BOREAS RSS-14 Level-1a GOES-7 Visible, Infrared, and Water Vapor Images Summary The level-1a BOREAS GOES-7 image data was collected by Remote Sensing Science Team 14 (RSS-14) personnel at the Florida State University and processed to level-1a products by BORIS personnel. The data cover the period of 01-January-1994 through 08-July-1995 with partial to complete coverage on the majority of the days. The data include three-bands with eight-bit pixel values. No major problems with the data have been identified. Note that the level-1a GOES-7 data are not contained on the BOREAS CD-ROM set. An inventory listing file is supplied on the CD-ROM to inform users of the data that were collected. This inventory file is also available as a companion file on the ORNL DAAC ftp site (ftp://www-eosdis.ornl.gov/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.dat). Level-1a GOES-7 images and image documentation may be viewed and the image data files downloaded using a convenient ORNL DAAC viewer utility (http://daacs.ESD.ORNL.Gov/BOREAS/viewers/viewG71a.html). Information presented includes counts of how many visible, infrared, and water vapor images are available for each day. The viewer also has links to the ORNL DAAC ftp directory and to another utility that will make a movie with daily GOES-7 Level-1a images. See section 15 for information about how to acquire level-1a GOES-7 images. 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-14 Level-1a GOES-7 Visible, Infrared, and Water Vapor Images 1.2 Data Set Introduction 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 processing the level-1 Geostationary Operational Environmental Satellite (GOES)-7 images acquired by Dr. Eric Smith of Florida State University (FSU) into level-1a products. 1.3 Objective/Purpose For BOREAS, the level-1a GOES-7 imagery, along with the other remotely sensed images, was collected in order to provide spatially extensive information over the primary study areas at varying spatial scales. The primary objective for the GOES-7 images in 1994 was to collect visible, infrared (IR), and water vapor channel data covering the BOREAS region at a sufficiently high temporal frequency for subsequent use in analyzing weather events and deriving temporal surface radiation parameters and patterns that existed during the Focused and Intensive Field Campaigns (FFCs and IFCs). The transition and shifting of satellites from GOES-7 to GOES-8 in 1995 enabled good quality images to be acquired over the BOREAS region four times per day from January to June, giving a reasonable monitoring data set. 1.4 Summary of Parameters The level-1a GOES-7 data from 1994 and 1995 in the BORIS contain the following parameters: image header and summary information; central geographic position; digital counts for half-hourly visible and IR images and digital counts for hourly water vapor images. 1.5 Discussion Dr. Smith provided BORIS with the level-1 GOES-7 images that were used to create the level-1a products. BORIS processed the level-1a GOES-7 images by: 1) summarizing and extracting header information from the level-1 GOES-7 images and placing it in an American Standard Code for Information Interchange (ASCII) file on disk, 2) reviewing the header file information for potential errors, 3) working with FSU personnel to remove erroneous files detected in step 2, 4) repackaging/reformatting the image data for a given day, 5) writing the reformatted data files to tape, and 6) loading the online data base with needed information. 1.6 Related Data Sets BOREAS RSS-14 Level-1 GOES-7 Images from 1994 and 1995 BOREAS RSS-14 Version-0 Level-2 GOES-7 Shortwave Radiation Data BOREAS RSS-14 Version-1 Level-2 GOES-7 Shortwave Radiation Images BOREAS RSS-14 Version-0 Level-2 GOES-7 Net Longwave Radiation Images BOREAS RSS-14 Version-0 Level-3 Gridded Radiometer and Satellite Radiation Images BOREAS RSS-14 Level-1 GOES-8 Images from 1995 and 1996 BOREAS RSS-14 Level-1a GOES-8 Images from 1995 and 1996 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Eric A. Smith, Professor Department of Meteorology Florida State University Tallahassee, FL 32306-3034 2.2 Title of Investigation GOES Imagery for the BOREAS Experimental Areas 2.3 Contact Information Contact 1 Jeffrey A. Newcomer NASA/GSFC Greenbelt, MD (301) 286-7858 (301) 286-0239 