Cover: Color-composite image of Thematic Mapper spectral bands 7,4,2 with the spatial enhancement 

of the SPOT high-resolution visible panchromatic band . The respective dates of the data are April 29 

and May 1, 1986 (SPOT Data copyright 1986 CNES). 
Processing and Analysis of Commercial 

Satellite Image Data of the Nuclear 

Accident Near Chernobyl, U.S.S.R. 

By FRANK G. SADOWSKI and STEVEN J. COVINGTON 

U.S. GEOLOGICAL SURVEY BULLETIN 1785 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1987 

For sale by the Superintendent of Documents, 

U.S. Government Printing Office, 

Washington, DC 20402 

Library of Congress Cataloging in Publication Data 

Sadowski, Frank G. 

Processing and analysis of commercial satellite image data of the nuclear 

accident near Chernobyl, U.S.S.R. 

(U.S. Geological Survey bulletin ; 1785) 

Bibliography: p. 

Supt. of Docs. no.: I 19.3:1785 

1. Chernobyl Nuclear Accident, Chernobyl, Ukraine, 1986. 2. Remote 

sensing-Ukraine-Chernobyl. I. Covington, Steven J. II. Title. Ill. Series. 

QE75.B9 no. 1785 557.3 s 87-600039 

[TK1362.S65] [363.1 '79] 
CONTENTS 

Abstract I 

Introduction I 

Acknowledgments I 

Background 1 

Chernobyl nuclear powerplant I 

Commercial satellite image data 2 

Data acquisition and processing procedures 2 

Image products and interpretations 4 

Conclusions I8 

References 18 

Appendix. Digital values of the piecewise linear contrast stretches applied to the 

April 29, 1986, Thematic Mapper data I9 

FIGURES 

1. Sketch map showing location and layout of Chernobyl nuclear powerplant 2 

2. Plot showing spectral band placement for Landsat Thematic Mapper and 

SPOT high-resolution visible sensors 3 

3. Image data acquired in each of the Thematic Mapper spectral bands on April 

29, 1986 5 

4. Color-composite image of Thematic Mapper quarter-scene showing regional 

view of the Chernobyl site on April 29, 1986 (spectral bands 4,3,2) 6 

5. Color-composite image of Thematic Mapper quarter-scene showing regional 

view of the Chernobyl site on April29, 1986 (spectral bands 7,4,2) 7 

6. Color-composite image of Thematic Mapper spectral bands 7 ,4,2 acquired on 

April29, 1986 8 

7. Plot showing Thematic Mapper spectral bands superimposed on radiant 

emission spectra of selected objects 9 

8. Plot showing brightness values of ground features in Thematic Mapper data of 

April 29, 1986 IO 

9. Color-composite image of Thematic Mapper spectral bands 7,4,2 acquired on 

June 6, 1985 I1 

10. Color-composite image of Thematic Mapper spectral bands 7,4,2 acquired on 

April 22, 1986 12 

11. Color-composite image of Thematic Mapper spectral bands 7 ,4,2 acquired on 

May 8, 1986 13 

12. Images of Thematic Mapper band 6 (thermal band) for the four dates 

studied 14 

13. Images showing cooling pond thermal patterns from Thematic Mapper band 6, 

color-coded relative to the adjacent river, for each of three dates 15 

14. SPOT high-resolution visible panchromatic image acquired on May 1, 

1986 16 

15. Color-composite image of Thematic Mapper spectral bands 7 ,4,2 with the 

spatial enhancement of the SPOT high-resolution visible panchromatic 

band I7 

TABLE 

1. Characteristics of the Landsat Thematic Mapper (TM) and SPOT highresolution visible (HRV) sensors 3 

Contents Ill 

Processing and Analysis of Commercial Satellite Image 

Data of the Nuclear Accident near Chernobyl, U.S.S.R. 

By Frank G. Sadowski 1 and Steven j. Covington1 

Abstract 

Advanced digital processing techniques were applied 

to Landsat-5 Thematic Mapper (TM) data and SPOT highresolution visible (HRV) panchromatic data to maximize the 

utility of images of a nuclear powerplant emergency at 

Chernobyl in the Soviet Ukraine. The images demonstrate 

the unique interpretive capabilities provided by the 

numerous spectral bands of the Thematic Mapper and the 

high spatial resolution of the SPOT HRV sensor. 

