May 2012 

NASA/TM–2012-217578 

Remote Measurement of Pollution—A 40-Year 

Langley Retrospective: Part II—Aerosols and 

Clouds 

Ellis E. Remsberg 

Langley Research Center, Hampton, Virginia 
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May 2012 

NASA/TM–2012-217578 

Remote Measurement of Pollution—A 40-Year 

Langley Retrospective: Part II—Aerosols and 

Clouds 

Ellis E. Remsberg 

Langley Research Center, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 
1

Contents

Abstract 3

Introduction 4

Studies of aerosols and clouds prior to the RMOP Report 6

(a) Background 6

(b) Expertise and recommendations from the members of the RMOP Panel 8

Evolution of measurement techniques and some key players at Langley 12

(a) A redirection toward satellite observations of the Earth/atmosphere 12

(b) Laser radar of lidar 14

(c) Solar occultation 17

(d) Limb emission and scattering 18

(e) Nadir-viewing photometry or radiometry 19

(f) Aerosol polarimetry 23

Research on aerosols and clouds from the time of RMOP to the early 1980s 25

Earth observations in the Space Shuttle era 29

(a) Changing priorities for satellite measurement technologies at Langley 29

(b) ERBE and SAGE II on the ERBS satellite of 1984 31

(c) HALOE on the UARS satellite of 1991 34

(d) ATMOS on the Space Shuttle 35

(e) The Lidar In-space Technology Experiment (LITE) 35

The era of NASA’s Earth Observing System (EOS) 37

(a) Toward studies of global climate science 37

(b) CERES 40

(c) SAGE III 41

(d) CALIPSO 42
2

(e) Complementary measurements within EOS and from the international community 42

Present-day, satellite remote sensing of Earth’s radiative budget and aerosols 44

(a) NASA’s Decadal Survey Plan and responses from Langley 44

(b) Recent scientific imperatives 46

Summary 48

Acknowledgements 49

Appendix A—Perspective of the author 50

Appendix B—Acronyms 54

References 64
3

Abstract

A workshop was convened in 1971 by the National Aeronautics and Space Administration 

(NASA) on the Remote Measurement of Pollution (RMOP), and the findings and 

recommendations of its participants are in a NASA Special Publication (NASA SP-285). The 

three primary workshop panels and their chairmen were focused on trace gas species (Will 

Kellogg), atmospheric particulates or aerosols (Verner Suomi), and water pollution (Gifford 

Ewing). Many of the workshop participants were specialists in the techniques that might be 

employed for regional to global-scale, remote measurements of the atmospheric parameters from 

Earth-orbiting satellites. In 2011 the author published a 40-year retrospective (or Part I) of the 

instrumental developments that were an outgrowth of the RMOP panel headed by Will Kellogg, 

i.e., on atmospheric temperature and gaseous species. The current report (or Part II) is an 

analogous retrospective of the vision of the panel led by Verner Suomi for the measurement of

particulates (or aerosols) and clouds and for their effects on Earth’s radiation budget. The class 

of measurement techniques includes laser radar or lidar, solar occultation, limb emission and 

scattering, nadir-viewing photometry or radiometry, and aerosol polarimetry. In addition, the 

retrospective refers to the scientific imperatives that led to those instrument developments of 

1971-2010. Contributions of the atmospheric technologists at the Langley Research Center are 

emphasized, and their progress is placed in the context of the parallel and complementary work 

from within the larger atmospheric science community.
4

1 Introduction

By the 1960s climate scientists wondered whether Earth’s environment could be altered due to 

anthropogenic activities, perhaps even globally [Landsberg, 1970]. This topic was also the focus 

of an MIT report entitled “Study of Man’s Impact on Climate” [SMIC, 1971]. The National 

Aeronautics and Space Administration (NASA) responded by emphasizing its Earth applications 

program. Making measurements of Earth’s environment was viewed as a natural extension of 

their ongoing efforts toward global weather observations from Space. Morris Tepper, Director 

of Meteorology Programs, and Jules Lehmann, Manager of Advanced Instrumentation and 

Sensor Engineering Programs, both at NASA Headquarters, directed that the Langley Research 

Center (LaRC) convene a Working Group on the topic of the Remote Measurement of Pollution 

(RMOP). A panel of experts met in August 1971 in Norfolk, Virginia. Their findings and 

recommendations can be found in NASA SP-285 [1971]. In particular, the panel reviewed and 

reported on the principles of remote sensing and the associated instrument techniques that ought 

to be considered for development and eventual deployment on a satellite platform. In Part I of 

his 40-year retrospective on the satellite measurement of atmospheric temperature and gaseous 

species, Remsberg [2011] concluded that “the historical evidence indicates that the findings of 

the RMOP Workshop Report represent the genesis of and blueprint for the satellite Earth-sensing 

programs within NASA for the following two decades”. The RMOP Report is an early precursor 

to NASA’s Decadal Survey for Earth Science and Applications from Space [NRC, 2007].

The present report (or Part II) extends the work of Remsberg [2011] and considers satellite

techniques for the measurement of particle air pollution and the sensing of clouds. Members of 

the Particle Air Pollution Panel of RMOP are in Table 1, and Verner Suomi was their Chairman. 

Member names in bold print are tied directly to measurement concepts that were successful from 

Space following RMOP. Since the term “particles” (or particulates) often brings to mind plumes 

from industrial smokestacks, the more general designation “atmospheric aerosols” will be used 

instead throughout much of this report. Section 2 provides the motivations for obtaining more 

and better measurements of aerosols and clouds. It also mentions the expertise of the members

of the Panel and reviews their recommendations in the RMOP Report. Section 3 recounts the

sensor development for the detection and measurement of aerosols and clouds that occurred at 

LaRC prior to RMOP and that continued through the decade of the 1970s. Measurement 

techniques that are reviewed include laser radar (or lidar), solar occultation, limb emission and 

scattering, nadir-viewing photometry or radiometry, and polarimetry. Several instrument 

scientists and program managers at LaRC are recognized for their key roles in those 

developments. Section 4 is a brief account of the primary satellite instruments and the findings 

from them about aerosols and clouds from 1970 to 1983, just before the era of the Space Shuttle.

Section 5 is focused on several satellite instruments from LaRC that were deployed on or from 

the Space Shuttle from 1984 to the mid 1990s. Section 6 describes briefly the prototype, but 

near-operational aerosol and cloud sensors of the follow-on Earth Observing System (EOS) era, 

and it places them in the context of similar observational programs of laboratories both in the 

U.S. and abroad. Section 7 reports on several new measurement approaches, based on

recommendations of the NRC [2007]. Section 8 reflects on the progress that has been made and 

the way ahead. An Appendix provides the prospective of the author for this review.
5

Table 1. RMOP members of the Particle Air Pollution Panel and their affiliations in 1971.

Verner Suomi, Univ. of Wisconsin, Panel Chair

Henry Blau, Jr., Arthur D. Little, Inc.

Charles Byvik, NASA Langley

Robert Fraser, NASA Goddard

Gerald Grams, NCAR

Thomas Haig, Univ. of Wisconsin

Franklin Harris, Jr., Old Dominion Univ.

Benjamin Herman, Univ. of Arizona

Alfred Holland, NASA Wallops Station

J. Don Lawrence, NASA Langley

William Matthews, MIT

S. Harvey Melfi, NASA Langley

G. D. Robinson, Univ. of Connecticut

Zdenek Sekera, UCLA
6

2 Studies of aerosols and clouds prior to the RMOP Report

(a) Background

The SMIC and the RMOP Working Groups posed a number of questions related to aerosols and 

clouds. In fact, their concerns would presage those of the current series of reports from the 

Intergovernmental Panel on Climate Change [e.g., IPCC, 2007]. For instance, does wind-borne 

dust or products of combustion alter the nature of cloudiness or precipitation by their role as 

condensation nuclei for the droplets [Bryson, 1974; CCSP, 2009]? Are contrails from aircraft 

increasing the frequency of occurrence of cirrus clouds in air flight corridors and altering the 

atmospheric energy budget of those regions [Angell and Korshover, 1975]? How can climate 

scientists better represent and verify effects of aerosols and clouds and the variations in surface 

reflectivity in model simulations [Vonder Haar and Suomi, 1971; Rasool and Schneider, 1971]?

Aerosols and clouds have implications for both air quality and climate. For example, 

stratospheric aerosols from large volcanic eruptions attenuate the incoming solar radiation and 

alter the transmissivity and reflectivity (or albedo) of the atmosphere. Will Kellogg of the 

National Center for Atmospheric Research (NCAR) and Chair of the companion Gas Species 

Panel of the RMOP study was well recognized for his work on the dispersion of smoke plumes

and of debris from high-altitude atomic bomb tests and later for his studies of the stratospheric 

aerosol layer [e.g., Kellogg, 1956; Kellogg et al., 1957; Kellogg et al., 1972]. Aerosol research 

in the 1950s and early 1960s in the U. S. was focused on the attachment of radioactive bomb 

debris onto aerosols in the stratosphere and its transport to and then within the troposphere 

[Junge, 1963; Reiter, 1971]. James Lodge, Richard Cadle, and Ed Martell at NCAR conducted

field studies of radioactive debris, tropospheric freezing nuclei, and stratospheric aerosols and 

their precursor gases during the 1960s.

William Castleman of Brookhaven National Laboratory (BNL) and James Friend of Isotopes, 

Inc., conducted studies of the composition, size distributions, and microphysical properties of the

stratospheric aerosols. Their work was an extension of earlier findings that were based on the 

cascade impactor and condensation nuclei counter measurements of Christian Junge and his 

colleagues at both the Air Force Cambridge Research Laboratory (AFCRL) and eventually at the 

Max-Planck Institute for Chemistry in Mainz, Germany [Junge and Manson, 1961; Chagnon and 

Junge, 1965]. Junge is perhaps best known for his characterization of the background 

stratospheric layer near 20 km [Junge, Chagnon, and Manson, 1961]. The so-called “Junge layer 

particles” were composed mostly of sulfate material. James Rosen of the University of 

Minnesota and later of Wyoming found that the tiny droplets above about 27 km were volatile in 

nature, according to their vaporization temperature within the heated inlet of his balloon-borne 

particle counter [Rosen, 1969]. He concluded that the Junge aerosols were most likely composed 

of concentrated aqueous solutions of sulfuric acid. 
7

Remsberg [1973] conducted laboratory measurements of bulk solutions of sulfuric acid in the 

mid-infrared and analyzed those data for their optical constants, both real and imaginary. Palmer 

and Williams [1975] verified the measurements of Remsberg and then extended the optical 

constants to the visible and near infrared wavelengths. Crutzen [1976] proposed that the bulk of 

the background stratospheric, Junge or sulfate layer has its primary source from the 

photodissociation of carbonyl sulfide (CSO). In March 1963 the volcanic eruption of Mt. Agung 

provided a large perturbation to the Junge layer and led to visible scattering and twilight 

refraction phenomena for a year of so thereafter [Volz, 1969]. Major eruptions from Fuego 

(1974), St. Helens (1980), El Chichon (1982), and Pinatubo (1991) would enhance the 

background layer in coming decades.

Other than ice particles and water droplets, aerosols in the troposphere range from desert dust 

composed of silicate compounds to organic, black carbon from the incomplete combustion of 

fires and in smoke plumes. Peterson and Weinman [1969] reported on the optical and scattering 

properties of silicates for interpreting of the radiative effects of wind-blown dust layers observed 

above and downwind from the Rajasthan Desert of northwest India by Reid Bryson of the 

University of Wisconsin. Twitty and Weinman [1971] calculated the optical and scattering 

properties of organic, black carbon smoke particles. Such information along with estimates of 

size distributions and particle shapes is required for interpreting remotely-sensed data about the 

spectral extinction, angular scattering, and polarization properties of the aerosol layers. It is also 

presumed that the properties of the aerosols are changing with time, as they grow, coalesce, 

sediment, and otherwise mix with and evolve chemically in the atmosphere. 

Smoke and aerosols from biomass burning or fossil-fuel combustion are sources of pollution in 

the lower troposphere, at least in urban regions and often extending across continental 

boundaries. The monitoring of atmospheric turbidity had been underway from ground stations in 

continental regions [Flowers et al., 1969]. In fact, increases in turbidity were believed to be 

responsible for the slight decrease of worldwide air temperatures since about 1940, despite the 

increasing amounts of atmospheric CO2 [McCormick and Ludwig, 1967; Peterson and Bryson, 

1968]. 

Photopolarimeters and imagers were being used to characterize the size distributions of the 

atmospheric dust and smoke plumes and to determine their scattering properties and effects on 

the transfer of radiation through them. Ground-based lidar instruments had been put in operation 

at a dozen or so stations worldwide. In particular, they were providing information about the 

seasonal and global-scale nature of volcanic aerosol layers in the lower stratosphere. Thus, the 

members of the atmospheric Particle Panel of RMOP felt that it was appropriate to ask whether 

such passive or active sensors could be operated from satellite platforms for a global survey of 

the properties and distributions of atmospheric aerosols and for a determination of their transport 

from one region to another.
8

A primary interest at that time for Verner Suomi, Chair of the Particle Air Pollution Panel, was 

on a more accurate determination of the effects of clouds on Earth’s albedo and ultimately on the 

radiation budget of the Earth and its atmosphere. Suomi had already successfully demonstrated 

his visible, spin-scan camera approach for viewing the Earth and its cloud cover from Advanced 

Technology Satellites (ATS) in geostationary orbits and was beginning to obtain tropical wind 

vectors using the displacements of the high clouds from sequences of their pictures (e.g., see 

review by Lewis et al. [2010]). Up until then, the presence of clouds was mostly a nuisance for 

the satellite remote measurement of tropospheric temperature and water vapor. Broadband 

infrared sounding techniques from Space required clear skies for obtaining the profiles of both, 

which were needed as input to global weather forecast models. Later, of course, the advent of 

satellite-borne microwave sounders provided for the necessary tropospheric temperature profiles 

in the presence of clouds [e.g., Staelin et al. 1977; Smith, 2010]. Two reviews of the developing, 

satellite radiation budget measurement programs at LaRC have been published by House et al. 

[1986] and Smith et al. [2011], and the reader is referred to their more complete, historical 

accounts of the subject. Studies of the diurnal nature of clouds, the distributions of cirrus clouds 

and polar stratospheric clouds (PSC), and the verification of the microphysical properties of and

radiative transfer within clouds are discussed briefly in the present report.

(b) Expertise and recommendations from the members of the RMOP Panel

Most of the members of the Particle Air Pollution Panel of Table 1 were selected for their 

specific theoretical or measurement expertise and understanding. An exception was Prof. 

William Matthews, a civil engineer and an organizer of the SMIC Report. He was a member of 

both the Gas Species and Particle Panels of RMOP because of his overall knowledge of the 

critical environmental problems of that time. Atmospheric aerosols have important biological 

and economic effects on local to regional scales and possibly on larger-scale, climatic effects. 

Biologically, high concentrations of particulates can lead to respiratory illnesses. Aerosols can 

damage plants and may also cause an increase in the acidity of precipitation, reducing the 

productivity of soils, forests, and fish stocks.

The other members of the Panel were conducting research on the composition, sizes, and 

distributions of atmosphere aerosols, as well as their sources and effects. To understand some of 

the likely measurement issues, Henry Blau and Alfred Holland had conducted laboratory studies 

of the aerosol scattering matrix for spheres and irregular particles, respectively. Franklin Harris, 

Jr., and Zdenek Sekera were involved with studies of the polarization of light by aerosols. Windblown dust and volcanic plumes are examples of natural occurrences of aerosols that affect 

visibility and the incoming solar radiation, sometimes for great distances from their source 

regions and for extended periods of time. Robert Fraser, Benjamin Herman, and G. D. Robinson 

analyzed how haze layers of the lower atmosphere scatter and otherwise reduce the incoming 

solar radiation to the ground. The Panel recognized that it is not easy to distinguish between 

natural and man-made particulate matter based on remote measurements of their visible 

extinction effects alone. Long-time records of atmospheric turbidity were available from a few 

stations that were far removed from local sources of pollution (e.g., Peterson and Bryson, 1968; 
9

Ellis and Pueschel, 1971). That turbidity data showed both short and long-term variations, much 

of which may have been related to variations in the transport within the lower atmosphere. The 

Panel believed that sorting out the causes of such variations might be achieved best with a near 

global-scale, satellite monitoring program.

G. D. Robinson and Verner Suomi felt that a more immediate task was the improvement of the 

understanding of Earth’s radiation budget. Robinson also reported that the interaction of 

aerosols with clouds could give rise to an increase in the absorption of shortwave radiation

[SMIC, 1971]. Suomi, Colonel Thomas Haig, and their colleagues at the Space Science and 

Engineering Center (SSEC) of the University of Wisconsin were advocates of observing the 

cloud cover and of determining the reflected and emitted components of the Earth/atmosphere 

radiation using instruments onboard Earth-orbiting and geostationary satellites [Smith et al., 

2011; House et al., 1986]. The RMOP report included recommendations for determining Earth’s 

radiation budget that undoubtedly spurred further satellite sensor development within both 

NASA and NOAA. A series of Synchronous Meteorological Satellites (SMS) was envisioned 

for this purpose—later renamed Geostationary Operational Environmental Satellite (or GOES).

Suomi and co-workers showed that one could relate the changes in the albedo over Los Angeles, 

as measured from the ATS-3 spacecraft, to the visibility and local particle count in the lower 

atmosphere over the city. They noted that their finding was “perhaps the first quantitative 

detection of pollution from a satellite” [NASA SP-285, 1971]. Photographs taken in 1968 by 

astronauts also showed clearly the effects of pollution hazes. NASA was developing an Earth 

Resources Technology Satellite (ERTS) for obtaining images of the Earth’s surface and cloud 

cover and its short-term and seasonal changes. ERTS-1 was launched in 1972 and later renamed 

Landsat-1. Its multi-spectral scanners (MSS) observed details about the reflectivity of clouds, 

vegetation, land and ice forms, as well as the presence and extent of haze layers on a global 

scale. 

Professor Suomi also developed and flew balloon-borne, radiometersondes for obtaining 

atmospheric profiles of the net infrared fluxes (irradiances) due to clouds, water vapor, and 

aerosol layers [Kuhn and Johnson, 1966; Suomi and Kuhn, 1958]. Interpretations of the flux 

profiles were limited to a large extent by a lack of information on the spectral (absorbing) 

characteristics and/or scattering properties of each of those sources of irradiance. Therefore, the 

Panel recommended the initiation of a coordinated, physio-optical research program, whose 

purpose would be to advance the understanding of the optical properties and radiative 

characteristics of the real atmosphere. Later, Peter Kuhn modified the flux radiometer for the 

detection of clear air turbulence (CAT), based on the signal fluctuations in the 26-35 μm band of 

water vapor [Kuhn et al., 1978]. 

The Particle Panel recommended the establishment of a world-wide network of atmospheric 

turbidity monitors to determine what changes, if any, were occurring due to man-made aerosols. 
10

They also recommended a number of supporting studies about the elements of the scattering 

matrix of atmospheric aerosols and on improvements in their mathematical and computational 

modeling. Members of the Panel realized that each of those aspects would be important for the 

development of models to assess the effects of both natural and man-made atmospheric aerosols 

on climate. Still, the Panel did not assemble a list of specific measurement requirements other 

than to note that it would be important to achieve good vertical resolution (~1 km) for the 

stratospheric aerosol layers and good horizontal resolution for tracking regional changes in 

tropospheric turbidity. With those issues in mind, Panel members J. Don Lawrence, Charles 

Byvik, Gerald Grams, and S. Harvey Melfi focused their attention on developing systems for the 

measurement of tropospheric and stratospheric aerosols using ground-based, backscatter lidar 

techniques.

