation in 1990, 

after providing data for five years. There was a strong desire to fly another Earth 

radiation budget instrument as soon as possible. Dr. Joanne Simpson, the First Lady of 

Meteorology1, was leading a team at the Goddard Space Flight Center, to develop a 

concept that would become the Tropical Rainfall Measuring Mission. The primary 

instrument for this mission was a Precipitation Radar. Other instruments would support 

this radar. The Proto-Flight Model of CERES was chosen to fly on this spacecraft to 

complement these instruments. This project was a collaborative effort between NASA 

and the Japanese Space Exploration Agency (JAXA). The spacecraft was built and 

launched by JAXA and the Precipitation Radar was built by JAXA. The remaining 

instruments, including the Proto-Flight Model of CERES, were supplied by NASA. 

Figure 26 is a drawing of the TRMM. The spacecraft was placed into a precessing orbit 

in November 1997. The CERES Proto Flight Model (PFM) began operating a month 

later. Initially, the instrument operation matched expectations. Unfortunately, an 

electronic component began to deteriorate and the instrument was turned off in order to 

preserve its remaining life for later use. 

1

Joanne Simpson was the first woman in the U. S. to receive a doctorate in meteorology. She made major 

advancements in tropical meteorology and received numerous awards, including the Carl Gustav Rossby 

Award, the highest award of the American Meteorology Society. 
33 

Figure 26: The Tropical Rainfall Measuring Mission spacecraft, showing CERES and the 

other TRMM instruments. 

The Terra and Aqua spacecraft would each carry two CERES instruments. One CERES 

would operate in cross-track scan so as to map the geographical distribution of radiation. 

The other CERES would operate in a biaxial mode to make measurements from which 

the amount of radiation in each direction as it leaves the atmosphere can be computed. 

Flight Models 1 and 2 were mounted on the Terra spacecraft, which was placed into orbit 

in December 1999 by an Atlas 2C launch vehicle. The contamination covers were opened 

in February 2000 and the two instruments began taking data. Flight Models (FMs) 3 and 

4 were placed on the Aqua spacecraft, which was launched in May 2002. In June 2002 

these two CERES radiometers began measuring the Earth’s radiation. As of 2013, there 

are more than 12 years of Earth radiation measurements from both CERES instruments 

on Terra and over 11 years of data from FM-3. Flight Model 4 lost the shortwave channel 

in 2008, after operating for 6 years. 

By the time of the Aqua launch, several changes had been made in key personnel in 

CERES. Edwin Harrison retired and Bruce Barkstrom moved first to head the ASDC and 

later left NASA to join NOAA. Bruce Wielicki became the CERES PI. Dr. Wielicki later 

became involved in exploring new, advanced mission and sensor concepts for climate 

research and Norman Loeb succeeded him as PI. Robert Lee retired and Kory Priestley 

became the head of the Instrument Working Group and the science lead for the CERES 

instruments and their further development. The Earth radiation torch had been passed to a 

new generation. 
34 

CERES FM-5 on the NPP Spacecraft 

After CERES instruments had been on Aqua for a few years, concern grew that the Earth 

Radiation Budget (ERB) Climate Data Record would be disrupted by failure of the aging 

CERES instruments. The scientific contributions using ERBE and CERES data were 

continuing and the need for the high quality measurements had become recognized by the 

scientific leadership in the climate community. Continuation of the ERB Climate Data 

Record had been identified as critical in the 2007 NRC Decadal Survey. Also, the World 

Climate Research Program in its report “The Global Climate Observing System” 

reiterated the need for ongoing Earth radiation budget data. NASA and NOAA agreed to 

fly the final existing CERES FM-5 on the National Polar-Orbiting Partnership NPP 

spacecraft to continue the critical Climate Data Record begun by the ERBE instruments 

in the mid 1980’s and continued by the CERES instruments on the Terra and Aqua 

spacecraft. The NPP spacecraft was placed in orbit 28 October 2011. Figure 27 shows the 

NPP spacecraft, with CERES FM-5. Once it was placed successfully in orbit and shown 

to operate well, this spacecraft was renamed the Suomi-NPP in honor of the Father of 

Satellite Meteorology. 

Figure 27: Layout of Suomi NPP Spacecraft, showing CERES and other instruments.
35 

CERES Accomplishments

The CERES instruments aboard the Terra and Aqua spacecraft have produced high 

quality data for over a decade. These data can be used for many investigations, e.g., yearto-year changes in climate. A number of data products are available to the science 

community. 

Improvement of Measurement Accuracies: One objective of CERES was to improve the 

radiometer to reduce measurement errors. Robert Lee and the TRW (now Northrop 

Grumman) engineering team used their experience with ERBE to improve the instrument 

design, including the on-board calibration devices, and the ground calibration of the 

instruments. Bob Lee and Kory Priestley used the accumulated knowledge to create 

better ways to calibrate the instruments on the ground and then in space in order to 

generate accurate radiances. 