INTRODUCTION 

This report presents the results of the processing 

and analysis of commercial satellite image data acquired 

over the nuclear powerplant at Chernobyl in the Soviet 

Ukraine. The images were acquired by the Landsat 

Thematic Mapper (TM) and the Systeme Probatoire 

d'Observation de la Terre (SPOT) high-resolution visible 

(HRV) sensors. Landsat is the United States' civil land 

remote sensing satellite system, and the SPOT satellite is 

operated by the French space agency Centre National 

d'Etudes Spatiales (CNES). 

The image data were obtained in a digital format 

and were processed by using advanced computerized 

techniques that included spatial filtering, contrast enhancement, color compositing, film recording, and, in 

one case, data merging and color transformation. Each 

technique was selected and used in a manner to maximize 

the interpretability of the satellite images. The results of 

the data processing and analysis illustrate the spectral 

and spatial capabilities of the two sensor systems and 

provide information about the severity and duration of 

the events unfolding at the powerplant site. 

Acknowledgments 

The images in this report were originally produced 

in a very short period of time in order to be responsive to 

information needs that were paramount soon after the 

accident at the Chernobyl nuclear powerplant. The 

1

TGS Technology, Inc. Work performed under U.S. 

Geological Survey contract 14-08-0001-22521. 

extraordinary efforts of several individuals at the U.S. 

Geological Survey's EROS Data Center contributed to 

the timely production of the image products. In particular, 

John L. Dwyer and Wayne A. Miller assisted in processing 

the Thematic Mapper data. Joy J. Hood, David J. 

Meyer, and June M. Thormodsgard were instrumental in 

processing the SPOT data and implementing the restoration and IHS software on Thematic Mapper data. 

Douglas R. Binnie, Ron R. Risty, Wayne A. Miller, 

Carolyn K. Morse, V. Annette McClaren, Susan M. 

Battista, and William D. Winn all had key roles in the 

production of final image products. 

BACKGROUND 

Chernobyl Nuclear Powerplant 

The Chernobyl nuclear powerplant is located in the 

Soviet Ukraine between the towns of Chernobyl (population 25,000) and Pripyat (population 10,000). The 

Pripyat River, flowing past the powerplant, is one of 

several tributaries feeding a reservoir, which supplies 

freshwater to the city of Kiev located 121 km (75 mi) 

south of of Chernobyl (inset, fig. 1). 

The powerplant is located adjacent to a pond 

(cooling reservoir, fig. 1), 12 km (7.4 mi) long, that 

supplies water to cool the reactors. The plant contains 

four reactors located in two separate buildings. Each 

reactor is capable of producing 1,000 megawatts of 

electrical power, making the Chernobyl plant a major 

source of energy for the central and western Ukraine, 

including the city of Kiev with its population of 2.4 

million people. 

As stated by the news media, the reactor that failed 

at Chernobyl was reactor number 4, the newest reactor at 

that facility, brought on line in 1983. The reactor, like the 

remaining three at that site, has no containment structure 

around it. Containment buildings are designed to prevent 

radiation from escaping into the atmosphere should a 

problem develop in the reactor core. From all accounts, 

an explosion occurred in the reactor core on Saturday, 

April 26, destroying part of the reactor building and 

igniting the graphite in the core. With no containment 

Introduction 1 
0 MILES 

--- Figure 1. The location and layout of the Chernobyl nuclear 

powerplant (adapted from Newsweek magazine, May 12, 

1986, p. 25; original artist, Christoph Blumrich). 

structure, the graphite fire was exposed to the open air, 

allowing it to burn at intense temperatures until smothered 

by air-dropped mixtures of sand and boron. 