Jeffrey.Newcomer@gsfc.nasa.gov Contact 2 Dr. Eric A. Smith Florida State University Tallahassee, FL (904) 644-4253 (904) 644-9639 esmith@metsat.met.fsu.edu 3. Theory of Measurements The GOES mission is to provide the nearly continuous, repetitive observations that are needed to predict, detect, and track severe weather. GOES spacecraft are equipped to observe and measure cloud cover, surface conditions, snow and ice cover, surface temperatures, and the vertical distributions of atmospheric temperature and humidity. They are also instrumented to measure solar X-rays and other energetics, collect and relay environmental data from platforms, and broadcast instrument data and environmental information products to ground stations. The GOES system includes the satellite (with the GOES instrumentation and direct downlink data transmission capability); the National Environmental Satellite, Data and Information Service (NESDIS) facility at Wallops Island, VA, and the ground systems at NESDIS. 4. Equipment 4.1 Sensor/Instrument Description The original GOES instrument was the Visible and Infrared Spin Scan Radiometer (VISSR), which was an outgrowth of the spin scan radiometer flown aboard several of the Applications Technology Satellite (ATS) series of the National Aeronautics and Space Administration (NASA) research satellites. The VISSR was first flown aboard Synchronous Meteorological Satellite (SMS)-1 and (SMS)-2 used by the National Oceanic and Atmospheric Administration (NOAA). GOES-1, -2 and -3 were operational satellites that flew the original VISSR instrument. GOES-4 through -7 were flown with a modified instrument package called the VISSR Atmospheric Sounder (VAS). A set of IRsensors was added to provide an atmospheric sounder capability. The VAS instrument system is an expansion of the VISSR system with improved structural design and some additional capabilities. It consists of the same type of scanning system, a telescope with lighter weight optics made from beryllium instead of conventional materials (glass, steel), eight visible detectors (25 x 24 µm Instantaneous Field of View (IFOV)), and six IR detectors. GOES-7 Channel Wavelength, um ------------- -------------- 1 (visible) 0.5-0.7 8 (IR) 11.17 10 (water vapor) 6.725 4.1.1 Collection Environment The data were acquired using the FSU direct readout ground system located in Tallahassee, FL, starting on 01-Jan-1994 and continued through 08-Jul-1995. GOES-7 orbited Earth in a geostationary orbit at an altitude of 42,000 km. 4.1.2 Source/Platform Launch and data-available dates for GOES-7 are: Satellite Launch Date Data Range --------- ----------- ----------------------- GOES-7 26-Feb-1987 25-Mar-1987 to mid-1995 4.1.3 Source/Platform Mission Objectives See Sections 1.3 and 3. 4.1.4 Key Variables Reflected radiation Emitted radiation Water vapor 4.1.5 Principles of Operation The VISSR instrument consists of a scanning system, telescope, and IR and visible sensors. The scanning system consists of a mirror that is stepped mechanically to provide north-to-south viewing, while the 100-rpm rotation of GOES provides west- to-east scanning. The mirror is stepped following each West to East scan. The mirror position is controlled by one of two optical encode wheels attached to the axis. Each step of the mirror causes a change of 192 mr in the scan angle, representing a distance of 6.9 km near nadir. A sequence of 1,821 scans over 18.21 minutes is performed to provide a "full disk" view from just beyond the northern Earth horizon to just beyond the southern Earth horizon. The scanning mirror reflects the received radiation into a 16-inch diameter telescope. A fiber-optics bundle is used to couple the telescope to eight visible detectors (sensitive to the 0.54- to 0.70- micrometer band). The fiber-optics bundle is configured such that each of the eight VIS sensors has a 20 (W-E) x 25 (N-S) mr field of view (FOV) on GOES-7. The sensors are arranged in a linear array oriented "north-south" (i.e., perpendicular to the scan direction), thus sweeping out eight parallel scan line paths as the satellite rotates. The FOV provides a ground resolution of 0.9 km (normally referred to as 1 km or 0.5 nautical mile). The system thus provides eight parallel visible data lines per west to east scan, covering the 6.9- km (normally referred to as 