Improvement of Radiation Directional Models: Another objective of CERES was to 

improve the accuracy of the fluxes by creating better bidirectional reflectance distribution 

functions (BRDFs) with which to compute fluxes from radiance measurements. This 

caused a dilemma, as several years of data would be needed to develop the new BRDFs 

before the fluxes could be computed more accurately. The solution to this problem was to 

use the earlier BRDFs to compute fluxes until the new BRDFs became available. Another 

edition of fluxes was then computed with the improved models. After enough 

measurements were available, Norman Loeb led the development of these models. 

CERES made more measurements for this purpose than had ever been made before, 

radiation transfer codes had an additional two decades of development, and computers to 

perform the needed calculations were immensely more powerful than for the ERBE 

generation of models. Previously, there had only been enough biaxial scanning 

measurements to develop BRDFs for 12 scene types, with coarse angular resolution. The 

new CERES BRDFs were defined for 200 scene types with much smaller angular 

intervals. Loeb’s new BRDFs greatly reduced the errors in fluxes. Figure 28 shows one 

view of the CERES BRDFs for overcast ice cloud. 

Figure 28: CERES Bidirectional Reflectance Distribution Function for overcast ice cloud, 

for Sun between 60o

 to 70o from overhead. (N. Loeb, private communication) 
36 

Surface and Atmospheric Radiation Budget: The new objective of CERES, to create a 

data product for the surface and atmospheric radiation budgets, was quite ambitious. To 

compute the fluxes of radiation at various levels within the atmosphere requires an 

immense amount of data to describe the atmosphere over the globe and then an incredible 

amount of computation involving radiative transfer codes to calculate the fluxes. Tom 

Charlock led the SARB Working Group to develop techniques and software for 

accomplishing these tasks. Fred Rose and Seiji Kato worked with Qiang Fu (University 

of Utah) to modify the Fu-Liou radiative transfer code for SARB application. To bridge 

the gap of MODIS aerosol optical depth retrieval and provide information on aerosol 

composition, an aerosol transport model developed at NCAR (MATCH) was also 

included in the routine SARB data processing. To facilitate validations of the surface 

fluxes from SARB with surface radiometer measurements, David Rutan developed a 

website (http://www-cave.larc.nasa.gov/cave/) that included all surface sites that are 

equipped with well-calibrated radiometers and greatly simplified the previously timeconsuming validation task. 

In addition, Tom Charlock, Greg Schuster, Bill Smith, Jr., Ken Rutledge, and Jerry 

Purgold established and operated a radiation monitoring station on the Chesapeake 

Lighthouse Platform in the Atlantic Ocean 25 km off the Virginia coast. Although there 

are many radiation monitoring stations on land, this oceanic station was unique and gave 

information for validating SARB results over ocean. At this ocean platform, a unique 

spectral photometer was mounted on a tracker to scan the ocean surface. Wenying Su 

utilized these data to verify the half-century old Cox and Munk model for directional 

distribution of sunlight reflected from the ocean surface. 

The next several figures show some data products that were generated by SARB. Figure 

29 is a global map of longwave radiation downward at the surface, or how much heat is 

radiated to the surface by the atmosphere. Figure 30 shows the longwave radiation flux 

away from the surface. Figure 31 shows the net shortwave radiation flux at the surface. 

The atmospheric divergence of longwave radiation between 500 mb and the surface is 

shown in figure 32. (The blue indicates that the atmosphere radiates downward to the 

surface, and the convention is that downward flux is negative.) Such information opens 

new areas of research into how radiation drives climate. Wenying Su compared the 

vertical flux profiles from SARB with those produced by the Hadley Center model and 

identified the deficiencies of cloud schemes at different heights. 

The SARB data processing enabled the generation of other useful radiation products. 

Wenying Su led efforts to produce ultraviolet (UV) radiation and Photosynthetically 

Active Radiation (PAR). UV radiation is divided into three bands (UVA, UVB, and 

UVC). UVB is associated with vitamin D production in the human body, but excessive 

exposure to UVB can also cause skin cancer. PAR is important to agriculture and 

forestry. Figure 33 shows the diffuse component of PAR over the contiguous United 

States. Maps of UV radiation (total, UVA, and UVB) are shown in figures 34, 35 and 36. 
37 

- 

Figure 29: Monthly-mean map of downward longwave radiation from the atmosphere to 

the surface for March 2005. 

Figure 30: Monthly-mean map of upward longwave radiation from the surface for March 

2005. 
38 

Figure 31: Monthly-mean map of net shortwave radiation at surface for March 2005. 

Figure 32: Atmospheric Radiation Divergence Longwave component, 

500mb to surface for March 2005. 
39 

Figure 33: Photosynthetically Active Radiation over contiguous US 

Diffuse Component, June 2005. 

 

 

 Figure 34: Monthly-Mean UV over contiguous United States, June 2005 
40 

Figure 35: Monthly-Mean UVA over contiguous United States, June 2005. 

Figure 36: Monthly-Mean UVB over coterminous United States, June 2005. 
41 

Scientific Achievements of CERES as of 2012 

• CERES observations (Kato et al., 2006) were used to show that rapid decreases in 

Arctic sea ice cover are accompanied by large increases in Moderate Resolution Imaging 

Spectroradiometer (MODIS) cloud cover and negligible changes in CERES shortwave 

(SW) TOA fluxes. These results suggest that changes in Arctic sea ice are compensated 

by changes in cloud cover. Consequently, any ice-albedo feedback could be dampened 

because of increased cloud cover. 