Commercial Satellite Image Data 

The satellite images presented in this report illustrate 

the current routinely available types of commercial 

satellite image data. The Landsat-5 TM data were 

acquired from the Earth Observation Satellite (EOSA T) 

Company of Lanham, Md., and the SPOT data were 

acquired from the SPOT Image Corporation, the U.S. 

subsidiary of the French company SPOT IMAGE. All 

data were purchased in computer-compatible tape format 

and processed at the U.S. Geological Survey's EROS 

Data Center in Sioux Falls, S. Dak. 

The characteristics of the data and the orbiting 

satellites are summarized in table 1 (U.S. Geological 

Survey and National Oceanic and Atmospheric Administration, 1984; Courtois and Weill, 1985). The 

Landsat TM data and SPOT data differ markedly in their 

spatial and spectral characteristics. Whereas SPOT data 

are acquired with a smaller instantaneous field-of-view 

(IFOV), which contributes to finer spatial resolution, 

TM data have more spectral bands. Figure 2 compares 

the placement of the spectral bands for each sensor. 

DATA ACQUISITION AND PROCESSING 

PROCEDURES 

The images in this report include four daytime 

scenes of Landsat-5 TM data and one scene of SPOT 

HRV 10-m panchromatic data. The TM and SPOT 

scenes consisted of P-data and Ievell B data respectivelydata that have been resampled in the process of applying 

systematic geometric corrections. The TM and SPOT 

scene acquisitions are summarized as follows: 

Landsat-5 TM scenes: 

Date Path/ Row Quadrant Landsat Scene I D 

6/06/85 I8I/24 3 y 5046208I85 xo 

4/22/86 I8I/24 3 y 5078208I40 xo 

4/29/86 I82/24 4 Y5078908200XO 

5/08/86 I8I/24 3 Y5079808I33XO 

SPOT scene: 

Date Instrument Mode Scene ID 

5/0I /86 HRVI Panchromatic S I H I86050 I 090706 

To produce images from the digital data, we used 

several computerized techniques of digital magnification, 

spatial filtering, contrast enhancement, color com positing, 

and film recording. Digital magnification was performed 

on some of the images by replicating pixel values to 

achieve a larger image scale. About half of the images 

were magnified by a spatial filtering technique designed 

to improve image sharpness in the TM data. The spatial 

filter is part of a TM image restoration software capability 

at the EROS Data Center (Wood and others, 1986). 

Overall image contrast was enhanced by applying a 

piecewise linear contrast stretch to the digital data of each 

scene. The contrast stretch redistributes the digital data 

brightness values to enhance their visual analog representation on film. Due to variations in data distribution 

among the bands, it was necessary to create unique 

stretches for bands 2-7. Band 1 was not used in any image, 

to reduce the influence of radiometric aberrations 

associated with atmospheric haze. The stretches applied 

to the April29, 1986, scene are presented in the Appendix. 

Additional digital processing was used to merge 

TM and SPOT data to produce a single image in which 

selected spectral characteristics of the TM data and the 

spatial detail of SPOT 10-m panchromatic data were 

portrayed. The procedure included using the image 

restoration software to resample the 30-m TM pixels to 

10-m pixels. The 10-m SPOT data were registered to the 

resampled TM data by using a second-order polynomial 

2 Processing and Analysis of Satellite Image Data near Chernobyl 
Table 1. Characteristics of the Landsat Thematic Mapper (TM) and SPOT high-resolution visible (HRV) sensors 

[M, multispectral mode; P, panchromatic mode; IFOV, instantaneous field of view. --,not applicable] 

Landsat-5 TM 

Launch date ..................... March 1, 1984 

Spectral bands (in micrometers) 

1 ............................. 0.45-0.52 

2 ............................. 0.52-0.60 

3 ............................. 0.63-0.69 

4 ............................. 0. 76-0.90 

5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 55- 1. 7 5 

6 ............................. 10.40-12.50 

7 ............................. 2.08-2.35 

Ground IFOV ................... 30 m X 30 m (Bands 1-5, 7) 

120 m X 120 m (Band 6) 

Orbit inclination (degrees) ......... 98.2 

Orbital altitude (kilometers) ....... 705 

Orbital nodal period (minutes) ..... 98.9 

Orbits per day ................... 14.6 

Equatorial crossing time (local solar time) 

Descending .................... 9:39 a.m. 