8 km or 4 miles) band scanned by each step of the scanning mirror. In addition, germanium relay lenses are used to pass received radiation to two mercury-cadmium-tellurium (HgCdTe) IR detectors by way of a 10.5- to 12.6- micrometer bandpass filter. The FOV of the IR detectors is 192 mr (equal to the north-south scan step angle); thus, the IR sensors provide equivalent coverage to the eight visible sensors. The output from the eight visible (VIS) detectors and from one of the two IR detectors (or an average of both IR detectors) is digitized onboard the satellite and transmitted to Earth in real time. The visible data are sampled every 2 microseconds, which yields visible samples spaced at increments of satellite rotation of 20.9 mr (assuming a nominal satellite spin rate of 100 rpm), or a near-nadir spacing of 3.0 km. Since the IR detector FOV is 192 mr, the IR data are therefore oversampled in the scan direction. The quantization of the IR data is 8 bits, and of the VIS 6 bits. The visible scanners are digitized with a square root digitizer for better signal-to-noise ratio. The oversampling of the IR data leads to the designation of the IR data as "4 x 2" IR data (4-mile resolution north-south, 2-mile resolution west-east). The full-resolution scan of all sensors in the mode produces about 226 MB of data per image. 4.1.6 Sensor/Instrument Measurement Geometry When the VISSR/VAS is installed in the spacecraft, its optical axis becomes parallel to the spacecraft spin axis, which must be parallel to Earth's spin axis. The VAS optical axis is thus perpendicular to the direction of the Earth scene. The optically flat scan mirror of the VAS, placed at a 45-degree angle to the VAS optical axis, directs the Earth scene into the VAS. The spinning is accomplished by stepping the scan mirror from 40 degrees, representing the north polar extreme, to 50 degrees, representing the south polar extreme. An angle position encoder integral with the mirror stepping mechanism converts the position information to electrical signals, which are sent to aid in reassembly of the Earth scene. The 10 degrees of mirror motion (resulting in 20 degrees of optical angle due to doubling the optical angle at the mirror) is divided into 1,821 steps, each representing 192 mr optically. At the image plane, a relatively large FOV is available. Each detector element is dimensional to define the FOV that its signal is intended to? represent. For example, the smallest IR field is 192 mr defined by a square detector 0.00315 inches on each side. (At synchronous altitude, 192 mr is equivalent to 5 miles along Earth's surface at the satellite's suborbital point). Two focal planes are used in the VAS. Visible spectrum signals are obtained at the principal focus. An optical fiber for each of the eight FOVs defines the field to be measured (25 x 24mr) and conveys the impinging light within that FOV to a photomultiplier tube, which converts the light intensity to a proportional electrical current. IR radiation must be sensed by solid-state detectors that are cooled to a low temperature to reduce their intrinsic electrical noise to a level below the electrical equivalent of the least intense radiation to be measured. This cooling is provided by a radiation cooler that radiates excess heat into space. Because of spacecraft design constraints, the cooler must be located away from the prime focal plane. The relay optics provide an appropriate location for an IR focusing mechanism and filter assembly out of the visible light path. The filter assembly contains an 11.2-cm disc, called a filter wheel, that houses 12 spectral-pass band filters. During each scan, one filter is placed in the IR path to acquire data in the desired spectral band. Any one of the filters can be positioned in the IR optical FOV within 350 milliseconds (i.e., during the time that the VAS telescope is not viewing Earth during a given spin). Filters are inserted in the IR path only and are used in the Multispectral Imaging (MSI) and sounding modes. While 38 channels are possible with the filter wheel detector combinations, only 13 bands can be transmitted. The scanning schedule and the various modes of operation are uploaded to an electronics module in the satellite. The satellite includes an onboard controller that can itself be reprogrammed