• CERES data were used to isolate the effect of large scale dynamics on the observed 

radiation budget and cloud properties in the tropics. Observed tropical mean changes can 

be as large as ±3 Wm-2, while the dynamical components are generally smaller than ±0.5 

Wm-2. 

• Trenberth and Fasullo (2009) used CERES Terra, ocean heat content, and reanalysis 

data to provide a summary of the overall energy balance for the global atmosphere, ocean 

and land domains. Of the 2.6 PW of net radiation into the system over ocean, 

approximately 0.4 PW are absorbed by the ocean, and 2.2 PW are transported from ocean 

to land by the atmosphere to compensate for the net radiation out of the system over land. 

Approximately 0.01 PW of the net flux imbalance goes into land and melting of ice. 

• The Intergovernmental Panel on Climate Change (IPCC; 2007) fourth assessment report 

recognized that measuring the radiation balance accurately is fundamental in quantifying 

the radiative forcing of the system as well as diagnosing the radiative properties of the 

atmosphere and surface, which are crucial for understanding radiative feedback 

processes. The report identified ERBS/CERES global net TOA radiation data as 

providing evidence for decadal changes in TOA radiative fluxes over the last two decades 

and that the changes in the planetary and tropical TOA radiative fluxes are consistent 

with independent global ocean heat-storage data. 

• CERES and other observations of the components of the water and energy cycles are 

used together with climate models to examine evidence for robust responses and links 

between the tropical energy and water cycles over the period 1979–2006. 

• CERES observations are used together with reanalysis data to determine new estimates 

of large-scale Arctic atmospheric energy budget. Monthly mean anomalies of budget 

terms are used to examine conditions leading to the extreme seasonal sea ice extent 

minimum of September 2005 and the role of the ice albedo feedback process. 

 
42 

Surface Radiation Budget 

Once LaRC had gotten the new start for the Earth Radiation Budget Experiment and the 

Radiation Sciences Branch had been formed, the organization was committed to work in 

the area of radiation budget. As the work on ERBE became organized, the question was 

raised by Wally Staylor, a member of the Radiation Sciences Branch, and others: Isn’t the 

radiation budget at the surface at least as important as it is at the top of the atmosphere? 

After all, we live at the surface. 

The importance of surface radiation budget is shown by the Earth's energy budget 

diagram below (figure 37). This diagram by Trenberth et al., 2009 is an updated version 

of a similar figure in "Understanding Climate Change" (National Academy of Sciences, 

1975). The diagram shows that parts of TOA incoming solar radiation (called insolation) 

are reflected back to space by clouds, the atmosphere, and the Earth's surface, all 

contributing to the reflected shortwave (SW) radiation (RSR) at the TOA. Some part of 

TOA insolation is absorbed by the atmosphere and clouds but close to half of it is 

absorbed at and warms the surface. The warm surface emits longwave (LW) radiation 

that is partly absorbed by greenhouse gases and clouds in the atmosphere, which in turn, 

radiate some of it in all directions. Some of the LW radiation emitted by the surface, and 

by the atmosphere and clouds constitutes the outgoing longwave radiation (OLR) at the 

TOA and escapes to space. RSR and OLR together constitute the radiation budget at the 

TOA. Surface loses a substantial portion of the absorbed SW energy through evaporation 

that, in turn, drives the hydrological cycle. 

Figure 37: The global annual mean Earth’s energy budget for the March 2000 to May 

2004 period (W m-2). The broad arrows indicate the schematic flow of energy in 

proportion to their importance. (Trenberth et al., Bull. Amer. Met. Soc, vol. 90, 2009) 
43 

In order to begin a project to work on Surface Radiation Budget, it was necessary to 

explain what is the scientific purpose, to what resolution in time and space, with what 

accuracy, what is the plan for accomplishing it, and what resources are required to 

accomplish it. In the mid-1980s, Tim Suttles collaborated with George Ohring of NOAA 

to write a white paper explaining the scientific and practical importance of surface 

radiation, listing investigations that could be made with a Surface Radiation Budget data 

set and outlining a project to develop such a data base. The timing was great. The World 

Climate Research Program (WCRP) was being organized. ERBE would provide the 

energy at the top of the atmosphere and as such would be an important part of the 

program. The SRB program, giving radiation at the surface, would be another key part of 

WCRP. Dr. Robert Schiffer, Program Manager for Radiation Sciences in NASA 

Headquarters, was working with Dr. William Rossow of Goddard Institute of Space 

Studies to establish the International Satellite Cloud Climatology Project (ISCCP) as a 

part of WCRP. The surface radiation is highly dependent on clouds, and ISCCP would 

provide the required information for computing the SRB. The proposed project to 

develop a Surface Radiation Budget Data Base was approved and began. In 1989, the 

Global Energy and Water-cycle Experiment (GEWEX) project was established under the 

WCRP. ISCCP, SRB and a global precipitation project were initial foci for the global 

satellite derived data sets. 

