NASA/TMm2000-209891, Vol. 43

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall and Jaime Nickeson, Editors

Volume 43

BOREAS RSS-2 Level 1B ASAS

Image Data: At-Sensor Radiance

in BSQ Format

C. Russell, SSAI

P.W. Dabney, Goddard Space Flight Center, Greenbelt, Maryland

W. Kovalick, D. Graham, and M. Bur, Raytheon ITSS

J.R. Irons, Goddard Space Flight Center, Greenbelt, Maryland

M. Tierney, Goddard Space Flight Center, Greenbelt, Maryland

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

July 2000

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NASA/TMm2000-209891, Vol. 43

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall and Jaime Nickeson, Editors

Volume 43

BOREAS RSS-2 Level 1B ASAS

Image Data: At-Sensor Radiance

in BSQ Format

C. Russell, SSAI

P.W. Dabney, Goddard Space Flight Center, Greenbelt, Maryland

W. Kovalick, D. Graham, and M. Bur, Raytheon ITSS

J.R. Irons, Goddard Space Flight Center, Greenbelt, Maryland

M. Tierney, Goddard Space Flight Center, Greenbelt, Maryland

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

July 2000
NASA Center for AeroSpace Information

7121 Standard Drive

Hanover, MD 21076-1320

Price Code: A17

Available from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Price Code: A10
BOREAS RSS-2 Level-lb ASAS Imagery: At-sensor Radiance in BSQ

Format

C. Russell, P. Dabney, W. Kovalick, D. Graham, M. Bur, J. Irons, M. Tierney

Summary

The BOREAS RSS-2 team used the ASAS instrument, mounted on the NASA C-130 aircraft, to create

at-sensor radiance images of various sites as a function of spectral wavelength, view geometry

(combinations of view zenith angle, view azimuth angle, solar zenith angle, and solar azimuth angle),

and altitude. The level-lb ASAS images of the BOREAS study areas were collected from April to

September 1994 and March to July 1996.

Note that only a sample of the Level-lb ASAS images are contained on the BOREAS CD-ROM

set. The sample files contain data collected on 04-August-1994 over the NSA-OBS site. Some of the

data files on the BOREAS CD-ROMs have been compressed using the Gzip program. See section 8.2

for details.

In addition to the sample image files, an inventory file is supplied on the CD-ROM to inform users

about all the data that were collected. See Sections 15 and 16 for information about how to acquire the

data not contained on the CD-ROM set.

Table of Contents

1) Data Set Overview

2) Investigator(s)

3) Theory of Measurements

4) Equipment

5) Data Acquisition Methods

6) Observations

7) Data Description

8) Data Organization

9) Data Manipulations

10) Errors

11) Notes

12) Application of the Data Set

13) Future Modifications and Plans

14) Software

15) Data Access

16) Output Products and Availability

17) References

18) Glossary of Terms

19) List of Acronyms

20) Document Information

1. Data Set Overview

1.1 Data Set Identification

BOREAS RSS-02 Level-lb ASAS Imagery: At-sensor Radiance in BSQ Format

1.2 Data Set Introduction

The level-lb Advanced Solid-state Array Spectroradiometer (ASAS) data set consists of a series of

62-band images in each site pass, where a site pass is one flight over a given target area. Each site pass

consists of up to 8 images, one at each of 8 look angles. The ASAS images were acquired from

Page 1
19-APR-1994to 17-SEP-1994,duringtheBOREASfield campaigns.

1.3 Objective/Purpose

The objectives were to collect multispectral, multiangle data during several field campaigns for a

variety of purposes: develop capabilities to remotely monitor the state of the snow pack in the boreal

forest; study the bidirectional reflectance properties of snow and boreal forest canopies with a snow

background; obtain bidirectional reflectance data for the early growing season; study the bidirectional

reflectance properties of boreal forest canopies, including phenological variations; and simulate

Multiangle Imaging SpectroRadiometer (MISR) data by acquiring data at or close to MISR view zenith

angles.

1.4 Summary of Parameters

The ASAS measures at-sensor radiance of surfaces as a function of spectral wavelength, view

geometry (combinations of view zenith angle, view azimuth angle, solar zenith angle, and solar

azimuth angle), and altitude.

1.5 Discussion

The main objectives of the BOReal Ecosystem-Atmosphere Study (BOREAS) conducted in

Manitoba and Saskatchewan throughout 1994 and 1996 are to improve process models that describe

the exchanges of energy, water, carbon, and trace constituents between the boreal forest and the

atmosphere, and to develop methods for applying the process models over large spatial scales using

remote sensing and other integrative modeling techniques. The Remote Sensing Science (RSS) group,

of which ASAS is a part, is responsible for developing linkages between optical and microwave

remote sensing and boreal zone biophysical parameters at various scales (leaf, canopy, and regional)

using measurements from field, aircraft and satellite sensors plus a range of radiative transfer models.

The experiment strategy for ASAS was to image the flux tower sites during each of the various

field campaigns. ASAS obtained coordinated measurements with the Portable Apparatus for the Rapid

Acquisition of Bidirectional Observations of Land and Atmosphere (PARABOLA) (on the ground) and

other remote sensing instruments (Compact Airborne Spectrographic Imager (CASI), Airborne

Visible-Infrared Imaging Spectrometer (AVIRIS), Moderate Resolution Imaging Spectroradiometer

(MODIS) Airborne Simulator (MAS), and Polarization and Directionality of Earth's Reflectances

(POLDER)) when and where possible. For each site, three sets of multiangle data were collected by

flying three flight lines in view azimuths that were parallel, perpendicular, and oblique to the solar

principal plane. View zenith angles corresponding to MISR angles were obtained for a number of data

sets.

1.6 Related Data Sets

BOREAS RSS-01 PARABOLA Surface Reflectance and Transmittance Data

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

RSS-02 ASAS Extracted Multi-angle Spectral Reflectance Factors

RSS-03 Helicopter-Mounted MMR Reflectance Data

RSS-03 Helicopter-Mounted SE-590 Reflectance Data

RSS-11

RSS-12

RSS-18

RSS- 19

RSS- 19

RSS-20

Ground Network of Sun Photometer Measurements

Automated Ground Sun Photometer Measurements in the SSA

Level-lb AVIRIS Imagery: At-sensor Radiance in BIL Format

1994 CASI At-sensor Radiance and Reflectance Images

1996 CASI At-sensor Radiance and Reflectance Images

POLDER C-130 Measurements of Surface BRDF

Page 2
2. Investigator(s)

2.1 Investigator(s) Name and Title

Dr. James R. Irons, ASAS Instrument Scientist

Philip W. Dabney, ASAS Instrument Engineer

2.2 Title of Investigation

Terrestrial Ecosystem Studies of the Boreal Forest Using Bidirectional Reflectances Acquired by a

Multispectral, Multiangle Imaging Spectroradiometer

2.3 Contact Information

Contact 1:

Jim Irons

Code 923

NASA GSFC

Greenbelt, MD 20771

(301) 614-6657

(301) 614-6695 (fax)

James.R.Irons. l@gsfc.nasa.gov

Contact 2:

Michael Bur

Code 923

NASA GSFC

Greenbelt, MD 20771

(301) 614-6661

(301) 614-6695 (fax)

Michael.J.Bur. l@gsfc.nasa.gov

Contact 3:

Jaime Nickeson

Raytheon ITSS

NASA GSFC

Code 923

Greenbelt, MD 20771

(301) 286-3373

(301) 286-0239 (fax)

Jaime.Nickeson@ gsfc.nasa.gov

ASAS information via the World Wide Web is available at http://asas.gsfc.nasa.gov/.

3. Theory of Measurements

ASAS is an airborne imaging spectroradiometer that was modified by National Aeronautics and Space

Administration (NASA) Goddard Space Flight Center (GSFC) to point off-nadir for the purpose of

remotely observing directional anisotropy of solar radiance reflected from terrestrial surfaces. The

instrument is capable of off-nadir pointing from approximately 70 ° forward to 55 ° aft along-track (in

the direction of flight). As the aircraft passes over the ground target, digital radiance measurements of

the target are recorded for a discrete sequence of fore-to-aft view zenith angles within this range.

The terms "tilt," "look," "point," or "view" angles generally are used interchangeably when

referring to the ASAS view zenith angles; however, the actual view zenith angle may vary from the

Page 3
angleatwhichthesensorispointeddueto anacross-trackangularcomponentto theview zenithangle.

Thisacross-trackangularcomponentislargestatanadir-pointingangle,andrelativelyinsignificantat

far off-nadirpointingangles.FortheBOREASdatacollectionflights,ASASimagedmoststudysites

at eightdifferenttilt angles:+70°, +60°, +45°, +26%nadir,-26°,-45%and-55°.Areasin theimagery

nearesthecenterdetectorswill haveview zenithanglesthesameasthetilt angle,but areasattheedges

of thearray(far left andfarrightof aline) mayhaveadifferentview zenithangle.Thevariationbytilt

angleisgivenbelow:

TILT ANGLE

(fore and/or aft)

70 °

60 °

55 °

45 °

26 °

00 o

VIEW ZEN ANGLE

(image center)

70 0 °

60 0 °

55 0 °

45 0 °

26 0 °

0 0 o

VIEW ZEN ANGLE

(image edges)

70 .2 °

60.4 °

55.5 °

45.7 °

27.5 °

9.4 °

For the Focused Field Campaign - Thaw (FFC-T) data sets, two additional view angles at +15 ° and

-15 ° were also acquired. Imaging of sites in the 70 ° off-nadir view angle is problematic, and this

particular angle may or may not be available in every data set. Data were acquired in 62 spectral bands

ranging from 404 - 1023 nanometers (nm) with a spectral resolution of approximately 10 nm in each

band.

4. Equipment

4.1 Sensor/Instrument Description

The ASAS instrument employs a cooled 1024 x 1024 element silicon charge-coupled device (CCD)

detector array to generate multispectral digital image data in a push-broom mode. The first 324 rows of

the CCD are masked. The next 186 rows are exposed to the output from the spectrometer. The final

516 rows are masked and used for readout of the array. Two of the rows under the mask collect smear

data that are used to remove smear effects and dark current from the data.

During the BOREAS missions, the operating method of the array was to bin every 3 rows into one

spectral band, which resulted in 62 spectral channels. In addition, every 2 detectors within each row

were binned resulting in 512 pixels (per row or line) in the output image data. In this configuration, the

spectral band centers, which range from 404 to 1023 nm, are spaced at approximately 10 nm. Each

spectral band has a full-width-at-half-maximum (FWHM) of approximately 10 nm.

4.1.1 Collection Environment

The ASAS instrument is mounted on the underside of the platform aircraft fuselage with the sensor

optics either slightly protruding into the slipstream or retracted into the fuselage pressure box,

depending on the view angle. As the aircraft approaches the target site from a distance, the ASAS

instrument is pointed forward-looking. A video camera bore-sighted with the ASAS optical head relays

a picture to an onboard monitor screen at the ASAS operators' station. This enables the operator to

identify the site and continue tracking it through a sequence of view angles as the aircraft proceeds on a

flight line over the site. When the site comes into view on the forward point, the operator begins the

data acquisition. The sequence is timed such that the view is at nadir when the aircraft is directly over

the site, and aft-looking views are taken after passing the site. Determining which views are

forwardscatter or backscatter requires examination of the aircraft heading and the solar azimuth angle,

given in the ASAS header.

During the 1994 BOREAS missions data were acquired as follows: Flux Towers - view azimuths

parallel, perpendicular and oblique to the solar principal plane; multiple view zenith angles. Transect or

Modeling Sub-Area Mapping Grids - nadir view zenith angle. In 1996, data over flux towers were

acquired in view azimuths parallel, oblique, and occasionally perpendicular to the solar principal plane.

Page 4
DuringtransectrunsbetweentheNorthernStudyArea(NSA)andSouthernStudyArea(SSA),data

wererecordedat anadirview zenithangle.

As theplatformaircraftflies forward,eachrowof 512detectorbinsiselectronicallyscannedto

generate62spectralchannelsof digital imagedatain apush-broommode.Thesignalsgeneratedby the

CCDdetectorsaresampledatarateof 38framelinespersecondto producethealong-trackdimension

of theimagery(imagelines).Thesampledsignalfromeachdetectoris digitizedto 12bitsandthe

digitaldataarestoredonahigh-densityS-VHSformattapeusingabufferedVeryLargeDataStorage

(VLDS)datarecorder.