Ascending ..................... 9:39 p.m. 

Repeat period (days) .............. 16 

Ground swath (kilometers) ........ 185 

UJ 

(/) 

z 

0 

a.. 

(/) 

UJ 

a: 

UJ 

> i= 

<( 

...J 

*At nadir. 

** Sensor design allows ±27 degrees off-nadir viewing capabilities. 

SPOT HRV 

February 21,1986 

0.50-0.59 (M), 0.51-0.73 (P) 

0.61-0.68 (M) 

0.79-0.89 (M) 

20 m X 20 m (M)* 

10 m X 10 m (P)* 

98.7 

832 

101.4 

14.2 

10:30 a.m. 

26 

117 when the two HRV instruments are 

pointed so as to cover adjacent 

fields, with 3 km overlap at nadir. 

60 at nadir. 

80 at extreme off-nadir.** 

~~~~~--~~~--~~~----~~~--~~~~--~~~~~~~----~~~~~ 

LANDSAT THEMATIC MAPPER I 1 1 '1 2 I ITJI 4 

SPOT HIGH RESOLUTION 

! M ultisbectral 

I COOJ 

r•nchj._om_a_tic ___ ___,_. 

REFLECTED INFRARED 

1.0 1.1 1.2 1.3 1.5 1.7. 1.9 2.1 2.3 14.0 WAVELENGTH IN MICROMETERS 

5 7 

Figure 2. Spectral band placement for the Landsat Thematic Mapper and the SPOT high-resolution visible sensors. 

Data Acquisition and Processing Procedures 3 
spatial model derived from 18 control points. The two 

data sets were then merged by using an intensity, hue, and 

saturation (IHS) transformation (Haydn and others, 

1982). This transformation maintained the hue (color) 

relationships of a selected three-band combination of 

TM data, while modulating the intensity of the TM data 

with values derived from the higher resolution SPOT 

data. Finally, the merged IHS data were transformed 

back into red-green-blue color space for reproduction on 

photographic film. 

Prior to creation of a film product of each image, 

annotation and collar work were digitally inserted into 

the scenes for informational content and reference. Color 

images were recorded onto Kodak2 2445 Aerocolor 

negative film using a Color FIRE 240 film recorder. The 

Color FIRE film recorder creates a color image by 

assigning an additive primary color (red, green, or blue, 

abbreviated R,G,B) to each of three selected spectral 

bands of the digital data. As an example, a combination 

of TM spectral bands 7 ,4,2 in R,G,B sequence would 

have band 7 assigned to the red Color FIRE channel, 

band 4 to the green channel, and band 2 to the blue 

channel. 

IMAGE PRODUCTS AND INTERPRETATIONS 

The image data acquired in each of the TM spectral 

bands on April 29, 1986, for the immediate area of the 

reactor site are presented in figure 3. In most circumstances, the levels of brightness associated with 

ground features in TM bands 1 through 5 and band 7 are 

attributable to solar reflectance. Figure 3 illustrates the 

relative changes in reflectance that occur for various 

ground features from band to band. Brightness variations 

in band 6 are attributable to emitted energy received at 

the sensor in the thermal infrared wavelength region; 

generally, warmer objects are brighter. The somewhat 

blurred appearance of the band 6 image is due to the 

coarser (120-m) IFOV that results in lower spatial 

resolution (table 1). 

When the multispectral data represented in figure 3 

are interpreted in conjunction with knowledge of terrain 

reflectance and emittance phenomena, a number of 

technical observations can be made about the conditions 

~t the reactor site on April 29, following the disaster 

reported to have occurred on April26. These observations 

are enhanced by comparing the image data of April29 to 

additional TM images ofthe site acquired before (June 6, 

1985, and April22, 1986) and some 12 days after (May 8, 

1986) the disaster. 

2Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the 

U.S. Geological Survey. 

Figures 4 and 5 show a regional view of the 

Chernobyl site on April 29. These images readily lend 

themselves to evaluations of agricultural, forest, and 

wetlands areas in the region. Figure 4 includes spectral 

bands 4,3,2 combined in the R,G,B color sequence. This 

combination provides the traditional color-infrared 

image, widely used for interpreting vegetation and soils 

information. Inspection of this color-composite image at 

larger scale provides some evidence of a darkened strip of 

ground on the west side of the reactor building that is not 