Panel members made several recommendations for research satellite instruments, too. For 

example, they felt that the geographical coverage of a stratospheric aerosol experiment should be 

extended to the higher latitudes, like the one proposed for the Orbiting Solar Observatory (or 

OSO-J) by Gas Species Panel member, Ted Pepin, of the University of Wyoming. They thought

that his approach could provide, quickly and economically, the basic data for understanding the 

global distribution of stratospheric aerosols. As an aside, it is noted that the originally-planned, 

OSO experiment was actually conducted on the Apollo-Soyuz Test Project as a Stratospheric 

Aerosol Measurements (ASTP/SAM) experiment in July 1975 [Pepin et al., 1977]. Further, they 

urged that a cooled infrared spectrometer be evaluated from a near-earth orbit for the sensing of 

distributions of small particles that could not be measured with photometers and, perhaps, for

furnishing information on the chemical nature of the particles, too. The Panel believed that it 

was possible to characterize and monitor atmospheric turbidity on a global scale by measuring 

the degree of polarization of upwelling radiation with fast-response photopolarimeters [Sekera, 

1967]. They recognized though that the target observation area would need to be kept in the 

field of view during a satellite traverse, in order to obtain information for a range of scattering 

angles. The Panel recommended that studies be made on the use of photopolarimeters from 

geostationary satellites, too. The Panel also urged that satellite-based lasers be developed for

monitoring the spatial distributions of tropospheric and stratospheric aerosols on a global basis.

Clouds reflect incoming solar shortwave radiation with an efficiency that depends on their 

thickness, or more specifically their optical depth. They also absorb infrared radiation from the 

Earth’s surface and from the surrounding atmosphere and re-emit it according to the atmospheric 

temperature at the altitude of the cloud top. In fact, the presence of clouds and their top height 

may be determined based on temperatures inferred from radiances in the so-called “infrared 

window” channels from satellite sounder measurements [e.g., Houghton, 1986]. But, operational 

sounder data from polar orbiting satellites are obtained at only two local times per day. Because 

cloud frequency and altitude vary diurnally, the sounder data carry time-of-day sampling 

uncertainties that make it difficult to obtain a good measure of the radiative budget of the 

Earth/atmosphere from a satellite platform. Distributions and occurrences of thin or subvisible 

cirrus clouds were not known well, and even thin cirrus can have a significant effect on the 

outgoing long-wave radiation [Liou, 1974]. Finally, the finite field-of-view (FOV) of the pixels 
11

making up satellite images means that the effects of subgrid-scale clouds were also not known 

well and had to be parameterized in climate models or estimated by other means for a proper 

interpretation of infrared imagery [Slingo, 1980]. Members of the SMIC Working Group asked 

for a satellite system for “monitoring the temporal and geographical distribution of the Earthatmosphere albedo and the outgoing flux (IR) over the entire globe with an accuracy of at least 

1%.”

The report of the RMOP Panel led by Suomi includes a discussion of the seemingly intractable 

problem of how to obtain information about the properties and effects of clouds and aerosols 

from measurements of their scattering, absorption, and transfer of atmospheric radiation. In one 

respect, the determination of the radiative budget of the atmosphere and of aerosol extinction 

profiles is fairly straightforward. One only needs to obtain accurate measurements of the

radiances or transmissions. In other words, one does not have to advance to the next step of

conducting retrievals of the remotely-sensed, radiance or transmission, as is most often the case 

for obtaining the state parameters of the atmosphere—its temperature versus pressure profiles 

and its gas species profiles. For that next step one must also have accurate forward models of the 

radiance or transmission, and those models are generally limited by uncertainties in the 

spectroscopic line parameters of the given minor or trace atmospheric gases. Yet, the

determination of Earth’s radiation budget from satellite altitude is based only on measurements 

of the incoming solar radiance and the outgoing reflected and emitted radiances at top-ofatmosphere (TOA), and one must know how those measurements vary throughout the day and 

night and across all seasons, at various spatial scales, and over a range of scattering angles. In 

order to know the effects of clouds and aerosols within the atmosphere itself, one must know 

their distributions with altitude and their macroscopic scattering and absorbing properties. It is 

also helpful to have an independent measure of the radiation budget at the surface of the Earth, in 

order to verify what is being inferred from the reflected shortwave measurements at TOA.

Clouds are also present at high latitudes of the lower stratosphere and in the upper mesosphere. 

Stanford and Davis [1974] considered why the so-called mother-of-pearl clouds (MPC) occurred 

in the polar lower stratosphere in winter. Pioneer researcher, Otto Jesse, was concerned with the 

formation and occurrence of noctilucent clouds (NLC) in the opposing summer season of the 

polar upper mesosphere and whether they might be connected to particles from large volcanic 

eruptions [Schroeder, 2001]. Knowledge was being obtained on both types of clouds from 

ground-based measurements of their scattering characteristics and from in situ measurements 

with high-altitude balloons or rocket probes. Poultney [1972] reported that cheap, low-power 

lasers having a high-pulse rate could provide ground-based measurements of the upper altitudes 

that would rival those from rocket probes. The Panel members believed that satellite 

observations obtained with photometers, radiometers, and lidar could provide improved 

space/time coverage and perhaps add some information about the cloud particles themselves.
12

3 Evolution of measurement techniques and some key players at Langley

(a) A redirection toward satellite observations of the Earth/atmosphere

In the 1960s Langley personnel were actively studying options for a Manned Orbital Research 

Laboratory (MORL) in preparation for Skylab and much later for a proposed International Space 

Station (ISS). However, toward the end of the decade much of that work was reassigned to the 

Marshall and Johnson Space Centers [Hansen, 1995]. Thus, part of the workforce at Langley 

was still in transition from the phase down of its Apollo and MORL activities and toward the 

planned development and demonstration of the Space Shuttle at the time of the RMOP 

Workshop in 1971. As reported in Remsberg [2011] and in the Introduction, the early part of the 

1970s was also when NASA was directed to focus more toward Earth applications and on what 

atmospheric measurements could be usefully conducted from a satellite or Earth-orbiting 

platform. Edgar Cortright, Center Director at Langley from 1968-1975, was largely responsible 

for implementing that vision, in addition to overseeing the Viking Project and the major ongoing 

research in aeronautics and in hypersonic flight at that time. Prior to coming to Langley, 

Cortright had served as Chief of the Advanced Technology Program, Assistant Director for the 

Lunar and Planetary Program, and most recently as Deputy Associate Administrator for Manned 

Space Flight at NASA Headquarters. In October 1970 Cortright announced a major 

reorganization and formed four research Directorates—Aeronautics, Space, Electronics, and 

Structures at Langley [Hansen, 1995]. Leading up to and immediately after that reorganization,

the conduct of Earth applications activities was ably directed by Eugene S. Love and William H. 

Michael, Jr., of the Space Directorate and by G. Barry Graves, James E. Stitt, Howard B. 

Edwards, William Croswell, John Dodgen, and William Mace within the Electronics Directorate.

Figure 1 is an outline of the atmospheric measurement programs at Langley from when they 

were primarily focused on aeronautics, to Earth applications since the time of the RMOP report 

of 1971, and then on to the planned activities for the upcoming decade. Much of the remote 

sensor development at Langley was initiated within the Instrument Research Division (IRD) 

from which the Flight Instrumentation Division (FID) was formed in 1965. FID personnel 

became engaged with testing and qualifying prototype instruments from balloon, rocket, or 

aircraft platforms. Measurement techniques for the effects of aerosols and clouds that they 

evaluated included: lidar, solar occultation, limb emission and scattering, photometry or 

radiometry, and polarimetry, as well as a number of ground-based and in situ aerosol and cloud 

droplet counting, sizing, and polarization techniques that would ultimately be used to validate or 

otherwise characterize the remotely-sensed observations. A brief review is provided in the 

following subsections of the early work at Langley for each of those remote sensing techniques 

(see upper right of Figure 1). Langley had already formed in 1964 the Office of Flight Projects 

to include Flight Reentry Programs, the Scout (rocket) Program with launches from Wallops 

Island, and the Applied Materials and Physics Division (AMPD). The latter organization was a 

reformulation of the Pilotless Aircraft Research Division (PARD). William O’Sullivan and 

colleagues of PARD and later AMPD developed and demonstrated several early communications 

satellites (ECHO and PAGEOS). His successors went on to develop sensors based on those of 

Verner Suomi for the measurement of Earth’s radiation budget from satellite orbit.
13

RMOP 

Workshop

1971

•Model atmospheres, ground 

to thermosphere for 

development of the X-15.

•Passive sensing studies of 

Earth’s CO2 horizon for 

spacecraft attitude/reentry.

•Laser sensing of fluid flow in 

wind tunnels and turbulence 

in the atmosphere

•Laser radar or lidar from Space.

•Satellite measurements by solar 

occultation (SO).

•Limb emission and scattering

•Nadir viewing photometry and 

radiometry for cirrus and aerosols.

•Aerosol polarimetry

1940’s Present

•Limb scattering from stratospheric aerosols for 

OMPS on NPOESS Preparatory Project (NPP).

•SO via SAGE III from International Space Station.

•High-spectral resolution lidar for the troposphere.

•Continuation of radiation budget record w/CERES.

•Further measurements of aerosols and clouds 

w/CALIPSO lidar.

Aeronautics Focus 

Remote Sensing Application

Sensors for the Next Decade

Figure 1. Time line of the development of techniques by NASA Langley for making 

measurements of atmospheric aerosols, clouds, and Earth’s radiation budget.
14

The report entitled “Research in Aeronautics and Space: Langley Research Center” is a useful 

summary of the research programs at Langley during the 1960s [Cortright, 1971]. One can 

easily discern some of the origins of atmospheric science research at Langley from that report. 

Of particular interest at that time was the ongoing need to characterize the effects of atmospheric 

drag and the accompanying heat load for spacecraft re-entering the atmosphere from low Earth 

orbit. In addition, it is noted therein that Langley was instrumental in the design of launch 

vehicles and their propulsion options for a combined U.S./Canadian meteorological sounding 

rocket program.

Sensor concepts for aerosols and clouds that have been demonstrated successfully from Earthorbit by Langley researchers are described in the following subsections, along with their primary 

advocates. The succession of satellite experiments is recounted in the subsequent chapters from 

the time of RMOP and on through to the Space Shuttle and EOS periods. Their achievements

are also placed within the context of concurrent measurement programs of other national and 

international research organizations.

(b) Laser radar or lidar

Soon after the development of the laser, optical engineers Don Robinson and Joe Goad of IRD 

adapted that new technology for purposes of flow visualization in wind tunnels and for small 

particle holography at Langley [NASA, 1970]. Others were already training their optical radar 

or lidar systems toward the sky for detecting atmospheric turbulence and for characterizing 

smoke plumes and pollutant haze layers in the lower atmosphere [Collis et al., 1964; Clemesha et 

al., 1966]. Giorgio Fiocco and RMOP Panel member Gerald Grams made observations of the 

Junge aerosol layer in the stratosphere [Fiocco and Grams, 1964] and its volcanic enhancements 

following the eruption of Mt. Agung [Grams and Fiocco, 1967]. Further, Grams and Burt 

Schuster of NCAR and Robert Fox and James Weinman of the University of Wisconsin went on 

to install an organic dye laser in a lightweight lidar system and to obtain measurements of the 

Junge layer from the NASA CV-990 aircraft over both the Pacific and the western Atlantic 

Ocean regions in the summer of 1971 [Fox et al., 1973]. They found backscattering ratios of 

order 1.1 or an aerosol scattering component of only 10%, indicating that the lower stratospheric 

layer was nearly devoid of any significant volcanic influence at that time. Paul Davis of 

Stanford Research Institute (SRI) also conducted lidar measurements from the CV-990 aircraft, 

looking for signatures of cirrus and of boundary haze layers, as part of the Barbados 

Oceanographic and Meteorological Experiment (BOMEX) during the summer of 1969 [Davis, 

1971]. His measurements were coupled with those from an airborne infrared radiometer, in an 

attempt to characterize the radiative forcing from the cirrus particles and the aerosol haze. 

During the late 1960s RMOP Panel members, S. Harvey Melfi and J. Don Lawrence, Jr., along 

with M. Patrick McCormick and Douglas Woodman mounted their pulsed, ruby lidar system 

onto a T-33 jet aircraft and obtained enhancements in backscatter, which they associated with 
15

regions of light turbulence [Lawrence et al., 1968]. Shortly after, Lawrence took a position as 

Chief Scientist of IRD, moving from the Physics Department of nearby College of William and 

Mary. Melfi and McCormick were also researchers in IRD. Lawrence and Melfi then moved to 

the newly formed Environmental and Space Sciences Division (ESSD) during the reorganization 

at Langley of 1970, while McCormick remained in IRD as Head of the Photo-Electronic 

Instrument Section. Along with William Hunt of Wyle Labs and William Fuller, Jr., they 

assembled a 48-inch mobile lidar system and then participated in a number of field measurement 

campaigns over the next decade. Lawrence and colleagues also contributed to BOMEX by 

conducting lidar observations from the cruise vessel S. S. Advance from Wilmington, NC, to the 

Barbados region and then to the mouth of Amazon River and back. They characterized the 

presence of dust layers in the lower stratosphere and also the dust at the top of the planetary 

boundary layer that had been transported westward from the African continent [Bach and Smith, 

1970]. Their efforts were sponsored by the Research Triangle Institute (RTI) of North Carolina 

just prior to the time that the Environmental Protection Agency (EPA) was formed. A 

cooperative relationship was maintained between Langley and the EPA for studies of regional air 

quality for at least the next decade, and Edgar Cortright was very supportive of those joint 

activities.

McCormick and Fuller of IRD and Lawrence and Melfi of ESSD, among others, made upgrades 

to the transmitter, receiver, and electronics for what was to become their signature, ground-based 

48-inch lidar system and much later a facility instrument at NASA Langley. Their first field 

campaign with the system was to Azusa, California, as part of a study activity of the air quality 

in the Los Angeles Basin in 1972. They also carried out routine measurements of the 

stratospheric layer over Langley during those years and were careful to maintain good 

calibrations for the system because of the very low aerosol backscattering ratios of that time

[e.g., Hunt and Poultney, 1975]. Langley remote sensors were an important part of the 

Department of Transportation’s Climatic Impact Assessment Program (DOT-CIAP) of the early 

1970s. Of course, Langley was also interested in the findings from CIAP because of the 

implications for its further research toward a supersonic transport (SST) aircraft.

Lawrence and Ron Greenwood were selected in 1973 to direct a NASA Environmental Quality 

Program Office (EQPO) at Langley at the request of Morris Tepper. Shortly thereafter, Melfi 

left Langley for a supervisory position at the newly-formed, EPA remote sensing laboratory in 

Las Vegas, NV. McCormick had assembled an array of remote and in situ aerosol measurement 

capabilities and personnel within a new Aerosol Research Branch (ARB) by 1975. Key persons 

included William Chu and David Woods along with RMOP Panel member, Franklin Harris, Jr., a 

NASA contractor at the nearby Old Dominion University Research Foundation (ODURF). 

Burton Northam, Head of a new Lidar Applications Section (LAS) in ESSD, recruited new 

employees, Edward Browell and Ellis Remsberg, plus Sherman Poultney and Carolyn Butler at 

ODURF in 1973-74. Together IRD and ESSD continued on with the calibration of the 48-inch 

lidar system and with the monitoring of the stratospheric aerosol layer. They also evaluated lidar 

techniques for their application to atmospheric measurements from the ground and from Space. 
16

The various techniques included resonance fluorescence, Raman scattering, and differential 

absorption lidar (DIAL), in addition to the more traditional method of laser backscattering.

McCormick and Northam conducted lidar measurements and compared them with University of 

Wyoming dustsonde profile measurements near San Angelo, Texas, in May of 1974, as part of

requirements to characterize the Stratospheric Aerosol Monitor (SAM II) and Limb Infrared 

Monitor of the Stratosphere (LIMS) prototype instruments that would fly eventually on Nimbus 

7 in 1978 [Northam et al., 1974; Remsberg et al., 1979]. However, they were all soon distracted 

by the much larger, lidar return signals that they observed at Langley, following a major eruption

in Guatemala of the Fuego volcano in October 1974 [McCormick and Fuller, 1975; Remsberg et 

al., 1982]. McCormick and Fuller went on to assemble a smaller, 14-inch ruby lidar system and 

began to conduct airborne surveys of the dispersal of volcanic aerosol layers and to validate 

satellite measurements of stratospheric aerosols and cirrus clouds. 

An Advanced Applications Flight Experiments (AAFE) Program Office was set up at Langley in 

the early 1970s and managed by Robert Parker, as directed by Cortright and by Leonard Jaffe 

and Jules Lehmann of NASA Headquarters [Croswell, www.ieeeghn.org ]. The purpose of the 

AAFE Program was to develop instrument concepts for eventual flight on a satellite platform. 

In addition, personnel in IRD and ESSD were assigned as technical monitors of study contracts 

to assess the potential of lidar measurements from an Earth-orbiting, Space Shuttle platform. An 

important outcome of those studies was that Langley and SRI submitted two separate proposals 

to an Announcement of Opportunity in 1976 from the NASA Office of Space Sciences (OSS) for 

the conduct of lidar measurements of Earth’s atmosphere on the Shuttle-based Spacelab I. 

Simulation studies indicated that it should be easy to obtain near global-scale characteristics of 

aerosols and clouds from a lidar system [Remsberg and Gordley, 1978; Russell et al., 1982]. The 

Langley proposal was entitled “Tropospheric Aerosol and Cloud Experiment (or TRACE)”, and 

it was designed to be a demonstration of what might be achievable with a lidar system from an 

Earth-orbiting platform. It received an excellent technical rating and had the strong support of 

Lawrence, Donald Hearth (Langley Director), and Paul Holloway (Director for Space). No 

selection was made though because of the cost involved and of the competing and overlapping 

interests within the OSS and Office of Applications (OA) Programs at NASA Headquarters. 

However, the managers at OSS and OA recognized the lidar expertise within Langley. They 

later combined their Shuttle Atmospheric Lidar Programs in cooperation with the Centre 

National d’Etudes Spatiales (CNES) of France, and that decision led to a Shuttle Lidar Program 

Office being set up at Langley [NASA, 1979].

During this time Edward Browell, James Hoell, Syed Ismail, and Scott Shipley of Langley and 

Robert Allen and Frank Mills of ODURF continued to develop and demonstrate the use of DIAL 

technologies within the Atmospheric and Environmental Sciences Division (AESD), headed by 

J. D. Lawrence. A focus for their work in the late 1970s and early 1980s was on the application 

of laser measurement techniques in field studies of the regional air quality. The EPA was keenly 

interested in understanding how urban haze plumes extended to the regional and continental 
17

scales. They relied on satellite imagery and the airborne, UV-DIAL lidar measurements of the 

haze layers for a verification of their model predictions of the transport of aerosols and ozone. In 

particular, Langley personnel participated in the EPA Persistent Elevated Pollution 

Episode/Northeast Regional Oxidant Study (PEPE/NEROS) program of 1980, as well as a 

subsequent study of pollution episodes in the Tidewater Virginia region [Browell et al., 1985; 

Shipley et al., 1984]. Joint studies led by researchers at the University of Wisconsin were also 

carried out using their airborne prototype, high-spectral resolution lidar (HSRL) instrument 

[Shipley et al., 1983] that was based on the initial optical radar measurements of aerosol-tomolecular backscatter ratios along with a frequency analysis of their Doppler-broadened spectra 

in the manner of Fiocco et al. [1971]. It was anticipated that advances in the HSRL technology 

could still be made for providing better measurement stability and aerosol-to-molecular 

discrimination.