4.1.2 Source/Platform

• 1994flights: NASA Ames Research Center (ARC) C-130B Earth Resources Aircraft.

• 1996 flights: NASA Wallops Flight Facility (WFF) C-130Q Aircraft.

4.1.3 Source/Platform Mission Objectives

Mission objectives were to collect multispectral, multiangle bidirectional reflectance data (acquired

as at-sensor radiances) over flux tower sites for study of boreal forest canopies and simulation of

MISR data by obtaining measurements at MISR view angles. Nadir multispectral data were acquired

over the modeling sub-areas in each study area (1994 only) and on transects between the SSA and

NSA. Multispectral, multiangle data were also collected over a calibration target in the SSA and several

other occasional targets of opportunity (see Sections 7.1.1 and 7.2.1).

4.1.4 Key Variables

ASAS measures at-sensor spectral radiance in the visible and near-infrared portion of the spectrum

as a function of view geometry.

4.1.5 Principles of Operation

The ASAS optical head is mounted in an open port in the underside of the C-130 aircraft. A

complex pointing mechanism incorporating a gimbal enables the sensor to view off-nadir, facilitating

movement in the horizontal, vertical, fore, aft, and yaw directions.

As the aircraft approaches the target site from a distance, the ASAS instrument is pointed

forward-looking. A video camera mounted adjacent to the ASAS optical head relays a picture to an

on-board monitor screen at the ASAS operator's station. This enables the operator to identify the site

and continue tracking it through a sequence of view angles as the aircraft proceeds on a flight line over

the site. When the site comes into view on the first forward angle, the operator initiates the data

acquisition process. The sequence is timed such that the view is at nadir when the aircraft is directly

over the site, and aft-looking views are taken after passing the site.

Yaw compensation can be performed by the operator (if necessary) to prevent the site from drifting

out of the field of view.

As the platform aircraft flies forward, each row of 1024 (spatial dimension) x 186 (spectral

dimension) array elements is electronically scanned. Every 2 elements in the spatial dimension and

every 3 elements in the spectral dimension are binned, which generates digital image data for 512

spatial pixels in 62 spectral channels. The signals generated by the CCD detectors are sampled at a rate

of 38 frame lines per second to produce the along-track dimension of the imagery (image lines) in

push-broom mode. The sampled signal from each detector is digitized to 12 bits and the digital data are

stored on a high-density S-VHS format tape using a buffered VLDS data recorder.

4.1.6 Sensor/Instrument Measurement Geometry

Radiation incident on the ASAS aperture is focused onto an entrance slit by an f/1.4 objective lens

with a 57.2 millimeters (mm) focal length. The entrance slit is 50 micrometers (_am) wide across-track,

and 23 _am wide along-track. The lens focuses incoming energy through the entrance slit into a 1:1

optical relay with an effective focal length of 76.3 mm in each half. In each half of the optical relay, a

90°-mirror prism folds the optical path to create a compact optical head. A transmission grating ruled at

75 lines per mm and blazed at 530 nanometers (nm) is located between the two prisms to disperse the

radiant energy into its wavelength spectrum, which is in turn directed by the second prism onto the 186

Page 5
rowsof thearrayin thefocalplane,wheretheCCDwasmounted.

Theinstantaneousfield-of-view(IFOV) of anASASpixel is afunctionof optics,detector

dimensions,tilt angle(viewangle),andaircraftaltitudeandattitude(pitchandroll). Theopticalsystem

includesanf/1.4objectivelenswith a57.2mmfocal length,providinga0.33radian(19.3°) total

angularacross-trackfield-of-view.Theindividualangularresolutionof thecenterdetectorsis 0.66

mradacross-track.Thealong-trackfield-of-viewis 0.44mrad.

Eachdetectorhasdimensionsof 19.0_amspatially(across-track)and19.0_amspectrally;

however,with abinningfactorof 2 in thespatialdimensionand3 in thespectraldimension,the

resultingarraypixel sizeis 38.0_amin thespatialdimensionand57_amin thespectraldimension.

SeeSection7.1.3for spatialresolution.

4.1.7 Manufacturer of Sensor/Instrument

TheASASinstrumentevolvedoveranumberof years.Theoriginaloptics,built by TRW,were

partof theScanningImagingSpectroradiometer(SIS)constructedin theearly 1970'sfor NASA's

JohnsonSpaceCenter(JSC).ASAS wascreatedin 1981whenacharge-injectiondevice(CID) silicon

detectorarray,madeby GE,wasincorporatedwith theopticalsystemfor ajoint programinvolving

NASA JSCandtheNavalOceanSystemsCenter.In 1984,thesensorwastransferredto NASA

GSFC,wheretheaircraft-mountingbracketwasmodifiedfor off-nadirpointing.

In late 1991,thepointingmechanismwasupgradedby NASA GSFCto allowview anglesof 70°

forwardto 55° aft,andto enableoperator-controlledaircraftyawcompensation.In 1992,theCID was

replacedwith aThomsonCSFModelTH7896A(high-speedversion)CCD silicondetectorarray.

BOREASdatawereacquiredwiththisCCD array.

4.2 Calibration

RadiometriccalibrationdatafortheBOREASexperimentwereacquiredfrom twoprimary

calibrationsources:1)a 1.2m diameterintegratinghemispherein theNASA GSFCcalibration

laboratory,and2) a30inchdiameter(0.76m) portablehemispherethatis ownedandoperatedby

GSFC.Thelattersourcewasusedforin situcalibrationdataacquisitionsinceit couldbepositioned

directlyundertheaircraft-mountedinstrument.Theintegratinghemisphereis operatedandmaintained

by theSensorDevelopmentandCharacterizationBranchat NASA GSFC.Up to 12levelsofradiance

canbeprovidedfor calibrationbyturningtheinternaltungstenfilamentlampsonor off. The

hemisphereis calibratedonanabsolutescalebycomparisonto theoutputfrom aNationalInstituteof

StandardsandTechnologytraceablecalibrationlampusingalaboratory-basedtransfer

spectroradiometer. In acalibrationrun,ASASisexposedto a 12-levelsequenceof spectralradiance

levelsfrom thehemisphere.Dark current(theresponseof theinstrumentunderconditionsof no

incidentradiation)isalsoacquired.

Theportablehemispherecanprovideupto sixdifferentradiancelevelsin additionto darkcurrent;

however,duringtheBOREASfield campaignsof 1994,only threelevelsprovidedby three30Watt

tungstenlampswereoperating.Forcalibrationof theportablehemisphere,usersshouldcontactBrian

Markhamor JohnSchaferof NASA GSFC.

Thedigitizedresponseof eachdetectorbin wasrecordedfor eachcalibrationsourceintensitylevel

by selectivelycontrollingthenumberof lampsturnedon.Whenpossible,datawereacquiredwith the

instrumentortheportablehemispherepositionedat twodifferentorientations,opposedby 180°, to

accountfor anynonuniformityin thereflectivesurfaceof thehemisphere.In someinstances,four

differentorientations,opposedby 90°,wereused.Calibrationdatawereacquiredfor eachopticalfilter

combination(atleastfour)usedby ASASduringtheBOREASfield campaigns.

Thedigitalresponsesof eachdetectorbin to themultiplehemisphereradiancelevelswereusedto

derivealinearradiometricresponsefunctionfor eachdetectorbin.To begin,anoffsetvaluewas

subtractedfromeachdigitalresponse.Theoffsetwasaweightedaverageof thedigital countsfrom

two maskeddetectorbinslocatedatthebeginningandendof eachilluminatedcolumnof detectorsin

thearray.Theweightingwasafunctionof therelativeproximityof eachilluminateddetectorbin to

eachmaskeddetectorbin alongadetectorcolumn.Theoffsetsubtractionremovesdarkcurrentsignal

and"contamination"from thesignalreadoutprocessfrom eachdigitalresponse.A mean

offset-correctedigitalresponsetoeachradiancelevelwasthencalculatedfor eachdetectorbin.

Page6
Least-squaresregressionwasusednextto expressdigitalresponseasalinearfunctionofradiancefor

eachdetectorbin.Notethatanindividualregressionline wasderivedfor eachof the31,744

illuminateddetectorbins.Theslopeof eachregressionline providedtheradiometricgain(i.e.,digital

countsperunitradiance)for eachdetectorbin.Alongeachrowof 512detectorbinsperspectralband,

thegainspeakatthecenterbin anddecreasewith distancefromthecenterdueto opticalvignetting.

TheradiometriccorrectionappliedtoASASdataacquiredin flight removesthedigitalresponse

variationduetobin-to-bingainvariationalonga spectralrow of 512detectorbins.A meangainvalue

wasfirst calculatedfor eachof the62rowsof detectorbins(i.e.,for eachspectralband).We referto

themeangainastheradiometricresolutionfactor.A list ofradiometricresolutionfactorsfor each

spectralband,in unitsof digital countspermW/(cm2* sr* _am),canbefoundin thefourthcolumnof

thetablein theAmericanStandardCodefor InformationInterchange(ASCII)headerecordof each

ASASsitepass(seesection8.2).Theradiometricresolutionfactorscanvarybetweendataacquisition

datesdependingonthefore-opticfilter combinationemployedatthetimeof acquisition.

Theradiometriccorrectionprocessscaleseachdigital countgeneratedin flight by eachdetectorbin

to themeangainforthebin's spectralband.An offsetisfirst subtractedfrom eachdatumandthenthe

offset-correcteddatumisdividedtheindividualgainfortheassociatedetectorbin.Thesetwo steps

produceadatavalueinunitsof radiance.Theradiancevalueis thenmultipliedby themeangainforthe

associatedspectralbandto returnthevalueto unitsof digital counts.Thescaleddigital countis saved

asanintegervaluein theradiometricallycorrecteddigital imageproduct.Theprocessisperformed

usingfloating-pointarithmeticuntil thefinal step,wherefloating-pointvaluesaretruncatedto integer

digital counts.Savingthedataasscaledintegervaluesreducesthevolumeof theradiometrically

correcteddigitalimagesandprecludestheexpressionof falseradiometricresolutionin thecorrected

values.

An investigatoranalyzingradiometricallycorrectedASASdatamayconvertthedigitalcountsto

unitsofradianceby simplydividingthedigital countsby theradiometricresolutionfactorprovidedfor

theassociatedspectralbandasprovidedin theASCIIheaderecord.Theresultwill beavaluein units

of mW/(cm2* sr* _am).To covertthisvalueto W/(m2 * sr* _am),multiply by 10.

Signal-to-noise(S/N)ratiosarealsomeasuredfrom theradiometriccalibrationdata.Equationsare

derivedthatprovidetheS/Nratioasafunctionof digital count.Theseequationsarebasically

second-order(usedfor 1994data)or third-order(usedfor 1996data)polynomialsthatcharacterize

progressivelyhigherS/Nratioswith increasingdigital count(until amaximumlevelisreached).A

maximumS/Nratioof approximately600wasobtainedfrom thecalibrationdataacquiredforthe

BOREASproject.

TheappropriateS/Nequationis storedin theASCIIheaderof eachASASimage.Theheaderalso

containsinformationonhow to applytheequationto eitherthedigitalcounts(beforetheradiometric

resolutionfactorsareapplied)or to theradiances(afterthefactorsareapplied)in eachchannel.The

S/Nratiosdid notvarygreatlyoverthecourseof theBOREASfield seasons.SomeexampleS/N

equationsapplicableto theBOREASASASdatacanbeseenin theSAMPLEheadergivenin Section

8.4.

Spectral Calibration

A McPhersonModel2850.5m doublemonochromatorservesasthespectralreferencesourcefor

ASAS.Light from themonochromatoris collimatedby aparabolicmirror anddirectedto theASAS

optics.Instrumentoutputis sampledevery0.5nan.Thebandcentershavebeencomputedby

determiningthecentroidof theareaundertheresponsecurvefor eachband.FWHMsweremeasured

directlyfrom theresponsecurves.

