November 78 - June 86 Global Composite
November 78 - June 86 Global Composite
For most regions of the world, the color of the ocean is determined primarily by the abundance of phytoplankton and their associated photosynthetic pigments. As the concentration of phytoplankton pigments increases, ocean color shifts from blue to green. Taking advantage of this change, NASA developed the Coastal Zone Color Scanner (CZCS) which was launched on the Nimbus-7 satellite in October 1978. During its 7 1/2 year lifetime (October 1978 - June 1986), CZCS acquired nearly 68,000 images, each covering up to 2 million square kilometers of ocean surface.
The Coastal Zone Color Scanner (CZCS) was a multi-spectral line scanner devoted principally to measurements of ocean color. It had six spectral bands (channels). There were four channels devoted to ocean color, each of 20 nanometer band width and centered at 443, 520, 550, and 670 nanometers. These are referred to as channels 1 through 4, respectively. Channel 5 sensed reflected solar radiance and had a 100 nanometer bandwidth centered at 750 nanometers and a dynamic range which was more suited to land. Channel 6 operated in the 10.5 to 12.5 micrometer region and sensed emitted thermal radiance for derivation of equivalent black body temperature. The CZCS level 1, 2 and 3 data products are available from the Goddard Space Flight Center (GSFC) Distributed Active Archive Center (DAAC).
Coastal Zone Color Scanner
The theory of measurement is based on the fact that the content of water, be it organic or inorganic particulate matter or dissolved substances, affects its color. Ocean water, containing very little particulate matter, scatters as a Rayleigh scatterer with the well known deep purple or bluish color of the ocean. As particulate matter is added to the water, the scattering characteristics are changed and the color is changed. Phytoplnakton, for instance, have specific absorption characteristics and normally change the water to a more greenish hue although some phytoplankton, such as the various red tide, can change the water to colors such as red, yellow, blue-green, or mahogany. By sensing the color with very high signal-to-noise ratios, the CZCS provides a mechanism for analyzing that color for the content of the water. Inorganic particulate matter in water, such as the terrigenous outflow from rivers, has a different color from organic material typically brownish in color but sometimes varying with red.
For further details, please consult The Nimbus 7 User's Guide (see reference below).
CZCS was launched aboard Nimbus-7 in October 1978. Due to the power demands of the various on-board experiments the CZCS operated on an intermittent schedule. The infra-red/temperature sensor (channel 6 10.5-12.5 microns) failed within the first year. Sometime in 1981 it was determined that the sensitivity of the other CZCS sensors was degrading with time, in particular channel 4. Sensitivity degradation was persistent and increased during the rest of the mission. In mid 1984 NIMBUS-7 Mission personnel experienced turn-on problems with the CZCS system which were related to power supply problems and the annual lower power summer season of NIMBUS-7. Also spontaneous shut down of the CZCS system began occurring. These also persisted for the rest of the mission. From March 9, 1986 to June, 1986 the CZCS system was given highest priority for the collection of a contemporaneous data set of ocean color. It was turned off in June at the start of the low power season with the intention of turning it back on in December when power conditions would be more favorable. Attempts to reactivate the CZCS system in December 1986 failured. The CZCS sensor was officially declared non-operational as of 18 December 1986.
NIMBUS-7 was launched in October 1978 and was a research-and-development satellite serving as a stabilized, earth-observing platform for the testing of advanced systems for sensing and collecting data in the pollution, oceanographic and meteorological disciplines. It provided an opportunity to assess each instrument's operation in the space environment and to collect a sizable body of data with the global and seasonal coverage needed for support of each experiment. The mission also extended and refined the sounding and atmospheric structure measurement capabilities demonstrated by experiments on previous Nimbus observatories.
Nimbus-7 sensors included experiments were a limb infrared monitoring of the stratosphere (LIMS), stratospheric and mesopheric sounder (SAMS), coastal-zone color scanner (CZCS), stratospheric aerosol measurement (SAM II), earth radiation budget (ERB), scanning multichannel microwave radiometer (SMMR), solar backscatter UV and total ozone mapping spectrometer (SBUV/TOMS), and temperature-humidity infrared radiometer (THIR). These sensors were capable of observing several parameters at and below the mesospheric levels. After 11 years in orbit, three experiments, SAM II, SBUV/TOMS, and ERB, are still functioning successfully. Several more years of operation are anticipated.
Nominal orbit parameters for the Nimbus-7 spacecraft are: Launch date 10/24/78 Orbit Sun-synchronous, near polar Nominal Altitude (km) 955 Inclination (deg) 104.9 Nodal Period (min.) 104 Equator Crossing Time 1200 noon (ascending) Nodal Increment (deg) 26.1
The CZCS was a cross-track scanning system. The Instrument Field of View (IFOV) of each detector was .865 mrad, yielding a resolution of 825 m at the satellite subpoint. The swath covered 1566 km in width from a maximum scan angle of approximately 40 degrees. Data were then transmitted to a receiving station at a rate of 800 kbps.
