BOREAS RSS-14 Level-1 GOES-7 Visible, Infrared and Water Vapor Images Summary The level-1 BOREAS GOES-7 image data were collected by Remote Sensing Science Team 14 (RSS-14) personnel at Florida State University (FSU) and delivered to BORIS. The data cover the period of 01-Jan-1994 through 08-Jul-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. 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-1 GOES-7 Visible, Infrared and Water Vapor Channel Images 1.2 Data Set Introduction See Section 1.3. 1.3 Objective/Purpose For BOREAS, the level-1 Geostationary Operational Environmental Satellite (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 1995, giving a reasonable monitoring data set. 1.4 Summary of Parameters The level-1 GOES-7 image data for 1994 and 1995 are digital counts for all bands. In addition to the image data, each data file has a header record that contains descriptive information (see Section 8.2). 1.5 Discussion None given. 1.6 Related Data Sets BOREAS RSS-14 Level-1a 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 Dr. Eric A. Smith Florida State University Tallahassee, FL (904) 644-4253 esmith@metsat.met.fsu.edu Contact 2 Dr. Harry J. Cooper Florida State University Tallahassee, FL (904) 644-6716 cooper@metsat.met.fsu.edu Contact 3 Jeffrey A. Newcomer NASA/GSFC Greenbelt, MD. 301) 286-7858 (301) 286-0239 Jeffrey.Newcomer@gsfc.nasa.gov 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 groundstations. 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) 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 IR sensors 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 microradian (µrad) Instantaneous Field of View (IFOV)) and six IR detectors. The images are centered at 55.0 degrees N and 102.0 degrees W. The visible band data cover the wavelength region of 0.5 to 0.7 micrometers (µm). The IR data are from GOES-7 channel 8 (11.17 (µm)) and the water vapor data are from channel 10 (6.725(µm)). GOES-7 Channel Wavelength, µm 1 (visible) 0.5-0.7 8 (IR) 11.17 10 (water vapor) 6.725 4.1.1 Collection Environment GOES-7 orbited Earth in a geostationary orbit at an altitude of 42,000 km. The data were acquired using the FSU Direct Readout Ground System located in Tallahasse FL, starting 01-Jan-1994 and continuing through 08-Jul-1995. 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, 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 mrin 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 VIS detectors (sensitive to the 0.54- to 0.70-µm 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 1- VIS 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-µm bandpass filter. The FOV of the IR detectors is 192 mr µrad (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 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 192mr, 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 CDA station 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 µrad 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 mrdefined 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 centimeter 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 Channels: 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 degrees C, or +/- 1 percent of full scale, whichever is larger. Inflight Calibration a. Visible Channels: The inflight calibration 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 ground station 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 channel is accomplished by monitoring the temperature of a blackbody. This blackbody is activated by command and introduced into the optical path just ahead of the infrared 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-1 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 192 mr. RESOLUTION (subsatellite) Visible 0.9 km IR 6.9 km ALTITUDE 35,600 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 thatare 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 GOES-7 image data were acquired using the FSU direct readout ground system located in Tallahassee, FL, starting on 01-Jan-1994 and continuing 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. The BOREAS level-1 GOES-7 images were subset from the full GOES-7 data frames to 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 1,000- x 1,000- km BOREAS region are: Latitude Longitude Northwest 59.97907 N 111.00000 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 temporal sequence of images for a given day is spatially aligned and stored in the "GOES Perfect Projection." 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 From 01-Jan-1994 through 31-Dec-1994, partial to complete data are available for 348 of the possible 365 days. From 01-Jan-1995 through 08-Jul-1995, partial data are available for 145 of the possible 189 days. 7.2.2 Temporal Coverage Map Not available at this revision. 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. Within a given day, some images may be missing. Partial to complete data are available on 348 out of the 365 days in 1994. 