BOREAS Level-0 AOCI Imagery: Digital Counts in BIL Format

Summary

The level-0 AOCI imagery, along with the other remotely sensed images,
was collected to provide spatially extensive information about radiant
energy over the primary BOREAS study areas. The AOCI was the only remote
sensing instrument flown with wavelength bands specific to the
investigation of various aquatic parameters such as chlorophyll content
and turbidity. Only one flight of the AOCI instrument was made onboard
the ER-2 aircraft on 21-Jul-1994 over the SSA.

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 Level-0 AOCI Imagery: Digital Counts in BIL Format

1.2 Data Set Introduction

The level-0 AOCI images contain 10 spectral bands that cover portions of
the electromagnetic spectrum from the visible through the thermal
infrared. The data are provided in the format that they were delivered
to BORIS.

1.3 Objective/Purpose

The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science effort
covered those activities that were BOREAS community-level activities or
required uniform data collection procedures across sites and time. These
activities included the acquisition, processing, and archiving of
10-band Airborne Ocean Color Imager (AOCI) image data collected on the
National Aeronautics and Space Administration\'s (NASA\'s) ER-2
aircraft.

For BOREAS, the AOCI imagery, along with the other remotely sensed
images, was collected in order to provide spatially extensive
information over the primary study areas. This information includes
detailed land cover, biophysical parameter maps such as fraction of
Photosynthetically Active Radiation (fPAR), and Leaf Area Index (LAI),
and surface thermal properties. The AOCI was the only remote sensing
instrument flown with wavelength bands specific to the investigation of
various aquatic parameters such as chlorophyll content and turbidity.

1.4 Summary of Parameters

AOCI level-0 image data in the BOREAS Information System (BORIS)
contains the following parameters:

original housekeeping and calibration information and bands 1 to 10 in
the NASA Ames Research Center (ARC) Band Interleaved by Line (BIL)
format.

1.5 Discussion

BORIS staff processed the AOCI level-0 images by:

1\) Extracting pertinent header information from the level-0 image
product and placing it in an American Standard Code for Information
Interchange (ASCII) file on disk

2\) Reading the information in the disk file and loading the online
database with needed information.

1.6 Related Data Sets

BOREAS Level-0 ER-2 Aerial Photography

BOREAS Level-0 Daedalus TMS Imagery: Digital Counts in BIL Format

BOREAS RSS-18 Level-1B AVIRIS Imagery: At-sensor Radiance in BIL Format

2\. Investigator(s)

2.1 Investigator(s) Name and Title

BOREAS Staff.

2.2 Title of Investigation

BOREAS Staff Science Aircraft Data Acquisition Program

2.3 Contact Information

Contact 1

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Jeffrey S. Myers

Aircraft Data and Sensor Facilities

NASA Ames Research Center

Moffett Field, CA

\(415\) 604-6253

\(415\) 604-4987 (fax)

jmyers@msmail.arc.nasa.gov

Contact 2

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Jeffrey A. Newcomer

NASA/GSFC

Greenbelt, MD

\(301\) 286-7858

\(301\) 286-0239 (fax)

Jeffrey.newcomer@gsfc.nasa.gov

3\. Theory of Measurements

The NASA Earth Resources Aircraft Program at ARC operates the ER-2
aircraft to acquire data for Earth science research. The AOCI instrument
used on the ER-2 aircraft collects radiance measurements in 10 total
spectral bands, with nine bands covering the visible and near-infrared
spectrum from 0.436 to 1.054 micrometers (µm), and one thermal-infrared
band covering 8.423 to 12.279 µm.

Thematic considerations have dictated, within technical constraints, the
choice of spectral band position and width in the AOCI sensor. These
bands were chosen after many years of analysis for their value in
discrimination of aquatic features.

4\. Equipment

4.1 Sensor/Instrument Description

The AOCI instrument was designed to gather information about the visible
reflectance and temperature characteristics of water bodies. The AOCI is
generally flown at high altitudes and provides 49.5-m resolution at
nadir at an altitude of 19,800 m. The AOCI is flown aboard NASA\'s ER-2
aircraft based at ARC.

The 10 spectral channels of the AOCI sensor have the following
bandpasses:

AOCI Channel Wavelength, µm

\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\-\--

1 0.436 - 0.455

2 0.481 - 0.501

3 0.511 - 0.531

4 0.554 - 0.575

5 0.610 - 0.631

6 0.655 - 0.676

7 0.741 - 0.800

8 0.831 - 0.897

9 0.989 - 1.054

10 8.423 - 12.279

4.1.1 Collection Environment

As part of the BOREAS Staff Science Data Collection Program, BORIS
distributed 10-band level-0 AOCI image data. The AOCI was flown on
NASA\'s ER-2 aircraft during the BOREAS mission (see the BOREAS
Experiment Plan for flight pattern details and objectives).