via the spacecraft command link. 4.1.7 Manufacturer of Sensor/Instrument Hughes Santa Barbara Remote Sensing (SBRS) Goleta, CA. 4.2 Calibration The VISSR channels are calibrated in a vacuum environment at five instrument temperature plateaus. Some adjustments are made to standardize the bit content and start time of the stretched data scans. Preflight Calibration a. Visible Channels: The visible channel calibration source is a quartz iodine lamp, the output of which is collimated and spectrally shaped using appropriate optical filters to create an output similar to the Sun over the spectral band of the VISSR visible channels. The output level of the calibration source is established by eight neutral density filters that provide a calibration range from 16% to 100% albedo. The absolute calibration accuracy of the VISSR visible channels is estimated to be +/- 10%. b. Thermal Channel: The VISSR thermal channels are calibrated at eight target scene temperatures between 180 and 315°K, using a temperature-controlled blackbody source. The estimated absolute calibration accuracy is +/- 1.5°C, or +/- 1% of full scale, whichever is larger. Inflight Calibration a. Visible Channels: In-flight calibration of the eight VISSR visible PMTs is accomplished by viewing the Sun through the complete visible channel optical train via a "side-looking," reduced-aperture collecting prism. The visible channel gains are adjusted in the groundstation processing to equalize the eight scanners. This is done to remove stripping of the images. Other gain adjustments are made occasionally for image clarity. Absolute calibrations with the Sun viewer are not part of the GOES operating procedure. However, some research programs have produced limited calibrations for parts of the GOES data record. b. Thermal Channels: The inflight calibration of the VISSR thermal channels is accomplished by monitoring the temperature of a black-body. This blackbody is activated by command and introduced into the optical path just ahead of the IR relay optical system. The space view by VISSR provides an approximately zero signal reference in the thermal bands that is used to establish the zero end of the measurement scale. The level-1a GOES-7 images have not had any calibration applied. Information on calibration procedures can be found at http://haboob.giss.nasa.gov/isccp.html. 4.2.1 Specifications IFOV Visible 25 x 24 mr. IR 192 x 192mr. RESOLUTION (subsatellite) Visible 0.9 km IR 6.9 km ALTITUDE 42,000 km GOES SPIN RATE 100 rpm. SCAN RATE 1,821 scans/min. SCAN RANGE approx. 60N to 60S degrees latitude SAMPLES/SCAN 3,822 IR and 15,288 visible samples per PMT detector per Earth scan GOES-7 for 1993 through November 1994 was stationed at approximately 0.0 degrees N, 112.57 degrees W. In November 1994, it was gradually moved westward so that by 23-Feb-1995, it was at approximately 0.0 degrees N, 136.1 degrees W. 4.2.1.1 Tolerance Not available at this revision. 4.2.2 Frequency of Calibration Calibration of the visible and IRchannels is performed after every scan using internal calibrators that are part of the VAS and VISSR instrumentation. However, routine calibrations are not made on the visible sensor. The calibration procedures for calculating visible radiances and IR brightness temperatures from counts follows Rossow et al. (1992) and Rossow et al. (1995). 4.2.3 Other Calibration Information It is pertinent to note that the IR values included in the VAS VISSR data stream are recalibrated values from NESDIS operations. No recalibration is performed on the normalized raw visible data. The Synchronous Data Buffer (SDB) uses a lookup table to replace the original IR data values transmitted from the satellite with recalibrated values that are intended to correspond to a predetermined data value versus temperature table. The lookup table is computed by NESDIS weekly, based on calibration parameters received from the instrument. More information on calibration procedures can be found at http://haboob.giss.nasa.gov/isccp.html. 5. Data Acquisition Methods The BOREAS level-1 GOES-7 images used in the level-1a product creation were obtained by Dr. Eric Smith at FSU and supplied to BORIS. The data were acquired using the FSU direct readout ground system located in Tallahassee, FL, starting on 01-Jan-1994 and continued through 08-Jul-1995. 