(c) Solar occultation

Prof. Alfred Nier of the University of Minnesota and his student, Ed Ney, did pioneering work in 

mass spectrometry for the separation and analysis of the isotopes of uranium in the early 1940s. 

Much later, Nier was responsible for the mass spectrometer that was on the Viking Lander 

spacecraft. Ney went on to conduct measurements from high altitude balloons of atmospheric 

cosmic rays. Both Ney and later J. D. Lawrence, Jr., worked under the guidance of Prof. Jesse 

Beams and were awarded doctoral degrees from the University of Virginia. Ney returned to 

Minnesota to accept a faculty appointment in Physics and Astronomy some years later. 

Lawrence and his student, M. Patrick McCormick, of The College of William and Mary stayed 

abreast of Ney and his research activities, as they undertook their early lidar studies of the 

stratosphere. Two graduate students of Ney, James Rosen and Theodore Pepin, had been 

conducting measurements with photoelectric particle counters from balloons from 1965 to 1968 

that showed the variability and characteristics of stratospheric aerosols and their apparent 

systematic changes with time. Before that, Rosen [1964] had been searching for evidence of 

meteoritic debris in the stratosphere. Pepin also evaluated solar occultation methods from the 

balloon platforms for sensing the aerosol layers. Later, Pepin and McCormick teamed up to 

conduct solar extinction measurements using a simple photometer with a diode detector, as part 

of the Apollo-Soyuz Test Project (or ASTP) [Pepin et al., 1977]. Comparison measurements for 

the ASTP mission were obtained near Kansas City by Rosen with his balloon-borne particle 

counter and by McCormick and Fuller with the 48-inch lidar system.

Pepin participated in the RMOP Workshop as a member of its Gas Species Panel and was 

initially interested in making occultation measurements of ozone. Based on the quality of the 

aerosol extinction from the photometer on ASTP, he and McCormick proposed the Stratospheric 

Aerosol Monitor II (SAM II) experiment for flight on the Nimbus 7 satellite in October 1978 and 

also the Stratospheric Aerosol and Gas Experiment (SAGE) that flew a few months later on an 

Applications Explorer Mission or AEM-2 satellite [McCormick et al., 1979; Russell, 1980]. Ed 

Mauldin, III, was the Instrument Manager for SAM II and SAGE. Philip Russell of SRI and 

RMOP Panel members, Grams and Benjamin Herman, were also members of the Science Teams 
18

for both experiments. Nimbus 7 was a polar orbiting satellite, which meant that SAM II obtained

solar occultation measurements only at the high latitudes. But, the AEM satellite operated from 

a highly-precessing orbit at an inclination of 55 degrees, which enabled SAGE to make 

occultation measurements across most latitudes of the southern and northern hemisphere at least 

within the time frame of a month or so. Together, these two satellite experiments provided 

global-scale information on the stratospheric aerosol layer for the first time. Their measurements 

were necessarily limited by the fact that tropospheric cloud tops along the occultation tangent 

path often obscured the setting or rising Sun. Otherwise, their visible to near-infrared (to 1-μm) 

measurements provided many advantages for obtaining the aerosol profiles with good vertical 

resolution and accuracy.

McCormick and Leonard McMaster brought additional researchers to Langley, including 

Thomas Swissler of Systems and Applied Sciences Corporation (SASC) and Adarsh Deepak. 

Soon after, Deepak formed an Institute for Atmospheric Optics and Remote Sensing (IFAORS) 

in Hampton, VA. William Chu, Swissler, and Pi Wang (IFAORS) developed the aerosol and gas 

species (ozone and NO2) algorithms for SAM II and SAGE. Patrick Hamill (SASC), Geoff Kent

(IFAORS), and Glenn Yue (IFAORS) provided detailed assessments of the quality of the aerosol 

profile data. SAM II operated from October 1978 until 1991 and then periodically until near the 

end of 1993. SAGE operated from late February 1979 through November 1981. Validation of 

the aerosol profiles is described in Russell et al. [1981; 1984]. Kent and McCormick [1984] is a 

good summary of stratospheric aerosol optical depth data from SAM II and SAGE. Distributions 

and occurrences of cirrus clouds indicated the low-altitude limit for the extinction profiles from 

SAGE [Woodbury and McCormick, 1983]. SAGE also observed the volcanic plume from the 

Mt. St. Helens eruption of May 1980 and its subsequent effects for the lower stratosphere of the 

northern hemisphere. In addition, SAM II provided good estimates for the first time of the 

wintertime occurrences of the so-named, polar stratospheric clouds (PSC). All during this time, 

Rosen and colleague David Hofmann of the University of Wyoming continued to make balloonborne, in situ measurements of the aerosols, and a number of other research groups conducted

routine measurements of the aerosol layers with their ground-based lidar instruments.

(d) Limb emission and scattering

In the late 1950s and early 1960s Langley navigation and guidance specialists conducted

measurements of the horizon as part of their development of sensor concepts for controlling the 

attitude of spacecraft in Earth orbit. They measured horizon radiances from the ultraviolet (uv) 

to the middle infrared region of the spectrum from a Javelin rocket flight out of the Wallops 

Flight Facility in 1961 [McKee et al., 1964]. They supported the launch of the Ariel 2 radio 

astronomy satellite from a Scout X-3 rocket in March 1964. Ariel 2 carried a photometric 

instrument from the UK Meteorological Office, and Miller [1967] reported on the attenuation of 

ultraviolet light by ozone from its measurements of the Earth’s limb and on their attenuation at 

380 nm by the stratospheric aerosol layer. At about the same time Langley researchers made 

complementary measurements in the near to middle infrared region with sensors mounted in the 

tail of an X-15 research aircraft [Jalink et al., 1968]. Their exploratory measurements of the 
19

infrared horizon eventually led to the radiance measurements and retrievals of atmospheric 

temperature and constituent profiles by the Limb Radiance Inversion Radiometer (LRIR) on 

Nimbus 6 in 1975 and by the LIMS experiment on Nimbus 7 in 1978. John Gille and James M. 

Russell III, Co-Team Leaders of LIMS and members of the RMOP Gas Species Panel, and 

Frederick House of Drexel University provided good estimates of the uncertainties that were 

present in the registration of the satellite-measured, limb radiances [Gille and Russell, 1984; 

Wilson et al., 1979]. 

With the sponsorship of Morris Tepper of NASA Headquarters and of J. D. Lawrence, Jr., the 

first International Interactive Workshop on Inversion Methods in Atmospheric Remote Sounding 

was hosted by M. P. McCormick and A. Deepak (IFAORS) in Williamsburg, VA, in December 

1976. Experts from that research community presented papers and shared their views on the 

information content that could be obtained from limb scattering, emission, and absorption 

measurements. Papers related to the retrieval and interpretation of stratospheric aerosol sizes and 

their optical parameters were presented by Malchow and Whitney [1977] and Chu [1977], and

by the RMOP Panel members, Herman [1977] and Pepin [1977]. They achieved quantitative 

results and placed estimates of uncertainty on the measurements and the retrieved parameters. 

They also showed that it should be possible to validate the various retrieved parameters against 

auxiliary measurements obtained from airborne sensors or with suitable, ground-based and 

balloon-borne techniques obtained along the tangent track viewed by the satellite instrument.

Cox [1981] reported on the significant absorption/emission signatures in the visible from clouds 

composed of water or ice. [Liou, 1981] considered the effects of clouds in the infrared, 

particularly in those spectral regions where the absorbing effects of gaseous H2O, CO2 and ozone 

are absent or weak. He also made recommendations for better measurements of the clouds, 

especially for cirrus (see also next two subsections). Since cirrus cloud particles are significant 

scatterers/absorbers/emitters in the visible through the infrared, they inhibit limb observations of 

the troposphere much of the time. As an example, the Nimbus 7 LIMS measurements were

sensitive to radiances from the tops of cirrus clouds, from PSCs, and to a lesser extent from the 

aerosols of the Junge layer. The Solar Mesosphere Explorer (SME) was a similar, limb-sounding 

experiment launched in October 1981 from a Delta rocket vehicle and managed by the Jet 

Propulsion Laboratory (JPL). SME made measurements of scattered and absorbed light in its 

ultraviolet and visible channels and of thermal emissions with its two infrared channels [Barth et 

al., 1983]. The presence of stratospheric aerosols from the eruption of the El Chichon volcano in 

April 1982 caused the top of that aerosol layer to became the effective low altitude limit for 

accurate retrievals of the SME profiles of ozone and NO2 in the uv and visible, at least for some 

months thereafter. Its infrared radiances from H2O were also severely affected by the aerosols. 

In Section 2 it was noted that Rosen [1971] had inferred that the aerosols were likely composed 

of aqueous H2SO4, which is a very effective absorber/emitter in the middle infrared.

(e) Nadir-viewing photometry or radiometry
20

In the summer of 1969 Langley and Old Dominion University (ODU) sponsored a preliminary 

design study for an operational Earth resources survey system. University faculty and a number 

of Langley researchers participated in that joint effort. The information contained in their final 

report led to the initial Earth applications activities at Langley [Carver et al., 1969]. It also was a 

basis for Langley’s involvement with the RMOP Panel on Water Pollution and the remote 

sensing measurements that they advocated. A natural local collaboration developed between 

Langley and the nearby Virginia Institute of Marine Sciences of The College of William and 

Mary and the Department of Oceanography at ODU and because of the mutual proximity to the 

Chesapeake Bay of all three organizations. Langley Director, Cortright, also formed a Space 

Technology Division as part of his new Space Directorate in 1970, but it soon took on the name 

Space Applications and Technology Division (SATD). Personnel in the Electromagnetics 

Research Branch of IRD were also using microwave radiometers to obtain state parameters of 

the sea surface [e.g., Swift, 1974]. With support from the AAFE Program, they went on to 

conduct airborne and satellite measurements using more-advanced radar scatterometer 

instruments over the next decade.

The first Earth Resources Technology Satellite (ERTS-1) contained sensors fashioned after those 

on Nimbus 4, an early meteorology satellite managed by NASA Goddard. ERTS-1 was 

launched into polar orbit on July 23, 1972 and was renamed Landsat-1. It carried a red-greenblue (RGB) vidicon camera and a 4-channel, multi-spectral scanner (MSS) radiometer operating 

in the infrared. Panel member, Robert Fraser, and colleagues from Goddard combined radiances 

from the MSS with calculated values from a radiative transfer model to estimate the mass of 

particulates in a vertical column of dust transported westward from northern African and across 

the Atlantic Ocean [Fraser, 1976]. Bruce Wielicki of Langley began to use Landsat MSS data by 

1980 to develop a higher-resolution source of “cloud truth” for calibrating the cloud properties 

determined from the lower spatial resolution, meteorological satellites [Wielicki and Welch, 

1986]. Although the Landsat MSS measurements suffered from an inadequate calibration 

standard for their radiances, they laid the ground work for the improved MODerate-resolution 

Imaging Spectro-radiometer (MODIS) instruments on the EOS satellites that are operating today 

[Shenk and Salomonson, 1972; Salomonson et al., 1989].

In the late 1950s Langley was focused on developing unmanned, large inflatable balloons to 

serve as passive communications satellites and to provide estimates of atmospheric drag in lowEarth orbits. Such orbital decay information was important for defining the controlled descents 

of the manned spacecraft that would soon follow. Knowledge about orbital drag was also 

important for the Mars Viking spacecraft, and the Viking Project was at the top of Cortright’s 

agenda during the late 1960s and for its Mars landings in 1976. Remote observations of Mars 

had already revealed occurrences of persistent dust storms at the surface of Mars, and those 

events became a focus of meteorological studies by Seymour Hess of Florida State University 

and Robert Henry of Langley soon after the spacecraft landed on Mars [Tillman et al., 1979].
21

Suomi and RMOP Panel member, G. D. Robinson, were more interested in making satellite 

measurements of Earth’s radiation budget, however [SMIC, 1971]. Joel Levine, who joined 

Langley Research Center in the late 1960s, was focused on studies of the atmospheres of other 

planets, including Mars. But prior to that time, he and Al Arking of the Goddard Institute for 

Space Studies (GISS) had reported on the relatively low, reflectivity or albedo that they obtained 

for the Earth and its atmosphere based on quasi-global data from TIROS VII [Arking and 

Levine, 1967]. Even so, they were mindful that the visible-channel reflectivities from TIROS 

needed to be corrected upward due to a probable degradation of its sensors during launch. 

Several years later, Vonder Haar and Suomi [1971] reported on their analyses of 39 months of 

radiation budget measurements. They obtained an estimate of the mean global albedo of 30% 

and found a net radiation balance, at least within the measurement accuracies of the radiometers.

In the mid-1970s Langley researchers, Linwood Callis, Robert Boughner, and V. Ramanathan 

(NASA/NRC Postdoctoral Fellow) turned their attention to the development of radiativeconvective models and calculated the effects of scattered radiation from the Earth’s surface and 

the atmosphere in the uv, visible, and infrared. Bruce Barkstrom, a radiation scattering and 

transfer specialist, was a faculty member of George Washington University from 1974-79 in its

Joint Institute for the Advancement of Flight Sciences (JIAFS) that was located at Langley. 

Others were considering how to improve on the measurement of Earth’s radiation budget, in part 

due to the directives from the RMOP Panel headed by Suomi and in response to his keen interest 

in the topic. G. L. Smith, Gary Gibson, Edwin Harrison, and colleagues of SATD conducted 

orbital analyses and offered Earth-viewing strategies for obtaining more complete measurements 

of Earth’s radiation budget from low Earth orbit [Smith et al., 2010]. They credit George Sweet 

of Langley for an initial satellite concept of three spherical integrating detectors, having different 

color coatings of black, white, and aluminum and thus different skin temperatures. His concept 

was titled Long-time Zonal Earth Energy Budget Experiment (LZEEBE), and its prospects were 

judged along with two other proposed measurement concepts from Suomi of Wisconsin and 

from Vonder Haar of Colorado State [Yates, 1977]. The LZEEBE and the Wisconsin concepts

required dedicated satellite platforms and orbits that were different from those of the operational 

TIROS satellite system. Although the LZEEBE concept was not selected for further funding, it 

eventually led to the design of Langley’s Earth Radiation Budget Experiment (ERBE) that would 

be launched from Space Shuttle in 1984. Barkstrom was hired by Langley in 1979 to be

Experiment Scientist and Science Team Leader of ERBE (see Sections 4 and 5). 

Prior to that time, G. L. Smith of Langley served as a member of the Experiment Teams for the 

Earth Radiation Budget (ERB) instruments on both Nimbus 6 and 7. The Nimbus satellites were 

polar orbiters and had the same sampling issues as TIROS in both space and time for the 

radiation budget parameters that they obtained, in addition to the adequacy of the calibrations of 

their radiances. Smith was concerned with how to relate wide FOV radiometer measurements to 

radiances emitted at a finer spatial resolution from the top-of-atmosphere [Smith and Green, 

1981]. There were also concerns about the low-resolution radiances measured at just two local 

times from polar orbiters. To that end, Patrick Minnis and Harrison analyzed GOES satellite 

imagery to estimate the effects of the diurnal variability of cloud radiances [Minnis and Harrison, 
22

1984]. McKee and Cox [1974] developed models of the scattering of visible radiation by clouds 

of finite horizontal extent, and Feddes and Liou [1977] considered the effects of multi-layered 

clouds on the upwelling radiances. All of these early results were used as an aid in the design of

the ERBE experiment that was launched in 1984. Excellent reviews of the radiation budget 

studies up to the time of ERBE can be found in House et al. [1986] and Smith et al. [2010].

Studies had been conducted on the transfer of radiation within the atmosphere before there were 

satellite sensors for making top-of-atmosphere measurements. For instance, Panel member, 

Robinson, co-authored one of the earliest theoretical studies of the loss of radiant energy to 

space, due to infrared emissions from the surface, from cloud layers, and from the diffuse water 

vapor, carbon dioxide, and ozone molecules [Goody and Robinson, 1951]. In addition, Suomi 

and colleagues obtained some initial measurements of profiles of net radiation in the atmosphere 

[Suomi et al., 1954]. John Gergen in collaboration with Ed Ney and colleagues at U. of 

Minnesota also conducted balloon-borne measurements of total atmospheric infrared radiation 

with their “Black Ball” integrating radiometers [Gergen, 1957]. However, the Black Ball 

measurements presented a number of uncertainties. Suomi’s flat plate radiometersonde

measurements were more consistent and easier to relate to the underlying surface or cloud scene. 

He also found that radiometersonde measurements near the tropopause were quite sensitive to

the presence of thin cirrus and ozone and to variations in upper tropospheric water vapor. 

Pilipowskyj et al. [1968] determined that the downward-directed, infrared irradiance (or flux)

that they measured in spring of 1965 from the subtropical lower stratosphere could not be 

explained by the presence of gaseous emitters. They postulated that the excess was due to large 

numbers of stratospheric aerosols of small radius, presumably composed of concentrated, 

aqueous sulfuric acid according to the independent, vapor pressure measurements of Rosen 

[1971]. The quantitative effects of each of these radiative sources are still be evaluated today,

but are being based now on combinations of better radiometric and lidar measurements, as will 

be noted in Section 6.

The role of clouds on the radiative balance, energetics, and circulation of the atmosphere was 

being considered well before the RMOP Workshop, based in part on the early balloon-borne and 

satellite-based radiometric measurements. Early on, Greenfield and Kellogg [1960] reported on 

their calculations of the spectral nature of the atmospheric infrared radiation fields that one could 

expect to observe looking down on the troposphere, perhaps eventually from a meteorological 

satellite. They showed that only about one-third of the surface radiation escapes in the tropics in 

the so-called “window region” from 8 to 13 micrometers. In other words, that “window” is not 

at all transparent. On the other hand, at the middle latitudes about two-thirds of the upward 

emission originates from the ground; the water vapor content of the atmosphere is much lower at 

middle latitudes. Similar variations with latitude were observed using the broadband radiation 

sensors of the early TIROS satellites [Nordberg et al., 1962]. Gergen [1965] also observed large 

variations with both time and space from balloon measurements of the outgoing infrared 

radiation at nighttime, and he thought that the changes were due primarily to cirrus clouds. Liou 

[1986] and Schiffer and Rossow [1983] concluded that the effects of cirrus clouds were one of 

the major unsolved components in weather and climate research. How to estimate the effects of 
23

aerosols and clouds on the transfer of radiation was addressed analytically by David Adamson of 

Langley [Adamson, 1975] and on the inference of the sea surface temperatures (SSTs) from 

satellite imagery by Xu and Smith [1986] and Xu and Sun [1991]. Section 6 points to progress 

that has been made on that issue by Langley researchers in the current decade, based on passive 

and active remote sensing techniques and combinations of satellite datasets obtained with them.

(f) Aerosol polarimetry

Diran Deirmendjian of the RAND Corporation and Alex Green of the University of Florida 

developed theoretical models for the detection of aerosol scattering from measurements of the 

intensity patterns of the solar aureole [Deirmendjian, 1959; Green et al., 1971]. However, they 

stressed that more work was needed to sort out the effects of the underlying surface reflectance 

on the scattering patterns. Hariharan [1969] assembled a breadboard photometer and obtained 

transmission measurements at three separate viewing angles from the beam direction and, thus, 

characterized the aerosols from their polarizing effects. Since the precision of his results were 

quite good, the polarimeter concept appeared promising for eventual operation from an airborne 

or a Space platform, as envisioned earlier by RMOP Panel Member Zdenek Sekera of UCLA. 