evident on earlier dates. However, additional information 

about the condition of the reactor is not apparent. 

Figure 5 includes TM band 7 -a longer wavelength 

near-infrared spectral band-in combination with TM 

bands 4 and 2 (R,G,B sequence). A large-scale view ofthe 

reactor site in this same band combination is shown in 

figure 6. A bright red spot can be seen in the powerplant 

complex near the location of reactor number 4, the 

farthest one from the cooling pond (see sketch in fig. 1). 

The color of the spot indicates a high brightness value in 

band 7 and corresponding low values in bands 4 and 2. 

This somewhat unusual combination of brightness values 

is indicative of a very high temperature heat source, 

suggesting the exposed burning graphite of the damaged 

reactor. 

Consideration of radiation theory and the analysis 

of brightness values in TM bands 1 through 5 and TM 

band 7 of the April 29 TM image provide evidence to 

support the interpretation of the red spot as a hightemperature heat source. In figure 7, the TM spectral 

bands have been superimposed on a set of radiant 

emission curves for selected objects at different temperatures. The curves demonstrate that terrain features near 

ambient temperatures of 290 K ( 17° C) radiate energy at 

long-wavelength regions, with a peak between 10 and 12 

pm (vicinity of TM band 6). However, as a feature 

becomes hotter, the intensity of the emitted energy 

increases and the radiation peak shifts toward shorter 

wavelengths. If the emitting feature's temperature was 

about 1,000 K (727°C), one would expect the emission 

peak to occur near the region ofTM band 7 and, to lesser 

degrees, in TM band 5 and the progressively shorter 

wavelength spectral bands. 

An analysis of the brightness values in the April29 

TM image provides results that are consistent with the 

above expectation. Figure 8 shows brightness values 

over the location of the damaged reactor compared with 

brightness values for portions of the adjacent undamaged 

reactor structure. The brightness values for the undamaged structure are relatively low in all bands, suggestive of reflectance from a dark (perhaps asphalt) roof 

surface. Brightness values over the damaged reactor, 

whil~ equivalent to those of the undamaged reactor 

structure in TM bands 1 through 4, display the increase in 

TM band 5 and, most noticeably, in band 7 that is 

4 Processing and Analysis of Satellite Image Data near Chernobyl 
"§_ 

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Image Products and Interpretations 5 
Figure 4. Color-composite image of a Thematic Mapper quarter-scene showing a regional view of the Chernobyl site on 

April 29, 1986. The spectral band combination is bands 4,3,2 (red,green,blue sequence). 

6 Processing and Analysis of Satellite Image Data near Chernobyl 
Figure 5. Color-composite image of a Thematic Mapper quarter-scene showing a regional view of the Chernobyl site on 

April 29, 1986 .. The spectral band combination is bands 7,4,2 (red,green,blue sequence). 

Image Products and Interpretations 7 
Figure 6. Color-composite image of Thematic Mapper spectral bands 7A,2 (red ,green,blue sequence) acquired on April29, 

1986. 

8 Processing and Analysis of Satellite Image Data near Chernobyl 
10 r-------------.----.--------------,---------------------------------~ 

E 

::l. 

. 

Ultraviolet 

'E 

u 10~~--~-------

~ Q) 

u 

c: 

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Q) 

.... 

c: 

ctl 

:0 0.1 ~----~------­ ~ 

~ u 

Q) 

~ 

en 0.01 ~----~-------

10- ~----~-------

10- ~----~------~ 

Wavelength 1~-tm I 

Near Infrared 

I t t \ t T~7 l TM3 TM4 TMS 

TM1 TM2 

Thermal Infrared 

20 50 00 

t 

TM6 

Figure 7. Thematic Mapper spectral bands superimposed on the radiant emission spectra of selected 

objects. 

characteristic of a very hot heat source. The differences in 

brightness values between the damaged reactor and the 

adjacent undamaged structure in each of bands 5 and 7 

can be attributed to the emitted component of total 

radiation observed by the sensor. 

The unambiguous interpretation of the damaged 

reactor requires knowing the brightness values of ground 

features in other bands in addition to TM band 7. The 