Page7
4.2.1 Specifications

ASAS spectral band centers and FWHMs applicable to 1994 and 1996 BOREAS data sets are as

follows:

Band Center FWHM Band Center FWHM

(nm) (nm) (nm) (nm)

1 404

2 413

3 423

4 432

5 441

6 451

7 460

8 470

9 480

i0 490

ii 500

12 509

13 519

14 529

15 539

16 549

17 559

18 569

19 579

20 589

21 600

22 610

23 620

24 630

25 640

26 650

27 661

28 671

29 681

30 691

31 701

9 5

9 5

9 5

i0 0

i0 0

i0 0

i0 0

i0 0

i0 5

i0 5

i0 0

i0 5

i0 0

i0 5

i0 5

i0 5

i0 0

i0 5

i0 5

ii 0

i0 5

ii 0

i0 5

i0 5

ii 0

i0 5

ii 0

i0 5

ii 0

ii 0

ii 0

32 711

33 722

34 732

35 742

36 752

37 763

38 773

39 783

40 794

41 804

42 814

43 825

44 835

45 846

46 856

47 866

48 877

49 887

50 897

51 908

52 918

53 929

54 939

55 949

56 960

57 970

58 981

59 991

60 i001

61 1012

62 1022

9 ii

1 ii

3 ii

6 ii

9 ii

2 ii

5 ii

8 ii

1 ii

5 ii

9 ii

3 ii

7 ii

0 ii

4 ii

8 ii

2 ii

6 ii

9 ii

3 ii

7 ii

0 ii

5 i0

9 ii

3 ii

7 ii

1 ii

5 i0

9 i0

2 i0

7 i0

4.2.1.1 Tolerance

Individual radiometric resolution factors for each spectral band were adopted in 1989 to account for

the variation of silicon detector response as a function of wavelength. With every detector bin

individually calibrated, each has its own gain, and as a result, its own specific resolution. A mean

resolution (the radiometric resolution factor) is determined for each channel, to which all 512 detector

bins within each channel are scaled. This results in very slight radiometric over-resolution of pixels

furthest away from the center, while pixels proximal to the center are slightly under-resolved

radiometrically.

Periodic horizontal striping of low brightness is apparent in some of the ASAS imagery acquired

for BOREAS. This artifact was caused by an internal array timing problem that resulted in shortened

integration times (and lower signal levels) for some data frames. Efforts have been made to identify

and correct these "low energy" frames but striping may occasionally be visible in some images, usually

at a frequency of every 6-7 lines (1994 Intensive Field Campaigns (IFCs) 1-3). For data sets collected

over the SSA during the 1994 FFC-T, the frequency is approximately 29 to 30 lines. This problem

was corrected before the 1996 field seasons.

Page 8
4.2.2 Frequency of Calibration

In general, ASAS acquires radiometric calibration data at least twice for each mission, with one

calibration set acquired prior to the mission, followed by a postmission calibration after the instrument

arrives back at GSFC. Radiometric calibration data were also acquired during some 1994 BOREAS

field campaigns using the portable integrating hemisphere described elsewhere in this document. In

1996, the portable hemisphere was used only in the winter field campaign. After several months of

quality control and related analyses, it was determined that calibration data acquired on the following

dates would be used to generate the gains for calibration of data acquired during the listed field

campaigns:

Acquisition Date Applicable BOREAS Field Data

01-JUN-94 1994 FFC-Thaw, IFC-I data

02-AUG-94 1994 IFC-2 data

17-SEP-94 1994 IFC-3 data

05-APR-96 1996 data

Laboratory spectral calibrations of ASAS were performed both before and after the 1994 BOREAS

field season. The spectral stability was also checked once in the middle of the field season using a

portable helium neon laser. It has been determined that the spectral calibration results from

13-Oct-1994 are most appropriate for all 1994 and 1996 BOREAS data sets.

4.2.3 Other Calibration Information

None.

5. Data Acquisition Methods

The ASAS instrument is mounted on the underside of the platform aircraft fuselage with the sensor

optics either slightly protruding into the slipstream or retracted into the fuselage pressure box,

depending on the view angle. As the aircraft approaches the target site from a distance, the ASAS

instrument is pointed forward-looking. A video camera bore-sighted with the ASAS optical head relays

a picture to an onboard monitor screen at the ASAS operators' station. This enables the operator to

identify the site and continue tracking it through a sequence of view angles as the aircraft proceeds on a

flight line over the site. When the site comes into view on the forward point, the operator begins the

data acquisition. The sequence is timed such that the view is at nadir when the aircraft is directly over

the site, and aft-looking views are taken after passing the site. Determining which views are

forwardscatter or backscatter requires examination of the aircraft heading and the solar azimuth angle,

given in the ASAS ASCII header.

During the 1994 BOREAS missions, data were acquired as follows: Flux Towers - view azimuths

parallel, perpendicular and oblique to the solar principal plane; multiple view zenith angles. Transect or

Modeling Sub-Area Mapping Grids - nadir view zenith angle. During the 1996 BOREAS missions,

data were acquired as follows: Flux Towers - view azimuths parallel, oblique, and occasionally

perpendicular to the solar principal plane; multiple view zenith angles. Transect - nadir view zenith

angle. Data over targets of opportunity in 1994 and 1996 usually were acquired only in the solar

principal plane and may be multiangle or nadir data.

As the platform aircraft flies forward, each row of 512 detector bins is electronically scanned to

generate 62 spectral channels of digital image data in a push-broom mode. The signals generated by the

CCD detectors are sampled at a rate of 38 frame lines per second to produce the along-track dimension

of the imagery (image lines). The sampled signal from each detector is digitized to 12 bits and the

digital data are stored on a high-density S-VHS format tape using a buffered VLDS data recorder.

Page 9
6. Observations

6.1 Data Notes

None.

6.2 Field Notes

The ASAS operators do not make extensive notes about field conditions during missions. ASAS

usually is not flown if atmospheric conditions are not sufficiently clear. If sky conditions are satisfied,

it is up to Principal Investigators to decide if field conditions are appropriate for data acquisition. Any

observations noted by ASAS operators are made at altitude, and if considered pertinent to the data, are

included in the ASAS header COMMENTS field.

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

The 1994 BOREAS sites acquired by ASAS consisted of six flux tower sites in the SSA and five

flux tower sites in the NSA. In addition, data were acquired over a calibration target in the SSA. In

1996, in addition to the flux towers, data were acquired over an "agricultural/open" area south of the

SSA_FEN and Namekus Lake during the winter field campaign. ASAS BOREAS imagery of the flux

tower sites (at a NADIR view) cover areas that are typically about 1.5-2.0 km wide and up to several

km long.

Nadir data over the auxiliary sites may be available in the Modeling Sub-Area Mapping Grid and

Transect Nadir data sets. Routine processing of the Modeling Sub-Area Grid and Transect data sets is

not planned at this time. After flux tower data sets have been provided to the BOREAS Information

System (BORIS), the Sub-Area and Transect data may be processed if there are requests from the user

community for these data.

The North American Datum of 1983 (NAD83) comer coordinates of the SSA are:

Latitude Longitude

Northwest 54.321 N 106.228 W

Northeast 54.225 N 104.237 W

Southwest 53.515 N 106.321 W

Southeast 53.420 N 104.368 W

The NAD83 corner coordinates of the NSA are:

Latitude Longitude

Northwest 56.249 N 98.825 W

Northeast 56.083 N 97.234 W

Southwest 55.542 N 99.045 W

Southeast 55.379 N 97.489 W

Site Latitude Longitude

SSA FEN

SSA OA

SSA OBS

SSA OJP

SSA YJP

53.801 N 104.619 W

53.629 N 106.198 W

53.988 N 105.119 W

53.916 N 104.690 W

53.876 N 104.647 W

Page 10
SSA YA 53

SSA AVIRIS CAL 53

SSA OPEN AG 53

SSA NAMEKUS LAKE 53

655 N 105.322 W

24 N 105.69 W

57 N 104.78 W

83 N 106.04 W

Denoted as SSA AGR or SSA AG

Denoted as SSA NAK

NSA ATE (NSA OA) 55

NSA FEN 55

NSA OBS 55

NSA OJP 55

NSA YJP 55

887 N 098.675 W

915 N 098.421 W

880 N 098.481 W

928 N 098.624 W

896 N 098.287 W

Could be denoted as NSA OA

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

Across-track direction:

ASAS spatial resolution in the x-direction is a function of the across-track field of view, view

angle, and the altitude of the platform aircraft. The across-track pixel size (in meters) is given in the

header of each ASAS image. Across-track pixels do not overlap.

Some examples of across-track spatial resolutions:

• At a nadir view angle and an altitude of 5000 m above ground level (AGL), the full-scene

across-track field of view is 1.7 kin, and the individual pixel size (across-track) is 3.3 m.

• At a 60 ° off-nadir view angle and an altitude of 5000 m AGL, the full-scene across-track field

of view is 3.4 kin, and the individual pixel size (across-track) is 6.6 m.

Along-track direction:

The along-track spatial resolution of an ASAS image pixel is more complicated. Two aspects are

involved:

• The ground footprint size.

• The distance over which the footprint is "smeared" as the aircraft advances.

The ground footprint is determined by the along-track IFOV in conjunction with the view angle and

aircraft altitude and attitude (mainly pitch). The IFOV is described in Section 5.1.5.

The radiance measurement recorded for a given pixel is representative of the ground area observed

as the pixel footprint moves forward by the ground distance of one frame (ASAS is a push-broom

scanner). The ground footprint will be larger for an off-nadir view angle than for a nadir view. For

example, at an altitude of 5,000 meters, the footprint in the along-track direction is approximately 8

meters at a view angle of 60 ° versus 2 meters for nadir.

Regardless of how large or small the footprint is, the ground distance over which a pixel is

"smeared" is determined by the data collection rate, which is a function of the aircraft speed, divided

by the frame rate. Given a fixed frame rate during the BOREAS data missions of 38 frames per second

and a typical aircraft ground speed of 220 knots, the spacing or smear distance between adjacent

frames is approximately 3 meters. Thus, an along-track footprint of 2 meters at nadir (using the

example above) would be smeared over a distance of 3 meters. This results in a 2 meter overlap and a

center-to-center distance of 3 meters between pixels of adjacent frames. The effective resolution is

therefore limited by the smearing.

All ASAS data sets are oversampled in the along-track direction. This means that each image line

somewhat overlaps the previous line, making the images appear more elongated than in reality. Images

are not oversampled in the across-track direction. This frame or line overlap is not corrected for during

operational ground processing.

An along-track (y-direction) pixel size in meters is given in the header of each ASAS image file.

This number is the aircraft speed divided by the frame rate, which equals the smear distance or

non-overlap portion of each pixel in the y-direction. The y-direction pixel size times the number of

Page 11
linesis approximatelyequalto thetotalgrounddistanceimagedby ASASfor agivenview angle.

Someexamplealong-trackpixel sizesduringBOREAS:

• 3.1m (groundspeed= 230knots)

• 3.2m (groundspeed= 235knots)

NOTE:BOREASASASdatawereacquiredataltitudesof approximately4600-5800m aboveground

for multiangleflux towerdata,and7000-8000m abovegroundfor nadirtransectdata.

7.1.4 Projection

The ASAS data are stored in the spatial frame in which they were collected. The digital image data

are not resampled in order to retain the radiometric integrity of each pixel. Consequently, the image

data are neither registered to a geographic projection nor are the image data view angle-corrected. The

digital images retain geometric distortion resulting from the off-nadir tilting, the rectangular ground

sample dimensions, and the variation in aircraft roll, pitch, and yaw during data acquisition.

Resampling and registration are left to the discretion of the investigators analyzing ASAS data.

7.1.5 Grid Description

The ASAS data are stored in the spatial frame in which they were collected.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

Date Sites

19-Apr-1994 SSA OBS, SSA OA, SSA OJP

20-Apr-1994 NSA OBS, NSA OJP, NSA YJP, NSA FEN

26-Hay-1994 SSA AVIRIS CAL

31-May-1994 SSA OA, SSA OJP

01-Jun-1994 SSA YJP

06-Jun-1994 SSA OBS, SSA FEN,

07-Jun-1994 NSA OBS, NSA OJP,

08-Jun-1994 NSA OA (NSA ATE)

SSA OJP

NSA YJP, NSA FEN

21-Ju1-1994 SSA OBS

23-Jui-1994 SSA YA,

24-Jui-1994 SSA OJP

04-Aug-1994 NSA OBS

SSA OA, SSA OJP, SSA YJP,

SSA AVIRIS CAL

SSA FEN, SSA YA 3

NSA OJP (smoke present)

SSA FEN

06-Sep-1994 NSA OA

13-Sep-1994 SSA OBS

16-Sep-1994 SSA OA,

17-Sep-1994 NSA OBS

(NSA ATE)

, SSA OJP, SSA YJP, SSA FEN

SSA AVIRIS CAL

NSA OA (NSA ATE), NSA OJP, NSA YJP, NSA FEN

04-Mar-1996 SSA OA, SSA OBS

ll-Mar-1996 SSA OA, SSA OBS, SSA YJP, SSA OJP,

12-Mar-1996 SSA AG, SSA OJP, SSA YJP, SSA OBS

18 Jui-1996 NSA OA (NSA ATE), NSA OJP, NSA FEN,

20-Jui-1996 SSA OBS, SSA OJP, SSA FEN, SSA OA

24-Jui-1996 NSA OJP, NSA OA (NSA ATE), NSA FEN

29-Jui-1996 SSA OBS, SSA OJP

30-Jui-1996 SSA YJP, SSA OJP, SSA YA, SSA OBS

SSA AG, SSA NAK

NSA OBS, NSA YJP

Page 12
7.2.2 Temporal Coverage Map

See Section 7.2.1.