The characterizations of aerosol and cloud particle distributions were a focus of the 1976 

Workshop on Inversion Methods in Atmospheric Remote Sensing sponsored by Tepper and 

Lawrence and hosted by M. P. McCormick and A. Deepak in Williamsburg, VA. In 1971 Prof. 

Sekera showed that the effects of aerosols and clouds on the transfer of atmospheric radiation

depend on the optical properties of the scattering/absorbing particles. He and Jacob Kuriyan

went on to model aerosol effects on the flux transfer of radiation through the atmosphere, and 

they checked their solutions against multi-spectral extinction measurements and angular 

scattering measurements via a polarimeter [Kuriyan, 1977]. They also envisioned making such 

measurements from a satellite. Deepak [1977] and Green and Klenk [1977] considered how to 

invert scattering patterns within the solar aureole and how to relate those patterns to the 

properties of the intervening aerosols. Twitty et al. [1976] conducted airborne measurements of 

the solar angular scatter using a scanning photometer and then inverted them to obtain aerosol 

size distributions. Their findings agreed reasonably with in situ measurements of the aerosols. 

Previously, Panel Member Al Holland demonstrated that non-spherical aerosols would also 

reduce the fraction of energy in the backscatter direction, as compared with that from spherical 

particles [Holland and Gagne, 1970]. Thus, it seemed likely that remote measurement 

techniques could be employed for the characterization of ice versus water clouds and for 

identifying the sources of aerosols in tropospheric haze layers, perhaps even from a satellite.

Panel Member, Ben Herman, described methods for inverting lidar angular scatter and solar 

extinction data for the determination of aerosol size distributions [Herman, 1977; Herman et al., 

1971]. Platt [1973] used lidar and radiometric measurements of cirrus clouds to obtain better 

estimates of their effects on the radiative budget, as recommended in the SMIC and RMOP 

reports. At about the same time, Gibson et al. [1977] reported that the backscatter and extinction 
24

coefficients for cirrus that they observed could not explained, if the cloud particles were spheres 

or randomly-oriented. Their findings indicated that one ought to be able to learn more about the 

nature of the ice crystals in the clouds from measurements of their depolarization ratios. Once 

again, it was clear that improved measurement methods would be needed to sort out the role of 

both aerosols and clouds on the transfer of radiation in the atmosphere and for specifying their 

effects properly in forecast studies with climate models.

Pioneering studies of the reflectivity of surfaces and suspended aerosols were also conducted in 

the laboratory by Jack Margolis and Dan McCleese of JPL and later by RMOP Panel Member, 

Robert Fraser, of NASA Goddard [Margolis et al., 1972; Mekler et al., 1984]. Their experiments 

provided important data for the verification of theoretical calculations of the diffuse reflectivity 

and the scattering of radiances by a layer of aerosols. Kaufman and Joseph [1982] devised 

methods for extracting quantitative information on surface albedo and aerosol extinction from 

satellite imagery. They employed a two-stream approximation for radiative transfer that William 

Meador and Willard Weaver of Langley used for planetary atmospheres [Meador and Weaver, 

1980]. Kaufman and Joseph showed that those methods were also successful when applied to a 

Landsat image of Saharan dust transported westward off the coast of North Africa.
25

4 Research on aerosols and clouds from the time of RMOP to the early 1980s

This section summarizes findings about aerosols and clouds from the early period of satellite 

observations, and it places them in the context of similar research programs elsewhere. To begin

with, the U. S. Atomic Energy Commission (AEC) had been assigned the responsibility of 

developing regulations, of monitoring for the effects of atmospheric bomb debris, and for the 

dispersion of radioactive pollutants from commercial nuclear power plants in accordance with 

the Atomic Energy Act Amendments of 1954. Elmer Reiter of Colorado State University

prepared a excellent compendium for AEC on the relationships between the distributions of 

radioactive bomb debris, stratospheric aerosols, and ozone [Reiter, 1971]. Elterman et al. [1969] 

and Rosen [1969] also contain extensive descriptions of what was known in 1971 about the 

distribution and character of the stratospheric aerosols. Early field measurement programs 

showed that there were correlations between the radioactive debris, aerosols, and ozone

[Kroening and Ney, 1962; Rosen, 1968; and Danielsen and Mohnen, 1977]. Further, Rosen et al. 

[1975] reported on positive correlations between stratospheric aerosols and ozone from series of 

balloon-borne profile measurements at selected station locations. They also showed that the 

altitude of the peak of the aerosol layer was closely related to the height of the tropopause and its 

variation with latitude and season. Reiter explained those correlations as being due to the effects

of atmospheric transport on their respective distributions.

Radiative effects of the volcanic aerosols from the 1963 eruption of Mount Agung in Indonesia 

were modeled successfully by Hansen et al. [1978]. They showed how the aerosols cooled the 

Earth’s surface and warmed the lower stratosphere, based on detailed information that was 

reported on the composition, size, and distributions of the aerosols [e.g., Cadle and Grams, 1975] 

and on the concurrent temperature observations. Cadle et al. [1976] and Itabe et al. [1977] 

simulated the global dispersion of the observed aerosol cloud from the 1974 eruption of Mount 

Fuego in Guatemala using state-of-the-art, two-dimensional transport models. Later, Karin 

Labitzke observed an increase of several degrees from her meteorological analyses at the Free 

University of Berlin of northern subtropical temperatures in the lower stratosphere following the 

1982 eruption of the El Chichon volcano in the Philippines. McCormick and colleagues

associated that warming with the enhanced aerosol extinction that they measured along

latitudinal transects with their airborne 14-in ruby lidar [Labitzke et al., 1983]. Shortly

thereafter, William Bandeen assembled a group of experts at NASA Goddard to assess the 

effects of aerosols and gases from El Chichon for the retrieval of Earth/atmosphere temperature

and ozone from the satellite sensors of that time [Bandeen and Fraser, 1982]. Bandeen’s report

includes findings of Michael King and Fraser of Goddard on the combined radiative effects of 

the volcanic aerosol layers for measurements of the atmosphere by remote sensors. They found

that sensor signals in the visible and ultraviolet were definitely affected; temperatures obtained 

from the infrared sounders were also affected slightly.

The National Air Pollution Control Administration (NAPCA) was established within the U. S. 

Department of Health, Education, and Welfare in 1965. NAPCA was primarily concerned with 

controlling vehicular emissions, but it also supported programs for the measurement of particle 
26

concentrations and the dispersal of smoke plumes from stationary power plants [e.g., Pilat and 

Ensor, 1970]. Both monitoring and regulatory functions were taken over by the EPA when it 

was established in 1971. The effects of tropospheric haze layers on the climate had also been 

estimated from a rather, straightforward calculation by Charlson and Pilat [1969], but they were 

careful to note the importance of having better information about the relative magnitude of the 

backscattering and absorption coefficients of the haze aerosols in addition to their total 

attenuation. Herman and Browning [1975] carried out more detailed radiative transfer 

calculations of the reflected solar flux, along with the sensitivity of those results to the primary 

variables of solar elevation angle, ground albedo, and aerosol refractive index. They showed that 

haze aerosols can either increase or decrease the reflected flux, depending on the underlying 

ground albedo. They expected a similar outcome for haze layers overlying a low cloud deck.

Rasool and Schneider [1971] conducted initial calculations of what to expect about the combined 

effects of increases in atmospheric carbon dioxide and in aerosols on Earth’s climate. James 

Hansen of NASA GISS and James Pollack of Cornell University also calculated reflectivity in 

the near infrared from both liquid water and ice clouds and then compared the values with

observations. Their goal was to develop better models of the effects of clouds for the transfer of 

atmospheric radiation [Hansen and Pollack, 1970].

As indicated earlier in Section 3e, observational studies of tropospheric haze layers were initiated 

using multi-spectral scanner data from Landsat-1 [Fraser, 1976] and with the Advanced Very 

High Resolution Radiometer (AVHRR) sensors on the NOAA satellites [Griggs, 1983]. Similar 

imagery was also available from the SMS or GOES sensors of NOAA and from the Defense 

Meteorological Satellite Program (DMSP) sensors of the Department of Defense (DOD). 

Weinman et al. [1981] evaluated the sensitivity of such sensors versus wavelength by calculating 

the effects of smoke clouds from brush fires that one should expect to see with a nadir-viewing, 

infrared channel centered at 11.5 micrometers, as opposed to radiances obtained at shorter 

wavelengths. The launch of TIROS-N in 1979 also marked the start of the routine monitoring of 

sea surface temperatures (SST) using AVHRR measurements [e.g., Ohring et al., 1989]. Thus, 

there was a critical need for the development of additional remote sensing techniques, as 

recommended by the RMOP Panel. The obvious goal was to obtain quantitative information 

about aerosols and clouds and their effects on the radiative budget of the Earth’s atmosphere.

The World Meteorological Organization (WMO) conducted an international Global Atmospheric 

Research Program (GARP) in the 1970s to obtain more comprehensive measurements of the 

troposphere and stratosphere for the overall purpose of improving general circulation and 

weather forecast models. Primary participants in addition to the U.S. were France, Great Britain, 

Japan, and the USSR, although scientists from about 20 nations were involved. The extensive 

BOMEX field experiment of the summer of 1969 was a precursor of the GARP Atlantic Tropical 

Experiment or GATE of 1974. Fleming and Cox [1974] of Colorado State University modeled 

the divergence of the net radiation in the presence of cirrus clouds in anticipation of the activities 

of GATE. They showed that the radiative budget at the surface of the Earth was most dependent 

on shortwave optical thicknesses of the clouds, while broadband emissivity was more important 

for their effects on the atmospheric heat budget. They verified the calculations with the aid of 
27

satellite photometry and cloud imagery obtained during BOMEX, plus some limited in situ and 

lidar measurements. William Shenk and Robert Curran of NASA Goddard had also begun to 

classify tropical cloud imagery, according to their broadband spectral signatures as seen with 

Medium Resolution Infrared Radiometer (MRIR) on Nimbus 3 during BOMEX [Shenk and 

Curran, 1973; Shenk et al., 1976]. They were able to discriminate between clear skies and cirrus 

cloud cover, using the MRIR radiances in the water vapor region of 6.5 to 7.0 μm. Their studies 

led to the inclusion of a Temperature-Humidity Infrared Radiometer (THIR) sensor on Nimbus 6 

and 7 as an aid to interpreting the measurements from the Earth radiation budget (ERB) 

instruments that were also onboard [Stowe, 1984]. 

The Nimbus 7 spacecraft of 1978 carried the SAM II sensor from Langley. SAM II obtained 

measurements of stratospheric clouds as well as aerosols, but only for the high latitudes because 

of the limitation for viewing an occultation event of the rising or setting Sun from a highinclination (98 ̊) polar orbit. The AEM-2 satellite of 1979 had an orbital inclination of only 56 ̊. 

Thus, its SAGE instrument obtained measurements of stratospheric particles across low and 

middle latitudes that were complementary to those of SAM II [Kent and McCormick, 1984]. In 

fact, the SAGE aerosol extinction measurements were also very useful for characterizing the 

dispersion of the volcanic layers from the eruption of Mt. St. Helens of 1980 [Deepak, 1982]. 

Prof. John Stanford of Iowa State University had been studying polar stratospheric clouds 

(PSCs), particularly their relationship with stratospheric water vapor and temperature [Stanford, 

1973; Stanford, 1977; Douglass and Stanford, 1982]. The SAM II experiment gave new 

information on the distribution and occurrence of the PSCs, and the airborne 14-in lidar of 

Langley provided information on the phase of the cloud particles from measurements of their 

depolarization ratios [Kent et al., 1986]. The Nimbus 7 LIMS experiment also observed regions 

of enhanced infrared limb emission in Arctic winter, most likely from PSCs. Austin et al. 

[1986a] were able to partially corroborate that inference based on their calculations of ice 

saturation using co-located temperatures from the Stratospheric Sounding Unit (SSU) and water 

vapor profiles from LIMS. At that time the existence of PSCs was largely a curiosity. 

Information about PSCs was limited to model studies for their formation and of the

microphysical growth and decay of their particles [Steele et al., 1983]. Until the mid 1980s it 

was still unclear whether or not PSCs contributed to a heterogeneous loss of ozone in polar 

springtime [e.g., McCormick and Trepte, 1986].

Nevertheless, the wealth of new data on PSCs, aerosols, and water vapor from SAM II, SAGE, 

and LIMS prompted Robert Watson and Robert Schiffer of NASA Headquarters to sponsor a 

Workshop on PSCs that was held in Virginia Beach, VA, in June 1983. Patrick Hamill of San 

Jose State University, Adarsh Deepak of IFAORS, and Leonard McMaster of Langley hosted the 

Workshop. They brought together a group of 20 experts, including James Pollack, Brian Toon, 

and Ed Danielsen of NASA Ames, James Hansen of NASA GISS, Andrew Heymsfield of 

NCAR, John DeLuisi and Dieter Kley of the NOAA Aeronomy Laboratory, and David Hofmann 

of University of Wyoming, among others. Attendees were grouped into two panels: Radiation 
28

Balance, Climate and Dynamics (led by Hansen) and Stratospheric Chemistry, Water Vapor, and 

Cloud Microphysics (led by M. P. McCormick). Much of the discussion within each panel was 

focused on trying to understand the nature of the satellite, airborne, balloon-borne, and groundbased observations of the PSCs and their precursor species. Each group formulated a number of 

outstanding questions, as summarized in the PSC Workshop Report [Hamill and McMaster, 

1984]. Their recommendations for further studies became the basis of research focused on 

PSCs, stratospheric aerosols, and heterogeneous chemical processes over the following decade,

supported with funds from NASA’s Upper Atmospheric Research Program.
29

5 Earth observations in the Space Shuttle era

(a) Changing priorities for satellite measurement technologies at Langley

Proposals were solicited by NASA as early as the mid 1970s for the design, assembly, and 

eventual demonstration of Shuttle-borne instruments for making improved observations of the 

Earth and its atmosphere. Many of the measurement concepts were an outgrowth of or 

reinforced by the RMOP Report and supported by funds from the AAFE Program. It was hoped 

that other Federal agencies or commercial interests might decide to underwrite the operational 

use of a prototype instrument upon its successful demonstration by NASA. For example, for the 

advancement of weather forecasting NASA had already formed a partnership with NOAA to 

improve the technology of the remote sensors for its weather satellites. Column ozone 

measurements were also demonstrated by NASA on Nimbus 4 and 7, and those prototype 

sensors became the basis of operational ozone measurements using a series of second-generation, 

Solar Backscatter Ultraviolet (SBUV 2) instruments beginning with the NOAA-9 spacecraft in 

1985 and continuing through NOAA-N’ of 2009. NASA also received a Congressional mandate 

to monitor atmospheric ozone as part of the Clean Air Act amendments of 1977. That 

monitoring activity began with the Total Ozone Mapping Spectrometer (TOMS) on Nimbus 7 in 

1978 and continued on with similar satellite instruments on the Meteor 3 spacecraft of Russia in 

1991 and on Earth Probe from a Pegasus launch in 1996. Total ozone is being measured today

with the Ozone Monitoring Instrument (OMI) on EOS Aura that was put into orbit in 2004. The 

OMI instrument was constructed by the Netherlands for NASA and is a cooperative effort with 

Finland.

Space Transportation System (STS) is the formal name for NASA’s Space Shuttle program, 

which was designed to ferry astronauts and instrument payloads to low Earth orbit (LEO). From 

the point of view of Earth observations STS was touted as an economical way to gather data with

an engineering model of an instrument, return it to Earth, and then to improve the instrument and 

re-evaluate it on another flight. The period for that operational approach extended from the early 

1980s to the mid 1990s, when the emphasis for the use of the Shuttle was changed toward the 

construction of the International Space Station (ISS). Since the Shuttle was launched from Cape 

Canaveral, it was not possible for an instrument to be tested from or inserted into the highinclination (polar), Sun-synchronous orbits that were the norm for NOAA’s TOVS and NASA’s

Nimbus satellites. On the other hand, the 57 ̊ inclination orbit of Space Shuttle was ideal for the 

launch of the ERBE and SAGE II instruments on the Earth Radiation Budget Satellite (ERBS) in 

1984, for the launch of the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere 

Research Satellite (UARS) in 1991, and for the demonstration of the Lidar In-space Technology 

Experiment (LITE) from the cargo bay of STS-64 in 1994. The focus of this section is on those

four Earth observation experiments from Langley. Although this review of the experiments is 

necessarily very brief, the reader can easily access descriptions of their design and operations 

and of an extensive set of published scientific findings based on their measurements. Findings

about the composition of the volcanic aerosols will also be noted later in this section, as deduced 

from flight observations on STS-45 in March 1992 of the Atmospheric Trace Molecule 

Spectroscopy (ATMOS) instrument of C. Barney Farmer and Michael Gunson of JPL.
30

In the early 1980s NASA and Langley changed their focus from studies of the urban to regionalscale pollution that was of interest to the EPA toward studies of long-range transport of aerosols 

and source gases and their consequences for climate and air quality on the global-scale. NASA 

concluded that its airborne campaigns should be more broadly supportive of the validation of 

satellite experiments and/or focused on obtaining a better understanding of specific atmospheric 

chemical, microphysical, and/or radiative processes [e.g., CCSP, 2009]. Thus, NASA shifted the 

emphasis of its Earth observation and applications programs toward the development of sensors 

that could operate from satellites or aircraft and provide data on the critical environmental issues 

of the current and coming decades. However, NASA also experienced cutbacks in the money 

that was available for the development and demonstration of new sensing concepts and improved 

technologies. Much of the success that was achieved from the mid 1980s and through the 1990s 

was a result of the funding that had been available through the AAFE Program in the 1970s and 

because of the urging of Morris Tepper and his three RMOP Panels.

During the Cortright era, Robert Hess and Frank Allario of Langley made the transition from 

plasma physics research and into the newly-formed ESSD headed by William Michaels. They 

and their colleagues, James Hoell and Glenn Sachse, began to develop gas lasers and solid state 

laser technologies for the remote sensing of the atmosphere. They also applied the laser 

heterodyne spectroscopy (LHS) technique for measurements of minor and trace gases from 

onboard aircraft. By 1982 much of their laser technology work was relocated to the Electronics 

Directorate, where Hess and his team became focused on the measurement of Doppler winds and 

gas species. Hess retired in 1995 after logging a distinguished, 50-year career [Hansen, 1995]. 

Allario had been Head of the Laser Physics and Applications Section, while he was in ESSD and 

AESD. In December 1982 he was selected as Chief of the Flight Electronics Division (FED), the 

new name for FID after 1976. Allario went on to lead the Electronics Directorate until his 

retirement in 1996. In all of those positions he advocated for opportunities to demonstrate active 

remote sensors from Space. Today, the members of the Laser Remote Sensing Branch of 

Langley’s Engineering Directorate are continuing to refine and apply those technologies for the 

sensing of the atmosphere with an eye toward making measurements of atmospheric winds from 

a Space platform [e.g., Koch et al., 2007].