These downward and upward components of SW and LW radiation described above 

constitute the surface radiation budget and each of these components needed to be 

derived with sufficient accuracy on a global scale. At the time, downward SW and LW 

components were mostly derived on local scales with bulk formulas that used local 

measurements of meteorological parameters such as temperature, humidity, and cloud 

cover. Upward LW fluxes were derived from local measurements of surface temperature. 

Upward SW fluxes were either measured directly or derived using surface albedo (when 

available). These methods were certainly not useful for deriving SRB on a global scale. 

Techniques would have to be developed to perform the calculations for all of these 

components. Radiative transfer models and detailed knowledge of atmospheric state 

variables (temperature, humidity, constituent concentrations, etc.) on a global scale are 

required to derive surface radiation parameters. Even though some radiative transfer 

models for deriving SRB components were available at the time, most of them were 

computationally intensive and inappropriate for use on a global scale. Computationally 

fast models would have to be developed and used with global scale meteorological inputs 

that became available recently from sounding instruments on board the TIROS-N 

satellites. 

In 1981, Shashi Gupta joined Ed Harrison's branch as a NASA/NRC postdoctoral 

research associate. Gupta had considerable experience in longwave radiative transfer and 

was assigned the task of developing LW radiative transfer models for the SRB project. 

By early 1983, he had developed a narrowband longwave model and published it in the 

Journal of Quantitative Spectroscopy and Radiative Transfer. This model used local 
44 

meteorological profiles to derive surface LW fluxes that compared well with what limited 

surface observations were available at the time. Experience with this model showed that, 

with computer resources available at the time, this model did not run fast enough to 

accomplish global scale processing on a long-term basis. Realizing this, Gupta 

immediately started on the development of a parameterized model based on the results 

obtained from the narrowband model. To ensure global applicability of the resulting 

parameterization Gupta used globally sampled satellite sounder profiles from the TIROS 

Operational Vertical Sounder (TOVS) and globally gathered radiosonde data as inputs. 

At the same time, working alongside Wayne Darnell and Wally Staylor of the Radiation 

Sciences Branch, his work resulted in two publications in the Journal of Climate and 

Applied Meteorology (1983 and 1986) validating the results of the narrowband model. 

The parameterized model was published in the Journal of Climate in 1989 with 

refinements to follow in the Journal of Applied Meteorology, 1992. 

At LaRC, Wally Staylor created an algorithm for computing the solar radiation at the 

surface, or downward shortwave flux, which took into account the effects of the 

atmosphere including clouds without having the detailed information required by the 

more sophisticated codes. This method worked for practically all cases and gave results 

which were as good as those from the complex codes, given the information available 

about the atmosphere. The upward shortwave flux could be computed from the 

downward shortwave flux if one knew the reflectivity, or albedo, of the surface. Maps of 

the albedo of the surface were developed for this purpose. A brief description of Staylor's 

methodology and initial results were published in the Journal of Climate (1988). Wally 

retired in 1994 without publishing his model or its origin. There was no clear derivation 

of the method from “first principles,” that is, one could not begin with known equations 

and get the equations that Staylor created. Consequently, the model was not accepted by 

the science community. That situation was substantially resolved in 2001 when Shashi 

Gupta, Dave Kratz, Paul Stackhouse, and Anne Wilber prepared a NASA Technical 

Publication establishing the scientific basis of the Staylor model. This model is 

continually updated and still used for quality assurance for SRB shortwave data products 

and was incorporated into the CERES (Clouds and the Earth’s Radiant Energy System) 

project to compute a fast estimate of fluxes. 

The parameterized SW model developed by Staylor and Gupta's LW parameterization 

were used to produce SRB parameters, initially on a 10o

 equal-area grid and then on a 5o

equal-area grid using TOVS meteorological inputs from NOAA-6 and NOAA-7 

satellites. The spatial resolution a TOVS measurement was about 300 km, so producing 

SRB data at higher spatial resolution was not considered scientifically sound. Anne 

Wilber and Nancy Ritchie provided programming and analysis support for developing the 

algorithms and creating the database. 

Once 3-hourly ISCCP-C1 data on a 2.5o

 equal-area grid became available starting in 

1988, the team restructured the code and produced SRB data on the ISCCP grid. Darnell 

et al. published surface SW and LW fluxes from these algorithms and ISCCP-C1 inputs 

for mid-seasonal months of 1983-1984 in the Journal of Geophysical Research (1992). 
45 

Figures 38 and 39 show examples of these results. Figure 38 shows the net shortwave 

flux (the Sun’s radiation flux minus the reflected flux), or total sunlight absorbed at the 

surface, for July 1983. Over most of the Earth between 30o

N and 30oS the absorbed flux 

is between 200 and 300 watts per square meter. In the mid-Atlantic Ocean, there is an 

area where the flux is over 330 watts per square meter. This is the location of the Azores 

High or Bermuda High, where there is little cloud cover. The clouds over India for the 

monsoon reduce the sunlight at the surface. South of 30oS, in Southern Hemisphere 

winter, the net shortwave flux decreases rapidly. Within the Antarctic Circle, it is polar 

night and the sunlight is zero. Figure 39 shows the net longwave flux, i.e. the radiation 

emitted by the surface minus the downward radiation from the atmosphere. The deserts of 

North Africa, the Middle East and the Southwest of the U. S. radiate a net of over 100 

watts per square meter. Antarctica gives off 75 watts per square meter. This large amount 

is because there is little cloud cover and the air has very little humidity, so that the air 

radiates very little back to the surface. Over the oceans south of 30o

S, the water is much 

warmer and radiates more than the ice of Antarctica, but there is much cloud and the air 

has much water vapor, so that the atmosphere radiates much radiation to the surface. . 