brightness values of the sand bar (from the river adjacent 

to the reactor complex) in figure 8 show that while some 

ground features can have equivalent brightness in TM 

band 7, their brightness in other TM bands helps to 

identify them as natural or man-made features having 

generally high solar reflectance. This observation applies 

also to the bright spot that appears at the left edge of the 

powerplant complex in figure 6. Although the identity of 

this feature is uncertain, its brightness values in all TM 

bands are not consistent with those of a high-temperature 

Image Products and Interpretations 9 
240 

-200 

Q) 

.D 

E 

;:, 

.: 160 

-~ .~ 

~ 

UJ 

(f) 120 z 

0 

a.. 

(f) 

UJ 

a: 80 a: 

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(f) 

z 

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(f) 40 

TM1 TM2 TM3 TM4 TM5 

THEMATIC MAPPER BANDS 

D Adjacent Undamaged Reactor Structure 

!88lj Damaged Reactor 

t2] Sand Bar 

TM7 

Figure 8. Brightness values of ground features in the 

Thematic Mapper data of April 29, 1986. 

heat source. The color-composite image of bands 7,4,2 

(R,G,B sequence) readily enables making such multispectral observations. 

Figures 9-11 show TM images from additional 

dates of observation over the Chernobyl reactor site that 

enable us to interpret changes related to the disaster. The 

image of April 22, 1986 (fig. 10), shows little obvious 

difference from the image acquired on June 6, 1985, 

suggesting that just before the disaster the reactor site was 

functioning much as it was nearly a year earlier. The 

image of April 29, 1986 (fig. 6), shows the anomalous 

heat source from reactor number 4 and the darkened strip 

of ground on the west side of the reactor that may have 

resulted from the explosions and (or) from reported 

attempts to smother the exposed burning graphite with 

helicopter-borne loads of sand and boron. The image of 

May 8, 1986 (fig. 11 ), shows that the bright red spot 

associated with the damaged reactor is no longer evident 

in TM band 7, indicating that the apparent temperature 

had dropped considerably since April29. Also, the water 

intake channels immediately south of the reactor structure 

appear dry, suggesting that the water supply inlet from 

the cooling pond is closed. 

Figure 12 enables comparison of the relative 

temperature of ground features in TM band 6 on each of 

the four dates. The high-temperature heat source associated with the damaged reactor does not appear on the 

April 29 image because TM band 6 is designed to be 

sensitive to the temperature range of 200 K to 340 K 

( -70° C to 70° C). This means that the very high apparent 

temperature of the damaged reactor cannot be detected. 

Under ideal conditions, the damaged reactor can only be 

detected as a feature at 340 K, only slightly higher than 

the ambient temperature of most terrain features. Given 

this lack of thermal contrast, the coarse 120-m IFOV of 

TM band 6 inhibits detection of the localized heat source. 

However, the brightness values of large, moderately 

warm structures in the reactor complex such as the 

turbine / generator halls are readily obvious on each date. 

It can be seen that the apparent temperature of these 

structures does not change dramatically between dates, 

even after the disaster, thus offering little indication of 

the disaster occurrence. 

The images in figure 12 show the thermal patterns 

of water in the cooling pond on each date studied. In 

figure 13, these thermal patterns have been color-coded 

relative to the adjacent river for the three dates that occur 

just before, during, and after the crisis associated with the 

burning reactor. The image of April 22 illustrates the 

temperature gradient of the cooling pond during normal 

operation. Warm (red) water, discharged from the plant 

at the outlet channel, is cooled as it circulates around the 

pond in a counterclockwise direction and then reenters 

the plant at the inlet channel. This temperature gradient 

is not evident on April29 or May 8, clearly indicating that 

the entire pond has approached a near-uniform temperature due to the cessation of normal operations on April 