Maintenance and operation of the instrument are the responsibility of
ARC. The ER-2 Experimenter\'s Handbook (supplemental) produced by the
High Altitude Missions Branch at ARC provides a description of the
instrument, calibration procedures, and data format.

4.1.2 Source/Platform

NASA\'s ER-2 Earth Resources Aircraft

4.1.3 Source/Platform Mission Objectives

The AOCI is a multispectral scanner built by Daedalus Enterprises,
designed for oceanographic remote sensing. The response of the
instrument is optimized for the low levels of radiance normally
associated with water scenes, so some bands may saturate over bright
terrestrial targets.

4.1.4 Key Variables

Emitted radiation, reflected radiation, and temperature.

4.1.5 Principles of Operation

None given.

4.1.6 Sensor/Instrument Measurement Geometry

Instantaneous Field-Of-View (IFOV) 2.5 mrad

Total Scan Angle 85 degrees

Pixels/Scan Line 716

Sensor footprint is 49.5 x 49.5 m at nadir at 19,800-m altitude.

4.1.7 Manufacturer of Sensor/Instrument

Daedalus Enterprises

Ann Arbor, MI

4.2 Calibration

4.2.1 Specifications

The wavelength ranges (in µm) of the bands for the AOCI are:

AOCI Channel Wavelength, µm

\-\-\-\-\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\-\--

1 0.436 - 0.455

2 0.481 - 0.501

3 0.511 - 0.531

4 0.554 - 0.575

5 0.610 - 0.631

6 0.655 - 0.676

7 0.741 - 0.800

8 0.831 - 0.897

9 0.989 - 1.054

10 8.423 - 12.279

DESIGN DATA:

IFOV 2.5 milliradians

Across-track FOV +/- 42.5°

Inflight calibration Integrating sphere and two

controllable blackbodies

Short wavelength array temperature 255 K

V/H range Variable 0.025 to 0.25

Scan rate Variable 10 to 100 scans/sec.

Scan speed ability One-third of the IFOV, scan

line to scan line

Data quantization 10-bits (1,024 discrete levels)

for bands 1 to 8 and

8-bits (256 discrete levels)

for bands 9 and 10

Number of video samples/scan line 716

Roll compensation +/-15°

Scan mirror 45° rotating mirror

4.2.1.1 Tolerance

Unknown.

4.2.2 Frequency of Calibration

The ARC Sensor Calibration Laboratory measures the Spectral Response
Function (SRF) of each band several times per year using a full-aperture
scanning monochromator. Radiometric calibration is regularly performed
using a low-intensity 30-in. integrating sphere with a 12-in. exit
aperture. The sphere is calibrated periodically against a National
Institute of Standards and Technology (NIST) standard reference source.
The SRF is then convolved with the measured sphere radiance to produce
in-band radiance for bands 1-9. The thermal-infrared band 10 is
calibrated with the two onboard blackbody reference sources that are
viewed before and after each scan line during the data acquisition,
together with the SRF measured in the laboratory.

4.2.3 Other Calibration Information

AOCI data may be intentionally overscanned, e.g., operated at some
integral multiple of the desired scan rate and then subsampled in
preprocessing. The subsampling factor is reported as a \"demagnification
factor.\"

5\. Data Acquisition Methods

As part of the BOREAS Staff Science Data Collection Program, BORIS
distributed 10-band level-0 AOCI image data. The AOCI was flown on
NASA\'s ER-2 aircraft during BOREAS (see the BOREAS Experiment Plan for
flight pattern details and objectives).

Maintenance and operation of the instrument are the responsibility of
ARC. The ER-2 Experimenter\'s Handbook (supplemental) produced by the
HIGH Altitude Missions Branch at ARC provides a description of the
instrument, calibration procedures, and data format.

6\. Observations

6.1 Data Notes

None.

6.2 Field Notes

None.

7\. Data Description

7.1 Spatial Characteristics

The BOREAS level-0 AOCI images cover the Southern Study Area (SSA),
which is located in the southwest portion of the overall BOREAS region.

7.1.1 Spatial Coverage

The North American Datun 1983 (NAD83) corner 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

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

The AOCI IFOV provides a footprint of 49.5 m at nadir at an altitude of
19,800 m, which was typical of the BOREAS flight.