7.2.3 Temporal Resolution

ASAS site passes may vary slightly in time duration, depending on the length of the flight line and

the aircraft speed. Typically one multiangle pass over a site has a duration of about 5 minutes.

7.3 Data Characteristics

Due to differences in the information that is available for ASAS data collected in 1994 and 1996,

the inventory tables given on the CD-ROM contain different sets of parameters. The following sections

describe the actual image data and the inventory files provided on the CD-ROM series.

7.3.1 Parameter/Variable

Image files:

Scaled at-sensor radiance: Values are stored in image files as digital

numbers (DNs) . To obtain radiance in units

described below (7.3.3) divide DN values by a

band-specific radiometric resolution factor.

The parameters contained in the inventory files on the CD-ROM are:

Column Name

SPATIAL COVERAGE

DATE OBS

START TIME

END TIME

PLATFORM

INSTRUMENT

NUM BANDS

PLATFORM ALTITUDE

ASAS VIEW ANG

ASAS SCAN RATE

MIN SOLAR ZEN ANG

MAX SOLAR ZEN ANG

MIN SOLAR AZ ANG

MAX SOLAR AZ ANG

C130 MISSION ID

C130 LINE NUM

C130 RUN NUM

C130 SITE

NW LATITUDE

NW LONGITUDE

NE LATITUDE

NE LONGITUDE

SW LATITUDE

SW LONGITUDE

SE LATITUDE

SE LONGITUDE

CRTFCN CODE

(missing

(missing

(missing

(missing

from the 1996 data)

from the 1996 data)

from the 1996 data)

from the 1996 data)

Page 13
7.3.2 Variable Description/Definition

Image files:

At-sensor radiance : The derived radiant energy incident on the sensor aperture

(after division by at the time of data collection in the specific ASAS

spectral radiometric wavelength regions.

resolution factor)

The descriptions of the parameters contained in the inventory files on the CD-ROM are:

Column Name Description

SPATIAL COVERAGE

DATE OBS

START TIME

END TIME

PLATFORM

INSTRUMENT

NUM BANDS

PLATFORM ALTITUDE

ASAS VIEW ANG

ASAS SCAN RATE

MIN SOLAR ZEN ANG

MAX SOLAR ZEN ANG

MIN SOLAR AZ ANG

MAX SOLAR AZ ANG

C130 MISSION ID

The general term used to denote the spatial area

over which the data were collected.

The date on which the data were collected.

The starting Greenwich Mean Time (GMT) for the

data collected.

The ending Greenwich Mean Time (GMT) for the data

collected.

The object (e.g., satellite, aircraft, tower,

person) that supported the instrument.

The name of the device used to make the

measurements.

The number of spectral bands in the data.

The nominal altitude of the data collection

platform above the target.

The list of view angles (in degrees) acquired by

the ASAS instrument on this site pass.

The ASAS sensor scans in a push-broom fashion one

row (frame) at a time. In the image header this

is referred to as the frame rate and is the

number of rows of image data captured per second.

The minimum angle from the surface normal

(straight up) to the sun during the data

collection.

The maximum angle from the surface normal

(straight up) to the sun during the data

collection.

The minimum azimuthal direction of the sun

during data collection expressed in clockwise

increments from North.

The maximum azimuthal direction of the sun

during data collection expressed in clockwise

increments from North.

The mission identifier assigned to the C130

mission in the form of YY-DDD-FF where YY is the

last two digits of the fiscal year, DDD is the

deployment number for "official" C130 missions

and is day of year for non-"official" C130

missions (i.e., no site coverage), and FF is the

flight number within the given deployment (00 is

given for non-"official" C130 missions) . An

example would be 94-006-04.

Note that the C 130_MISSION_ID, C 130_LINE_NUM, C 130_RUN_NUM, and C 130_SITE

Page 14
columns are missing from the 1996 data. The mission information in 1994 was provided by personnel

in the NASA Earth Resources Aircraft Program at NASA/ARC. In 1996, the C130 aircraft was

provided by the NASA/WFF, which did not create this mission information. The reference to

"non-official" C130 missions above applies primarily to sun photometer data from the C130 platform

in 1994 (RSS-12) where data was collected on the tarmac and possibly within flight, but the "official"

C130 mission was aborted before or slightly after takeoff.

C130 LINE NUH

C130 RUN NUH

C130 SITE

NW LATITUDE

NW LONGITUDE

NE LATITUDE

NE LONGITUDE

SW LATITUDE

SW LONGITUDE

SE LATITUDE

SE LONGITUDE

CRTFCN CODE

The number of the C130 line in its flights over

the BOREAS area as given in the flight logs.

Zero values are given for non-"official" C130

missions and for data between C130 sites or

lines.

The number of the C130 run in its flights over

the BOREAS area as given in the flight logs.

Zero value is given for non-"official" C130

missions and data between C130 sites, lines or

runs.

The C130 site designator as given in the flight

logs. PRE is used for data taken from the airport

to the first "official" C130 site, BTW is used

for data taken between two "official" C130 sites,

DSC is used for data taken after the last

"official" C130 site, TRN is used for transect

data, and YTH and YPA are used for data taken at

the YTH and YPA airports (aircraft never left the

ground).

The NAD83 based latitude coordinate of the

northwest corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

northwest corner of the minimum bounding

rectangle for the data.

The NAD83 based latitude coordinate of the

northeast corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

northeast corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

southwest corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

southwest corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

southeast corner of the minimum bounding

rectangle for the data.

The NAD83 based longitude coordinate of the

southeast corner of the minimum bounding

rectangle for the data.

The BOREAS certification level of the data.

Examples are CPI (Checked by PI), CGR (Certified

by Group), PRE (Preliminary), and CPI-??? (CPI

but questionable).

Page 15
7.3.3 Unit of Measurement

Image files:

DN/spectral radiometric : At-sensor radiance in units of mW/ (cm 2 * sr * _lm) .

resolution factor The band-specific radiometric resolution factors are

stored in each ASAS image header. To obtain units of

W/ (m 2 * sr * _lm), multiply mW/ (cm 2 * sr * _lm) by i0.

The measurement units for the parameters contained in the inventory files on the CD-ROM are:

Column Name Units

SPATIAL COVERAGE [none]

DATE OBS [DD-MON-YY]

START TIME [HHMM GMT]

END TIME [HHMM GMT]

PLATFORM [none]

INSTRUMENT [none]

NUM BANDS [counts]

PLATFORM ALTITUDE [meters]

ASAS VIEW ANG [none]

ASAS SCAN RATE [unitless]

MIN SOLAR ZEN ANG [degrees]

MAX SOLAR ZEN ANG [degrees]

MIN SOLAR AZ ANG [degrees]

MAX SOLAR AZ ANG [degrees]

C130 MISSION ID [none]

C130 LINE NUM [none]

C130 RUN NUM [none]

C130 SITE [none]

NW LATITUDE [degrees]

NW LONGITUDE [degrees]

NE LATITUDE [degrees]

NE LONGITUDE [degrees]

SW LATITUDE [degrees]

SW LONGITUDE [degrees]

SE LATITUDE [degrees]

SE LONGITUDE [degrees]

CRTFCN CODE [none]

(Missing from the 1996 data)

(Missing from the 1996 data)

(Missing from the 1996 data)

(Missing from the 1996 data)

7.3.4 Data Source

Image files: At-sensor radiance is derived from calibrating the acquired ASAS image counts. The

sources of the parameter values contained in the inventory files on the CD-ROM are:

Column Name Data Source

SPATIAL COVERAGE

DATE OBS

START TIME

END TIME

PLATFORM

INSTRUMENT

NUM BANDS

PLATFORM ALTITUDE

ASAS VIEW ANG

[Assigned by BORIS]

[ASAS image header]

[ASAS image header]

[ASAS image header]

[ASAS image header]

[Assigned by BORIS]

[ASAS image header]

[ASAS image header]

[ASAS image header]

Page 16
ASAS SCAN RATE

MIN SOLAR ZEN ANG

MAX SOLAR ZEN ANG

MIN SOLAR AZ ANG

MAX SOLAR AZ ANG

C130 MISSION ID

C130 LINE NUM

C130 RUN NUM

C130 SITE

NW LATITUDE

NW LONGITUDE

NE LATITUDE

NE LONGITUDE

SW LATITUDE

SW LONGITUDE

SE LATITUDE

SE LONGITUDE

CRTFCN CODE

[ASAS image header]

[ASAS image header]

[ASAS image header]

[iSiS image header]

[iSiS image header]

[iSiS image header] (Missing from the 1996 data)

[iSiS image header] (Missing from the 1996 data)

[iSiS image header] (Missing from the 1996 data)

[iSiS image header] (Missing from the 1996 data)

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Computed by BORIS]

[Assigned by BORIS]

7.3.5 Data Range

Image files: Scaled at-sensor radiance (DNs) - 12-bit data range (0-4095) stored in 16-bit integers

The range of parameter values contained in the inventory file for the 1994 data on the CD-ROM is:

Column Name

Minimum Maximum Missng Unrel Below Data

Data Data Data Data Detect Not

Value Value Value Value Limit Cllctd

SPATIAL COVERAGE N/A N/A None None None None

DATE OBS 19-APR-94 17-SEP-94 None None None None

START TIME 1527 2112 None None None None

END TIME 1529 2115 None None None None

PLATFORM C130 C130 None None None None

INSTRUMENT N/A N/A None None None None

NUM BANDS 62 62 None None None None

PLATFORM ALTITUDE 4633 5791.2 None None None None

ASAS VIEW ANG N/A N/A None None None None

ASAS SCAN RATE 38 38 None None None None

MIN SOLAR ZEN ANG 33.5 61.1 None None None None

MAX SOLAR ZEN ANG 33.5 61.4 None None None None

MIN SOLAR AZ ANG 108.4 228.6 None None None None

MAX SOLAR AZ ANG 109.1 229.6 None None None None

C130 MISSION ID 94-004-10 94-009-09 None None None None

C130 LINE NUM i01 703 None None None None

C130 RUN NUM 1 3 None None None None

C130 SITE 429 431 None None None None

NW LATITUDE 53.24665 55.94083 None None None None

NW LONGITUDE -106.21453 -98.29598 None None None None

NE LATITUDE 53.24525 55.93712 None None None None

NE LONGITUDE -106.18277 -98.25648 None None None None

SW LATITUDE 53.22982 55.92403 None None None None

SW LONGITUDE -106.21694 -98.3016 None None None None

SE LATITUDE 53.22822 55.92094 None None None None

SE LONGITUDE -106.18487 -98.26697 None None None None

CRTFCN CODE CPI-PRE CPI-PRE None None None None

Page 17
Minimum Data Value --

Maximum Data Value --

Missng Data Value --

Unrel Data Value --

Below Detect Limit --

Data Not Cllctd --

The minimum value found in the column.

The maximum value found in the column.

The value that indicates missing data. This is used to

indicate that an attempt was made to determine the

parameter value, but the attempt was unsuccessful.

The value that indicates unreliable data. This is used

to indicate an attempt was made to determine the

parameter value, but the value was deemed to be

unreliable by the analysis personnel.

The value that indicates parameter values below the

instruments detection limits. This is used to

indicate that an attempt was made to determine the

parameter value, but the analysis personnel determined

that the parameter value was below the detection

limit of the instrumentation.

This value indicates that no attempt was made to

determine the parameter value. This usually

indicates that BORIS combined several similar but

not identical data sets into the same data base table

but this particular science team did not

measure that parameter.

Blank

N/A

None

-- Indicates that blank spaces are used to denote that type of value.

-- Indicates that the value is not applicable to the respective column.

-- Indicates that no values of that sort were found in the column.

