TITLE: GOES-10 Imager Data [NOAA/CLASS] CONTACTS: Steve Williams NCAR/EOL P.O. Box 3000 Boulder, CO 80307-3000 phone: 303-497-8164 email: firstname.lastname@example.org 1.0 DATA SET OVERVIEW This data set contains 1-km resolution GOES-10 channel 1 (visible) and 4-km resolution GOES channel 2-5 data in netcdf format. These data were retrieved from the NOAA CLASS archive. The data cover the T-REX period (1 March to 30 April 2006). They cover the region from 34-40 N and 115-126 W. This data set includes data from all sector scans that cover this region, including any rapid scan or super rapid scan sectors. 2.0 INSTRUMENT DESCRIPTION The Geostationary Operational Environmental Satellite (GOES) series of satellites is owned and operated by the National Oceanic and Atmospheric Administration (NOAA). The GOES spacecraft is positioned 35,790 km (22,240 statute miles) above the equator allowing it to view a major portion of the Western Hemisphere including southern Canada, the contiguous 48 states, major portions of the eastern Pacific Ocean and western Atlantic Ocean and Central and South America. Because the Atlantic and Pacific basins strongly impact the weather over the United States, coverage is typically provided by two GOES spacecraft, one at 75 E west longitude (GOES East) and the other at 135E west longitude (GOES West). The Imager instrument is designed to sense radiant and solar-reflected energy from sampled areas of the Earth's surface and atmosphere. The Imager's five spectral channels simultaneously sweep an 8 km north-south (N/S) longitudinal swath along an east-west (E/W) latitudinal path by means of a two-axis gimballed mirror scan system. Beamsplitters separate the spectral channels into the various IR detector sets. Channel Detector Type Nominal Square IGFOV at nadir ----------------------------------------------------------- 1 (Visible) Silicon 1 km 2 (Shortwave) InSb 4 km 3 (Moisture) HgCdTe 8 km (4 km GOES 12/N/O/P) 4 (Longwave 1) HgCdTe 4 km 5 (Longwave 2) HgCdTe 4 km Imager Instrument Parameters: Parameter Performance --------------------------------------------- FOV defining element Detector Channel-to-channel alignment 28 microrad (1.0 km) at nadir Radiometric calibration 300 K internal blackbody and space view Signal quantizing 10 bits, all channels Scan capability Full earth, sector, area Output data rate 2,620,800 b/s Imaging areas 20.8 Deg E/W by 19 Deg N/S Imaging Channels Allocation: Channel Number Wavelength Range (microm) Range of Measurement --------------------------------------------------------------- 1 0.55 to 0.75 1.6 to 100% albedo 2 (GOES 8/9/10) 3.80 to 4.00 4 to 320 K 3 (GOES 8/9/10/11) 6.50 to 7.00 4 to 320 K 4 10.20 to 11.20 4 to 320 K 5 (GOES 8/9/10/11) 11.50 to 12.50 4 to 320 K 3.0 DATA COLLECTION AND PROCESSING NCAR/EOL conducted no processing or quality control on these data. The GOES Support System includes the Command and Data Acquisition (CDA) Station at Wallops Island, VA, and the Satellite Operations and Control Center (SOCC) at Suitland, MD. At the CDA station, raw instrument data and telemetry are read out from the satellite. Data are processed, calibrated, earth-located and converted to GOES Variable data format (GVAR) and rebroadcast to the satellite along with spacecraft command schedules. The GVAR data are then broadcast to direct readout users. SOCC is responsible for the overall safety of the spacecraft, scheduling of the instruments, data quality and performance. Continuous monitoring and checks are conducted on orbital position, image navigation and registration, and various subsystems including primary imager and sounder instruments. It is also responsible for planning and operating the ground system equipment for GVAR acquisition at NESDIS, the initial stage of product processing. The Imager scans pre-determined areas in alternate directions on alternate lines. The imaging area is defined by a coordinate system related to the instrument's orthogonal scan axis. During imaging operations a scan line is generated by rotating the scanning mirror in the east-west direction while concurrently sampling each of the active imaging detectors. At the end of the line, the Imager scan mirror performs a turnaround, which involves stepping the mirror to the next scan line and reversing the direction of the mirror. The next scan is then acquired by rotating the scanning mirror in the opposite, west-east direction, again with concurrent detector sampling. Detector sampling occurs within the context of a repeating data block format. In general, all visible detectors are sampled four times for each data block (four times 1 km wide); while each of the active