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 AOCI_L0.doc 04/17/98