7.4 Sample Data Record

The sample data record is not provided nor applicable for image data. The following are wrapped

versions of sample records from the 1994 inventory file on the CD-ROM:

SPATIAL COVERAGE,DATE OBS,START TIME,END TIME,PLATFORM, INSTRUMENT,NUM BANDS,

PLATFORM ALTITUDE,ASAS VIEW ANG,ASAS SCAN RATE,MIN SOLAR ZEN ANG,

MAX SOLAR ZEN ANG,MIN SOLAR AZ ANG,MAX SOLAR AZ ANG,CI30 MISSION ID,

C130 LINE NUM, CI30 RUN NUM, CI30 SITE,NW LATITUDE,NW LONGITUDE,NE LATITUDE,

NE LONGITUDE,SW LATITUDE,SW LONGITUDE,SE LATITUDE,SE LONGITUDE,CRTFCN CODE

'SSA-OBS', 19-APR-94, 1713, 1715, 'C130', 'ASAS', 62, 4633.0,

'60 45 26 15 0 -15 -26 -45-55',38,47.6,47.8,143.5,144.3, '94-004-10',101,1,

'429',53.99938,-105.13468,53.99769,-105.10065,53.97925,-105.13757,53.97755,

-i05..i0356, 'CPI-PRE'

'SSA-OBS',I9-APR-94,1724,1727, 'C130', 'ASAS',62,4633.0,

'60 45 26 15 0 -15 -26 -45-55',38,46.6,46.8,147.3,148.1,'94-004-10',103,1,'429'

53.99613,-105.13056,53.99489,-105.10564,53.98204,-105.13259,53.9808,-105.10768,

'CPI-PRE'

Page 18
Thefollowing arewrappedversionsof samplerecordsfromthe 1996inventoryfile ontheCD-ROM:

SPATIAL COVERAGE,DATE OBS,START TIME,END TIME,PLATFORM, INSTRUMENT,NUM BANDS,

PLATFORM ALTITUDE,ASAS VIEW ANG,ASAS SCAN RATE,MIN SOLAR ZEN ANG,

MAX SOLAR ZEN ANG,MIN SOLAR AZ ANG,MAX SOLAR AZ ANG,NW LATITUDE,NW LONGITUDE,

NE LATITUDE,NE LONGITUDE,SW LATITUDE,SW LONGITUDE,SE LATITUDE,SE LONGITUDE,

CRTFCN CODE

'SSA-9OA',04-MAR-96,1754,1757, 'C130', 'ASAS',62,4419.6

38,62.0,62.2,156.8,157.5,53.64802,-106.21728,53.64626

-i06.22125,53.612,-i06.17826, 'CPI-PRE'

'SSA-9OA',04-MAR-96,1832,1835, 'C130', 'ASAS',62,4480.6 '60 45 26 0 -26 -45',

38,60.3,60.4,167.4,168.1,53.64069,-106.21943,53.63882 -i0 6.17382,53.6212,

-i06.22169,53.61933,-i06.1761, 'CPI-PRE'

'60 45 26 0 -26 -45 -55',

-106.17425,53.61376,

8. Data Organization

8.1 Data Granularity

The smallest obtainable unit of data is a complete ASAS site pass, which consists of 5 to l0 images

per site at multiple view angles acquired by the ASAS instrument as it approaches and passes a given

target.

8.2 Data Format(s)

8.2.1 Uncompressed Data Files

The CD-ROM inventory listing file consists of numerical and character fields of varying length

separated by commas. The character fields are enclosed with single apostrophe marks. There are no

spaces between the fields.

One level- lb ASAS image product consists of a series of files in which the first file is an ASCII

header file followed by a series of image data files. The ASCII header file consists of 80-byte ASCII

character records that describe the whole image product and give general acquisition information.

Each image file consists of a series of logical records that are 8,192 bytes in length. The first

record contains ASCII header information in a format described below. Within the physical header

record, the logical header records are delimited with a new line character, enabling recognition of the

end of each header record component. Subsequent file records of 8,192 bytes contain eight logical

image records of 1,024 bytes each. The 1,024 bytes contain 512 two-byte (16-bit) integer pixel values

that are scaled at-sensor radiances. The byte ordering is high-order byte first. The image lines are

ordered band-sequentially; that is, all lines for band 1, followed by all lines for band 2, and so forth

for all 62 bands. The number of lines per view angle may vary. The total number of records per file

equals the number of lines in the image times the number of bands (62) plus NUM_HDR_BYTES

listed in the header. There are no end-of-record or other special characters between logical records.

A sample ASAS ASCII header record appears below:

EXAMPLE BOREAS ASAS IMAGE HEADER FORMAT (with some explanations added)

ASAS2 HDR VERSION: 2.83

NUM HDR BYTES:8192

FILE NAME: tilt +26.cai

TYPE OF DATA: IN-FLIGHT

#

#DATE INFORMATION

#

LOCAL DATE: 26MAY94

Page 19
START DATE GMT: 26MAY94 17:26:55

STOP DATE GMT: 26MAY94 17:27:08

SOLAR AZIMUTH(deg) : 143.7

SOLAR ZENITH(deg) : 38.3

#

#IMAGE SIZE INFORMATION

#

NUM LINES: 512 (can vary)

NUM PIXELS: 512

NUM BANDS: 62

DATA TYPE: UNSIGNED INTEGER*2

DATA ORDERING: SUN UNIX (Based on SunOs 4.1.3)

FORMAT: BAND SEQUENTIAL

STARTING LINE: 31268 (From beginning of Level 0 product)

STARTING PIXEL:I

ACROSS TRACK PIXEL SIZE(m) : 4.1

ALONG TRACK PIXEL SIZE(m) : 3.2 (non-overlap portion)

IMAGE DESCRIPTION:

#

#GEOGRAPHIC LOCATION INFORMATION

#

GLOBAL REGION: North America

COUNTRY: Canada

POLITICAL SUBDIVISION: Saskatchewan

GEOGRAPHICAL REGION: Boreal forest

LAT CENTER: 53.24000 (refers to target site, not image center)

LON CENTER: -105.69000

RADIUS (km) : 1.346

#

#MISSION INFORMATION

#

PROJECT: BOREAS

FLIGHT PROJ NUM: 43002

MISSION NUM: 406

FLIGHT NUM: 02

LINE NUM: 601

RUN NUM: 2

SITE NUM: 6 (C-130 site designation only)

SITE: SSA AVCAL

SITE DESCRIPTOR: AVIRIS CAL SITE

INVESTIGATOR: Dr. J. Irons

#

#COMMENTS

#

Perpendicular (relation to solar principal plane)

#

#INSTRUMENT INFORMATION

#

TILT ANGLE: 26 (angle at which sensor is pointed, in degrees)

FRAME RATE: 38 (frames per second)

#

#AIRCRAFT INFORMATION

FLIGHT FACILITY: NASA/AMES

PLATFORM: NASA C-130

(refers to target site, not image center)

Page 20
ALTITUDE AGL(m) : 5608 .3 (AGL = above ground level)

GROUND SPEED (knots) : 240

HEADING (deg) : 322

#

#PROCESSING INFORMATION

#

PROCESSING DATE: 26JUN95

PROCESSING FACILITY: NASA GSFC

PROCESSING LEVEL: IB (EOS designation)

PROCESSING HISTORY: dd swapcomp decom borcal energizer hdrstats

#

#CALIBRATION INFORMATION

#

SPECTRAL CAL DATE: 13OCT94

RAD CAL DATE: 02AUG94

RAD CAL SOURCE: Hemisphere, Integrating

SOURCE CAL DATE: 31JUL94

S/N FORMULA ORDER: 2 (See Section 5.2 A for discussion)

S/N FORMULA COEFFICIENTS (of S/N ratios)

CO 1.707e+00

Cl 2.905e-01

C2 -2.867e-05

(proc programs)

S/N DESCRIPTION: S/N = C0 + CI*DN + C2*DN^2 (using coefficients above) or S/N =

CO + Cl*Radiance + C2*Radiance^2 where CO, Cl, and C2 are given in the table

below. (This second equation using radiance should read S/N : S/N(C0) +

S/N(Cl)*Radiance + S/N(C2)*Radiance^2 where S/N(C0), S/N(CI), and S/N(C2) are

given in the table below.)

UNITS: DN/RAD RES FACT = mW cm-2 sr-i _m-i (RAD MEAN is in these units)

BAND CENTER FWHM

RAD RES RAD S/N S/N (C0) S/N (CI)

FACT MEAN MEAN

S/N(C2)

404 3

413 7

423 2

432 4

441 7

451 4

460 9

9.5

9 5

9 5

i0 0

i0 0

i0 0

i0 0

41

49

59

7O

79

94

115

0 24

0 42

0 75

1 03

1 38

1 68

1 85

4

i0

21

35

54

8O

ii0

1 707e+00

1 707e+00

1 707e+00

1 707e+00

1 707e+00

1 707e+00

1 707e+00

i 191e+01

1 423e+01

1 714e+01

2 033e+01

2 295e+01

2 731e+01

3 341e+01

-4 819e-02

-6 884e-02

-9 980e-02

-i 405e-01

-i 789e-01

-2 533e-01

-3 792e-01

(channels 8 through 58 will be here; S/N ratios highest in middle channels)

59 991.5 10.5 13 3.36 14

60 1001.9 10.5 9 3.37 i0

61 1012.2 10.5 6 3.36 8

62 1022.7 10.5 3 3.48 5

#

#END HDR (Marks end of header text)

1.707e+00

1.707e+00

1.707e+00

1.707e+00

3 776e+00

2 614e+00

1 743e+00

8 715e-01

-4.845e-03

-2.322e-03

-i.032e-03

-2.580e-04

To determine forward scatter and backward scatter, compare aircraft heading to solar azimuth angle. If

the plane was heading into the sun, forward (positive) points are forward scatter and aft (negative)

points are backscatter. If the plane was heading away from the sun, forward points are backscatter and

Page 21
aft points are forward scatter.

The terms "tilt," "look," "point," or "view" angles generally are used interchangeably when

referring to the ASAS view zenith angles, however the actual view zenith angle may vary from the

angle at which the sensor is pointed due to an across-track angular component to the view zenith angle.

This across-track angular component is largest at a nadir-pointing angle, and relatively insignificant at

far off-nadir pointing angles. For the BOREAS data collection flights, ASAS imaged most study sites

at 8 different tilt angles: +70 °, +60 °, +45 °, +26 °, nadir, -26 °, -45 °, and -55 °. Areas in the imagery

nearest the center detectors will have view zenith angles the same as the tilt angle, but areas at the edges

of the array (far left and far right of a line) may have a different view zenith angle. The variation by tilt

angle is given below:

TILT ANGLE

(fore and/or aft)

70 °

60 °

55 °

45 °

26 °

00 o

VIEW ZEN ANGLE

(image center)

70 0 °

60 0 °

55 0 °

45 0 °

26 0 °

0 0 o

VIEW ZEN ANGLE

(image edges)

70 .2 °

60.4 °

55.5 °

45.7 °

27.5 °

9.4 °

8.2.2 Compressed CD-ROM Files

On the BOREAS CD-ROMs, the ASCII header file for each image is stored as ASCII text;

however, the binary image files have been compressed with the Gzip compression program (file name

*.gz). These data have been compressed using gzip version 1.2.4 and the high compression (-9)

option (Copyright (C) 1992-1993 Jean-loup Gailly). Gzip (GNU zip) uses the Lempel-Ziv algorithm

(Welch, 1994) used in the zip and PKZIP programs. The compressed files may be uncompressed

using gzip (-d option) or gunzip. Gzip is available from many websites (for example, ftp site

prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in both executable and source

code form. Versions of the decompression software for various systems are included on the

CD-ROMs.

9. Data Manipulations

9.1 Formulae

Not applicable.

9.1.1 Derivation Techniques and Algorithms

Not applicable.

9.2 Data Processing Sequence

9.2.1 Processing Steps

For any given ASAS data set, the processing programs used to generate the data are listed in the

ASAS header. In general, operational processing of 1994 data required six primary steps and

operational processing of 1996 data required four primary steps. The all-inclusive list of programs is

as follows, and these steps are described below: dd, swapcomp, decom, borcal, energizer, and

hdrstats

ASAS measurements are stored on high-density S-VHS format tape using a Metrum buffered

VLDS data recorder. The raw data are transferred to magnetic disk and 8-mm tape using a VLDS unit

interfaced to a Unix workstation. These data consist of continual streams of frames in which each

frame contains the combined image data for all 62 input channels and 2 smear data channels plus

header and navigational information (if available) for a single image line. The data transfer process

involves the Unix "dd" utility for reading the raw data and a program developed in-house called

Page 22
"swapcomp"for swappingandcomplementingthebytesof each16-bitpixel wherebyte-swappingis

necessary.Byte swappingwasnot neededfor 1996data.