26. The overall pond temperature was still warmer than 

the river on April 29, and it had cooled to very near the 

river temperature by May 8. (The land area in these 

images is represented by the reflectance patterns in TM 

band 4; thus, land brightness values have no relationship 

to relative temperature.) 

Figure 14 shows the Chernobyl reactor site as 

acquired by the high-resolution visible (HRV) imaging 

sensor of the French SPOT satellite on May I, 1986. The 

10-m spatial resolution of this panchromatic image 

reveals greater spatial detail in the vicinity of the reactor 

site than noted on the TM images. 

The result of combining the 10-m spatial resolution 

of the SPOT data with the multispectral (bands 7,4,2) 

data of the Thematic Mapper is shown in figure 15. This 

image vividly illustrates the advantages of each of these 

two types of commercial satellite image data. Simply 

stated, much of the multispectral information available 

only in the TM data can be observed in the context of the 

higher spatial resolution SPOT data. 

10 Processing and Analysis of Satellite Image Data near Chernobyl 
Figure 9. Color-composite image of Thematic Mapper spectral bands 7,4,2 (red,green,blue sequence) acquired on june 6, 

1985. 

Image Products and Interpretations 11 
Figure 10. Color-composite image of Thematic Mapper spectral bands 7,4,2 (red,green,blue sequence) acquired on April 

22, 1986. 

12 Processing and Analysis of Satellite Image Data near Chernobyl 
Figure 11. Color-composite image of Thematic Mapper spectral bands 7,4,2 (red,green,blue sequence) acquired on May 8, 

1986. 

Image Products and Interpretations 13 
Figure 12. I mages of Thematic Mapper band 6 (thermal band) for the four dates studied. 

14 Processing and Analysis of Satellite Image Data near Chernobyl 
Figure 13. Images showing cooling pond thermal patterns from TM band 6, color-coded relative to the adjacent river, for 

each of three dates. (Land brightness values are from TM band 4.) 

Image Products and Interpretations 15 
Figure 14. SPOT high-resolution visible panchromatic image acquired on May 1, 1986 (SPOT Data © 1986 CNES). 

16 Processing and Analysis of Satellite Image Data near Chernobyl 
Figure 15. Color-composite image of Thematic Mapper spectral bands 7,4,2 with the spatial enhancement of the SPOT 

high-resolution visible panchromatic band. The respective dates of the data are April29 and May 1,1986 (SPOT Data © 1986 

CNES). 

Image Products and Interpretations 17 
CONCLUSIONS 

Images of Landsat-5 TM data and SPOT HRV 

panchromatic data acquired over the Chernobyl nuclear 

powerplant have illustrated the following spectral and 

spatial capabilities and limitations of currently available 

commercial satellite image data: 

• The Landsat Thematic Mapper can show direct 

evidence of high-temperature heat sources in the longwavelength near-infrared spectral bands unique to this 

sensor. TM data of April 29, 1986, showed intermediate 

and high brightness values for the damaged reactor in 

TM bands 5 and 7, respectively, that are attributed to 

emitted (thermal) radiation from the exposed burning 

graphite. A color-composite image of bands 7,4,2 (R,G,B 

sequence) was particularly useful for observing the 

damaged reactor. 

• TM band 6 (the thermal band) showed no hightemperature response from the damaged reactor due to 

the limited range of temperature response designed for 

this band and the coarse 120-m IFOV. This band was 

specifically designed to be highly sensitive to temperature 

variations in earth surface features that are near ambient 

air temperature. As an example, TM band 6 enabled us to 

observe differences in water-temperature gradients in the 

cooling pond adjacent to the powerplant complex before 

and after the disaster. 

• The SPOT I 0-m panchromatic image revealed 

significantly greater spatial detail in the vicinity of the 

reactor site. Shadow details associated with larger features 

may allow for approximations of heights. 

• An image of merged TM and SPOT data enabled 

us to observe much of the multispectral information 

available only in the TM data in the context of the higher 

spatial resolution SPOT data. 