Samples/ Samples/ Quantizing Bands Scan Sec Resolution 1 through 6 1,970 94,560 8-bit (256 levels)
NASA
Prelaunch calibration of the CZCS used a 76 centimeter diameter integrating sphere as a source of diffuse radiance for channels 1 through 5 and a blackbody source for calibration of channel 6. The integrating sphere was especially constructed for calibration of the CZCS and was calibrated from a standard lamp from the National Bureau of Standards utilizing a spectrometer and another integrating sphere to transfer calibration from the lamp to the sphere.
In addition to the sphere and the blackbody, a collimator was used to calibrate the CZCS in vacuum testing. In-flight calibration of the CZCS is accomplished for the first five bands by using a built-in incandescent light source. This in-flight calibration source was calibrated using the instrument itself as a transfer against the referenced sphere output.
Channel 6 is calibrated by viewing the blackened housing of the instrument whose temperature is monitored. Deep space is another calibration viewed during the 360 degrees rotation of the scan mirror.
The raw data from the six channels of the CZCS were either directly transmitted to the ground station in real-time or recorded on the satellite tape recorder for later playback and transmission to the ground station. Data were stored on magnetic tape and sent to the Image Processing Division (IPD) at Goddard Space Flight Center (GSFC). In addition to radiance measurements, these data also include the calibration lamp data and Image Location Data (ILT).
Spatial Coverage is global with an emphasis on coastal regions.
REGION ulc lat.,lon. lrc lat.,lon. North Atlantic 69.873, -88.506 -19.951, 1.318 N.E. Pacific 61.260, -162.334 -28.564, -72.500 South America 19.600, -114.873 -70.225, -25.049 Mediterranean 69.873, -34.014 -19.951, 55.811 India 31.025, 10.811 -58.799, 100.635 Japan 66.812, 89.912 -23.643, 179.736 Australia 16.963, 89.912 -72.861, 179.736
Composited earth-gridded data are binned to a fixed, linear latitude-longitude (equal angle) grid of dimension 1024 (latitude) x 2048 (longitude) with ~18.5 km resolution at the equator.
Visible and infrared radiances were measured in six spectral channels by CZCS. The spectral region and band widths of the six channels and primary use of each are indicated in the following table:
Channel/Band Spectral Band Primary purpose (micrometers) ------------ ------------- --------------------------- 1 0.433 - 0.453 Chlorophyll absorption 2 0.510 - 0.530 Chlorophyll correlation 3 0.540 - 0.560 Yellow substance 4 0.660 - 0.680 Aerosol correction 5 0.700 - 0.800 Land/cloud flag 6 10.5 - 12.5 Surface temperature; failed shortly after launch
Level 2 and Level 3 Parameters
Level Parameter Unit Resolution 1 Calibrated radiances mW/(cm2.sr.micron) 1 km x 1km 1a Calibrated radiances mW/(cm2.sr.micron) 4 km x 4 km 2 Pigment Concentration mg/m3 4 km x 4 km Diffuse Attenuation Coeff none 4 km x 4 km Normalized water-leaving mW/(cm2.sr.micron) 4 km x 4 km radiance @ 440 nm Normalized water-leaving mW/(cm2.sr.micron) 4 km x 4 km radiance @ 520 nm Normalized water-leaving mW/(cm2.sr.micron) 4 km x 4 km radiance @ 550 nm Aerosol radiance @ 670 nm mW/(cm2.sr.micron) 4 km x 4 km 3 All none 20km
The following lists the data formats of the various CZCS products:
Data Format Level 1 CRTT Level 1a DSP Level 2 DSP Level 3 PST DSP Level 3 COMP DSP Level 3 flat files FLAT IMAGE FILES
Calibrated Radiance and Temperature Tape (CRTT) FORMAT:
The original Level 1 CZCS data was produced and stored on 9-track magnetic volumes in CRTT Tape format. The CRTT Tape format has been retained for the most part. The Nimbus-7 Coastal Zone Color Scanner Level 1 Data Product User's Guide for a complete description of the CRTT Tape format. This Guide may be ordered from the DAAC User Support Office (see Data Access below). When the data were transferred onto digital optical disks, the files in CRTT Tape format were modified slightly to create files in CRTT Archive format. The level 1 files available from the DAAC are in CRTT Archive format. The CZCS Revised Level 1 Format document details the differences between the CRTT Tape and Archive formats.
The University of Miami's Rosentiel School of Marine and Atmospheric Sciences has written a program called CRRTWRITE which will generate a CRT format tape from NASA CRTT Archive format files.
DSP FORMAT
Level 1a, level 2, level 3 PST images and level 3 COMP images are in DSP format. DSP is a user-interactive satellite data analysis package that was developed at the Rosenstiel School of Marine and Atmospheric Sciences (University of Miami). DSP operates on either DEC-VAX or Unix Workstation computers. The primary application of this package is for the processing and interpretation of CZCS and Advanced Very High Resolution Radiometer (AVHRR) data. DSP images can be converted to the SEAPAK format using the SEAPAK package (see description below).
For more information on the DSP format please contact the Rosenstiel School of Marine and Atmospheric Sciences at the University of Miami (see DSP, section 4.3.2).