Decommutatinga singlebandof dataencompassingall view anglescreatesaquicklookimagefor

eachsitepass.Linecoordinatesof eachview anglesubsetaremanuallyselected,omittingareasof

instrument"slew"andnoncoverageof thesite.

Next,all bandsof eachview anglesubsetin thesitepassaredecommutated.Eachlineof datais

extractedandwrittento disk in band-sequential format.Eachview anglesubsetis storedin aseparate

file with anASCIIheaderautomaticallypopulatedwith entriesretrievedfromanonlinedatabase

containinginformationaboutthespecificprojectandsites.

At thispoint,imagefiles consistof a seriesof logicalrecords1,024bytesin length.Thefirst

severalrecordsstoretheheaderinformation.Subsequentrecordscontainband-sequential integer*2

data.Eachrecordrepresents512pixels.

Radiometriccalibrationis performednextusingthein-houseprogram"borcal."It appliesthe

calibrationgainsderivedfrom theselectedradiometriccalibrationsource(usuallytheintegrating

hemisphere)lampdatato eachpixel. Theoutputformatisidenticalto theinputformatexceptthatthe2

smearbandsareremoved.Thecalibrationprocedureis describedin Section4.2.

Thenextprocessingstepfor BOREASASASdatais correctionof low-energyframesresulting

from anarraysignalreadoutproblem,for dataaffectedby thisoccurrence.Section4.2.1discussesthis

problem.Theprogram"energizer"attemptsto correcttheaffectedframes.Dataareparsedfour

separatetimesto determinewhichframesfit thecriteriaforreducedenergyor signallevelscausedby

thetimingproblem.Thefirst passinvolvestheprofiling of totalenergyversusframe,smoothingthe

profile to removehighandlow frequencynoise,andflaggingof suspectframesusingameanvalue

threshold.Subsequentpassesattemptto refinethelist of suspectframesbasedontheexpected

frequency.Formostof theBOREAS1994data,thefrequencyof low-energylinesis every6-7

frames.After thesuspectframesareidentified,theyaremultipliedby acorrective-weightingfactor

determinedfrom thecalibrationdata.Dataacquiredin 1996did notcontainlow-energyframes.

Thelastoperationalprocessingstepis calculationof themeansceneradiancelevelsfor all bandsof

eachview angleimagein a sitepass.Thein-house"hdrstats"programcomputesthemeanradiances

[in mW/(cm2* sr* pm)] andstoresthemin theASCIIheaderof eachimage.

BORISpersonnelprocessedtheASASimagesby: Usingdevelopedsoftwareto extract

informationfrom theimageheaderanddatafiles for loggingintotherelationaldatabaseSelecting

randomimagesfor visualreviewonacomputerscreen,CopyingtheASCII andcompressingthe

binaryimagefiles for useontheCD-ROMset.

9.2.2 Processing Changes

Forthemostpart,mostof theprocessingstepsoutlinedin Section9.2.1applyto all 1994and

1996BOREASdatasets.However,theremaybesomeinter-IFCdifferencesin thedata

characteristics:

Thedataacquiredfor eachIFC mayhavea specificsetof calibrationgains,radiometricresolution

factors,andS/Nratios,dependingonwhichcalibrationdatawereused.

Thefrequencyof occurrencefor thelow-energyframestripingwasevery6-7linesfor all 1994

IFCsexceptfor SSAFFC-Tdata,wherethefrequencywasapproximately29-30lines.Low-energy

framesdidnot occurin 1996datasets.

For 1994IFCs 1,2,3, andall 1996IFCs,datawereacquiredatthefollowing eightview angles:

+70°, +60°, +45°, +26°, nadir,-26°,-45°, and-55°. Forthe1994FFC-T,+15° and-15° view angles

wereincludedin thesequence.Theseanglesdescribetheview anglesthatwereattemptedbutnot

necessarilyachievedin all cases.

S/Nratiocalculationsfor 1996datausedthirdorderpolynomialequationsinsteadof second-order

polynomials.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

See Section 9.2.

Page 23
9.3.2 Calculated Variables

Radiance.

9.4 Graphs and Plots

Not applicable.

10. Errors

10.1 Sources of Error

Potential sources of uncertainty associated with ASAS spectral radiance include the following

factors: spectral radiance from the integrating hemisphere; spectral radiance from the portable

hemisphere; transfer of spectral radiance to ASAS detector elements; and spectral calibration of the

ASAS detector elements. Other factors such as polarization sensitivity, signal cross-talk between

detectors, and stray light may contribute to the uncertainty, but these factors have not been evaluated.

10.2 Quality Assessment

10.2.1 Data Validation by Source

During processing, frequency histograms of selected channels for each view angle are plotted and

examined manually for anomalies. Images are also displayed and visually analyzed for target coverage,

data dropouts, saturation, and other potential problems.

10.2.2 Confidence Level/Accuracy Judgment

The uncertainty associated with ASAS spectral radiance values is approximately 6%. This number

is the root-sum-square of the uncertainties contributed by the following factors: spectral radiance from

the integrating hemisphere (5% uncertainty); transfer of spectral radiance to ASAS detector elements

(2% uncertainty); and spectral calibration of the ASAS detector elements (1% uncertainty). The

uncertainty associated with the radiance of the portable hemisphere has not been determined, however

it is probably similar to that of the integrating hemisphere. Other factors such as polarization

sensitivity, signal cross-talk between detectors, and stray light may contribute to the uncertainty, but

these factors have not been evaluated.

10.2.3 Measurement Error for Parameters

The uncertainty associated with ASAS spectral radiance values is approximately 6%.

10.2.4 Additional Quality Assessments

Spectral response curves for selected training areas are plotted and examined for known

atmospheric absorption features. These plots are also compared to similar measurements made by other

instruments, if data are available.

10.2.5 Data Verification by Data Center

BOREAS Information System staff developed software to read, verify, and extract information

contained in the ASAS image header files. This information was reviewed and loaded into the

relational data base. In addition, several random images were reviewed visually on a video display. No

problems were found during the reviews.

Page 24
1 1. Notes

11.1 Limitations of the Data

ASAS data acquired over the SSA calibration target (a soil field) were atmospherically corrected

and compared to ground measurements. The results show ASAS to agree well with the ground

observations between 490 and 870 nm. Below 490 nm and above 870 nm, the ASAS response falls

below the expected level.

Though a specific sequence of view angles from +70 ° to -55 ° was attempted for each flight line

over the flux tower sites, not all look angles were achieved every time. (Often the 70 ° off-nadir view

missed the site or contained too much distortion for inclusion in the data set.)

The data are not geo-rectified, geo-registered, or atmospherically corrected.

11.2 Known Problems with the Data

Image Data:

• Several of the 31,744 detectors in the ASAS array are inoperable; these will produce vertical

striping in the spectral channel in which they occur.

• The correction for low-energy frames (lines) due to the array timing problem may not be

successful in all data sets and some frames (lines) may exhibit nonbright horizontal striping.

• ASAS data acquired over the SSA calibration target (a soil field) were atmospherically

corrected and compared to ground measurements. The results show ASAS to agree very well

with the ground observations between 490 and 870 nm. Below 490 nm and above 870 nm,

the ASAS response falls below the expected level.

• Though a specific sequence of view angles from +70 ° to -55 ° was attempted for each flight

line over the flux tower sites, not all look angles were achieved every time. (Often the 70 °

oft-nadir view missed the site or contained too much distortion for inclusion in the data set.)

Header Information:

• The altitude, heading, and ground speed parameters in the image headers originated from

operator flight logs and therefore may not be completely accurate. If such parameters are very

important to the user, navigation data (taken by the C-130 crew), which are available from

NASA ARC or BORIS for 1994 data sets, should independently corroborate them.

Navigation data for 1996 summer flights may be available from SLICER staff at NASA

GSFC.

• There is a known incorrect aircraft heading in one of the ASAS data sets: the heading for

7/21/94 L701R1 SSA_FEN should read 228 ° instead of 37 °.

• Site elevations in the headers may show discrepancies among the same sites, and

discrepancies with elevations listed in BORIS. Elevations retrieved from topographic maps

were systematically lower than Global Positioning System (GPS) elevations listed in BORIS.

The value listed in the ASAS header represents only an approximate elevation for the site and

should not be interpreted as an exact, accurate value.

• A SOURCE_CAL_DATE of 00JUL01 should read 31JUL94.

• The column RAD_MEAN may be missing from some headers.

• S/N_MEANS of negative integers are invalid.

• The S/N_DESCRIPTION gives two equations:

S/N = CO + CI*DN + C2*DN2

(This equation uses digital numbers (DN) and the spectrally invariant coefficients listed above the

equation as CO, C 1, and C2)

S/N = CO + Cl*Radiance + C2*Radiance2

Page 25
whereCO,C1,andC2aregivenin thetablebelow.Thissecondequationusingradianceshouldread

S/N = S/N(C0)+ S/N(C1)*Radiance+ S/N(C2)*Radiance2

whereS/N(C0),S/N(C1),andS/N(C2)aregivenin thetablebelow.

S/N(C0),S/N(C1),andS/N(C2)arecoefficientswhichvary spectrallyandthedesignationS/N(C#)is

just adescriptorortermto distinguishthespectrallyvariantcoefficientslistedin thetablefrom the

spectrallyinvariantoneslistedabovethetable,i.e.it doesnotmeanS/Nmultipliedby thecoefficient.

11.3 Usage Guidance

At present,theprovidedASASdataarenotgeo-rectifiedorgeo-located,noraretheycorrectedfor

atmosphericeffects.Accurateaccountingof atmosphericeffectsontheat-sensorradiance

measurementsiveryimportant,sinceASASdataacquisitioninvolvesobservationsthroughvarying

pathlengths.

Usersshouldview ASASimagesthoroughlyin all spectralbandsof interestandselectstudyareas

carefully.ChecktheASASASCII headerfor eachdataset'sappropriatespectralradiometricresolution

factorsandS/Nratios.Usespecialcautionworkingwith channelsbelow490nmor above870nm

(seeSection11.1).

BeforeuncompressingtheGzipfilesonCD-ROM,besurethatyouhaveenoughdisk spaceto

holdtheuncompresseddatafiles.Thenusetheappropriatedecompressionprogramprovidedonthe

CD-ROM for yourspecificsystem.

11.4 Other Relevant Information

None.

12. Application of the Data Set

These data can be used for a variety of studies, including:

• To characterize directional anisotropy of solar radiance reflected from terrestrial surfaces.

• To classify surface land cover types.

• To estimate hemispherical reflectance (albedo).

• To relate multiangle reflected radiances to biomass, species, stand structure, surface

roughness, surface composition, Leaf Area Index (LAI), reflected Photosynthetically Active

Radiation (PAR), absorbed PAR, and the fraction of absorbed PAR (fAPAR) (preferably

done after removal of atmospheric effects). - As input to atmospheric correction algorithms. -

To characterize atmospheric effects through different path lengths of atmosphere. - For

Bidirectional Reflectance Distribution Function (BRDF) modeling and validation, after

removal of atmospheric effects and geometric registration.

13. Future Modifications and Plans

Possible atmospheric correction and geographic registration of whole images and multiangle site

passes for selected dates and sites (probably not the entire BOREAS ASAS archive).

Page 26
14. Software

14.1 Software Description

Software for simple analysis of ASAS data is available through the ASAS World Wide Web site.

The software is written in the Interactive Data Language (IDL) and requires a licensed copy of the

commercial IDL package from Research Systems, Inc., in order to be run. Software procedures are

provided for performing image input/output, retrieving the contents of image headers, displaying

images, creating histograms, enhancing images, and generic image manipulation.

14.2 Software Access

The analysis software can be downloaded through a Web browser by accessing the following URL

and clicking on "Processing and analysis software":

http://asas.gsfc.nasa.gov/doc/processing.html

Another link under the section "IDL software" can then be selected to view the list of available IDL

programs. The "save" or "save as" features under the "File" menu in most web browsers may be used

to download the programs as text files. For details on the use of each program, consult the embedded

documentation at the top of each program.