7.1.4 Projection

The BOREAS level-0 AOCI images are stored in their original data
collection frame with increasing pixel sizes from nadir to the scanning
extremes based on the scan angle.

7.1.5 Grid Description

The BOREAS level-0 AOCI images are stored in their original data
collection frame with increasing pixel sizes from nadir to the scanning
extremes based on the scan angle.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

The level-0 AOCI image data were collected on 21-Jul-1994.

7.2.2 Temporal Coverage Map

IFC# Dates

\-\-\-\-- \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

IFC-2 21-Jul-1994

7.2.3 Temporal Resolution

Images were acquired only on 21-Jul-1994.

7.3 Data Characteristics

Data characteristics are defined in the companion data definition file
(aoci0bil.def).

7.3.1 Parameter/Variable

The parameter contained in the image data files is:

Digital Number (DN)

7.3.2 Variable Description/Definition

For the image data files:

Digital Number (DN) - The quantized DN derived by the AOCI scanning
system for

the respective channel.

7.3.3 Unit of Measurement

For the image data files:

Digital Number (DN) - counts

7.3.4 Data Source

The level-0 AOCI image bands were collected by the AOCI instrument on
the ER2 aircraft. The raw data were decommutated, processed, and sent to
BORIS by personnel within the High Altitude Aircraft Branch at NASA ARC.

7.3.5 Data Range

The maximum range of DNs in each level-0 AOCI image band is limited from
0 to 1023 (10 bits) and is stored in a 16-bit (2-byte) field.

7.4 Sample Data Record

Sample data format shown in the companion data definition file
(aoci0bil.def).

8\. Data Organization

Although the image inventory is contained on the BOREAS CD-ROM set, the
actual level-0 AOCI images are not. Sample data records are shown in the
companion data definition file (aoci0bil.def).

8.1 Data Granularity

The smallest unit of level-0 AOCI data is the entire tape of data
covering the flights on 21-Jul-1994.

8.2 Data Format(s)

A level-0 AOCI tape contains one header file followed by up to 50 files
containing data from AOCI flight lines. For BOREAS, the single level-0
tape contains the header file followed by 15 image data files.

The header file contains one record of 9,192 bytes that contain a
mixture of ASCII and binary values. The multibyte integer fields are
stored as high-order byte first. The contents of the header record
fields are:

Bytes Description

\-\-\-\-\-\-\-\--
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

1 - 80 Data Description (ASCII characters, e.g., 'AOCI (CANADA)')

81 - 90 Flight Number (ASCII characters, e.g., 92-120)

91 - 120 Data Collection Date (ASCII characters, e.g., 21-JULY-1994)

121 - 150 Data Decommutation Date (ASCII characters)

151 - 180 Archive Tape Creation Date (ASCII characters)

181 - 182 Aircraft Number (binary 16-bit integer, value of 708)

183 - 184 Scanner Type (ASCII characters, 'DA')

185 - 186 Reel Number (binary 16-bit integer)

187 - 188 Expected Number of Reels (binary 16-bit integer)

189 - 198 Filler bytes

199 - 200 Number of Channels Processed (binary 16-bit integer)

(Erroneous value of 12 on the BOREAS tape; should be 10)

201 - 224 Channel numbers (binary 16-bit integers)

(Erroneous values of 11 and 12 on BOREAS tape; should be 1 to 10)

225 - 236 Filler bytes

237 - 238 Mode used to specify flight line boundaries (ASCII characters)

(AL = all data contained in one flight line)

(SL = selected scan lines) (BOREAS tape)

(GM = selected times)

239 - 240 Number of operator-specified flight line intervals

(binary 16-bit integer) (15 for BOREAS tape)

241 - 244 Start of flight line interval number 1 (binary 32-bit integer)

245 - 248 Start of flight line interval number 2 (binary 32-bit integer)

.

.

437 - 440 Start of flight line interval number 50 (binary 32-bit
integer)

441 - 444 End of flight line interval number 1 (binary 32-bit integer)

445 - 448 End of flight line interval number 2 (binary 32-bit integer)

.

.

637 - 640 End of flight line interval number 50 (binary 32-bit integer)

641 - 9192 Filler bytes

Each level-0 AOCI image from a given flight is contained in one tape
file. A physical tape record of 14,820 bytes contains 10 logical records
of 1482 bytes which contain housekeeping information (50 bytes) and the
image data (1432 bytes) from the 10 AOCI spectral bands in BIL order.
The bytes of the 16-bit and 32-bit values in the housekeeping
information are ordered as high-order byte first. The detailed structure
of each logical record is:

AOCI Logical Data Record Structure

Bytes 1 - 50 Housekeeping Information

1 - 2 Data Frame Status (16-bit integer)

0 implies the data are good; nonzero implies they are bad.