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 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. See the companion file (goes71.def) for more information. 7.3.1 Parameter/Variable The parameter contained in the image data files is: Digital Number (DN) For the image data files: Digital Number (DN) - The quantized DN derived by the GOES-7 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-1 GOES-7 image bands were collected by the VISSR instrument on the GOES-7 spacecraft. The raw data were received, processed and subset, and sent to BORIS by personnel within the Department of Meteorology at Florida State University (FSU). 7.3.5 Data Range The maximum range of DNs in each GOES image band is limited from 0 to 255 so that the values can be stored in a single 8-bit (1-byte) field. None -- Indicates that no values of that sort were found in the column. 7.4 Sample Data Record A sample data record for the level-1 GOES-7 images is not available here. 8. Data Organization Although the image inventory is contained on the BOREAS CD-ROM set, the actual level-1 GOES-7 images are not. See section 15 for information about how to obtain the data. 8.1 Data Granularity The smallest unit of data for level-1 GOES images is the set of images that comprise the acquisitions for a given day from 0 to 2400 Greenwich Mean Time (GMT). This includes all of the visible, IR, and water vapor images acquired during that 24-hour period along with the reference latitude and longitude coordinate files for the visible, IR, and water vapor images. Due to reception or transmission problems, the number of images varies between days. Also, since each image acquisition is contained in a separate file, the number of files for a given day will vary. 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. See the companion file (goes71.def) for more information. A tape of level-1 GOES-7 images contains data from multiple days organized with all the data of day 1 followed by all the data from day 2, etc. The data files for a given day are arranged with the visible images first, followed by the IR images, and then the water vapor images similar to this: Day 1 Visible Channel Time 1 Visible Channel Time 2 Visible Channel Time 3 . . . Visible Channel Time i Infrared Channel Time 1 Infrared Channel Time 2 Infrared Channel Time 3 . . . Infrared Channel Time j Water Vapor Channel Time 1 Water Vapor Channel Time 2 Water Vapor Channel Time 3 . . . Water Vapor Channel Time k Day 2 Visible Channel Time 1 . . Infrared Channel Time 1 . . Water Vapor Channel Time 1 . . Water Vapor Channel Time k . . . Day n Note that because of missing images caused by reception or transmission problems, image file m in any of the visible, IR, or water vapor sequences does not necessarily correspond to the same time as image file m in any other day. The time fields in the header records must be checked to find the three image channels collected at the same time. The level-1 data were processed to level- 1a products that have missing images zero-filled, resulting in images collected at the same time on different days being in the same file position. The data files were generated on a DELL PC system and written to tape with a Silicon Graphics system. A file of level-1 GOES-7 imagery can contain visible, IR, or water vapor data. The way to distinguish between the file types is by the size of the file and the information contained in the header record at the beginning of each file. The first record of each image file is a header record. Multiple-byte numeric integer fields are stored as high order byte first. The decimal number fields are Institute of Electrical and Electronics Engineers (IEEE) 4-byte floating point values. Character fields are stored as expected. The format and contents of the header records are: Bytes Description ------- -------------------------------------------------- 1 - 4 Integer number of pixels per image line. (Binary) 5 - 8 Projection. A "p" indicates a GOES "perfect" projection, which means the satellite movement has been factored out of the image. A raw image has projection "e". American Standard Code for Information Interchange (ASCII) 9 - 12 CreationDate. The image date in YYDDD format, where the DDD is the day of year. A number of 94025 in this field indicates day 25 of 1994. (Binary) 13 - 16 CreationTime. The image GMT time in HHMM format. A number of 905 indicates 9:05 GMT; 2233 is 22:33 GMT. BOREAS images are recorded at the beginning of every half hour. The "on-the-hour" images are usually between 1 and 5 minutes after the hour and the "half- hour" images are usually between 31 and 35 minutes after the hour. (Binary) 17 - 20 Band. Can be "vis ","ir ", or "b10 " (water vapor). (ASCII) 21 - 24 Not Used. (ASCII) 25 - 28 Decimal latitude of the center of the image in radians. The BOREAS