6. Observations 6.1 Data Notes Not available at this revision. 6.2 Field Notes Not applicable. 7. Data Description 7.1 Spatial Characteristics The VISSR scanning system consists of a mirror that is stepped mechanically to provide north-to-south viewing, while the rotation of GOES provides west-to-east scanning. The mirror is stepped following each west-to-east scan. A sequence of 1,821 scans over 18.21 minutes is performed to provide a "full disk" view from just beyond the northern Earth horizon to just beyond the southern Earth horizon. Based on the level-1 GOES-7 images, the BOREAS level-1a GOES images essentially cover the entire 1,000- km x 1,000- km BOREAS region. This contains the Northern Study Area (NSA), the Southern Study Area (SSA), the transect region between the SSA and NSA, and some surrounding area. 7.1.1 Spatial Coverage Based on information contained in the reference latitude and longitude files for the visible, IR, and water vapor bands (see Section 8.2), the following values represent the nominal coverage of the various bands: Visible Visible Latitude Longitude ---------- ----------- Northwest 64.757 N 107.037 W Northeast 65.911 N 87.120 W Southwest 47.646 N 109.210 W Southeast 47.916 N 98.087 W IR IR Latitude Longitude ---------- ----------- Northwest 64.807 N 107.045 W Northeast 65.957 N 87.156 W Southwest 47.758 N 109.212 W Southeast 48.028 N 98.096 W Water Vapor Water Vapor Latitude Longitude ---------- ------------ Northwest 64.605 N 107.088 W Northeast 65.728 N 87.410 W Southwest 47.758 N 109.212 W Southeast 48.028 N 98.096 W The NAD83 corner coordinates of the BOREAS region are: Latitude Longitude -------- --------- Northwest 59.97907 N 111.000 W Northeast 58.84379 N 93.50224 W Southwest 51.00000 N 111.00000 W Southeast 50.08913 N 96.96951 W 7.1.2 Spatial Coverage Map Not available at this time. 7.1.3 Spatial Resolution The spatial resolution of each pixel is dependent on the off-nadir scan angle of the sensor and increases from nadir to the scanning extremes. The satellite subpoint resolution of the various channels is: North/South East/West ----------- --------- Visible 1 km 1 km IR 8 km 4 km Water Vapor 16 km 4 km The spatial dimensions of each pixel can be calculated from the provided latitude and longitude coordinate information (see Section 8.2). 7.1.4 Projection The BOREAS level-1a GOES-7 images are stored in the same GOES "perfect" projection as the level-1 images. The "perfect" projection indicates that the satellite movement between temporal acquisitions has been removed so that the images are aligned spatially. Detailed information about the projection is not currently available. 7.1.5 Grid Description Not available at this revision. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage In 1994, the period of data acquisition was from 01-Jan-1994 through 31-Dec- 1994. During this period, whole days of data are missing, leaving 348 days with partial or complete acquisitions. In 1995, the GOES-7 data were collected from 01-Jan-1995 to 08-July. In Jul-1995, the data sequence was continued with data from GOES-8 (see BOREAS GOES-8 data sets). 7.2.2 Temporal Coverage Map Not available at this time. 7.2.3 Temporal Resolution During 1994, the visible and IR images were acquired on the hour and 30 minutes after the hour, 24 hours a day. The water vapor channel data are available only at the top of the hour. Partial to complete data are available on 348 out of the 365 days in 1994. Within a given day, some images may be missing. Where a level-1 image was missing at a particular time, a "fill" image containing all zeros was inserted in the level-1a data set. The transition and shifting of satellites from GOES-7 to GOES-8 in 1995 enabled good quality images to be acquired over the BOREAS region a maximum of 12 times per day from January to July, giving a reasonable monitoring data set. After 08- Jul-1995, the GOES images were acquired from the GOES-8 satellite (see BOREAS GOES-8 data sets). 