This was soon followed by the publication of cloud radiative effects on surface fluxes by 

Gupta et al. in J. Geophysical Research (1993) and sample SW and LW results from that 

work for July 1985 are shown on figures 40 and 41 respectively. 

Figure 38: Distribution of net shortwave flux at surface for July 1983 

(Watts per square meter). 
46 

Figure 39: Distribution of net longwave flux at surface for July 1983 

(Watts per square meter). 

Figure 40: Distribution of shortwave cloud forcing at surface for July 1985 

(Watts per square meter). 
47 

Figure 41: Distribution of LW cloud radiative effect at the surface for July 1985 

(Watts per square meter). 

In the meantime, several national and international programs were started for measuring 

both SW and LW fluxes from ground-based radiometers with the express purpose of 

validating satellite retrievals of surface fluxes. A program for measurements of surface 

radiation was set up at LaRC under the leadership of Dr. Charles Whitlock. Charlie set up 

field experiments to measure radiation components at the surface at forested locations. 

These experiments would provide data to validate the algorithms being developed and 

also give the team experience with the kinds of data they would be receiving from, soon 

to be available, measurements from around the world. Charlie enlisted Gerald Purgold as 

the experiment technician. Purgold had the necessary expertise in hardware and 

electronics and that made the measurement program successful. The LaRC group made 

full use of available surface measurements to validate their products and the effort was 

documented in the above-mentioned publications. Based on experience and confidence 

gained from validation of their products, the LaRC group processed the entire record of 

ISCCP-C1 data that covered an eight-year period (July 1983 to June 1991). This data set 

was announced and made available to the worldwide science community through a brief 

report in the GEWEX News, a newsletter published by the International GEWEX Project 

Office (IGPO). Validation of the eight-year data set and a climatology of SRB products 

based those data were published in the Journal of Climate (1999). 
48 

Wayne Darnell retired in 1995, and the modeling program was consolidated with the 

measurement program under Whitlock's leadership. Whitlock retired in 1996 and Paul 

Stackhouse, who had just earned his Ph.D. in atmospheric sciences from Colorado State 

University, joined the LaRC CERES team. He led the development of a radiative transfer 

based longwave algorithm that was subsequently approved by GEWEX to become the 

official GEWEX LW flux algorithm. Stackhouse was subsequently selected to lead the 

SRB Program in 1997. 

Stackhouse steered the program toward deriving SRB at a resolution of 1 degree. To 

achieve that objective, he started with ISCCP data for individual measurements and 

derived required cloud properties on a 1-degree resolution. The Pinker and Laszlo (1992) 

radiative transfer model for SW and the Fu et al. (1997) model for LW provided greater 

detail and were brought in as primary processing algorithms. Staylor's parameterized 

algorithm for SW and Gupta's algorithm for LW were retained for the purpose of quality 

assurance. A reanalysis data product from the Global Modeling and Assimilation Office 

(GMAO) at NASA GSFC, designated as GEOS-1, was chosen to provide meteorological 

inputs for the models. (Reanalysis data sets are generated to provide the best possible 

description of the atmosphere and surface for researchers.) The SRB team now included 

Paul Stackhouse, Shashi Gupta, Stephen Cox, and Colleen Mikovitz to share the 

increased modeling, data handling, and product validation responsibilities as Nancy 

Ritchie left and Anne Wilber was reasssigned. 

The NASA/GEWEX SRB products have continued to improve over the last two decades 

because of the improvements to the algorithms based on insights gained from continuing 

validation. Newer versions of ISCCP and GEOS data sets also contributed to product 

improvements and to the length of the data record because of the increasing coverage 

period. A 12-year data set was made public in 2004, followed by the 22-year Release in 

2006, and 24.5-year Release in 2011. Each release was announced in the GEWEX News. 

In addition to the importance of SRB data for scientific investigations, these data have 

many other applications: solar power, building design, agriculture, etc. In order for these 

data to be used, it was necessary to connect with the industries that had uses for the data. 

Often this meant discussions to find how the data would be used and in what form it was 

needed for various applications. Also, to connect with them required letting the 

industries know that the data were available and how to get it. A Bridge Builder is 

required to bridge the chasm between the scientists who produce these data sets and the 

people who use them in practical applications. Roberta DiPasquale was given this task. 

She attended conferences and meetings outside the usual science arena in order to meet 

the practical users and their needs. The SRB team then generated data products in the 

form that these users needed. The Surface meteorology and Solar Energy (SSE) web site 

created in 1997 made it possible to provide information to the renewable energy industry. 