latitude is 0.959931 radians, or 55.0 degrees N. (Binary) 29 - 32 Decimal longitude of the center of the image in radians. The BOREAS longitude is -1.780236 radians, or -102.0 degrees (102.0 W). (Binary) 33 - 36 ULLine. The integer starting line number of the full disc image from which this subset image was copied. (Binary) 37 - 40 ULElement. The integer starting pixel/element number of the full-disc image from which this subset image was copied. This together with the ULLine value specifies the "upper-left" point of the subset image relative to the satellite full-disc image. The coordinate system used here is specific to the Environmental Satellite Data, Inc. (ESD) software that archives the images. (Binary) 41 - 44 LineRes. The integer ground resolution, in kilometers, of an image line. For BOREAS visible bands, it is 1; for BOREAS IR bands, it is 8; for BOREAS water vapor bands, it is 16. (Binary) 45 - 48 ElementRes. The integer ground resolution, in kilometers, of an image element. For BOREAS visible bands, it is 1; for BOREAS IR bands, it is 4; for BOREAS water vapor bands, it is 4. (Binary) 49 - 52 Lines. The integer number of lines in the image. For BOREAS visible bands, it is 1024; for BOREAS IR bands, it is 128; for BOREAS water vapor bands, it is 64. (Binary) 53 - 56 Elements. The number of elements in each line of the image. For BOREAS visible bands, it is 1024; for BOREAS IR bands, it is 256; for BOREAS water vapor bands, it is 256. The total image size in bytes is 512 + (Lines * Elements). (Binary) 57 - 60 Prefix [4]. Four-character text prefix. For BOREAS images, it is "bor". (ASCII) 61 - 64 Range. The integer number of counts in the images. For BOREAS visible bands, it is 64 (i.e., the byte value of the images range from 0 to 63). For BOREAS IR and water vapor bands, it is 256 (0-255). (Binary) 65 - 76 Not Used. (ASCII) 77 - 80 CreationDate2. Integer used only for extra processing of images. (Binary) 81 - 84 CreationTime2. Integer used only for extra processing of images. (Binary) 85 - 88 ProjLat. Decimal value, not used. Value should be 0. (Binary) 89 - 92 ProjLon. Decimal value, not used. Value should be 0 -1.964717. (Binary) 93 - 96 Height. Decimal value for the satellite's "height" in kilometers. It should be 42000.0. (Binary) 97 - 512 Not used for the level-1 GOES images, but defined as: 97 - 112 Junk3 (ASCII) 113 - 116 DataType (ASCII) 117 - 120 Junk4 (ASCII) 121 - 144 Comments (ASCII) 145 - 160 DateTime (ASCII) 161 - 216 Junk5 (ASCII) 217 - 228 Directory (ASCII) 229 - 296 Junk6 (ASCII) 297 - 300 Suffix (ASCII) 301 - 374 Junk7 (ASCII) 375 - 382 Filename (ASCII) 383 - 454 Junk8 (ASCII) 455 - 462 ColorTable (ASCII) 463 - 510 Junk9 (ASCII) 511 - 512 Junk10 (ASCII) A file of visible channel data on tape consists of 2,049 records of 512 bytes each. The first 512-byte record is a header record. The next 2,048 records comprise the visible image contains unsigned 6-bit counts (i.e., values of 0 to 63) stored in 8-bit (1-byte) values for the 1,024 pixels in each of 1,024 lines. Two successive 512-byte tape records must be concatenated to make each of the 1,024 byte image lines. The pixels of a visible image have a nominal 1-km (north-south) x 1-km (east-west) spatial resolution. A file of IR channel data on tape consists of 65 records of 512 bytes each. The first 512-byte record is a header record. The next 64 records comprise the IR image which contains unsigned 8-bit counts (i.e., values of 0 to 255) stored in 8-bit (1-byte) values for the 256 pixels in each of 128 lines. Each 512-byte record contains two 256-pixel image lines. The pixels of an IR image have a nominal 8-km (north-south) x 4-km (east-west) spatial resolution. A file of water vapor channel data on tape consists of 33 records of 512 bytes each. The first 512-byte record is a header record. The next 32 records comprise the water vapor image, which contains unsigned 8-bit counts (i.e., values of 0 to 255) stored in 8-bit (1-byte) values for the 256 pixels in each of 64 lines. Each 512-byte record contains two 256-pixel image lines. The pixels of a water vapor image have a nominal 16-km (north-south) x 4-km (east-west) spatial resolution. The six reference latitude and longitude files for all of the GOES-7 images collected in 1994 are on a separate tape from the images because the latitude and longitude files were delivered after the level-1 images were reviewed and processed. The six files consist of a pair of latitude and longitude files for each of the visible, IR, and water vapor image types. 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 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. 