10 Interpolated data

20 Repeated data

30 Zero fill data

3 - 4 Run Number (16-bit integer)

5 - 8 Scan line count (32-bit integer)

9 - 12 Panel Thumbwheel switches (32-bit integer)

Consists of 8 digits in the form YYFFFJJJ

where YY is the last two digits of the year (e.g., 94)

FFF is flight number (e.g., 120)

JJJ is day of the year (e.g., 202)

13 - 14 Blackbody #1 Thermal Reference Temperature (16-bit integer)

(hundredths of degrees C)

15 - 16 Blackbody #2 Thermal Reference Temperature (16-bit integer)

(hundredths of degrees C)

17 - 18 Scan Speed (16-bit integer) (tenths of scans per second)

19 - 20 Greenwich Mean Time (GMT) hours (16-bit integer)

21 - 22 Minutes of the hour (16-bit integer)

23 - 24 Tenths of seconds (16-bit integer)

25 - 26 Demagnification value \* 100 (16-bit integer)

(Set to 100 to indicate unity, i.e., no demagnification)

27 - 28 Filler (16-bit integer)

29 - 30 Gain Value (times 1000) (16-bit integer)

31 - 32 Channel Number (16-bit integer)

33 - 36 Time (32-bit integer)

(7 digits in the form of hhmmsst where hh is the hour,

mm is the minutes, ss is the seconds, and t is the tenths

of a second)

37 - 38 Blackbody #1 Response (16-bit integer) (Counts)

(What the sensor sees when it looks at Blackbody #1)

39 - 40 Blackbody #2 Response (16-bit integer) (Counts)

(What the sensor sees when it looks at Blackbody #2)

41 - 42 Aircraft Roll angle counts (16-bit integer)

(0.03 degrees per count or 0.06 degrees per pixel)

(Positive values indicate rotation of the aircraft in a

clockwise direction when viewed from the front;

negative values indicate counterclockwise rotation)

43 - 50 Filler bytes

Bytes 51 - 1482 Binary Image data

51 - 52 Digital count for pixel #1 of the scan line (16-bit integer)

53 - 54 Image data for pixel #2 of the scan line (16-bit integer)

.

.

1481 - 1482 Image data for pixel #716 of the scan line (16-bit integer)

9\. Data Manipulations

9.1 Formulae

None.

9.1.1 Derivation Techniques and Algorithms

None.

9.2 Data Processing Sequence

9.2.1 Processing Steps

BORIS staff processed the level-0 AOCI imagery by:

1\) Creating duplicate copies of the original image data tapes

2\) Extracting information from the tape to ASCII files on disk

3\) Using the extracted ASCII disk file information to inventory the
images by date and location in the online data base

9.2.2 Processing Changes

None.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

None.

9.3.2 Calculated Variables

None.

9.4 Graphs and Plots

None.

10\. Errors

10.1 Sources of Error

None given.

10.2 Quality Assessment

10.2.1 Data Validation by Source

Spectral errors could arise because of image-wide signal-to-noise ratio,
saturation, cross-talk, spikes, or response normalization caused by a
change in gain.

10.2.2 Confidence Level/Accuracy Judgment

None given.

10.2.3 Measurement Error for Parameters

None given.

10.2.4 Additional Quality Assessments

None given.

10.2.5 Data Verification by Data Center

BORIS staff reviewed the AOCI images through software that summarized
the housekeeping information in the records of each flight line and
histogrammed the image bands to gather minimum, maximum, mean, and
standard deviation values that were then reviewed before loading the
information into the data base. No anomalous values were noted.

11\. Notes

11.1 Limitations of the Data

None given.

11.2 Known Problems with the Data

To date, no discrepancies or problems have been noted in the data.

11.3 Usage Guidance

None given.

11.4 Other Relevant Information

None given.

12\. Application of the Data Set

The level-0 AOCI images could be used for studying land surface or water
properties contained in the imaged areas.

13\. Future Modifications and Plans

None.

14\. Software

14.1 Software Description

BORIS staff developed software and command procedures for:

1\) Extracting header information from level-0 AOCI images on tape and
writing it

to ASCII files on disk

2\) Reading the ASCII disk file and logging the level-0 AOCI image
products into

the Oracle data base tables

14.2 Software Access

The software is written in C and is operational on VAX 6410 and MicroVAX
3100 systems at GSFC. The primary dependencies in the software are the
tape input/output (I/O) library and the Oracle data base utility
routines.