Users of this site include the U. S. Air Force, U. S. Department of State, U. S. 

Department of Energy, USDA Forest Service, USGS Headquarters, NOAA, the World 

Bank, UNESCO, American Society of Heating, Refrigeration and Air Conditioning 

Engineers (ASHRAE), BP Solar, Shell Renewables and Duke Solar Energy. The 
49 

experience with the SRB data users outside the scientific community demonstrated 

clearly that it is not sufficient for scientists to put their data in an archive, even though it 

is accessible by the web. A Bridge Builder is needed to make the necessary connections 

with a broader community of users. 

One early application of SRB data was for design of solar cookers and solar powered 

refrigerators for refugee camps in the Sahel. Accurate estimates of solar energy available 

at the surface were essential for determining collector areas required for running a solar 

cooker and/or a refrigerator. A noteworthy method of using the SRB data set is the 

Renewable Energy Technology Screen (RETScreen) International Project, which was 

developed by Natural Resources Canada. RETScreen is a tool that allows engineers, 

technicians and architects to design energy-efficient buildings. It has more than 230 users 

in over 220 countries. The Surface Radiation Budget Data Archive has been used by 

numerous researchers for studying climate. It is also a trove of information for practical 

applications, for designers of solar power plants, buildings, etc. There are many uses that 

could not be imagined at the beginning of the project. 

Future Planned Earth Radiation Budget Research 

Enough spare parts were produced or purchased to build another copy of CERES, the 

FM-6. This instrument will be launched on the first NOAA/NASA Joint Polar Satellite 

System (JPSS-1). For future missions, proposals to develop and build the next-generation 

instrument called Radiation Budget Instrument (RBI) are now being evaluated. The 

present CERES was designed in the early 1990s with 1980s technology and many of the 

key components are no longer available or feasible to produce. Thus, building another 

exact copy of the current CERES instrument was not a viable option. 

The understanding of the Earth’s radiation budget and capability to develop highly 

accurate radiometers for use in orbit has led to the Climate Absolute Radiance and 

Refractivity Observatory (CLARREO) Project. The Langley-led CLARREO mission will 

provide the first observations of the full spectrum of energy reflected and emitted from 

the Earth: the same spectrum that drives climate change forcing, response, and climate 

sensitivity. CLARREO will provide the first spectral fingerprints of climate change and 

can avoid the uncertainty of instantaneous retrievals from satellites. Furthermore, 

CLARREO will provide the first space-based laboratory to measure the Earth while 

continually verifying the measurements against international standards, a process that 

will improve the accuracy of the whole climate measurement system. In doing so, 

CLARREO will produce a benchmark of the Earth's climate, providing a standard that 

can be confidently compared with measurements of climate change 5, 10, 20, even 50 

years after the mission's launch. Bruce Wielicki serves as CLARREO Mission 

Scientist. David Young served as the mission's first Project Scientist; Rosemary Baize 

transitioned to that role after Young accepted a Center leadership position. The 

CLARREO mission team includes leading climate modelers and observation scientists 

from different universities and agencies. A key contributor from Langley is Marty 
50 

Mlynczak who leads efforts to develop a new instrument to measure the far infrared part 

of the spectrum. The CLARREO team successfully completed a Mission Concept Review 

in fall 2010 and is currently in an extended planning phase to explore alternative, lower 

cost implementation strategies and reduce technical risk. The expected launch date is no 

earlier than 2023. An overview of the CLARREO mission is given in an October 2013 

article in the Bulletin of the American Meteorological Society by Wielicki et al. 
51 

Peer Reviews of Langley Radiation Research 

The research conducted in the Science Directorate is periodically reviewed by scientists 

from outside Langley, who have distinguished themselves by their contributions. From 

the beginning these reviews have rated the work of the branch very highly. One reviewer 

said the branch is “like swans: graceful, yet paddling furiously underneath.” 

In the 2007 External Peer Review Report, it is stated that “The panel was universally 

impressed with the high quality and relevance of the science being performed. The 

program has demonstrated unprecedented leadership in space-borne earth radiation 

budget studies which are having major impacts upon scientific research outside of 

NASA.” “The CERES work is first rate and first class. The care and precision associated 

with calibration of the instrument and maintaining the data record are to be commended. 

Dr. Bruce Wielicki and the rest of the CERES investigators have clearly thought through 

the issue of providing outstanding and usable extended period climate records. The fusion 

of the data from other instruments, combined with models, to produce outstanding 

measurements of radiative fluxes serves as a benchmark for the community.” 

Reflections on Radiation Budget At Langley Research Center 

Earth radiation budget work at Langley Research Center began with the recognition of 

need for measurements leading to scientific data products and the areas that required 

work. A Team was formed to address these areas. Starting with a proposal for a passive 

spacecraft, they also pursued other concepts through grants. The Team polled several 

climate scientists to learn their requirements: what did they need, at what time and space 

resolution and accuracy. These questions were finally answered by a panel of the 

National Academy of Science. The result was that the original concept was discarded and 

one of the approaches studied under a grant was adopted. Success was won by 

perseverance and flexibility of the Team. The Team consisted of engineers with 

backgrounds in basic physics and mathematics and a willingness to learn. This last trait is 

required in a research environment, where one is always moving beyond the known into 

the unknown. The team approach has been continued through ERBE and CERES. 