The current retrospective does not include an account of the early work on remote measurements 

of water quality. Those activities were de-emphasized at Langley in the early 1980s, in part due 

to the demonstrated success of the Coastal Zone Color Scanner (CZCS) experiment of 

NOAA/NASA Goddard (e.g., see Section 5 of Remsberg [2011]). The CZCS measurement 

concept was defined in the early 1970s and operated successfully on Nimbus 7 from 1978 to 

1986, providing multi-spectral imagery similar to that from the MSS on Landsat but with 

improved S/N and with corrections for the intervening atmospheric aerosols above water 

surfaces [Hovis et al., 1980]. The Langley organizations of SATD and ESSD and their personnel 

were reformed initially in 1976 into two divisions focused on remote sensing studies of the 

atmospheric and marine environment, respectively—AESD headed by Lawrence and the Marine 
31

Applications and Technology Division (MATD) headed by Brian Pritchard. However, by 1982 

many of the researchers in MATD had been integrated into the atmospheric and radiation budget 

research activities within AESD. At about the same time McCormick’s Branch (ARB) was 

moved to AESD from IRD. A Radiation Sciences Branch (RSB) was also formed under the 

leadership of Edwin Harrison. However, the satellite Earth observation programs were still 

managed from within Langley’s Projects Office. AESD was becoming well-known as the Earth 

Science organization within Langley; it was renamed simply as the Atmospheric Sciences 

Division (ASD) in 1982.

All during the 1970s researchers in IRD and in FID/FED had been demonstrating their 

considerable expertise toward the application of microwave remote sensing techniques 

[Croswell, www.ieeeghn.org]. Linwood Jones and Calvin Swift conducted airborne 

measurements with a radar scatterometer funded by the AAFE Program in support of similar 

measurements of sea surface winds from Skylab [Jones et al., 1981]. Jones was a member of the 

Science Team for a Seasat-A Scatterometer System (SASS) that operated successfully for three 

months in 1978 on the Seasat-1 satellite managed by JPL [Born et al., 1979]. Another 

instrument on Seasat was a copy of the scanning multichannel microwave radiometer (SMMR) 

of NASA Goddard that was flown on Nimbus 7 later that same year. Nimbus 7 SMMR was very 

successful and obtained nearly 9 years of sea surface temperatures, sea ice coverage, sea-surface 

winds, column water vapor, and rainfall rates [Gloersen et al., 1984]. The Langley group also 

had competition from Charles Elachi of JPL, who was preparing his Shuttle Imaging Radar (SIRA) for observations of the Earth’s surface as part of an engineering flight of the Space Shuttle in 

November 1981 [Elachi et al., 1986]. Even so, the deletion of a proposed National Oceanic 

Satellite System (NOSS) [Ruttenberg, 1981] from the NASA/NOAA budget of FY 1982 was a 

key factor in the decision by Langley Director, Donald Hearth, to transition away from satellite 

microwave remote sensing activities. Funding was also reduced in the NASA/NOAA budget for

any further development of the relevant microwave technologies. Langley funded a final study 

showing that it was feasible to transfer their current technologies to other Federal agencies and/or 

commercial users [Akey, 1981]. Croswell, Jones, and Swift left Langley shortly after and carried 

on with their successful careers in the private sector and/or academia.

(b) ERBE and SAGE II on the ERBS satellite of 1984

Dedicated measurements of Earth’s radiation budget were begun with the ERB instruments on 

the polar orbiting satellites Nimbus 6 and 7, even though their measurements were taken at just 

two local times each day. Instead, Langley’s ERBE instrument as launched on ERBS from the 

Space Shuttle Challenger (STS-41G) in 1984 was in a slowly precessing orbit. ERBE obtained

measurements across most all local times in about 2 months and provided some information on

the diurnally-varying effects of clouds. ERBE consisted of a scanner and a non-scanner

radiometer package. The scanner package contained three scanning radiometers—a shortwave, a 

longwave, and a total radiometer. The nonscanner package consisted of two wide-field-of-view 

(WFOV) radiometers for measuring shortwave and total radiation and for viewing the entire 

Earth disc. ERBE also had two medium-field-of-view (MFOV) radiometers that observed over a 
32

much smaller solid angle. The nonscanner also included a solar monitoring radiometer. 

Instrument packages identical to these were flown on the polar orbiters, NOAA-9 and NOAA10, but with different Equator crossing times (0230 and 0730 LST, respectively). Barkstrom and 

Smith [1986] provides an excellent overview of the rationale for and initial results from ERBE.

Although Langley was assigned the responsibility for the Earth Radiation Budget Project (and 

ERBE) in 1978, the final experiment design was a melding of three separate proposals including 

one from Langley, another from Suomi of University of Wisconsin and a third proposal headed 

by Vonder Haar of Colorado State University [Yates, 1977]. Descriptions of the early 

developments that led to the ERBE concept can be found in Barkstrom and Hall [1982] and in 

more detail in Smith et al. [2010]. Several individuals at Langley were particularly important to 

the effort, including George Sweet, Bruce Barkstrom and the 17 members of his ERBE Science 

Team, Cal Broome and Charles Woerner (Project Managers), Jack Cooper (Experiment 

Manager), Glenn Taylor (Instrument Manager), Mike Luther and Leonard Kopia (Instrument 

Engineers), and James Kibler (Head, Data Management Team). Paul Holloway, Director for 

Space at the time, gave his full support to the effort. Harry Press, who earlier in his career was 

an aeronautical researcher at NACA Langley [e.g., Press and Houbolt, 1955], was Manager of

the NASA Headquarters Meteorology Program Office in 1978 and located at NASA Goddard. 

In accordance with recommendations from an independent National Academy of Science Panel, 

Press made certain that the instrument package would meet the scientific requirements for 

obtaining improved measurements of Earth’s radiation budget. The final selection was made by 

Morris Tepper, and shortly thereafter the core science effort at Langley was consolidated into 

Lawrence’s AESD within the Radiation Sciences Branch, headed by Edwin Harrison.

The ERBE nonscanner operated for 15 years and the scanner for five. The ERBE datasets and 

the validation criteria for judging their acceptability can be found in Barkstrom et al. [1989]. 

Wielicki and Green [1989], Charlock and Ramanathan [1985], and Ramanathan et al. [1989] 

determined the effects of cloud radiative forcing on the radiation budget using the ERBE data. 

In fact, Harrison et al. [1990] found that clouds cool the Earth on the average and for all seasons. 

On the other hand, Prabhakara et al. [1993] used ERBE data to show that cirrus clouds are very 

effective in trapping the outgoing longwave radiation. ERBE also provided the first accurate 

diurnal variations of regional radiative parameters over the globe for climate studies, and its data 

represented a new “radiation standard” for validating and improving general circulation models 

and for the purpose of assessing model studies of climate sensitivity.

ERBS also carried aloft the Stratospheric Aerosol and Gas Experiment II (or SAGE II)

[McCormick et al., 1989]. Note that SAGE I operations had ended in November 1981 due to the 

failure of its power systems. That meant that no occultation measurements had been obtained for 

the low and middle latitudes during the period directly following the eruption of El Chichon in 

April 1982. Principal Investigator, M. P. McCormick of Langley, knew that such a data gap in 

the aerosol record was a missed opportunity; he and his colleagues at Langley and at Ball 

Aerospace looked forward to continuing those measurements with SAGE II on ERBS. The 
33

Science Team was expanded from that of SAGE I to include Derek Cunnold, Giorgio Fiocco,

Motokazu Hirono, Ron Nagatani, Jacqueline Lenoble, David Murcray, and David Rind 

[McCormick, 1987]. As it turned out, SAGE II operated successfully from 1984 to 2005. SAGE 

II monitored the decay of the aerosol layer from several years after the El Chichon event and its 

approach to “background conditions” and then witnessed the immense eruption cloud from the 

Mt. Pinatubo volcano in June 1991 and its subsequent dispersal and implications for tracer 

transport [e.g., Pitari, 1993]. Joe Zawodny, Science Mission Manager at Langley for ERBS, 

noted recently that the 21-year record of aerosol data from SAGE II is almost as important as its 

record of ozone measurements. Early on, the SAGE I data of 1979-1981 and the SAGE II data 

1984-1990 were used to generate a climatological distribution for the “background” stratospheric 

aerosols [Hitchman et al., 1994]. Further, the long time series of aerosol data from SAGE II, as 

described by Thomason and Peter [2006], is important for the assessments of climate models for

the effects of volcanic aerosols on the global surface temperatures. 

In the early 1980s the inability of stratospheric chemistry/transport models to properly simulate 

the wintertime abundance on nitric acid vapor (HNO3), as measured by the Nimbus 7 LIMS 

experiment, led to the prospect that heterogeneous chemical reactions were converting NOx to 

HNO3 on surfaces of stratospheric aerosols [Austin et al. 1986b]. A co-author on that 

LIMS/model study, Susan Solomon of the NOAA Aeronomy Laboratory, became focused on the 

likelihood that heterogeneous chemical processes on surfaces of PSC particles were releasing 

chlorine radicals that were responsible for the catalytic loss of polar stratospheric ozone 

[Solomon et al., 1986]. The Airborne Antarctic Ozone Experiment (AAOE) campaign of 1987 

obtained crucial measurements of ozone and chlorine monoxide (ClO) that essentially confirmed 

the hypothesis of Solomon et al. Upon this realization of the causes of the observed loss of polar 

ozone in springtime, it became clear that the measurements from SAM II and SAGE II could 

provide the critical time series data about aerosol surface area versus altitude and latitude for 

modeling the effects of those heterogeneous reactions [see Thomason and Peter, 2006, and 

references therein]. Although the aerosol extinction measurements of SAGE II were similar to 

those of SAGE I, the SAGE II instrument contained 4 aerosol channels (from 0.385 to 1 μm) for 

estimating aerosol concentrations and the size distribution parameters that were needed for the 

calculation of aerosol surface area. Extensive correlative measurements were conducted for

those aerosol parameters [Russell and McCormick, 1989], in accord with the stated goal of Don 

Lawrence toward the attainment of more useful, quantitative information from the satellite-borne 

remote sensors. 

The validity of the volcanic aerosol parameters from the SAGE II data was also evaluated by 

Glenn Yue, Lamont Poole, M. P. McCormick, Robert Veiga, and Pi Wang from Langley, at least

for the 6-month period following the Pinatubo eruption [Yue et al., 1995]. They found good 

agreement between the SAGE II aerosol extinction profiles and the lidar profiles obtained by 

their colleagues in Italy. However, they also found that the observed ozone had become reduced 

somewhat from that at the altitude of the volcanic aerosol layer just prior to the eruption. 

Solomon et al. [1996] showed that such changes at the mid latitudes were also consistent with

their model simulations that included a heterogeneous loss of ozone at middle latitudes. Thus,
34

while estimates of the stratospheric aerosol optical depth (AOD) were important for studies of 

the Earth’s radiation budget, estimates of aerosol surface area were more important for 

understanding the effects of aerosols on ozone.

(c) HALOE on the UARS satellite of 1991

The HALOE instrument used a gas filter approach for the measurement of trace gas profiles in 

the stratosphere by solar occultation absorption [Russell et al., 1993]. The concept was proposed 

in 1975 and selected for development under the NASA Office of Applications AAFE Program in 

1976. Its design phase was completed late in 1979. A brassboard model was constructed and 

tested in the laboratory and then from onboard flights of the high-altitude, Convair 990 aircraft in 

the early 1980s. Originally, it was hoped that HALOE might be ready in time to be considered 

for ERBS and its launch in 1984, but the readiness of the gas filter technology was not really 

clear until it was demonstrated in an initial flight of the Measurement of Air Pollution by 

Satellite (MAPS) instrument on an engineering flight of the Space Shuttle in November 1981. 

Nevertheless, HALOE had been selected for a flight opportunity on UARS that was scheduled 

for launch from the Space Shuttle in autumn 1989 [Reber et al., 1993]. Due to the tragic loss of 

the Shuttle Challenger in 1986, that opportunity was delayed until September 1991 or 16 years 

from the time of the initial HALOE proposal. Even so, HALOE went on to operate nearly 

flawlessly from 1991 to November 2005—a significant tribute to James Russell III, HALOE 

Principal Investigator of Langley. He was assisted by a dedicated team of engineers and 

technicians, initially at TRW Corporation and then within Langley and by a number of software 

specialists plus the members of his HALOE Science Team. Project management for HALOE 

was handled by James Raper, Dewey Smith, Thomas Jones, Lloyd Keafer, and Edward Sullivan. 

Engineering design and testing was led by Antony Jalink, Robert Spiers, Charley Stump, Alvin 

Moore, and Donald Hesketh, while Larry Gordley (GATS, Inc.), Jae Park, and Lance Deaver led 

the software development. Edward Sullivan, John Wells, and Warren Hypes were involved with 

the HALOE instrument operations and the sets of correlative measurements for the assessment of 

the quality of the HALOE data, particularly during its initial 3-yr period. Al Beswick, Gale 

Harvey, Curtis Rinsland, and Mary Ann Smith of Langley and Chris Benner and Malathy Devi 

of The College of William and Mary conducted and analyzed the important spectroscopic 

measurements of the HALOE instrument prior to flight, as well as during the development of the 

forward model of the HALOE retrieval algorithm.

The HALOE instrument included gas filter channels for four trace gases (HCl, HF, CH4, and 

NO), plus four radiometer channels for O3, H2O, CO2, and NO2. Mark Hervig (GATS, Inc.) led 

the development of an algorithm for the retrieval of aerosol extinction profiles from the four 

additional radiometer channels that were in tandem with the gas filter channels. The extinction 

profiles that he obtained were evaluated against co-located aerosol measurements from SAGE II 

and from balloon-borne optical particle counters of Terry Deshler at the University of Wyoming 

[Hervig and Deshler, 2002]. Measurements of aerosol extinction at mid infrared wavelengths 

can be related most directly to their mass density profiles, although Hervig supplied estimates of 

their surface area density profiles, too.
35

From 1991 through 1992 the aerosol extinction profiles from HALOE were enhanced because of 

the volcanic layers from the eruption of Mt. Pinatubo. Aerosol extinction effects were more 

noticeable for those UARS experiments that operated in the infrared limb emission mode, i.e., 

the Cryogenic Limb Array Etalon Spectrometer (CLAES) and the Improved Stratospheric and 

Mesospheric Sounder (ISAMS). In fact, Eluszkiewicz et al. [1997] diagnosed the effects of the 

volcanic aerosols from the CLAES data on the diabatic heating rates and the net circulation of

the stratosphere. Aerosol extinction profiles from the visible wavelengths of SAGE II were 

affected, too, and for many more months. Grainger et al. [1993] reported good agreement from 

their analyses of infrared emission from the spectral channels of the UARS ISAMS instrument, 

using optical constants for concentrated aqueous sulfuric acid for the aerosols. Halperin and 

Murcray [1987] came to similar conclusions from earlier analyses of mid infrared spectra of the 

El Chichon aerosol layer that they obtained from their balloon-borne infrared limb spectrometer.

(d) ATMOS on the Space Shuttle

The Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer of 

Barney Farmer of JPL was flown four different times on the Space Shuttle—in 1985, 1992, 

1993, and 1994. James Russell was a scientific collaborator for ATMOS on its initial flight in 

1985. He focused on an assessment of its retrieved profiles of the nitrogen oxide gases in the 

stratosphere [Russell et al., 1988]. The second flight of ATMOS occurred from March 24 to 

April 2, 1992, or 9 months following the eruption of Mt. Pinatubo. Curtis Rinsland of Langley 

analyzed the broad underlying variations in the ATMOS transmission spectra at mid infrared 

wavelengths for extinction due to aerosols composed of sulfate material [Rinsland et al., 1994].

Their forward model for the aerosol extinction was based on aerosol size distributions estimated 

from concurrent SAGE II measurements and also using refractive indices (real and imaginary

components) appropriate for concentrated aqueous sulfuric acid. They reported reasonably good 

agreement between their model and the spectral variations of the observed transmission 

measurements from ATMOS. The findings from the ATMOS data and from the UARS ISAMS 

data are quite in line with the early conclusion of Rosen [1971] that the boiling point of

stratospheric aerosols is consistent with that of a concentrated solution of aqueous sulfuric acid.

(e) The Lidar In-space Technology Experiment (LITE)

 

Cirrus clouds were identified as a major unsolved component in weather and climate studies by 

Bretherton and Suomi [1983] in their proposed plan for an International Satellite Cloud 

Climatology Project (or ISCCP). In response, Thomas et al. [1990] of the University College of 

Wales used their ground-based, doubled Nd/YAG lidar system for determining the polarizing 

character of cirrus cloud crystals. At about the same time Ed Eloranta and colleagues at the 

University of Wisconsin upgraded their HSRL instrument that had been initially supported with 

funds from the AAFE Program. As a result of their increased transmitter power with a CuCl 

laser and of their modifications to the configuration of the system receiver, the Wisconsin group 
36

was able to obtain stronger backscatter returns and more details about cirrus particles from their 

measurements, too [Grund and Eloranta, 1991]. The field programs associated with the First 

ISCCP Regional Experiment (or FIRE), managed by Scott Wagner and David McDougal of 

Langley, provided information about the scattering and radiative properties of the cloud particles 

and was very helpful for the interpretation of the spectral imagery from the satellite sensors [e.g., 

McDougal, 1993; Cox et al., 1987; Winker and Vaughan, 1987]. 

As indicated in Section 3b, the development of lidar technologies was continuing to thrive under 

the leadership of M. Patrick McCormick and Ed Browell, among many others, and at the urging 

of Lawrence. McCormick used his 14-inch ruby lidar in field programs designed to corroborate 

the aerosol measurements from SAM II and SAGE II. He also led the deployment of several 

airborne in situ sensors for the purpose of characterizing the scattering properties of the aerosol 

particles. Ed Browell led Langley’s participation in a number of dedicated airborne field 

measurement campaigns for ozone and water vapor with his DIAL instruments, which also 

provided important information about the aerosol backscatter profiles in the troposphere and 

lowermost stratosphere [Browell et al., 1998]. Browell was ably assisted during this period by 

Scott Shipley, Syed Ismail, William Grant, Carolyn Butler, Susan Kooi, Marta Fenn, Robert 

Allen, and Arlen Carter.

In 1985 Langley researchers carried out design studies for a spaceborne lidar demonstration 

experiment, using hardware similar to that of the airborne 14-inch lidar of McCormick and 

Fuller. A science steering group submitted a proposal for an instrument called LITE in May 

1990 [McCormick et al., 1993], and LITE became a payload on the flight of STS-64 on

September 9, 1994. The LITE experiment team acquired 53 hours of backscatter data, and the 

detail from the sequences of the orbital backscatter profiles that they were able to see was quite 

astounding. Thus, the relatively simple, LITE experiment provided new information about 

tropospheric aerosols in the boundary layer and above, plus information about the vertical 

structure and continuity of thin cirrus clouds near the tropopause [Winker et al., 1996]. Such 

detail would allow for improved estimates of the effects of aerosols and clouds on the transfer of 

radiation throughout the troposphere. Data of this kind were what Suomi and Bretherton were 

hoping to obtain, when they put forth in their vision of 1983 that such quantitative information

would be important to have. It was also the culmination of what Lawrence hoped to see from a 

spaceborne lidar mission. All through his time at Langley from 1967 until his retirement from 

NASA in 1994, Lawrence had promoted the lidar research activities with an eye toward the

achievement of the successful operations of LITE from the Space Shuttle.
37

6 The era of NASA’s Earth Observing System (EOS)

(a) Toward studies of global climate science

This section contains a brief review of NASA’s EOS program and places it in the context of the 

Earth observation activities of the international community. Because of their proven capabilities 

of making satellite measurements of Earth’s radiation budget with ERBE and of atmospheric 

aerosols with SAGE II and LITE, Langley’s engineering and atmospheric science teams were 

well positioned to apply their knowledge to the growing research field of global climate change.