Note: This software is the property of the U.S. Government. It is available without charge but is

not intended for commercial redistribution. No guarantees are provided as to the accuracy or reliability

of the code.

Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and PKZIP

commands.

15. Data Access

The level-lb ASAS imagery is available from the Earth Observing System Data and Information

System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center

(DAAC).

15.1 Contact Information

For BOREAS data and documentation please contact:

ORNL DAAC User Services

Oak Ridge National Laboratory

P.O. Box 2008 MS-6407

Oak Ridge, TN 37831-6407

Phone: (423) 241-3952

Fax: (423) 574-4665

E-mail: ornldaac@ornl.gov or ornl@eos.nasa.gov

15.2 Data Center Identification

Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory

(ORNL) Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics

http://www-eosdis.ornl.gov/.

15.3 Procedures for Obtaining Data

Users may obtain data directly through the ORNL DAAC online search and order system

[http://www-eosdis.ornl.gov/] and the anonymous FTP site [ftp://www-eosdis.ornl.gov/data/] or by

contacting User Services by electronic mail, telephone, fax, letter, or personal visit using the contact

information in Section 15.1.

Page 27
15.4 Data Center Status/Plans

The ORNL DAAC is the primary source for BOREAS field measurement, image, GIS, and

hardcopy data products. The BOREAS CD-ROM and data referenced or listed in inventories on the

CD-ROM are available from the ORNL DAAC.

16. Output Products and Availability

16.1 Tape Products

The BOREAS Level-lb ASAS data can be made available on 8-ram or Digital Archive Tape (DAT)

media.

16.2 Film Products

Color aerial photographs and video records were made during data collection. The video record

includes aircraft crew cabin intercom conversations and an audible tone that was initiated each time the

sensor was triggered. The BOREAS data base contains an inventory of available BOREAS aircraft

flight documentation, such as flight logs, videotapes, and photographs.

16.3 Other Products

A sample set of the ASAS IMAGES ARE AVAILABLE ON THE BOREAS CD-ROM SET. See

Section 15 for information about how to obtain the other data that are available.

17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

ASAS INFORMATION VIA THE WORLD WIDE WEB http://asas.gsfc.nasa.gov/

Kovalick, W. and D. Graham. 1991. ASAS Programmer's Manual, Hughes STX, Code 923, NASA

GSFC, Greenbelt, MD (in-house document).

Welch, T.A. 1984. A Technique for High Performance Data Compression. IEEE Computer, Vol. 17,

No. 6, pp. 8-19.

17.2 Journal Articles and Study Reports

Many of the following articles describe data from the first generation CID array (prior to 1991).

Radiometric resolution factors and spectral band centers differ among the various ASAS data sets.

Abuelgasim, A.A. and A. Strahler. 1994. Modeling bi-directional radiance measurements collected by

the Advanced Solid-state Array Spectroradiometer (ASAS) over Oregon Transect conifer forests.

Remote Sens. Environ. 47:261-275.

Abuelgasim, A.A., S. Gopal, J.R. Irons, and A.H. Strahler. 1996. Classification of ASAS multiangle

and multispectral measurements using artificial neural networks. Remote Sens. Environ. 57:79-87.

Barnsley, M.J., P. Lewis, M. Sutherland, and J.-P. Muller. 1997. Estimating land surface albedo in

the HAPEX-Sahel southern super-site: inversion of two BRDF models against multiple angle ASAS

images. J. Hydrology 188-189:749-778.

Brown de Colstoun, E.C., C.L. Walthall, C.A. Russell, and J.R. Irons. 1995. Estimating the fraction

of absorbed photosynthetically active radiation (fAPAR) at FIFE with airborne bi-directional spectral

reflectance data. J. Geophys. Res. 100:25,523-25,535.

Page 28
Deering,D.W., E.M. Middleton, J.R.Irons,B.L. Blad, E.A. Walter-Shea,C.J.Hays,C.L.

Walthall, T.F.Eck,S.P.Ahmad,andB.P.Banerjee.1992.Prairiegrasslandbi-directional

reflectancesmeasuredby differentinstrumentsat theFIFEsite.J.Geophys.Res.97:18,887-18,903.

Guinness,E.A., R.A. Arvidson, J.R.Irons, andD.J.Harding.1991.Surfacescatteringproperties

estimatedfrom modelingairbornemultipleemissionanglereflectancedata.Geophys.Res.Letters

18(11):2051-2054.

Hall, D.K., J.L.Foster,J.R.Irons,andP.W.Dabney.1993.Airbornebi-directionalradiancesof

snowcoveredsurfacesin Montana,USA.Annalsof Glaciology17:35-40.

Irons, J.R.,K.J. Ranson,D.L. Williams, R.R. Irish, andF.G.Huegel.1991.An off-nadir pointing

imagingspectroradiometerforterrestrialecosystemstudies.IEEETrans.onGeoscienceandRemote

Sensing29(1):66-74.

Johnson,L.F. 1994.Multiple view zenithangleobservationsof reflectancefrom ponderosapine

stands,Int. J.RemoteSens.15:3859-3865.

Lawrence,W.T., D.L. Williams, K.J. Ranson,J.R.Irons,andC.L. Walthall. 1994.Comparative

analysisof dataacquiredbythreenarrow-bandairbornespectroradiometersoversubborealvegetation.

RemoteSens.Environ.47:204-215.

Moran,M.S., R.D. Jackson,T.R. Clarke,J.Qi, F. Cabot,K.J. Thome,andB.L. Markham.1995.

Reflectancefactorretrievalfrom LandsatTM andSPOTHRV datafor bright anddarktargets.Remote

Sens.Env. 52:218:230.

Newcomer,J.,D. Landis,S.Conrad,S.Curd,K. Huemmrich,D. Knapp,A. Morrell, J.Nickeson,

A. Papagno,D. Rinker,R.Strub,T. Twine,F. Hall, andP.Sellers,eds.2000.CollectedDataof The

BorealEcosystem-AtmosphereStudy.NASA. CD-ROM.

Qi, J.,M.S. Moran,F. Cabot,andG. Dedieu.1995.Normalizationof sun/viewangleeffectsusing

spectralalbedo-basedvegetationindices.RemoteSens.Env. 52:207-217.

Ranson,K.J., J.R.Irons,andD.L. Williams. 1994.Multispectralbi-directionalreflectanceof

northernforestcanopieswith theAdvancedSolid-stateArray Spectroradiometer(ASAS).Remote

Sens.Env.47:276-289.

Russell,C.A., C.L. Walthall, J.R.Irons, andE.C.Brown deColstoun.1995.Comparisonof

airborneandsurfacespectralbi-directionalreflectancefactors,spectralhemisphericalreflectanceand

spectralvegetationindices.J.Geophys.Res.100:25,509-25,522.

Russell,C.A.,J.R.Irons,andP.W.Dabney.1997.Bidirectionalreflectanceof selectedBOREAS

sitesfrom multiangleairbornedata.J.Geophys.Res.102(D24):29,505-29,516.

Schaaf,C.B.andA.H. Strahler.1994.Validationof bi-directionalandhemisphericalreflectances

from ageometric-opticalmodelusingASASimageryandpyranometermeasurementsof aspruce

forest.RemoteSens.Env.49:138-144.

Sellers,P.andF.Hall. 1994.BorealEcosystem-AtmosphereStudy:ExperimentPlan.Version

1994-3.0,NASA BOREASReport(EXPLAN 94).

Sellers,P.andF.Hall. 1996.BorealEcosystem-AtmosphereStudy:ExperimentPlan.Version

1996-2.0,NASA BOREASReport(EXPLAN 96).

Page29
Sellers,P.,F. Hall, andK.F. Huemmrich.1996.BorealEcosystem-AtmosphereStudy:1994

Operations.NASA BOREASReport(OPSDOC94).

Sellers,P.,F. Hall, andK.F. Huemmrich.1997.BorealEcosystem-AtmosphereStudy:1996

Operations.NASA BOREASReport(OPSDOC96).

Sellers,P.,F. Hall, H. Margolis,B. Kelly, D. Baldocchi,G. denHartog,J.Cihlar, M.G. Ryan,B.

Goodison,P.Crill, K.J.Ranson,D. Lettenmaier,andD.E. Wickland. 1995.Theboreal

ecosystem-atmospherestudy(BOREAS):anoverviewandearlyresultsfrom the1994field year.

Bulletinof theAmericanMeteorologicalSociety.76(9):1549-1577.

Sellers,P.J.,F.G.Hall, R.D.Kelly, A. Black, D. Baldocchi,J. Berry, M. Ryan,K.J. Ranson,P.M.

Crill, D.P.Lettenmaier,H. Margolis,J.Cihlar, J.Newcomer,D. Fitzjarrald,P.G.Jarvis,S.T.

Gower,D. Halliwell, D. Williams, B. Goodison,D.E.Wickland, andF.E.Guertin.1997.BOREAS

in 1997:ExperimentOverview,ScientificResultsandFutureDirections.Journalof Geophysical

Research102(D24):28,731-28,770.

Shepard,M.K., R.E.Arvidson,andE.A. Guinness.1993.Specularscatteringonaterrestrialplaya

andimplicationsfor planetarysurfacestudies,J.Geophys.Res.98(E10):18,707-18,718.

Staenz,K., R.P.Gauthier,D.J.Williams, andP.M.Teillet. 1995.Thebehaviorof theanisotropic

reflectanceof apecanorchardderivedfrom multiviewandmultiscaleimagingspectrometerdata.

RemoteSens.Env. 52:122-136.

vanLeeuwen,W.J.D.,A.R. Huete,C.L. Walthall, S.D.Prince,A. Begue,andJ.L. Roujean.1997.

Deconvolutionof remotelysensedspectralmixturesforretrievalof LAI, fAPAR andsoilbrightness.

J.Hydrology 188-189:697-724.

CONFERENCE PROCEEDINGS, TALKS, SYMPOSIUMS

Abuelgasim,A. andS.Gopal.1994.Classificationof multiangleandmultispectralASASdatausinga

hybridneuralnetworkmodel.IGARSS'94Digest,3: 1670-1672.

Allison, D. andJ.-P.Muller. 1992.An automatedsystemfor sub-pixelcorrectionandgeocodingof

multi-spectralandmulti-lookaerialimagery.Proc.XVII Congress,Int. Soc.Photogramm.andRem.

Sens.,WashingtonD.C., Aug.2-14,29(B2)pp. 275-285.

Allison, D., M.J. Barnsley,P.Lewis, N. Dyble, andJ.-P.Muller. 1994.Precisegeometric

registrationof ASASairbornedatafor landsurfaceBRDF studies.IGARSS'94Digest,3:1655-1657.

Birk, R.J.andT.B. McCord.1994.Airbornehyperspectralsensorsystems.47thNationalAerospace

andElectronicsConf.,Dayton,OH,May 23-27.

Brown deColstoun,E.C.,C.L. Walthall, C.A. Russell,andJ.R.Irons. 1994.Estimatingthefraction

of absorbedphotosyntheticallyactiveradiation(fAPAR)from off-nadirairbornemeasurements.

IGARSS'94Digest,3: 1823-1825.

Cabot,F., J.Qi, M.S. Moran,andG. Dedieu.1994.Testof surfacebi-directionalreflectancemodels

with surfacemeasurements: resultsandconsequencesfor theuseofremotelysenseddata.Sixth

InternationalSymposiumonPhysicalMeasurementsandSignaturesin RemoteSensing,Jan17-21,

Val d'Isere,France.

Chong-guang,Z., W. Jun,andA.H. Strahler.1994.A newregistrationalgorithmfor ASAS

multi-angleimages.IGARSS'94Digest,3:1658-1660.

Page30
Dabney,P.W.,J.R.Irons, J.W. Travis,M.S. Kasten,andS.Bhardwaj.1994.Impactof recent

enhancementsandupgradesof theAdvancedSolid-stateArraySpectroradiometer(ASAS).

IGARSS'94Digest,3:1649-1651.

Diner, D.J.,S.R.Paradise,andJ.Martonchik.1994.Developmentof anaerosolopacityretrieval

algorithmfor usewith multi-anglelandsurfaceimages.IGARSS'94Digest,3:1664-1666.

Gatlin, J.A.,E.M. Middleton,J.R.Irons,andJ.W.Robinson.1991.Theapplicationof high spectral

resolutionandspatialresolutionimagingspectrometersforlocatingdownedaircraft.Proceedingsof

theInternationalGeoscienceandRemoteSensingSymposium,Espoo,Finland,v. 3: 1363-1366.