7.3 Data Characteristics Level-1a GOES-7 image documentation may be viewed and the image data files downloaded using a convenient ORNL DAAC viewer utility (http://daacs.ESD.ORNL.Gov/BOREAS/viewers/viewG71a.html). Information presented includes counts of how many visible, infrared, and water vapor images are available for each day. The viewer also has links to the ORNL DAAC ftp directory and to another utility that will make a movie with daily GOES-7 Level-1a images. See section 15 for information about how to acquire level-1a GOES-7 images. The inventory listing file that is available as a companion file on the ORNL DAAC ftp site (ftp://www-eosdis.ornl.gov/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.dat) is accompanied by a data definition companion file (/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.def) that describes its contents. 7.4 Sample Data Record A sample data record for the level-1 GOES-7 images is not available here. The inventory listing file that is available as a companion file on the ORNL DAAC ftp site (/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.dat) is accompanied by a data definition companion file (/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.def) that contains a sample data record of the inventory file. 8. Data Organization 8.1 Data Granularity The smallest unit of data for level-1a GOES-7 image data is a single level-1a image. This includes extracted descriptive information in ASCII form; all visible, IR, and water vapor images collected within a given day of 0 to 2400 Greenwich Mean Time (GMT), and the reference latitude and longitude files for the images. 8.2 Data Format(s) The inventory listing file consists of numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe marks. There are no spaces between the fields. The inventory listing file that is available as a companion file on the ORNL DAAC ftp site (/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.dat) is accompanied by a data definition companion file (/data/boreas/RSS/goes71a/comp/rss14_goes7_l1a_inv.def) that contains a sample data record of the inventory file. One day of level-1a GOES-7 data is contained in four physical files: 1) ASCII header file 2) Visible image data file 3) IR image data file 4) Water vapor image data file Reference latitude and longitude files for the visible, IR, and water vapor image data are also available. The ASCII header file contains 80-byte ASCII records that describe the level-1a product; provide summary and detailed information about the good and zero-filled images for the given day; and contain descriptive header information extracted from the visible, IR, and water vapor images present. One GOES-7 visible image contains 1,024 unsigned 6-bit counts (i.e., values from 0 to 63) stored in unsigned 8-bit (1-byte) values in each of 1,024 lines. A full day of visible image data consists of 48 half-hourly images. The sequence of image times in the file is 0000, 0030, 0100, 0130, ... 2300, 2330 GMT. If a given half-hourly visible image was not acquired, the level-1a product contains a set of 1,024 records containing 1,024 values of 0. The presence of these zero-filled images is shown in the ASCII header file. Placing these zero-filled images in the file for missing acquisitions keeps the images from the same time in the same physical location in each daily file. One GOES-7 IRimage contains 256 unsigned 8-bit counts (i.e., values from 0 to 255) stored in unsigned 8-bit (1-byte) values in each of 128 lines. A full day of IR image data consists of 48 half-hourly images. The sequence of image times in the file is 0000, 0030, 0100, 0130, ... 2300, 2330 GMT. If a given half-hourly IR image was not acquired, the level-1a product contains a set of 128 records containing 256 values of 0. The presence of these zero-filled images is shown in the ASCII header file. Placing these zero-filled images in the file for missing acquisitions keeps the images from the same time in the same physical location in each daily file. One GOES-7 water vapor image contains 256 unsigned 8-bit counts (i.e., values from 0 to 255) stored in unsigned 8-bit (1-byte) values in each of 64 lines. A full day of water vapor image data consists of 24 hourly images. The sequence of image times in the file is 0000, 0100, 0200, ... 