The projects were accomplished by a team of in-house scientists and contractor support 

staff working closely to design and build the best instruments within their abilities. 

Observers have often commented on the openness and close collaboration between the 

civil servants and their contractor colleagues. 

The Science Teams that were formed from researchers from various government 

laboratories and universities gave an excellent return on the investments in these projects. 

In addition to studies that had been outlined at the beginning, important investigations 

were accomplished that had never been anticipated. 
52 

Annotated Bibliography 

Although Vern Suomi demonstrated the use of non-scanning radiometers to make 

measurements of the Earth’s radiation budget, the use of scanning radiometer data to 

compute the Earth’s radiation balance was shown by this paper: 

Raschke, E., T. H. Vonder Haar, W. R. Bandeen, and M. Pasternak, 1973: The annual 

radiation balance of the earth-atmosphere system during 1969 - 1970 from 

Nimbus 3 measurements. J. Atmos. Sci., 30, no. 3, Apr., pp 341 - 364. 

The ERB instrument and the application of the measurements from the ERB instrument 

that flew aboard the Nimbus 7 are described by: 

Jacobowitz, H., H. V. Soule, H. L. Kyle, F. B. House and the Nimbus-7 ERB experiment 

team, 1984: The earth radiation budget (ERB) experiment: An overview. J. 

Geophys. Res., 89, pp 5021 - 5038. 

Accurate measurements of Earth radiation budget must include measurements over all 

times of day. The design of the orbits of a system of spacecraft was defined by: 

Harrison, E. F., P. Minnis, and G. G. Gibson, 1983: Orbital and cloud cover sampling 

analyses for multi-satellite Earth radiation budget experiments. J. Spacecraft and 

Rockets, 20, 491-495. 

A series of papers was written to explain the ERBE project and the processing methods 

of the data. This collection was published in Reviews of Geophysics in 1986. The overall 

project and the scientific purposes were described by: 

Barkstrom, B. R. and G. L. Smith, 1986: The Earth Radiation Budget Experiment: 

Science and Implementation. Rev. of Geophys., 24, 379-390. 

The scanning and non-scanning radiometers are described by: 

Kopia, L. P., 1986: Earth Radiation Budget Experiment scanner instrument. Rev. 

Geophys., 24, 400-406

Luther, M. R., J. E. Cooper and G. R. Taylor, 1986: The Earth Radiation Budget 

Experiment non-scanning instrument. Rev. of Geophys., 24, 391-399. 

The bidirectional reflectance distribution models that were used to account for the 

directionality of the reflected solar and emitted longwave radiation are described by: 

Suttles, J. T., R. N. Green, P. Minnis, G. L. Smith, W. F. Staylor, B. A. Wielicki, I. J. 

Walker, D. E. Young, V. R. Taylor and L. L. Stowe, 1988: Angular Radiation 

Models for the Earth-Atmosphere System. Vol. I: Shortwave Models. NASA 

Ref. Pub. 1184. 
53 

Suttles, J. T., R. N. Green, G. L. Smith, B. A. Wielicki, I. J. Walker, V. R. Taylor, and L. 

L. Stowe: Angular radiation models for earth-atmosphere system, Vol. II - 

Longwave radiation. NASA RP-1184, 1989. 

These models were used not only by ERBE, but also by CERES for the first edition of 

data products and by the ScaRaB and Geostationary Earth Radiation Budget (GERB) 

projects. 

Some of the scientific results of ERBE are published in these journal articles: 

Harrison, E. F., D. R. Brooks, P. Minnis, B. A. Wielicki, W. F. Staylor, G. G. Gibson, D. 

F. Young and F. M. Denn, 1988: First estimates of the diurnal variation of 

longwave radiation from the multiple-satellite Earth Radiation Budget Experiment 

(ERBE). Bull. Amer. Met. Soc., 69, 1144-1151. 

Minnis, P., E. F. Harrison, L. L. Stowe, G. G. Gibson, F. M. Denn, D. R. Doelling, and 

W. L. Smith, Jr., 1993: Radiative climate forcing by the Mt. Pinatubo eruption. 

Science, 259. 

Barkstrom, B. R., E. F. Harrison, G. L. Smith, R. N. Green, J. F. Kibler, R. D. Cess, and 

the ERBE Science Team, 1989: Earth Radiation Budget Experiment (ERBE) 

archival and April 1985 results. Bull. Amer. Met. Soc., 70, pp. 1254-1262. 

Ramanathan, V., R. D. Cess, E. F. Harrison, P. Minnis, B. R. Barkstrom, E. Ahmed, and 

D. Hartmann, 1989: Cloud-radiative forcing and climate: Results from the Earth 

Radiation Budget Experiment. Science, 243, pp. 57-63. 

Ramanathan, V., 1987: The role of Earth radiation budget studies in climate and general 

circulation research. J. Geophys. Res., 92, 4075-4095. 