The response of TM bands 5 and 7 to the emitted 

radiation from the damaged reactor provides evidence to 

suggest broader application of these spectral bands for 

detecting and monitoring other high-temperature thermal 

anomalies on the earth's surface. Studies elsewhere have 

begun to demonstrate application to thermal features of 

active volcanoes. These include the use ofTM band 7 for 

portraying the intense heat emission of a volcano in 

eruption (EOSA T Corporation, 1986) and a recent 

discovery of a significant thermal anomaly on Lascar 

volcano in northern Chile (P. W. Francis and D.A. 

Rothery, written commun., 1986). At the EROS Data 

Center, evaluations of band 5 and, more importantly, 

band 7 in TM images have provided the capability to 

observe the flames at the perimeter of rangeland fires in 

east-central Africa. 

An analysis of TM images acquired before and 

after the disaster enabled several technical observations 

about the conditions of the reactor site: 

• An image of April 22, 1986, showed little obvious 

difference from an image acquired on June 6, 1985, 

suggesting that, four days before the accident, the reactor 

site was functioning much as it was nearly a year earlier. 

• An image of May 8, 1986, showed that the high 

brightness values associated with the damaged reactor in 

TM bands 5 and 7 on April 29, 1986, were no longer 

evident, indicating a significant reduction in the apparent 

temperature of the damaged reactor. 

• A darkened strip of ground on the west side of 

reactor number 4, evident on the two images following 

the disaster, may be a blast effect that resulted from the 

explosion or debris associated with reported attempts to 

smother the exposed burning graphite with sand and 

boron. 

• Water intake channels adjacent to the south side of 

the reactor structure appear to be dry on May 8, 

suggesting that the water supply inlet from the cooling 

pond is closed. 

• Images of TM band 6 show a large gradient in 

water temperature in the cooling pond during the normal 

operation of the plant on June 6, 1985, and April 22, 

1986. The lack of a water-temperature gradient in the 

pond on April 29 and May 8, 1986, indicates that the 

entire pond has approached a near-uniform temperature 

due to the cessation of normal operations. 

REFERENCES 

Courtois, M. , and Weill, G., 1985, The SPOT satellite system, 

in Schnaph, A., ed., Monitoring Earth's oceans, land, and 

atmosphere from space- Sensors, systems, and applications; v. 97 of Progress in Astronautics and Aeronautics: 

New York , American Institute of Aeronautics and 

Astronautics, Inc., 830 p. 

EOSA T Corporation, 1986, Augustine volcano Thematic 

Mapper image: Landsat Data Users Notes, v. I, no . 3, p. 

1-2. 

Haydn, R., Dalke, G., Henkel, J., and Bare, J., 1982, Application 

of the I HS color transform to the processing of multisensor 

data and image enhancement, in International Symposium 

on Remote Sensing of Environment, First Thematic 

Conference: Remote Sensing of Arid and Semi-Arid 

Lands, Cairo, Egypt, January 1982, Proceedings: Environmental Research Institute of Michigan, Ann Arbor, Mich., 

p. 599-616. 

U.S. Geological Survey and National Oceanic and Atmospheric 

Administration, 1984, Landsat 4 data users handbook: 

Reston, Va ., U.S. Geological Survey. 

Wood , L.M ., Schowengerdt, R.A., and Meyer, D.J. , 1986, 

Restoration for sampled imaging systems, in Applications 

of Digital Image Processing IX, SPIE International 

Symposium on Optical and Optoelectronic Applied 

Sciences and Engineering, 30th, Proceedings: San Diego, 

Calif., v. 697, p. 333-340. 

18 Processing and Analysis of Satellite Image Data near Chernobyl 
Appendix. Digital values of the piecewise linear contrast stretches applied to the April29, 1986, Thematic Mapper (TM) data 

TM Band 

2 3 4 5 6 7 

Input Output Input Output Input Output Input Output Input Output Input Output 

0 0 0 0 0 0 0 0 0 0 0 0 

28 0 27 0 15 0 7 0 105 0 39 115 

41 115 46 128 37 40 34 40 132 135 100 210 

66 210 83 210 55 140 75 130 156 255 160 255 

92 255 121 255 104 220 137 210 255 255 255 255 

255 255 255 255 172 255 200 255 

255 255 255 255 

Appendix 19