15\. Data Access

15.1 Contact Information

Ms. Beth McCowan

BOREAS Data Manager

NASA/GSFC

Greenbelt, MD

\(301\) 286-4005

\(301\) 286-0239 (fax)

beth@ltpmail.gsfc.nasa.gov

15.2 Data Center Identification

See Section 15.1.

15.3 Procedures for Obtaining Data

Users may place requests by telephone, electronic mail, or fax.

15.4 Data Center Status/Plans

The level-0 AOCI image data are available from the Earth Observing
System Data and Information System (EOSDIS) Oak Ridge National
Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS
contact at ORNL is:

ORNL DAAC User Services

Oak Ridge National Laboratory

\(865\) 241-3952

ornldaac@ornl.gov

ornl@eos.nasa.gov

16\. Output Products and Availability

16.1 Tape Products

The BOREAS level-0 AOCI data can be made available on 1600- or 6250- BPI
9-track, 8-mm, or DAT tapes.

16.2 Film Products

None.

16.3 Other Products

Although the image inventory is contained on the BOREAS CD-ROM set, the
actual level-0 AOCI images are not. See section 15 for information about
how to obtain the data.

17\. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

NASA. 1990. ER-2 Earth Resources Aircraft Experimenter\'s Handbook.
National Aeronautics and Space Administration, Ames Research Center,
Moffett Field, California.

Airborne Instrumentation Research Project - Flight Summary Report
Series. 1994. NASA Ames Research Center. Airborne Missions and
Applications Division, Moffett Field, California, 94035.

17.2 Journal Articles and Study Reports

Sellers, P., and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study:
Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN-94).

Sellers, P., and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study:
Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN-96).

Sellers, P., F. Hall, and K. F. Huemmrich. 1994. Boreal
Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC
94).

Sellers, P., F. Hall, and K. F. Huemmrich. 1997. Boreal
Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC
96).

Sellers, P., F. Hall, and K. F. Huemmrich. 1994. Boreal
Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC
94).

Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den
Hartog, J. Cihlar, M. G. Ryan, B. Goodison, P. Crill, K. J. Ranson, D.
Lettenmaier, and D. E. Wickland. 1995. The boreal ecosystem-atmosphere
study (BOREAS): an overview and early results from the 1994 field year.
Bulletin of the American Meteorological Society. 76(9):1549-1577.

Sellers, P., and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue
(in press).

17.3 Archive/DBMS Usage Documentation

The collected eata of BOREAS are currently archived at the NASA/GSFC.

18\. Glossary of Terms

None.

19\. List of Acronyms

AOCI - Airborne Ocean Color Imager

ARC - Ames Research Center

ASCII - American Standard Code for Information Interchange

BIK - Band Interleaved by Line

BOREAS - BOReal Ecosystem-Atmosphere Study

BORIS - BOREAS Information System

BPI - Byte per inch

CCT - Computer Compatible Tape

CD-ROM - Compact Disk-Read-Only Memory

DAAC - Distributed Active Archive Center

DAT - Digital Archive Tape

EOS - Earth Observing System

EOSDIS - EOS Data and Information System

FOV - Field-Of-View

fPAR - fractionf of Photosynthetically Active Radiation

GMT - Greenwich Mean Time

GSFC - Goddard Space FLight Center

IFOV - Instantaneous Field-of-View

I/O - Input/Output

LAI - Leaf Area Index

NAD83 - North American Datum 1983

NASA - National Aeronautics and Space Administration

NIST - Natioanl Institute of Standards and Technology

NSA - Northern Study Area

ORNL - Oak Ridge National Laboratory

PANP - Prince Albert National Park

SRF - Spectral Response Function

SSA - Southern Study Area

µm - micrometers

URL - Uniform Resource Locator

20\. Document Information

20.1 Document Revision Date

Written: 05-Nov-1996

Last Updated: 26-Feb-1998

20.2 Document Review Dates

BORIS Review: 20-May-1997

Science Review: 20-May-1997

20.3 Document ID

20.4 Citation

The BOREAS level-0 AOCI data were collected and processed from the
original aircraft tapes by personnel of the High Altitude Aircraft
Branch at ARC. Their contributions to providing this data set are
greatly appreciated.

20.5 Document Curator

20.6 Document URL

Keywords

ER-2

AOCI