Three satellite instruments from Langley will be emphasized and discussed in turn in the next 

subsections: Clouds and the Earth’s Radiant Energy System (CERES), SAGE III, and CloudAerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Then a following 

subsection will describe how their measurements are complementary with those of the other EOS 

instruments and from the satellite observing systems of the international community. 

Conway [2007] devotes two entire chapters to the fitful beginnings of EOS in his historical 

account of NASA’s atmospheric science programs. He notes that the initial planning for a U. S. 

climate observing system got underway in 1977, following closely on the earlier SMIC and 

RMOP reports. Verner Suomi urged once again that NASA and NOAA coordinate their

planning for global climate observations. However, the necessary funding for NOAA to move 

ahead with its plan was cut back sharply in the early 1980s, along with their participation in the 

development of the necessary measurements and the transfer of new technologies from NASA. 

Still, NASA continued with developing improved satellite Earth observation techniques but at a 

much slower pace. It was nearly ten years later in 1988 that NASA issued an Announcement of 

Opportunity (AO) for instrument proposals, science teams, and interdisciplinary investigation 

teams for EOS.

An EOS Handbook provides the historical perspective and time line of activities within the EOS

Program [Parkinson et al., 2006]. NASA’s initial vision for EOS was to conduct 15 years of 

Earth observations from sets of three successive satellites, each one having a complement of 

identical instruments. Payload instruments were selected in 1989, based in large part on the 

technologies that were an outgrowth of AAFE. The WMO also hosted a meeting in 1988 on 

global climate change, which led to the creation of the first IPCC Panel. Thus, it soon became 

clear that the international community would be embarking on its own satellite programs for 

monitoring Earth and its atmosphere. As the cost of the U. S. EOS initiative grew larger in the 

1990s, the NASA vision was scaled back to just three distinct satellite Earth observation 

platforms. Each of the eventual platforms, Terra, Aqua, and Aura, had a different overall

scientific objective, and the requirement was scrapped for each of them to have two follow-on 

satellite platforms with identical instruments and spaced over intervals of five years. Instead, it 

was decided that it would be more appropriate to collaborate with our international colleagues 

and to promote a mutual exchange of datasets.
38

It was also realized that it may not have been a good idea to keep fixed the measurement 

technologies and data processing systems for an entire 15-yr monitoring period. As part of 

NASA’s Mission to Planet Earth (MTPE) initiative of 1993, lead NASA Center roles were 

assigned to Goddard (Earth System Science), Langley (Atmospheric Science), JPL (Instrument 

Technology), and Stennis (Commercial Remote Sensing). Programs were also re-established in 

the mid-1990s for the development of advanced technologies for making observations from 

Space—reminiscent of the foregoing AAFE program. Those technology programs included the 

New Millenium Program (NMP), the Instrument Incubator Program (IIP), and the Earth System 

Science Pathfinder (ESSP) Program of the NASA Headquarters Science Mission Directorate

(SMD); today their Program Offices are located at JPL, Goddard, and Langley, respectively. 

The NASA EOS Program also brought about a change in philosophy in the management of the 

experiments that would be selected. Two classes of instruments were considered: Facility 

instruments, such as Moderate-resolution imaging spectroradiometer (MODIS) [King et al., 

2003] on Terra and the Atmospheric Infrared Sounder (AIRS) on Aqua, and PI-led instruments, 

such as the Multi-angle Imaging Spectro-Radiometer (MISR) [Diner et al., 1999]. Initial data 

retrieval algorithms would have to be made available prior to flight and documented in 

Algorithm Theoretical Basis Documents (ATBD), and the data products would be provided to 

the science community via an EOS Data and Information System (or EOSDIS). Effectively, this 

requirement meant that in order for a given experiment to be selected, its measurement concept 

must have a certain established heritage. Langley had that capability with ERBE and SAGE II.

 

Significant personnel changes occurred in ASD at Langley in the mid 1990s, following the 

retirement of Lawrence. McCormick was moving ahead at that time with his new satellite 

instruments, SAGE III, and another lidar, CALIPSO. Russell was developing Sounding of the 

Atmosphere using Broadband Emission Radiometry (SABER), an experiment supported by the 

NASA’s Office of Space Sciences (OSS). However, they did not have an experiment on one of 

the three primary EOS platforms. They decided to take their retirement from NASA in 1996 and

enlarge their opportunities at nearby Hampton University (HU), where they founded its Center 

for the Atmospheric Sciences (CAS). They also continued with their respective Principal 

Investigator roles for SAGE II and HALOE. Robert Seals, who had worked earlier in the Upper 

Atmosphere Program Office of Shelby Tilford at NASA Headquarters, served as an interim 

Chief directly after Lawrence. Seals had been involved with the UARS Upper Atmosphere Data 

Pilot in support of Tilford and later with the Atmospheric Effects of Aviation Program (AEAP) 

of Howard Wesoky in the Office of Aeronautics and Space Technology (OAST) at NASA 

Headquarters. But Seals would soon move to assist Roy Dunkum in managing the EOS 

Distributed Active Archive Center (DAAC) at Langley. Darrell Branscome then appointed Jerry 

Newsom to be the Acting Chief of ASD until William Smith, Sr., of the University of Wisconsin 

and its Cooperative Institute for Meteorological Satellite Studies (CIMSS) took the helm in 1997. 

Smith was already integrally involved with developing improved satellite sounders for both the 

EOS and the next-generation, polar and geostationary satellites for NOAA. Of course, he had 

been an important player in the design of the radiation budget sensors and the interpretation of 

their measurements from Nimbus 6 and 7 and from ERBS. He was also very supportive of the 

impending launch of CERES on the Tropical Rainfall Measurement Mission (TRMM) satellite.
39

Up and coming researchers began to assume leadership roles for the several experiments 

proposed by Langley for EOS. For example, although the CERES experiment was led initially 

by Bruce Barkstrom, that role was handed off to Bruce Wielicki in 1996 and then to Norman 

Loeb in 2007. Barkstrom became involved at that time with helping to streamline the operations 

and to reduce the costs of NASA’s immense EOSDIS. Another atmospheric scientist, Patrick 

Minnis, had been working with Edwin Harrison in the early 1980s to estimate the role of 

diurnally-varying clouds in the interpretation of the radiation budget measurements from ERBE 

[Minnis and Harrison, 1984]. Later, he and David Young verified those estimates using the data 

from ERBE plus spectral radiance measurements from the AVHRR sensors on the NOAA GOES 

satellites. As an aside, Minnis received early training in the atmospheric sciences at Colorado 

State University from Professor Steven Cox, who had been a graduate student of Verner Suomi 

at the same time as Thomas Vonder Haar. In the late 1980s Minnis commenced working for his

Doctoral Degree under the guidance of Prof. K.N. Liou at the University of Utah, where they 

became focused on the inference of cirrus cloud properties from satellite-observed visible and 

infrared radiances. That work led later to his studies of the effects of contrails from aircraft and 

their transformation to cirrus particles [Minnis et al., 1998]. Charles Whitlock, Thomas 

Charlock, and later Paul Stackhouse (from Colorado State) led a team of researchers focused on 

the surface and atmospheric radiation budget (SARB), an important component of the Earth 

radiation budget and an expected by-product of the upcoming measurements from CERES.

Stackhouse also began to assemble the short-wave datasets and to analyze them for their seasonal 

and regional differences and for their solar energy potential. 

Lamont Poole of McCormick’s ARB returned to graduate school at the University of Arizona,

where Sean Twomey and RMOP Panelist Benjamin Herman were faculty members. Poole 

conducted theoretical and analytical studies to determine the probable composition and sizes of 

the PSC-type particles from measurements of their depolarization ratios of the return signals 

from his airborne lidar system [Poole et al. 1988]. David Winker, a lidar specialist, worked with 

Poole and Mary Osborn (Hughes STX) to conduct similar airborne lidar studies of the Pinatubo 

aerosols in 1991. Winker then served as Deputy Project Scientist for the LITE experiment, and 

went on to be the Principal Investigator for CALIPSO. Mike Pitts and Charles (Chip) Trepte 

were graduate students in the early 1980s at Georgia Tech under the guidance of Derek Cunnold 

(SAGE II Science Team Member). They came to Langley to provide validation support for the 

SAGE datasets on ozone and aerosols at that time. Trepte attended the University of Wisconsin 

and was awarded his doctoral degree in the early 1990s under the guidance of Professor Matthew 

Hitchman. Together, they analyzed time series of the stratosphere aerosol distributions from 

SAGE II and found that the tracer-like characteristics of the aerosol layer revealed the effects of 

the tropical quasi-biennial oscillation. Trepte and Pitts would later assume leading roles in the 

processing and scientific use of the cloud and aerosol data from CALIPSO.

Marty Mlynczak, who received his M. S. degree under the guidance of Verner Suomi in 1984, 

began his career at Langley as a member of the HALOE Project. He obtained his doctoral 

degree from the University of Michigan in 1989 on the topic of non-local thermodynamic effects 
40

(NLTE) and retrieval algorithms for mesospheric ozone. Upon James Russell’s move to HU in 

1996, Marty retained his role as Associate Principal Investigator for SABER and continued in 

that role through its launch in late 2001 and beyond. In 1996 John Wells and Ellis Remsberg 

carried on with the responsibilities for the ongoing HALOE Project in coordination with Russell. 

Joseph Zawodny, who came to Langley in 1988 from the NOAA Aeronomy Lab, served as

Project Scientist for SAGE II from 1996-2005. Larry Thomason came to Langley in 1989 from 

the Air Force Geophysics Laboratories and from the University of Arizona before that, where he 

worked with Professors John Reagan and Benjamin Herman. Thomason subsequently led a 

study of the long-term changes in the stratospheric aerosol layer, based primarily on the 

measurements from SAGE II [Thomason et al., 2008]. William Chu, an original member of the 

SAGE II experiment team, became Project Scientist for the EOS experiment SAGE III that was 

launched onboard the Russian Meteor 3M spacecraft late in 2001. David Flittner, Didier Rault, 

Pitts, Poole, Thomason, and Trepte were important contributors to the SAGE III Project, as well. 

Leonard McMaster, who had been the Assistant Head of McCormick’s ARB for many years, 

advanced to serve as the Chief of the Atmospheric Sciences Division from 2001 to 2006. Lelia 

Vann returned to the University of Arizona and was awarded her doctoral degree in atmospheric 

science in 2003. She was nominated to succeed McMaster in 2006 and is Chief of the current 

Science Directorate (SD) at Langley. 

New ground-based and airborne lidar systems were being developed during this period for the 

purpose of making more detailed measurements of aerosols and clouds. Rich Ferrare came to 

Langley from Goddard, where he had been working with former RMOP Panel member, Harvey 

Melfi. Rich has conducted lidar measurements at the Department of Energy’s Atmospheric 

Radiation Measurement (ARM) site in Oklahoma, as well as in numerous other field programs. 

Chris Hostetler, of the University of Illinois (faculty advisor, Chester Gardner) and Jonathan 

Hair, of Colorado State University (faculty advisor, Joe She) were hired at Langley in the middle 

to late 1990s, whereupon they undertook the development of a new-generation HSRL system. 

Ferrare, Hostetler, and Hair are demonstrating the technologies that will be critical to the 

measurement strategies for aerosols and clouds and their effects on the radiation budget and 

climate in the coming decades (see Section 7).

(b) CERES

The optimal orbits for making the necessary spatial and time-resolved measurements of Earth’s 

radiation budget were determined from simulation studies carried out primarily by Edwin 

Harrison and Gary Gibson [Harrison et al., 1990]. In fact, Harrison’s group conducted orbital 

analyses for the trade studies of many of the instruments proposed for EOS. In particular,

CERES was an investigation to examine the role of cloud/radiation feedbacks for the Earth’s 

climate system [Wielicki et al., 1996]. The CERES investigators planned to incorporate the

simultaneous cloud property data derived using the EOS narrowband imagers and profilers, 

MODIS and AIRS, to provide a consistent set of cloud/radiation datasets, including SW and LW 

radiative fluxes at the surface and at several selected levels within the atmosphere.
41

Excellent summaries of the Earth radiation budget studies at Langley prior to CERES, plus a 

description of the series of CERES instruments that have been flown so far can be found in 

Smith et al. [2010] and Smith et al. [2011]. The proto-flight model of the CERES instrument 

was flown in 1997 on the TRMM spacecraft, which was in a precessing orbit with an inclination 

of 35 ̊, at an altitude of 350 km, and having a footprint size at the ground of 10 km. That first

instrument operated successfully for 9 months, after which it was turned off because of problems

with the TRMM power supply. Two more CERES instruments began their operations from the 

Terra spacecraft in early 2000, and another pair of instruments would obtain measurements from 

onboard the Aqua spacecraft to be launched in 2002. All along, a major goal of CERES has been 

to measure the Earth’s radiation budget more accurately and over a period of at least at decade 

for the purpose of verifying the variations of Earth’s radiation budget, as predicted by climate 

models on both the regional and global scales. That effort includes the critical interannual 

variations in the global net radiation and their relation to El Nino/Southern Oscillation (ENSO) 

events. Loeb et al. [2006] made use of data from both MODIS and MISR for improving the 

angular distribution models (ADM) that they employed for analyzing the TOA radiative flux 

measurements from CERES. Sun et al. [2004] developed additional ADMs based on the 

Polarization and Directionality of the Earth’s Reflectance (POLDER) measurements [Deschamps 

et al., 1994] on the Japanese ADEOS satellite, in order to characterize the phase function of ice 

particles and the effects of cirrus on the measured reflectivity at TOA. Over the years the 

various CERES sub-teams have worked to bring about a fusion of data from across 11 

instruments on 7 spacecraft, in order to obtain the first long-term, integrated observations of the 

broadband, surface-to-TOA values of Earth’s radiation budget.

(c) SAGE III

SAGE III was a NASA EOS instrument launched into a Sun-synchronous orbit aboard the 

Russian Meteor 3M spacecraft in December 2001. Its measurement heritage follows that of the 

earlier SAM II and SAGE experiments. The SAGE III instrument had a total of nine aerosol 

channels with center wavelengths from 384 nm to 1545 nm and using charge-coupled device 

(CCD) detector arrays to improve their measurement S/N [Chu et al., 2002]. Aerosol profile 

measurements were obtained from February 2002 through March 2006. They were made mainly 

at the higher latitudes, where chemical processes on surfaces of aerosols and PSCs led to an

enhanced loss of polar ozone during winter/spring. SAGE III was also an early example of the 

international cooperation that has been part of the overall success of NASA’s EOS Program.

The quality of the SAGE III aerosol data was verified initially by comparisons with those from 

SAGE II [Thomason and Taha, 2003; Yue et al., 2005] and from the Polar Ozone and Aerosol 

Measurement (POAM) satellite instrument [Thomason et al., 2007]. Comparisons were also

conducted as part of a dedicated NASA airborne campaign, entitled SAGE III Ozone Loss and 

Validation Experiment (or SOLVE II). In particular, Russell et al. [2005] found reasonably good 

agreement between the aerosol optical depth measurements from SAGE III and from their 

airborne sun photometer during SOLVE II. Later, Thomason et al. [2010] reported better
42

accuracies for the SAGE III aerosol extinction profiles based on an improved, Version 4 

algorithm.

(d) CALIPSO

Immediately following the LITE mission of 1994, design studies were begun at Langley for a 

free-flying, spaceborne lidar. The basic instrument system was kept fairly simple and closely 

related to that of LITE. A proposal was submitted to the NASA ESSP program in May 1998,

and it was selected for funding in December. This lidar experiment is a combined effort between 

the U. S. and France, entitled Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations 

(or CALIPSO) [Winker et al., 2003]. CALIPSO was launched in late April 2006 and began its 

continuous backscatter measurements by mid June. CALIPSO is in flight formation as part of

EOS Aqua and its A-Train constellation of satellites and is still operational in 2012—a major 

achievement. CALIPSO, along with its companion cloud radar on CloudSat [Stephens et al., 

2002], is providing a multi-year global view of the vertical structure of aerosols and clouds that

is crucial to determining their role in the climate system [Winker et al., 2010]. The CALIPSO 

payload consists of a two-wavelength polarization lidar system from Ball Aerospace and 

Technologies Corporation (BATC) for the determination of optical and microphysical properties 

of aerosols and cloud layers in the troposphere. The excellent performance for the two flight 

lasers can be traced to the 3-year life test that was carried out from 1998 to 2001 with a spacequalified, prototype laser—the so-called risk reduction laser or RRL [Winker et al., 2003]. The 

CALIPSO experiment also includes a visible, wide field camera (WFC) and the imaging infrared 

radiometer (IIR), both supplied by the French Space Agency (CNES). Together, the data from 

the three instruments are being used to identify aerosols and cloud layers and their reflective and 

absorbing properties [Winker et al., 2009].

An important design study by Langley was focused on how to maintain and properly characterize 

the polarized signals at the CALIPSO system receiver [Alvarez et al., 2006]. Then, Hu [2007]

developed an algorithm for delineating the phase of the water in cloud particles, based on the 

linear polarization measurements obtained with the lidar system. In another application the 

tropospheric returns from CALIPSO have been used to characterize dust aerosols in remote 

regions of the globe, where they have not been sampled well by any other means [Huang et al., 

2007]. Numerous other research groups are making use of the CALIPSO datasets. In fact, there 

are already more than 500 publications and/or presentations related to the CALIPSO experiment 

or that rely on its datasets (see http://www-calipso.larc.nasa.gov ).

(e) Complementary measurements within EOS and from the international community

Other EOS instruments are also focused on clouds and the radiation budget. For instance, 

information from MODIS on Terra and Aqua is being used to help with the interpretation of the 

CERES data, and the MISR instrument on Terra is providing information about cloud height 

[Davies and Molloy, 2012]. Geostationary Earth radiation budget (GERB) data from Europe’s 
43

Meteosat Second Generation (MSG) satellite are being combined with the radiances from its 

companion instrument, Spinning Enhanced Visible and Infrared Imager (SEVIRI), which 

provides information on cloud particle phase and size [Sandford et al., 2003; Bugliaro et al., 

2011; Dammann et al., 2002]. In addition, the SABER instrument of Langley is providing

information on the energetics and radiative budgets of the mesosphere and lower thermosphere 

and their variations in response to the changes of the solar cycle [Mlynczak, 1997; Mlynczak et 

al., 2010]. 

Another satellite in the EOS A-Train formation is PARASOL, carrying the French instrument 

POLDER for obtaining polarization measurements of aerosols and their Stokes parameters. In 

many respects the MISR and POLDER measurements of tropospheric aerosols are 

complementary to those from CALIPSO. Stratospheric aerosols and PSCs were observed by the 

series of Polar Ozone and Aerosol Measurement (POAM) instruments of the Naval Research 

Laboratories (NRL) [e.g., Fromm et al., 1999], by the Global Ozone Monitoring by Occultation 

of Stars (GOMOS) instrument on ENVISAT [Valhellemont et al., 2005], from the Atmospheric 

Chemistry Experiment (ACE) on the Canadian SciSat [Bernath et al., 2005], and with the

SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) 

experiment on ENVISAT [Ovigneur et al., 2011]. Stratospheric aerosol measurements were also

obtained from the Optical Spectrograph and InfraRed Imaging System (OSIRIS) on the Swedish 

satellite Odin and were used in an intercomparison study of similar products from SAGE III

[Bourassa et al., 2012]. Finally, the Solar Occultation for Ice Experiment (SOFIE) must be 

mentioned, in part because it has its heritage from the HALOE Project at Langley [Gordley et al., 

2009]. SOFIE was launched on the Aeronomy of Ice in the Mesosphere (AIM) satellite in 2007. 