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms 9.2 Data Processing Sequence 9.2.1 Processing Steps FSU created the daily level-1 GOES-7 image sets by: 1) acquiring the data via Direct Readout Ground Station at FSU, 2) using ESD software to minimize satellite wobble for image alignment, 3) sectoring the data to cover only the BOREAS region, 4) storing the data on optical disk and 8-mm tape, and 5) writing the images for a given day to DAT and 8 mm tape. BORIS processed the level-1 GOES-7 images by: 1) copying the DAT tape to an 8-mm version, 2) checking the summary information sent by FSU with data processing results, and 3) inventorying the level-1 images in the online data base. 9.2.2 Processing Changes None. 9.3 Calculations 9.3.1 Special Corrections/Adjustments The scene-to-scene wobble has been minimized by using proprietary ESD remapping software. Details of this processing can be obtained by contacting ESD at: Environmental Satellite Data, Inc. 5200 Auth Road Suitland, MD 20746 (301) 423-2113 9.3.2 Calculated Variables None. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error A potential, but unlikely, source of error is the possible mismatch of image header information with the corresponding image data. Because the automated nature of this processing, this scenario is very unlikely. 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 BORIS checking of the delivered level-1 images with developed software identified some time and other data problems that resulted in some images being deleted from the initial delivery. These images are not included in the current data set. Based on FSU and BORIS quality checks, the data set is considered to be properly inventoried and described. The actual quality of the images in relation to clarity or missing scan lines or drop outs was not assessed. 10.2.3 Measurement Error for Parameters None. 10.2.4 Additional Quality Assessments The level-1 GOES-7 images were visually scanned for unusable data by FSU staff. 10.2.5 Data Verification by Data Center See Section 9.2.1. 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 Although the image inventory is contained on the BOREAS CD-ROM set, the actual level-1 GOES-7 images are not. See section 15 for information about how to acquire actual level-1 GOES-7 images. 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 As noted in Section 9.2, FSU acquires the downlinked raw images on a DELL PC system, transfers them to a Silicon Graphics system, and writes the data to tape. For further information regarding the ESD software used at FSU, please contact: Environmental Satellite Data, Inc. 5200 Auth Road Suitland, MD 20746 (301) 423-2113 BORIS developed software and command procedures for: 1) extracting header information from the level-1 GOES-7 images on tape and writing it to ASCII files on disk for quality checking, 2) inventorying the level-1 images in the online data base by using the extracted header information files, 3) creating binary files of scaled latitude and longitude coordinates from the original ASCII files, 4) writing the latitude and longitude files to tape. The BROIS 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 BORIS software is available upon request (see Section 15.1). 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 Nelson 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-1 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-1 GOES 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-1 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, M.D. Roiter 1996, International Satellite Cloud Climatology Project (ISCCP) New Radiance Calibrations. WMO/TD-No. 736. World Meteorological Organization. Rossow, W.B., C.L. Brest, 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, 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.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, and F.E. Guertin. 1997. BOREAS in 1997: Experiment overview, scientific results and future directions. Journal of Geophysical Research, 102(D24): 28,731-28,770. 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 FFC - Focused Field Campaign FOV - Field of View EOS - Earth Observing System EOSDIS - EOS Data and Information System ESD - Environmental Satellite Data, Inc. GMT - Greenwich Mean Time GOES - Geostationary Operational Environmental Satellite GSFC - Goddard Space Flight Center IEEE - Institute of Electrical and Electronics Engineers 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 NSA - Northern Study Area NESDIS - National Environmental Satellite, Data and Information Service NOAA - National Oceanic and Atmospheric Administration 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 Infrared Spin Scan Radiometer 20. Document Information 20.1 Document Revision Dates Written: 12-Dec-1994 Last Updated: 01-Dec-1997 20.2 Document Review Dates BORIS Review: 05-Nov-1996 Science Review: 22-Jan-1997 20.3 Document ID 20.4 Citation The GOES-7 data were provided by E.A. Smith and H.J. Cooper of the Department of Meteorology, FSU. 20.5 Document Curator 20.6 Document URL Keywords GOES-7 EMITTED RADIATION REFLECTED RADIATION WATER VAPOR RSS14_GOES7_L1.doc 04/17/98