Harding,D.J.andJ.R.Irons. 1990.Bi-directionalradianceof playaandvolcanicsurfaces:Advanced

SolidstateArray Spectroradiometer(ASAS)measurementsof LunarCratervolcanicfield,Nevada.

Proc.of theIGARSS'90Symposium,Univ. of Maryland,CollegePark,MD, v.2:1361-1363.

Huete,A.R.,H.Y. Liu, and H.Q. Liu. 1994. Directional vegetation index interactions in ASAS

imagery. IGARSS'94 Digest, 3:1813-1814.

Irons, J.R. and R.R. Irish. 1988. Sensor calibration for multiple direction reflectance observations.

SPIE Proceedings Vol. 924, Recent Advances in Sensors, Radiometry, and Data Processing for

Remote Sensing, p. 109-119.

Irons, J.R., B.W. Meeson, P.W. Dabney, W.M. Kovalick, D.W. Graham, and D.S. Hahn. 1992. A

data base of ASAS digital image data. Proc. 12th Annual International Geoscience & Remote Sens.

Symp., IGARSS'92, Vol. I, Houston, TX, 26-29 May, 1992:517-519.

Irons, J.R., F.G. Huegel, and R.R. Irish. 1989. Prairie grass hemispherical reflectances from

airborne multi-directional observations. Proc. of 19th Conf. on Agriculture and Forest Meteorology

and the Ninth Conf. on Biometeorology and Aerobiology, March 7-10, 1989, Charleston, SC,

published by American Meteorological Society, Boston, MA.

Irons, J.R., K.J. Ranson, D.L. Williams, and R.R. Irish. 1989. Forest and grassland ecosystem

studies using the Advanced Solidstate Array Spectroradiometer. Proceedings of the International

Geoscience and Remote Sensing Symposium, Vancouver, Canada, v. 3: 1761-1764.

Irons, J.R., P.W. Dabney, J. Paddon, R.R. Irish, and C.A. Russell. 1990. Advanced Solidstate

Array Spectroradiometer (ASAS) support of 1989 field experiments. SPIE Proceedings Vol. 1298,

Imaging Spectroscopy of the Terrestrial Environment, April 16-17, 1990, Orlando, FL.

Johnson, L.F. and D.L. Peterson. 1994. Estimation of forest canopy leaf area index using directional

ASAS measurements. IGARSS'94 Digest, 3:1819-1822.

Kovalick, W.M., D.W. Graham, and M. Bur. 1994. Data processing and calibration of the Advanced

Solid-state Array Spectroradiometer. IGARSS'94 Digest, 3:1652-1654.

Lewis, P., M.J. Barnsley, M. Sutherland, and J.P. Muller. 1995. Estimating land surface albedo in

the HAPEX-Sahel experiment: Model-based inversions using ASAS data. IGARSS'95 Digest,

Florence, Italy, July 10-14, 1995:2221-2223.

Liang, S. and A.H. Strahler. 1993. BRDF retrieval from multiangle remotely sensed data. SPIE

Proceedings Vol. 1938, Recent Advances in Sensors, Radiometric Calibration, and Processing of

Remotely Sensed Data, April 14-16, 1993, Orlando, FL.

Page 31
Markham,B.L., J.R.Irons, D.W. Deering,R.N. Halthore,R.R. Irish, R.D. Jackson,M.S. Moran,

S.F.Biggar,D.I. Gellman,B.G. Grant,J.M. Palmer,andP.N.Slater.1990.Radiometriccalibration

of aircraftandsatellitesensorsatWhiteSands,NM. Proceedingsof theInternationalGeoscienceand

RemoteSensingSymposium,CollegePark,MD, v. 1:515-518.

Martonchik,J.V.andJ.E.Conel.1994.Retrievalof surfacereflectanceandatmosphericproperties

usingASASimagery.IGARSS'94Digest,3:1661-1663.

Qi, J.,F. Cabot,M.S. Moran,G. Dedieu,andK.J.Thome.1994.Biophysicalparameterretrievals

usingbi-directionalmeasurements.IGARSS'94Digest,3:1816-1818,1994.

Schaaf,C.B.,X. Li, andA.H. Strahler.1994.Validationof canopybi-directionalreflectancemodels

with ASASimageryof a spruceforestin Maine.IGARSS'94Digest,3:1832-1834.

Staenz,K., R.P.Gauthier,andP.M. Telliet. 1993.Bi-directional-reflectanceffectsderivedfrom

ASASimageryof apecanorchard.SPIEProceedingsVol. 1937,ImagingSpectrometryof the

TerrestrialEnvironment,April 14-16,1993,Orlando,FL.

Teillet,P.M. andJ.R.Irons. 1990.Spectralvariability effectsontheatmosphericcorrectionof

imagingspectrometerdatafor surfacereflectanceretrieval.Proc.of theISPRSCommissionVII

Mid-Term Symposium:GlobalandEnvironmentalMonitoringTechniquesandImpacts,Victoria,BC,

Canada:579-583.

vanLeeuwen,W.J.D.,A.R. Huete,andC.L. Walthall. 1994.Biophysicalinterpretationof aspectral

mixturemodelbasedonaradiativetransfermodelandobservationaldata.IGARSS'94Digest,

3:1458-1460.

CD-ROM COLLECTIONS

Angelici, G.L., J.W.Skiles,andL.Z. Popovici.1992.OTTER:OregonTransectEcosystemResearch

Project,CollectedData,Volume 1,Version1,Satellite,aircraftandgroundmeasurements, CD-ROM

USA_NASA_PLDS_OT_0001,NASA/ARC.

Arvidson, R.E.,M.A. Dale-Bannister,E.A. Guinness,S.H.Slavney,andT.C. Stein. 1991.Archive

of GeologicRemoteSensingFieldExperiment,Data-Release1.0,CD-ROMVolume

USA_NASA_PDS_GR_001,NASA PlanetaryDataSystem,JPL,Pasadena,CA.

ASASatmosphericallycorrectedreflectancefactortablesfor selectedsitescanbefoundin CD-ROM

USA_NASA_PLDS_FIFE_0001:SurfaceObservationsandNon-ImageDataSets(underGrabBag

category).

Strebel,D.E.,D.R. Landis,J.A. Newcomer,B.W. Meeson,P.A. Agbu, andJ.M.P. McManus.

1992.CollectedDataof theFirstISLSCPFieldExperiment,Volume4:ASAS& PBMRImagery

1987& 1989,CD-ROMUSA_NASA_PLDS_FIFE_0004,NASA GSFC.

17.3 Arehive/DBMS Usage Documentation

None.

None.

18. Glossary of Terms

Page 32
19. List of Acronyms

AGL

ARC

ASAS

ASCII

AVIRIS

BOREAS

BORIS

BRDF

CASI

CCD

CD-ROM

CID

DAAC

DAT

DN

EOS

EOSDIS

fAPAR

FFC-T

FFC-W

FWHM

GIS

GMT

GPS

GSFC

HDR

IDL

IFC

IFOV

JSC

LAI

MAS

MISR

MODIS

NAD83

NASA

NSA

OA

OBS

OJP

ORNL

PANP

PAR

- Above Ground Level

- A_nes Research Center

- Advanced Solid-state Array Spectroradiometer

- American Standard Code for Information Interchange

- Airborne Visible-Infrared Imaging Spectrometer

- BOReal Ecosystem-Atmosphere Study

- BOREAS Information System

- Bidirectional Reflectance Distribution Function

- Compact Airborne Spectrographic Imager

- Charge-Coupled Device

- Compact Disk - Read-Only Memory

- Charge-Injection Device

- Distributed Active Archive Center

- Digital Archive Tape

- Digital Number

- Earth Observing System

- EOS Data and Information System

- fraction of absorbed PAR

- Focused Field Campaign - Thaw

- Focused Field Campaign - Winter

- Full-Width-at-Half-Maximum

- Geographic Information System

- Greenwich Mean Time

- Global Positioning System

- Goddard Space Flight Center

- Header

- Interactive Data Language

- Intensive Field Campaign

- Instantaneous Field-of-View

- Johnson Space Center

- Leaf Area Index

- MODIS Airborne Simulator

- Multi-angle Imaging SpectroRadiometer

- Moderate Resolution Imaging Spectroradiometer

- North American Datum of 1983

- National Aeronautics and Space Administration

- Northern Study Area

- Old Aspen

- Old Black Spruce

- Old Jack Pine

- Oak Ridge National Laboratory

- Prince Albert National Park

- Photosynthetically Active Radiation

PARABOLA- Portable Apparatus for the Rapid Acquisition of Bidirectional

Observations of Land and Atmosphere

POLDER

RSS

S/N

SIS

SLICER

SPP

SSA

- Polarization and Directionality of Earth's Reflectances

- Remote Sensing Science

- Signal-to-Noise

- Scanning Imaging Spectroradiometer

- Scanning Lidar Imager of Canopies by Echo Recovery

- Solar Principal Plane

- Southern Study Area

Page 33
URL

VLDS

WFF

YA

YJP

- Uniform Resource Locator

- Very Large Data Storage

- Wallops Flight Facility

- Young Aspen

- Young Jack Pine

20. Document Information

20.1 Document Revision Dates

Written: 01-Aug- 1995

Updated: 03-Nov- 1999

20.2 Document Review Date

BORIS Review: 09-Sep- 1997

Science Review: 03-Dec- 1997

20.3 Document ID

20.4 Citation

When using these data, please acknowledge James R. Irons and Philip W. Dabney for providing

ASAS data and include citations of relevant papers in Section 17.2.

If using data from the BOREAS CD-ROM series, also reference the data as:

Irons, J.R. and P.W. Dabney, "Terrestrial Ecosystem Studies of the Boreal Forest Using

Bidirectional Reflectances Acquired by a Multispectral, Multiangle Imaging Spectroradiometer." In

Collected Data of The Boreal Ecosystem-Atmosphere Study. Eds. J. Newcomer, D. Landis, S.

Conrad, S. Curd, K. Huemmrich, D. Knapp, A. Morrell, J. Nickeson, A. Papagno, D. Rinker, R.

Strub, T. Twine, F. Hall, and P. Sellers. CD-ROM. NASA, 2000.

Also, cite the BOREAS CD-ROM set as:

Newcomer, J., D. Landis, S. Conrad, S. Curd, K. Huemmrich, D. Knapp, A. Morrell, J.

Nickeson, A. Papagno, D. Rinker, R. Strub, T. Twine, F. Hall, and P. Sellers, eds. Collected Data of

The Boreal Ecosystem-Atmosphere Study. NASA. CD-ROM. NASA, 2000.

20.5 Document Curator

20.6 Document URL

Page 34
REPORT DOCUMENTATION PAGE FormApproved

OMB No. 0704-0188

Public reporting burden for this collection of informationis estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson

Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

July 2000 Technical Memorandum

4. TITLE AND SUBTITLE

Technical Report Series on the Boreal Ecosystem-Atmosphere Study (BOREAS)

BOREAS RSS-2 Level-lB ASAS Image Data: At-Sensor Radiance in

BSQ Format

6. AUTHOR(S)

C. Russell, R Dabney, W. Kovalick, D. Graham, M. Bur, J. Irons,

and M. Tierney

Forrest G. Hall and Jaime Nickeson, Editors

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS (ES)

Goddard Space Flight Center

Greenbelt, Maryland 20771

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS (ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

5. FUNDING NUMBERS

923

RTOP: 923-462-33-01

8. PEFORMING ORGANIZATION

REPORT NUMBER

2000-03136-0

10. SPONSORING / MONITORING

AGENCY REPORT NUMBER

TM--2000-209891

Vol. 43

11. SUPPLEMENTARY NOTES

C. Russell: SSAI; W. Kovalick, D. Graham, M. Bur, and J. Nickeson: Raytheon ITSS

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Report available from the NASA Center for AeroSpace Information,

7121 Standard Drive, Hanover, MD 21076-1320. (301) 621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The BOREAS RSS-2 team used the ASAS instrument, mounted on the NASA C-130 aircraft, to create

at-sensor radiance images of various sites as a function of spectral wavelength, view geometry (combinations of view zenith angle, view azimuth angle, solar zenith angle, and solar azimuth angle), and

altitude. The level-lb ASAS images of the BOREAS study areas were collected from April to September 1994 and March to July 1996.

14. SUBJECT TERMS

BOREAS, remote sensing science, ASAS instrument.

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