The AIM Project is led by James Russell at nearby Hampton University, and SOFIE is still 

operating successfully today. Its measurements are being used to characterize and explain the 

occurrence and persistence of the polar mesospheric clouds that occur in summer at the high 

latitudes.

Although the measurement technologies for the EOS instruments were mature when they were 

selected in the early 1990s for a flight opportunity, it is important to recognize that their 

algorithms were still undergoing improvements post-launch. Once their initial data were 

evaluated, improved versions of those datasets were generated for the wider benefit of the 

atmospheric research community. One might say that the EOS experiments have really been 

providing research datasets because their information content is still being assessed by the 

atmospheric scientists as they study the data. The wisdom of the proponents of the EOS program 

is evident from the fact that the datasets from the multiple instruments have been truly

complementary for a more complete assessment of the role of clouds and aerosols on Earth’s 

radiation budget and for those processes that affect the climate. There has also been redundancy 

for the measurements from some of the instruments, such that one can directly compare their 

joint findings and obtain a better idea of their mutual uncertainties. That insight has been

important especially for the design of the next-generation, operational remote sensors onboard

the renamed, Suomi NPP (or National Polar-orbiting Partnership) satellite that was launched by 

NASA on behalf of NOAA in November 2011.
44

7 Present-day, satellite remote sensing of Earth’s radiative budget and aerosols

(a) NASA’s Decadal Survey Plan and responses from Langley

NASA is now following the recommendations found in the National Research Council’s 

Decadal-Scale blueprint for the Earth Sciences [NRC, 2007]. In effect, the vision of the NRC 

Report builds on the accomplishments since RMOP and EOS but urges that the U. S. 

government reinvest in new Earth observing systems. The Report notes alarmingly that future 

plans for Earth observations and for the follow-on, operational Joint Polar Satellite System 

(JPSS) “are generally less capable than their Earth Observing System (EOS) counterparts”. The 

NRC panel did not prioritize the recommended Earth Science measurements but simply placed 

the various instrument concepts into Tier 1, 2, or 3 categories, according to their demonstrated 

technical readiness levels (TRL).

Following the issuance of the NRC Report, NASA and NOAA restored the Ozone Mapping and 

Profiling Suite (OMPS) onto the Suomi NPP that was launched in November 2011. Didier Rault 

of LaRC and Robert Loughman of Hampton University are using their limb-scatter algorithm for 

obtaining the aerosol profiles for the retrieval of lower stratospheric ozone from OMPS [Rault 

and Loughman, 2007]. A copy of the CERES instrument is also aboard Suomi NPP. Initial 

results indicate that it is working well, according to CERES Instrument Scientist, Kory Priestley 

of Langley. In addition, William Smith of Hampton University and Daniel Zhou, Allen Larar, 

and Xu Liu at Langley have shown that one can obtain very high resolution, surface spectral 

emissivities (SSE) from the Infrared Atmospheric Sounding Interferometer (IASI) aboard the 

European Metop-A satellite, and they are able to clearly distinguish the variations in the land 

skin temperature from those of the surface emissivity [Zhou et al., 2011]. Such information is 

important for determining variations in the forcings on the surface boundary layer within

operational forecast models. Zhou and colleagues are currently applying their algorithms to the 

radiances from the Cross-track Infrared Sounder (CrIS) instrument of Suomi NPP.

The reader should bear in mind that the members of the NRC panel anticipated that both the 

Orbiting Carbon Observatory (OCO) satellite of JPL and the Glory satellite of NASA 

GSFC/GISS would be launched and operated successfully, prior to the full implementation of 

their blueprint. Unfortunately, both missions failed to achieve orbit—OCO in 2009 and Glory in 

2011; they are being rescheduled for second flight opportunities in the near future but at the cost 

of delaying some of the goals of the original NRC report. The payload for Glory includes an 

Aerosol Polarimetry Sensor (APS), a high-spatial resolution cloud camera, and a Total Irradiance 

Monitor (TIM). The combined measurements of Glory are intended to characterize the 

microphysical and optical properties of aerosols over a range of surface and atmospheric 

conditions [Mishchenko et al., 2004].

The NRC Report recommended providing at least two new satellite opportunities related to the 

observed climatic effects of gases, clouds, and aerosols: (1) a Tier 1, Climate Absolute Radiance 
45

and Refractivity Observatory (CLARREO) mission of low cost for tracking regional changes in 

the outgoing radiance with an absolute, spectrally-resolved interferometer and (2) a Tier 2 

Aerosol/Cloud/Ecosystems (ACE) mission of higher cost, consisting of a backscatter lidar, a 

multi-angle polarimeter, and a Doppler radar focused on studies of the radiative effects of 

aerosols and clouds. Candidate instruments were proposed by Langley for those mission 

opportunities, and they are introduced briefly in this subsection.

The importance of having accurate spectral radiance measurements from CLARREO was

demonstrated by Harries et al. [2001], using measurements from 1996 of the Interferometric 

Monitor of Greenhouse gases (IMG) instrument on board the Japanese ADEOS satellite and their

comparisons with measurements from the Infrared Interferometric Spectrometer (IRIS) on

Nimbus 4 taken some 27 years earlier. Harries et al. [2001] detected variations in the outgoing 

longwave radiation at specific wavelengths, and related them to the changes in the greenhouse 

gases over that time span. The measurement and calibration requirements for conducting a more 

dedicated, joint NOAA/NASA climate monitoring mission are outlined in Ohring et al. [2005]. 

The concept of CLARREO that was highlighted in the NRC Report is an outgrowth of that 

study, and Bruce Wielicki and David Young of Langley have proposed a set of instruments for 

the mission based on their experience with CERES. Of particular importance is the fact that they 

would measure for the first time the spectral variations of the outgoing radiance from Space 

across the far infrared region of 15 to 50 μm. Outgoing radiance in that spectral region is 

sensitive to emissions from cirrus clouds and from atmospheric water vapor [Kratz et al., 2005]. 

A balloon-borne, far infrared instrument entitled Far-InfraRed Spectroscopy of the Troposphere 

(FIRST) was developed by Langley under the NASA IIP. Initial measurements were made by 

Marty Mlynczak and colleagues from high altitudes in a demonstration of FIRST [Mlynczak et 

al., 2005]. However, due to funding constraints the CLARREO mission has been dropped from 

the current NASA budget projection as a Tier 1 mission and is undergoing further study. 

Hopefully, a climate monitoring mission of this general design will be restored in the near future.

Ramanathan et al. [2001] argued that human activities are releasing tiny particles into the 

atmosphere and that these aerosols enhance scattering and absorption of solar radiation. Such 

particles may also produce brighter clouds that are less efficient at releasing precipitation and 

that increase the solar heating of the atmosphere. The IPCC Report [2007] emphasizes that these

direct and indirect aerosol forcing effects are complex and represent a major uncertainty for the 

understanding and prediction of global climate change. Such is the goal of the Tier 2 ACE 

mission concept. A new-generation, airborne HSRL (lidar) instrument [Hair et al., 2008] has 

been proposed by Langley in support of ACE. HSRL has been used successfully to obtain 

datasets on aerosol extinction, aerosol optical thickness, aerosol backscatter, and depolarization 

ratios as part of 18 separate field missions over North America since 2006 (see also Burton et al.

[2012]). For several of those field campaigns the HSRL instrument was flown along with the 

research scanning polarimeter (RSP) of Brian Cairns of NASA GISS—the RSP is a prototype for

the measurements to be obtained with Glory. The HSRL and RSP prototype instruments 

represent a candidate payload for the Tier 2 ACE satellite mission called for in the NRC Report.
46

Recently, NASA has also been considering instruments for scientific operations from onboard 

the International Space Station (ISS). In fact, following the launch of SAGE III on the Russian 

Meteor-3M spacecraft in 2001, Langley and Ball Aerospace and Technologies Corporation built 

a second instrument with the hope that it could be attached to the ISS in 2005. However, that 

opportunity was put on hold due to a change in the design of ISS, so the copy of the SAGE III 

instrument was stored in a Clean Room at Langley. After the assembly of the ISS was complete 

and upon the retirement of the Space Shuttle vehicle, NASA renewed solicitations for instrument

payloads that might be easily accommodated and operated from onboard the ISS. Joe Zawodny 

and Patrick McCormick proposed to upgrade and re-calibrate SAGE III for ISS, in order to 

restart the long time series of measurements of aerosols and ozone of the low and middle 

latitudes that they had obtained earlier with SAGE II. In support of that goal, Vernier et al. 

[2009] had already extended the SAGE II time series of aerosols with the aid of the 

measurements from CALIPSO, at least since mid 2006. Soon thereafter, Solomon et al. [2011] 

reported that the variations of the near-background, stratospheric aerosol layer can explain the 

observed reductions in the expected rate of increase in global surface temperatures due to the 

greenhouse gases. Thus, keeping track of the changes for the stratospheric aerosols is critical to 

an understanding of the global surface climate, too. In early 2012 the efforts of Langley to put a 

copy of SAGE III on ISS were approved to proceed on to Phase B instrument development and 

testing. The refurbished SAGE III instrument is tentatively scheduled to be ferried from the 

Kennedy Space Center into low Earth orbit by late 2014 and attached by astronauts to the ISS.

(b) Recent scientific imperatives

Many of the original atmospheric concerns of the SMIC and RMOP reports about the effects of 

clouds and aerosols have been answered by the research community, at least qualitatively, in the 

years that have followed. Yet as if often the case, new and more quantitative measurements are 

being asked for, and there is now a desire to know about the effects of the observed changes both 

regionally and on the global scale. This subsection relates several instances where researchers at 

Langley are making progress toward the understanding of those effects.

Hansen et al. [2005] stressed that the reliability of a climate model simulation ought to be tested 

against observations, but only if the relevant datasets have been properly characterized and/or 

combined. In their commentary Trenberth and Fusallo [2010] reported on a recent disparity for 

changes in the net radiation versus the heat content of the oceans, implying that there has been 

“missing energy” in the system since 2005. They concluded that the “observations are unable to 

fully account for the recent energy variability”. Loeb et al. [2012] re-examined the multi-year

measurements of Earth’s net radiation budget using the reflected solar and emitted thermal 

radiation from CERES and the incoming solar radiation from the Total Irradiance Monitor (TIM) 

instrument on the Solar Radiation and Climate Experiment (SORCE) satellite, but normalized to 

the estimates of the upper ocean heat uptake from the Argo network of buoys that provide better

sampling of the ocean temperatures. Their more detailed analysis indicates no energy imbalance 
47

on annual timescales, especially after considering the uncertainties for the respective datasets. 

More importantly, the relative variations of the net radiation and the buoy data agree, too.

Langley researchers are also making scientific advances about the effects of clouds and aerosols 

by considering the multiple satellite and airborne datasets. As an example, Kato et al. [2011] 

employed cloud data from CALIPSO and CloudSat with radiances from MODIS to gain better 

estimates of both the top-of-atmosphere (TOA) flux and fluxes at the Earth’s surface. Sun et al. 

[2011] combined CERES, MODIS, CALIPSO, and AIRS data to obtain a quantitative 

assessment of the influence of subvisual clouds on Earth’s shortwave radiation. Atmospheric 

aerosols have an impact on the vertical development of clouds and on precipitation, in large part 

due to their radiative effects as pointed out by Li et al. [2011] and Bollasina et al. [2011]. In 

order to quantify those effects better, Langley researchers have conducted calculations based on

observed datasets from field campaigns with regard to the transport and radiative effects of

mineral dust layers and of carbonaceous aerosols from biomass burning activities [Fairlie et al., 

2007; Natarajan et al., 2012]. Such studies are important for obtaining a good characterization of 

effects of the aerosols for simulations of air quality and the regional climate and for estimating

the aerosol optical depth (AOD) and particulate loading from the MODIS and MISR datasets.

Trenberth et al. [2010] showed that in order for climate models to simulate changes in the TOA 

net fluxes properly, they must include effects of volcanic aerosols in addition to other factors 

such as the sea surface temperatures. Further, Solomon et al. [2011] concluded that even the 

rather minor variations of the background stratospheric aerosols are important for such 

simulations. Thomason et al. [2008] produced time series of aerosol extinction and surface area 

density (SAD) from the SAGE II data. SAD is an important parameter for determining the 

effects of heterogeneous chemistry for ozone in the lower stratosphere. Currently, Larry 

Thomason is finding somewhat larger, but more accurate values of total SAD by combining the 

infrared aerosol extinctions from HALOE with those from the shorter wavelengths of SAGE II.

Pitts et al. [2009] have been able to distinguish among the several types of particles that compose 

PSCs, based on their examination of the CALIPSO data. Vernier et al. [2009] also uncovered a 

somewhat unexpected finding about the aerosol backscatter profiles from CALIPSO in the 

tropical mid stratosphere. Often it is presumed that the lidar backscatter signal above about 30 to 

32 km is wholly due to the molecular scatter component. However, when Vernier et al. used

operational satellite temperature profiles for their calculations of the molecular scatter

contribution, they found that the observed total-to-molecular backscattering ratios from 

CALIPSO remained larger than 1.0 up to 35 km or so. Thus, by re-normalizing the CALIPSO

scattering ratio profiles to the higher altitude range of 36 to 39 km, they obtained larger AOD 

values for the lower stratosphere, too. This new insight has been applied to the generation of

corrected time series of the stratospheric AOD from the combined series of SAGE II, CALIPSO, 

and GOMOS aerosol measurements [Vernier et al., 2011]. Thus, model studies can now be 

conducted on the radiative effects of variations of aerosols for the global climate with better 

accuracy, as for example in the recent analyses of Booth et al. [2012]. 
48

8 Summary

It is amazing to reflect on the very significant amount of progress that has been achieved in the 

40-year period since the call of Landsberg [1970] for the activation of an adequate worldwide 

monitoring system for an assessment of possible anthropogenic changes on the climate. His 

urging came at a time when the “subject of climatology” was still somewhat qualitative and 

descriptive. As a measure of the average weather, climatology was often thought of in terms of 

its role for the economic geography and the living conditions characteristic of a region. 

Concerns about aerosols were focused more toward the air quality and visibility in a local region 

than to their effects on the global climate. The radiative and microphysical effects of persistent 

contrails within known air corridors had been estimated but were largely unverified at that time. 

It was clear that better knowledge was critically needed on the radiative, microphysical, and 

chemical forcings of the aerosols and clouds, in order to make assessments of changes in the air 

quality and for studies of variations of the regional and global climate.

Will Kellogg, G. D. Robinson, and Williams Mathews of the SMIC Study Group of 1971 were 

asked by Morris Tepper to take leading roles in the RMOP Workshop. Verner Suomi was 

recruited to lead the Particulate Panel of the RMOP. The participants of both studies were truly 

visionary, in that they saw the importance of making Earth/atmosphere measurements both 

globally and from Space. They were also correct in asking for the development and calibration 

of the diverse measurement techniques for obtaining quantitative estimates of the aerosols and 

clouds and of the surface emissivity. Langley researchers have played key roles since that time 

in the demonstration of the passive radiometric and photometric techniques and of active laser 

radar (lidar) sensors, both in the laboratory and from balloon and airborne platforms. The 

leaders of AESD/ASD, Don Lawrence and later William Smith and Leonard McMaster, served 

as important advocates for moving the various technologies toward their demonstration and 

ultimate use from satellite orbit. Lelia Vann, current leader of the Science Directorate (SD), 

continues to support those goals. The author provided some highlights of that progress in his

report at the 10th History Symposium of the American Meteorological Society (AMS); his 

presentation can be viewed at the online site for the meeting [Remsberg et al., 2012].

Some of the scientific questions raised in the RMOP Report have already been sorted out with 

regard to the atmospheric processes related to aerosols and clouds. Yet, the various 

observational datasets must still be merged together carefully, and the uncertainties for their 

respective measurements need to be decreased further [IPCC, 2007]. Certainly, the overarching 

issues for climate change are contentious and not going away. The task ahead is to proceed with 

a dedicated monitoring for any changes in the Earth/atmosphere radiation budget and land/sea 

changes and to be able to predict with more certainty the effects of the long-lived, atmospheric 

greenhouse gases and of the natural and manmade aerosols. It is also clear that this important

task will require close cooperation among researchers, innovative approaches for the

observational satellite systems of the future, and commitments from governmental agencies, such 

as NASA, NOAA, and ESA [NRC, 2012].
49

Acknowledgements. The author (EER) developed this historical retrospective as a Distinguished 

Research Associate at Langley, a program administered by Dennis Bushnell. He was supported 

by Gary Gibson, Malcolm Ko, Bruce Doddridge, and Lelia Vann in this activity. EER

coordinated his findings with those of G. Lou Smith, who assembled a separate, more detailed 

retrospective of the satellite radiation budget measurements by Langley. EER also benefitted 

from the recollections of William Hunt, Edward Browell, M. P. McCormick, and S. Harvey 

Melfi about the early developments of lidar at Langley. He recognizes four persons who made a 

positive difference in his career, but sadly who are no longer with us. There was Frank Low, the 

eminent infrared astronomer, who died in 2009 but who really ignited the interest of EER in 

atmospheric science during the early 1960s. Professor Bryce Crawford, Jr., a leader in molecular 

spectroscopy at the University of Minnesota, gave EER the opportunity to carry out the

laboratory measurements for the infrared optical constants of aqueous solutions of sulfuric acid, 

nitric acid, and ammonium sulfate. Years later, Curtis Rinsland of Langley used those optical 

constants to verify that sulfuric acid was a major component of the stratospheric aerosol layer 

following the eruption of the Pinatubo volcano. Professor Conway Leovy was the sponsor for 

EER, when he was a visiting researcher at the University of Washington during 1983/84. Leovy 

and EER were members of the Nimbus 7 LIMS Science Team. However, Conway is also 

remembered for his participation with the Viking mission of 1976 and for his analyses of the dust 

storms on Mars and what he inferred from them about its surface winds. Regretfully, Crawford, 

Rinsland, and Leovy died in 2011; their amazing scientific contributions live on.
50

Appendix A—Perspective of the author

This account by EER of the RMOP activity and its legacy is shaped necessarily by his own 

background and experience. EER was introduced to remote sensing studies of the atmosphere in 

1962, upon his acceptance into a Cooperative Work/Study undergraduate program at what was 

then known as the Virginia Polytechnic Institute (or VPI) in Blacksburg, VA. His seven, 

alternating work quarters were spent at the National Radio Astronomy Observatory (NRAO) in 

Green Bank, WV, from 1962-65. He received his job assignment for each work quarter from 

John Findlay, Deputy Director of NRAO. Findlay had been a noted British ionospheric physicist

at Cambridge University before coming to NRAO as a designer of radio telescope antennas. 

Along with Will Kellogg, Findlay was a founding member of the Committee on Space Research 

(COSPAR) in 1958. Findlay also served as Chair of the Lunar and Planetary Missions Board

from 1967-71, when he advised NASA on the planning and conduct of missions to the planets 

and the Moon and its manned Apollo missions.