Overviews of CERES are given in: 

Wielicki, B. A., B. R. Barkstrom, E. F. Harrison, R. B. Lee III, G. L. Smith, and J. E. 

Cooper, 1996: Clouds and the Earth's Radiant Energy System (CERES): An 

Earth Observing System Experiment. Bull. Amer. Met. Soc., 77, No. 5, pp. 853-

868, May 1996. 

Smith, G. L., K. J. Priestley, and N. G. Loeb, 2013: CERES, from Design to Data. Trans. 

Geophys. & Remote Sensing. 

An overview of CLARREO is given in: 

Wielicki, B. A., D. F. Young, M. G. Mlynczak, K. J. Thome, S. Leroy, J. Corliss, J. G. 

Anderson, C.O. Ao, R. Bantges, F. Best, K. Bowman, H. Brindley, J. J. Butler, W. 

Collins, J. A. Dykema, D. R. Doelling, D. R. Feldman, N. Fox, X. Huang, R. 

Holz, Y. Huang, Z. Jin, D. Jennings, D. G. Johnson, K. Jucks, S. Kato, D. B. 

Kirk-Davidoff, R. Knuteson, G. Kopp, D. P. Kratz, X. Liu, C. Lukashin, A. J. 

Mannucci, N. Phojanamongkolkij, P. Pilewskie, V. Ramaswamy, H. Rivercomb, 

J. Rice, Y. Roberts, C. M. Roithmayr, F. Rose, S. Sandford, E. L. Shirley, W. L. 
54 

Smith Sr., B. Soden, P. W. Speth, W. Sun, P. C. Taylor, D. Tobin, and X. Xiong, 

2013: Achieving Climate Change Absolute Accuracy in Orbit. Bull. Amer. Met. 

Soc., 94, No. 10, October. 

Some of the scientific results from CERES are published in these journal articles: 

Wielicki, B. A., T. Wong, R. P. Allan, A. Slingo, J. T. Kiehl, B. J. Soden, C.T. Gorton, 

A. J. Miller, S-K. Yang, D. A. Randall, F. Robertson, J. Susskind, and H. 

Jacobowitz, 2002: Evidence for Large Decadal Variability in the Tropical Mean 

Radiative Energy Budget. Science, 295, pp. 841-844. 

Lin, B., B.A. Wielicki, L. H. Chambers, Y. Hu, and K-M. Xu, 2002: The Iris 

Hypothesis: A Negative or Positive Cloud Feedback? Journal of Climate, 15, No. 

1, pp. 3-7. 

Loeb, N.G. and N. Manalo-Smith, 2005: Top-of-atmosphere direct radiative effect of 

aerosols over global oceans from merged CERES and MODIS observations. J. 

Climate , 18 (17), pp. 3506-3526. 

Stackhouse, P.W., Jr., S. J. Cox, S. K. Gupta, M. Chiaachio, and J. C. Mikovitz, 2000: 

The WCRP/GEWEX Surface Radiation Budget Project Release 2: An assessment 

of surface fluxes at 1 degree resolution. International Radiation Symposium 

2000. St. Petersburg, Russia, pp. 24-29 July. 

Whitlock, C. H., T. P. Charlock, W. F. Staylor, R. T. Pinker, I. Laszlo, A. Ohmura, H. 

Gilgen, T. Konzelman, R. C. DiPasquale, C. D. Moats, S. R. LeCroy, and N. A. 

Ritchey, 1995: First Global WCRP Shortwave Surface Radiation Budget Dataset. 

Bulletin of the American Meteorological Society, 76, pp. 905-922.

The Chesapeake Lighthouse ocean experiment site is described by the following paper: 

Rutledge, C. K., G. L. Schuster, T. P. Charlock, F. M. Denn, W. L. Smith Jr., B. E. 

Fabbri, J. J. Madigan Jr., and R. J. Knapp, 2006: Offshore Radiation Observations 

for Climate Research at the CERES Ocean Validation Experiment: A New 

“Laboratory” for Retrieval Algorithm Testing. Bull. American Met. Soc., 87, pp. 

1211-1222. 
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In the 1970s research studies concentrating on satellite measurements of Earth’s radiation budget started at the NASA Langley Research 

Center. Since that beginning, considerable effort has been devoted to developing measurement techniques, data analysis methods, and 

time-space sampling strategies to meet the radiation budget science requirements for climate studies. Implementation and success of the 

Earth Radiation Budget Experiment (ERBE) and the Clouds and the Earth’s Radiant Energy System (CERES) was due to the remarkable

teamwork of many engineers, scientists, and data analysts. Data from ERBE have provided a new understanding of the effects of clouds, 

aerosols, and El Nino/La Nina oscillation on the Earth’s radiation. CERES spacecraft instruments have extended the time coverage with high 

quality climate data records for over a decade. Using ERBE and CERES measurements these teams have created information about radiation 

at the top of the atmosphere, at the surface, and throughout the atmosphere for a better understanding of our climate. They have also 

generated surface radiation products for designers of solar power plants and buildings and numerous other applications. 

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Atmosphere; CERES; Clouds; ERBE; Radiation; Radiation budget

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