2300 GMT. If a given hourly water vapor image was not acquired, the level-1a product contains a set of 64 records containing 256 values of 0. The presence of these zero-filled images is shown in the ASCII header file. Placing these zero-filled images in the file for missing acquisitions keeps the images from the same time in the same physical location in each daily file. The reference latitude and longitude files for the visible images each consist of 1,024 records of 4,096 bytes. Each record of 4,096 bytes contains 1,024 signed 32-bit (4-byte) integer latitude or longitude values. The bytes of each 32-bit value are stored as low-order byte first. The unit of each latitude and longitude value is thousandths of a degree. To get the original decimal degree values, divide each value by 1,000. The reference latitude and longitude files for the IR images each consist of 128 records of 1,024 bytes. Each record of 1,024 bytes contains 256 signed 32-bit (4- byte) integer latitude or longitude values. The bytes of each 32-bit value are stored as low-order byte first. The unit of each latitude and longitude value is thousandths of a degree. To get the original decimal degree values, divide each value by 1,000. The reference latitude and longitude files for the water vapor images each consist of 64 records of 1024 bytes. Each record of 1,024 bytes contains 256 signed 32- bit (4-byte) integer latitude or longitude values. The bytes of each 32-bit value are stored as low-order byte first. The unit of each latitude and longitude value is thousandths of a degree. To get the original decimal degree values, divide each value by 1,000. 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms Using the BOREAS level-1 GOES-7 product as input, the data were processed to level-1a products. The processing included: 1) Separating the header record and image data records contained in level-1 GOES image files 2) Unpacking the header record information for use in processing control and output to the level-1a ASCII header file 3) Filling missing images with zero-filled records 4) Writing the four files for each day's data to disk 5) Copying a 4-week period of daily files to tape 6) Appending the reference latitude and longitude files to the tapes. 9.2 Data Processing Sequence 9.2.1 Processing Steps See Section 9.1.1. 9.2.2 Processing Changes None. 9.3 Calculations See Section 9.1.1. 9.3.1 Special Corrections/Adjustments See Section 9.1.1. 9.3.2 Calculated Variables See Section 9.1.1. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error The level-1a processing depended on the times provided in the level-1 GOES-7 image header records. If the time in the level-1 GOES-7 header record was incorrect, the image would have been placed in the incorrect sequence in the level-1a product. Any mixup between visible, IR, and water vapor images could not occur because file size checking was done during processing. 10.2 Quality Assessment 10.2.1 Data Validation by Source Whatever the processing level, the geometric quality of the image depends on the accuracy of the viewing geometry. Spectral errors could arise because of image-wide signal-to-noise ratio, saturation, cross-talk, spikes, or response normalization caused by change in gain. 10.2.2 Confidence Level/Accuracy Judgment Not available at this revision. 10.2.3 Measurement Error for Parameters Not available at this revision. 10.2.4 Additional Quality Assessments The level-1 GOES-7 images used to create the level-1a products were visually scanned for bad periods by FSU staff. 10.2.5 Data Verification by Data Center See Section 9.1.1. 11. Notes 11.1 Limitations of the Data Not available at this revision. 11.2 Known Problems with the Data To date, the following discrepancies/problems have been noted in the data: 1) Occasional reception problems, especially during NOAA rapid-scan operations, may result in some images being truncated at the northern edge (top of image). When this occurs, visual review by FSU staff has ensured that the BOREAS areas of interest are still present. 11.3 Usage Guidance None. 11.4 Other Relevant Information None. 12. Application of the Data Set These data were collected for the purpose of deriving surface radiation fields from the temporal series of images. The data can certainly be used for this purpose or other atmospheric and surface monitoring activities. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description BORIS developed software and command procedures for: 1) extracting header information from level-1 GOES-7 images on tape and writing it to ASCII files on disk for initial quality checking, 2) processing the files of level-1 GOES data for a given day to a level-1a product, 3) writing the level-1a GOES image files from tape to disk, 4) creating binary files of scaled latitude and longitude coordinates from the original ASCII files, 5) appending the latitude and longitude files to tape. This software is written in C and is operational on VAX 6410, MicroVAX, and VAXstation systems at GSFC. The primary dependencies in the software are the tape I/O library and the Oracle data base utility routines. 14.2 Software Access All of the described software is available upon request. BORIS staff would appreciate being informed of any problems discovered with the software, but cannot guarantee that they will be fixed. 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-1a GOES-7 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 Oak Ridge, TN (423) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 16. Output Products and Availability 16.1 Tape Products The level-1a GOES-7 data can be made available on 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-1a GOES-7 images are not. See section 15 for information about how to obtain the data. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Rossow, W.B., C.L. Brest, and M. Roiter. 1996, International Satellite Cloud Climatology Project (ISCCP) New Radiance Calibrations. WMO/TD-No. 736. World Meteorological Organization. Rossow, W.B., C.L. Brest, and M.D. Rotier. 1995, International Satellite Cloud Climatology Project (ISCCP): Update of radiance calibration report. Technical Document, World Climate Research Programme (ICSU and WMO), Geneva, Switzerland, 76 pp. Rossow, W.B., Y. Desormeaux, C.L. Brest, and A. Walker. 1992, International Satellite Cloud Climatology Project (ISCCP): Radiance calibration report. WMO/Technical Document No. 520, World Climate Research Programme and World Meteorological Organization (ICSU and WMO), Geneva, Switzerland, 104 pp. 17.2 Journal Articles and Study Reports Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., 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. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPSDOC 94). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPSDOC 96). 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., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press). 17.3 Archive/DBMS Usage Documentation The Collected Data of the BOReal Ecosystem-Atmosphere Study (BOREAS) are currently archived at the NASA Goddard Space Flight Center. 18. Glossary of Terms None. 19. List of Acronyms ASCII - American Standard Code for Information Interchange ATS - Application Technology Satellite 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 DN - Digital Number EOS - Earth Observing System EOSDIS - EOS Data and Information System ESD - Environmental Satellite Data, Inc. FFC - Focused Field Campaign FOV - Field of View GMT - Grenwich Mean Time GOES - Geostationary Operational Environmental Satellite GSFC - Goddard Space Flight Center IFC - Intensive Field Campaign IFOV - Instantaneous Field-of-View IR - Infrared ISLSCP - International Satellite Land Surface Climatology Project MB - Megabyte MR - Microradian MSI - Multispectral Imaging NASA - National Aeronautics and Space Administration NESDIS - National Environmental Satellite, Data and Information Service NOAA - National Oceanic and Atmospheric Administration NSA - Northern Study Area ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SBRS - Santa Barbara Remote Sensing SDB - Synchronous Data Buffer SMS - Synchronous Meteorological Satellite SSA - Southern Study Area URL - Uniform Resource Locator VAS - VISSR Atmospheric Sounder VISSR - Visible and IR Spin Scan Radiometer 20. Document Information 20.1 Document Revision Dates Written: 25-Jul-1995 Last Updated: 26-Feb-1998 20.2 Document Review Dates BORIS Review: 05-Nov-1996 Science Review: 15-Apr-1997 20.3 Document ID 20.4 Citation The level-1a GOES-7 images resulted from a joint effort between BOREAS staff at NASA/GSFC and Dr. Eric Smith of FSU. The original data were acquired by FSU and processed to level-1 products. The present Level-1a product was created by BORIS. The respective contributions of the above individuals and agencies to completing this data set are greatly appreciated. 20.5 Document Curator 20.6 Document URL Keywords GOES-7 EMITTED RADIATION REFLECTED RADIATION WATER VAPOR RSS14_GOES7_L1A.doc 04/17/98