In the early 1960s Torleiv Orhaug and V. R. Venugopal reported that variations in atmospheric 

water vapor and subvisible cirrus were the likely primary cause of fluctuating and interfering 

noise effects for the transmission of sub-millimeter to centimeter wavelength signals from 

astronomical sources to the ground-based telescopes at Green Bank [Venugopal, 1963]. In 1964 

at the direction of Frank Low and Arnold Davidson, EER conducted and analyzed daily 

measurements of the transmission and absorption of the direct sunlight in a water vapor band 

centered at 0.9375 micrometers and as a function of the zenith angle of the Sun or the 

atmospheric mass path. Measurements were also taken at 0.880 micrometers, a nearby reference 

wavelength that was unaffected by the water vapor absorption. Frank Low concluded from the 

data that the skies over Green Bank were not always ideal for millimeter-wave astronomy, 

although he went on to report on a number of scientific findings from exploratory measurements 

of the planets and the Moon with his 5-ft prototype instrument at Green Bank [Low, 1966]. Low 

and Davidson surveyed a number of dryer locations with their same hand-held, spectral 

hygrometers, as part of a study to determine a suitable location for a proposed, 36-ft infrared 

telescope. The Kitt Peak National Observatory, AZ, was the site that they decided upon. The 

telescope was built according to a design by Findlay, and they began routine operations in early

1968. It is noted that it was the early, innovative work of Frank Low and his low-noise, infrared 

detector technology that led the astronomy community to consider and develop the InfraRed 

Astronomical Satellite (IRAS) in 1983, the Infrared Space Observatory in 1995, the Herschel 

telescope in 2009, and to give a top priority to NASA’s James Webb Space Telescope (JWST). 

EER shifted away from Physics and began graduate studies in the Department of Meteorology at 

the University of Wisconsin in 1966. His research studies were on the effects of water vapor and 

aerosols on the transfer of radiation in the atmosphere—a focus area of Professor James 

Weinman, his thesis advisor for both the MS and PhD degrees. His MS degree work consisted 

of an analysis of photographic transparencies of scattered sunlight from near the Earth’s horizon

that were obtained by astronauts L. Gordon Cooper and Charles “Pete” Conrad from Gemini III, 

IV, and V. He related the vertical extent of the scattering layers and of the profiles of their blue-
51

to-red ratios to the presence and sizes of the stratospheric aerosols. EER also held semesterlong, teaching assistantships at that time with Professor Verner Suomi, with climatologist 

Eberhard Wahl, and with synoptic meteorologist Frank Sechrist. He remembers witnessing at 

the U. of Wisconsin in 1967 the first, RGB-color, global-scale images from Suomi’s Spin-Scan 

Camera that was on NASA’s ATS-3 satellite.

EER enjoyed a chance meeting with Christian Junge, the namesake of the stratospheric aerosol 

layer, when Junge was visiting Reid Bryson at Wisconsin in 1969. Shortly thereafter, Junge 

became a Work Group Leader for the SMIC Study Report. That same year Professor James 

Weinman introduced EER to Ed Ney at University of Minnesota, but it was not until many years 

later that EER learned that Ney had shifted his attention to infrared astronomy in the mid 1960s 

based in part on the work of Frank Low. Further, EER did not meet James Rosen at that time 

because Rosen had already taken a position at the University of Wyoming. Thus, EER was 

unaware that Rosen had already obtained particle counter data indicating that sulfuric acid was a 

likely constituent of the stratospheric aerosol layer. Instead, based on information that he would 

glean from the International Critical Tables and solution eutectic diagrams, EER concluded that 

the most likely composition for the aerosols was aqueous solutions of concentrated sulfuric acid 

or its ternary mixture with nitric acid. But data on the optical constants of these materials did not 

exist for confirming their presence in infrared spectra of the atmospheric aerosol layers.

At the urging of Weinman and upon an invitation from Professor Bryce Crawford, Jr., EER

relocated to the Molecular Spectroscopy Laboratory (MSL) group in the Chemistry Department 

at Minnesota in September 1969. Crawford and his postdoctoral student Donald Lavery 

instructed EER on how to take the measurements in the mid-infrared and over a range of 

incidence angles with their laboratory spectrometer. He applied their very sensitive technique of 

attenuated total reflectance (ATR) spectroscopy to the concentrated aqueous solutions of sulfuric 

acid, nitric acid, and also ammonium sulfate [Remsberg et al., 1974]. It was a bold (or in the 

case of EER, naive) undertaking because all the other members of the MSL group at that time 

were focused on making spectral measurements and obtaining line assignments of simple 

triatomic molecules in their gaseous state. But after making a number of attempts, EER obtained 

good quality laboratory spectra from his solution samples by June 1970.

Shortly after his return to Wisconsin, EER presented his new datasets and optical constants at an 

NCAR Workshop on atmospheric particulates [Remsberg, 1971]. He then used his newly 

acquired data to calculate aerosol extinction profiles and provide an explanation for the excess 

emission that Pilipowskyj et al. [1968] observed in the lower stratosphere using Suomi’s 

radiometersondes and as verified with ground-based lidar soundings. EER also searched for

signatures of those materials in balloon-borne, measurements of limb infrared spectra of the 

lower stratosphere that had been obtained by David Murcray of the University of Denver. 

However, the balloon flights of Murcray were made in early 1969, when the aerosol loading in 

the stratosphere was small. As a result, EER was unable to conclusively determine whether the 

aerosols of that time were due to any of the three materials that he had measured in the 
52

laboratory. In addition, many in the research community were openly skeptical that sulfuric acid 

was really an important component of stratospheric aerosols, despite the indications from the 

vaporization temperatures of the particles that were sampled and heated in the balloon-borne 

counters of Rosen [1971]. In fact, only years later did Rinsland et al. [1994] confirm that

sulfuric acid was the best candidate for explaining the rather broad absorption features in the 

spectra from the Pinatubo aerosols that they observed and analyzed from the 1992 flight of 

ATMOS—or some 9 months after the eruption of the volcano. The optical constant data of EER 

that Rinsland used have since been added to the refractive index database of HIgh-resolution 

TRANsmission (HITRAN), as discussed by Massie and Goldman [2003].

In the meantime, Frank Low had carried out infrared observations of Venus with a telescope at 

the Catalina Observing Station of the University of Arizona in 1967 and found broad absorption 

features in the 8 to 12 micrometer region [Gillett et al., 1968]. Hanel et al. [1968] observed mid 

infrared emission spectra for Venus from the Harvard Observatory in 1967 using their Michelson 

interferometer. They reported an absorption feature at about 11.2 micrometers that they could 

not identify. Later though, A. T. Young [1974] was able to fit the broad features in both their 

sets of spectra with his simulations based on the data of Remsberg [1973] for 75% by weight 

aqueous sulfuric acid. Samuelson et al. [1975] also found a reasonable match of the spectra that 

they obtained at MacDonald Observatory in 1969, based on the optical constants of EER.

EER came to NASA Langley in 1971 and worked as a contract employee through The College of 

William and Mary and then with ODURF the following year. Based on his recent PhD work, he 

simulated limb infrared emission signals that one might expect to see from a balloon-borne 

prototype of the Nimbus 7 LIMS experiment. He developed specifications for a dedicated 

aerosol channel in the window region of the spectrum, but the data from that channel in an

instrument on a balloon test flight out of White Sands, NM, were unsuitable for making a 

confirming analysis. A similar aerosol channel was specified for the Nimbus 7 LIMS 

experiment, but it was deleted from the flight model of that instrument as a cost saving measure. 

It is worth noting though that because of the large effect of the aerosol emission from the El 

Chichon volcano on the limb infrared measurements of the SME satellite in 1982, the limb 

infrared emission instruments on UARS (i.e., CLAES and ISAMS) did include separate channels 

for the purpose of measuring the broadband emission from just the aerosols.

In the late 1960s and the 1970s Ney and Pepin adopted the spectral hygrometer or solar 

differential absorption approach of Low and Davidson [1965] for judging the changes in column 

water vapor during periods when they were making infrared observations from high altitude 

balloons. Landau [1982] improved on that initial hygrometer, so that it would be possible to 

observe either the Sun or the Moon (day and night sky conditions). In both cases they kept the 

same pair of wavelengths, 0.9375 and 0.880 micrometers, used by Low and Davidson. Later, 

McCormick and Pepin also made use of the 0.94 micrometer region for their solar occultation 

measurements of water vapor with the SAGE II instrument.
53

EER was hired as an employee in the Lidar Applications Section of ESSD at NASA Langley in 

1973. J. D. Lawrence, Jr., was fully supportive of his activities during that time, especially those 

related to analyses of the stratospheric aerosols observed with the 48-inch lidar and to the

feasibility studies that he made with regard to a future lidar system operating from the Space 

Shuttle. However, by 1980 EER became fully focused on the validation and characterization of 

the measurements of temperature and gaseous species from Nimbus 7 LIMS and on any possible 

contaminating effects for their profiles from the unmeasured aerosols and clouds. From there he 

went on to analyze solar occultation measurements from the UARS HALOE experiment for the 

distributions and trends of water vapor throughout the middle atmosphere. His involvement in 

the remote sensing of the middle atmosphere extends from 1980 until 2010, a span of time when 

he was a member of the LIMS, HALOE, and SABER Project and/or Science Teams.
54

Appendix B—Acronyms

AAFE Advanced Applications Flight Experiments

AAOE Airborne Antarctic Ozone Experiment

ACE Atmospheric Chemistry Experiment

ACE Aerosol/Cloud/Ecosystems

ADEOS ADvanced Earth Observing Satellite

ADM Angular Distribution Model

AEAP Atmospheric Effects of Aviation Program

AEC Atomic Energy Commission

AEM Atmospheric Explorer Mission

AESD Atmospheric Environmental Sciences Division

AFCRL Air Force Cambridge Research Laboratories

AIM Aeronomy of Ice in the Mesosphere

AIRS Atmospheric Infrared Sounder

AMPD Applied Materials and Physics Division

AMS American Meteorological Society

AOD Aerosol Optical Depth

APS Aerosol Polarimetry Sensor

ARB Aerosol Research Branch

ARM Atmospheric Radiation Measurement

ASD Atmospheric Science Division

ASTP Apollo-Soyuz Test Project

ATBD Algorithm Theoretical Basis Document

ATMOS Atmospheric Trace Molecule Spectroscopy

ATR Attenuated Total Reflectance

ATS Advanced Technology Satellite
55

AVHRR Advanced Very High Resolution Radiometer

BATC Ball Aerospace and Technologies Corporation

BOMEX Barbados Oceanographic and Meteorological Experiment

BNL Brookhaven National Laboratories

CALIPSO Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

CAS Center for the Atmospheric Sciences

CAT Clear Air Turbulence

CERES Clouds and the Earth’s Radiant Energy System 

CIAP Climatic Impact Assessment Program

CIMATS Correlation Interferometer for the Measurement of Atmospheric Trace Species

CIMSS Cooperative Institute for Meteorological Satellite Studies

CLAES Cryogenic Limb Array Etalon Spectrometer

CLARREO CLimate Absolute Radiance and REfractivity Observatory

CNES Centre National d’Etudes Spatiales

COSPAR Committee on Space Research

CrIS Cross-track Infrared Sounder

COS Carbonyl Sulfide

CZCS Coastal Zone Color Scanner

DAAC Distributed Active Archive Center

DIAL DIfferential Absorption Lidar

DMSP Defense Meteorological Satellite Program

DOD Department of Defense
56

DOT Department of Transportation

ENVISAT ENVIronmental SATellite

ENSO El Nino/Southern Oscillation

EOS Earth Observing System

EOSDIS EOS Data and Information System

EPA Environmental Protection Agency

EQPO Environmental Quality Program Office

ERB Earth Radiation Budget

ERBE Earth Radiation Budget Experiment

ERBS Earth Radiation Budget Satellite

ERTS Earth Resources Technology Satellite

ESA European Space Agency

ESSD Environmental and Space Sciences Division

ESSP Earth System Science Pathfinder

FED Flight Electronics Division

FID Flight Instrumentation Division

FIRE First ISCCP Regional Experiment

FIRST Far-InfraRed Spectroscopy of the Troposphere

FOV Field-Of-View

GARP Global Atmospheric Research Program

GATE GARP Atlantic Tropical Experiment
57

GATS Gordley and Associates Technical Software

GeoCAPE Geostationary Coastal and Air Pollution Events

GERB Geostationary Earth Radiation Budget

GISS Goddard Institute for Space Studies

GOES Geostationary Operational Environmental Satellite

GOMOS Global Ozone Monitoring by Occultation of Stars

GSFC Goddard Space Flight Center

HALOE HALogen Occultation Experiment

HITRAN HIgh-resolution TRANsmission

HSRL High Spectral Resolution Lidar

HU Hampton University

IASI Infrared Atmospheric Sounding Interferometer

IFAORS Institute For Atmospheric Optics and Remote Sensing

IIP Instrument Incubator Program

IIR Imaging Infrared Radiometer

IMG Interferometric Monitor of Greenhouse gases

IPCC Intergovernmental Panel on Climate Change

IR InfraRed

IRAS InfraRed Astronomical Satellite

IRD Instrument Research Division

IRIS InfraRed Interferometer Spectrometer

ISAMS Improved Stratospheric And Mesospheric Sounder
58

ISCCP International Satellite Cloud Climatology Project

ISS International Space Station

JIAFS Joint Institute for the Advancement of Flight Sciences

JPL Jet Propulsion Laboratory

JPSS Joint Polar Satellite System

JWST James Webb Space Telescope

LaRC Langley Research Center

LAS Lidar Applications Section

LEO Low Earth Orbit

LHS Laser Heterodyne Spectroscopy

LIMS Limb Infrared Monitor of the Stratosphere

LITE Lidar In-space Technology Experiment

LRIR Limb Radiance Inversion Radiometer

LW Long-Wave

LZEEBE Long-time Zonal Earth Energy Budget Experiment

MAPS Measurement of Air Pollution from Satellites

MATD Marine Applications and Technology Division

MFOV Medium Field-Of-View

MISR Multi-angle Imaging Spectro-Radiometer

MIT Massachusetts Institute of Technology

MSL Molecular Spectroscopy Laboratory
59

MODIS MODerate-resolution Imaging Spectro-radiometer

MORL Manned Orbital Research Laboratory

MPC Mother-of-Pearl Clouds

MRIR Medium Resolution Infrared Radiometer

MSG Meteosat Second Generation

MSS Multi-Spectral Scanner

MTPE Mission To Planet Earth

NACA National Advisory Committee for Aeronautics

NAPCA National Air Pollution Control Adminstration

NASA National Aeronautics and Space Administration

NCAR National Center for Atmospheric Research

NEROS NorthEast Regional Oxidant Study

NLC NoctiLucent Clouds

NMP New Millenium Program

NOAA National Oceanic and Atmospheric Administration

NOSS National Oceanic Satellite System

NPOESS National Polar-orbiting Operational Environmental Satellite System

NPP National Polar-orbiting Partnership

NRAO National Radio Astronomy Observatory

NRC National Research Council

NRL Naval Research Laboratory

OA Office of Applications
60

OAST Office of Aeronautics and Space Technology

OCO Orbiting Carbon Observatory

ODURF Old Dominion University Research Foundation

OMI Ozone Monitoring Instrument

OMPS Ozone Mapping and Profiler Suite

OSIRIS Optical Spectrograph and InfraRed Imaging System

OSO Orbiting Solar Observatory

OSS Office of Space Sciences

PAGEOS Passive Geodetic Earth Orbiting Satellite

PARASOL Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled 

with Observations from a Lidar

PARD Pilotless Aircraft Research Division

PEPE Persistent Elevated Pollution Episode

POAM Polar Ozone and Aerosol Measurement

POLDER Polarization and Directionality of the Earth’s Reflectance

PSC Polar Stratospheric Clouds

RGB Red-Green-Blue

RMOP Remote Measurement Of Pollution

RRL Risk Reduction Laser

RSB Radiation Sciences Branch

RSP Research Scanning Polarimeter

RTI Research Triangle Institute
61

SABER Sounding of the Atmosphere using Broadband Emission Radiometry

SAD Surface Aerosol Density

SARB Surface and Atmospheric Radiation Budget

SAGE Stratospheric Aerosol and Gas Experiment

SAM Stratospheric Aerosol Monitor

SASC Systems and Applied Sciences Corporation

SASS Seasat-A Scatterometer System

SATD Space Applications and Technology Division

SBUV Solar Backscatter Ultra-Violet

SCIAMACHY SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY

SD Science Directorate

SEVIRI Spinning Enhanced Visible and Infrared Imager

SIR Shuttle Imaging Radar

SMD Science Mission Directorate

SME Solar Mesosphere Explorer

SMIC Study of Man’s Impact on Climate

SMMR Scanning Multichannel Microwave Radiometer

SMS Synchronous Meteorological Satellite 

S/N Signal-to-Noise

SO Solar Occultation

SOFIE Solar Occultation For Ice Experiment

SOLVE SAGE III Ozone Loss and Validation Experiment

SORCE Solar Radiation and Climate Experiment

SRI Stanford Research Institute
62

SSE Surface Spectral Emissivities

SSEC Space Science and Engineering Center

SST SuperSonic Transport

SSTs Sea Surface Temperatures

SSU Stratospheric Sounding Unit

STS Space Transportation System

SW Short-Wave

THIR Temperature Humidity Infrared Radiometer

TIM Total Irradiance Monitor

TIROS Television InfraRed Observation Satellite

TOA Top-Of-Atmosphere

TOMS Total Ozone Mapping Spectrometer

TOVS TIROS Operational Vertical Sounder

TRACE TRopospheric Aerosol and Cloud Experiment

TRL Technical Readiness Level

TRMM Tropical Rainfall Measuring Mission

TRW Thompson Ramo Wooldridge

UARS Upper Atmosphere Research Satellite

UK United Kingdom

VPI Virginia Polytechnic Institute
63

WFC Wide Field Camera

WFOV Wide Field-Of-View

WMO World Meteorological Organization
64

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Remote Measurement of Pollution - A 40-Year Langley Retrospective: Part 

II - Aerosols and Clouds

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Remsberg, Ellis E.

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NASA Langley Research Center

Hampton, VA 23681-2199

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A workshop was convened in 1971 by the National Aeronautics and Space Administration (NASA) on the Remote Measurement of Pollution (RMOP), and the 

findings and recommendations of its participants are in a NASA Special Publication (NASA SP-285). The three primary workshop panels and their chairmen 

were focused on trace gas species (Will Kellogg), atmospheric particulates or aerosols (Verner Suomi), and water pollution (Gifford Ewing). Many of the 

workshop participants were specialists in the techniques that might be employed for regional to global-scale, remote measurements of the atmospheric 

parameters from Earth-orbiting satellites. In 2011 the author published a 40-year retrospective (or Part I) of the instrumental developments that were an 

outgrowth of the RMOP panel headed by Will Kellogg, i.e., on atmospheric temperature and gaseous species. The current report (or Part II) is an analogous 

retrospective of the vision of the panel led by Verner Suomi for the measurement of particulates (or aerosols) and clouds and for their effects on Earth’s 

radiation budget. The class of measurement techniques includes laser radar or lidar, solar occultation, limb emission and scattering, nadir-viewing photometry 

or radiometry, and aerosol polarimetry. In addition, the retrospective refers to the scientific imperatives that led to those instrument developments of 

1971-2010. Contributions of the atmospheric technologists at the Langley Research Center are emphasized, and their progress is placed in the context of the 

parallel and complementary work from within the larger atmospheric science community. 

15. SUBJECT TERMS

Earth radiation budget; aerosols; clouds; history; pollution; remote sensing; satellite

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