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: sfw@ucar.edu
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.