IR detectors is sampled once per data block (one times 4 km wide). GOES-WEST Imager Scan Sectors in Routine Mode> Frame Name Boundaries Duration Scan Times (mm:ss) (UTC) ------------------------------------------------------------------ Full Earth Earth Edge 26:10 0000, 0300, etc Northern Hemisphere 0-66N/90W-170E 9:00 xx00, xx30 Southern Hemisphere 0-45S/115W-170E 7:00 xx22, xx52 PACUS 12-60N/90-175W 5:00 xx15, xx45 During GOES Rapid Scan Operations (RSO), four views of the continental United States (CONUS) are provided at approximately 7.5 minute intervals in a half hour period. A northern hemisphere scan for both GOES East and GOES West satellites is also included in the 30 minute cycle. This yields eight views of the continental U.S. per hour. During GOES Super Rapid Scan Operations (SRSO), approximately 10 one-minute interval scans are provided every half hour using prescribed 1000 x 1000 km sectors. The remaining time in the half hour cycle is devoted to scans of the northern hemisphere and CONUS (or sub-CONUS for GOES-WEST). The raw data in the visible channel are relativized and normalized at the CDA, but no calibration is applied. The raw data in the IR channels are calibrated using spacelooks and a heated internal blackbody. The spacelook calibration positions the scanning mirror at an extreme E-W coordinate permitting a view of space. The frequency of these spacelooks depends on the activity of the instrument. The rates vary from once every second to once every 36.6 seconds. A Blackbody calibration sequence is initiated every 30 minutes. During the sequence, the scanning mirror is rotated in the N-S direction through an angle of approximately 180 degrees to present a view of the Blackbody surface to the imaging detectors. The Blackbody surface temperature is maintained at a nominal 290. K. For more information on GOES calibration see http://www.oso.noaa.gov/goes/goes-calibration/index.htm. 4.0 DATA FORMAT AND FILE NAMING 4.1 File Naming conventions goes10.2006.120.000014.BAND_01.L0010391 where: goes10 is the satellite 2006 is the year 120 is Julian day 000014 is the scan start time (hhmmss - UTC) BAND_01 is the channel included (here visible) There are also metadata files containing information on bad lines that are named as above except in the place of BAND_XX there is meta. 4.2 Data Format These data are in netcdf format. Complete information on netcdf format is available from UCAR Unidata: http://www.unidata.ucar.edu/software/netcdf/ Satellites measure upwelling radiation from the Earth. Visible radiation is generally what our eyes see. Infrared radiation is sensitive to the temperature of the surface (e.g., clouds, oceans, etc). The satellites sensor converts radiation falling on the sensor to a voltage which is generally reported in counts (often ranging from 0-255 counts for 1-byte data or 0-1023 for 10-bit data). Satellite image calibration is the conversion of this count value to a radiance, which is then often converted to a temperature (for infrared) or reflectance (for visible). The netCDF files raw provide satellite data from the Area files. So data in netCDF files must first be converted from 16-bit to 10-bit data by dividing by 32. Then use this result to calibrate the IR observations to radiance or brightness temperature and the visible observations to radiance or scaled reflectance. Information on the conversion from 10-bit data to radiance/brightness temperature/reflectance can be found at: The GVAR calibration is described on the NESDIS website: http://www.oso.noaa.gov/goes/goes-calibration/index.htm Calibration information is also available from NASA at the GOES Project Office: http://goes.gsfc.nasa.gov/text/imager.calibration.html http://www2.ncdc.noaa.gov/docs/klm/ AVHRR Level 1b data are present as a collection of data sets. Each data set contains data of one type for a discrete time period. Thus, for AVHRR, there are separate HRPT, LAC, and GAC data sets. Time periods are arbitrary subsets of orbits, and may cross orbits (i.e., may contain data along a portion of an orbital track that includes the ascending node, the reference point for counting orbits). Generally, GAC data sets are available for corresponding time periods and usually have a three to five minute overlap between consecutive data sets. Level 1b (following FGGE terminology) is raw data in 10 bit precision that have been quality controlled, assembled into discrete data sets, and to which Earth location and calibration information has been appended, but not applied. Other parameters appended are: time codes, quality indicators, solar zenith angles, and telemetry. 5.0 DATA REMARKS 6.0 REFERENCES None.