LEVEL 3 FLAT IMAGE FILE FORMAT
Several additional time/space composites (climatological, seasonal, annual, regional) also exist as single parameter images. These are available as flat data files, without any headers, metadata or compositing statistics. These include full resolution global 2048 (longitude) x 1024 (latitude) pixel images as well as reduced resolution global 512 x 512 pixel images subsampled from the full global images with a 4 x 2 reduction factor. These regional images (spatial coordinates tabulated in section 9 above) are 512 x 512 pixel images at full resolution of the global product. They are simply a sector of the full global 2048 x 1024 composite grid. They are composed of 512 records, each record 512 eight bit bytes and each pixel value given by a count ranging between 0 and 255. Please consult the CZCS README file available from the GSFC DAAC for further information on these level 3 flat image files.
Information is not available yet.
The greatest problem encountered in analyzing the CZCS data was in the correction for atmospheric interference. In the visible portion of the spectrum, the largest contribution to the signal received by the CZCS is from the atmosphere. Rayleigh and aerosol scattering in the atmosphere must be compensated for before a high degree of accuracy in the determination of pigment concentration and diffuse attenuation coefficient can be obtained. The calibration procedure is quite complex and will not be discussed in detail here. In essence the Rayleigh component is assumed constant and can be subtracted from the signal. Aerosol scattering is variable and is measured by assuming that the red region of the spectrum is completely absorbed by the ocean surface and is therefore returning no signal to the instrument. From this assumption, aerosol scattering can be calculated for the rest of the visible spectrum. References 11.2.b and 11.2.c describe these principles in detail. The final data are in the form of calibrated radiances.
Chlorophyll concentration algorithms were used to reduce the data produced from the Level I radiance data base to concentration imagery. Basically, these algorithms use radiance data ratios to determine concentrations. Channels 1 and 3 were used for concentrations less than 1.5 mg/m**3 and channels 2 and 3 for concentrations above that level. These algorithms also account for the atmospheric scattering present, both Rayleigh and aerosol, by empirical coefficients in the equations for concentration. The Rayleigh component was assumed constant and can be subtracted from the signal. Aerosol scattering is variable and was measured by assuming that the red region of the spectrum is completely absorbed by the ocean surface and is therefore returning no signal to the instrument.
At the IPD at GSFC the data were converted from voltages to radiances for bands 1 through 5, and to equivalent blackbody temperatures for band 6. Algorithms developed by the CZCS Nimbus Experiment Team (NET) were then applied to produce data of suspended and dissolved materials on the water. These algorithms were improved several times during the lifespan of the instrument, especially for retrieval of water properties in sediment-laden coastal regions.
The Level 1 radiance data were used to produce black and white images. The data were then processed through a pigment concentration algorithm and diffuse attenuation coefficient algorithm to produce Level 2 and 3 products. The images have been written onto both Calibrated Radiance Chlorophyll Sediment Tapes (CRCSTs) and Sony optical disks. The optical disk images were generated using a newer algorithm than that used to generate the CRCSTs. The Level 3 products are global mosaics of derived parameters in image format.
The entire CZCS digital archive has been converted from the original 1600-bpi magnetic tape to Sony digital optical disk at the NASA/GSFC Space Data and Computing Division. The data format is nearly identical to the Calibrated Radiance and Temperature Tape (CRTT) product.
The Level 2 data were reprocessed at the Goddard Space Flight Center using the DSP analysis/processing system (see RELATED SOFTWARE) developed by the Rosenstiel School for Marine and Atmospheric Science at the University of Miami. DSP offers improved algorithms for the derivation of diffuse attenuation coefficient, water-leaving radiance, and aerosol radiances. After reprocessing, Level 3 image products were then produced from these Level 2 products.
Several large ship expeditions have been made to validate the derived CZCS data products. Most of these were conducted off the North American coasts, but other investigations in European and South African waters have also been conducted.
Data verification and correlation were done using data obtained from a number of research vessels:
Nov 1978 RV GYRE and RV ATHENA II Jun 1979 RV ATHENA II and RV OCEANUS Sep 1979 RV NEW HORIZONS and USC VELARO
The CZCS has performed better than its design requirements for signal-to-noise ratio in all channels. The table below shows the minimum signal-to-noise ratio specified for the instrument at its most sensitive gain setting.
Channel/ Signal/Noise Band Ratio (mW/cm**2-ster) Radiance NETD Temp 1 150 5.41 2 140 3.50 3 125 2.86 4 100 1.34 5 100 10.8 6 N/A N/A 0.220K 270K
In the worst case, the concentration can be determined within a factor of 2 of the actual concentration.
Information is not available yet.
Information is not available yet.
The Goddard DAAC has not performed data verification on the CZCS dataset.
There is an analog optical disk browse and order facility for quickly searching through the entire Level 2 and Level 3 data sets. Data can be ordered on-line. Several regional browse facilities have been established by NASA at academic and research institutions.
Due to the limited duty cycle (10%) and the non-uniform coverage, sampling was highly skewed. Temporal sampling frequency also varied, resulting in potential errors. These limitations should be considered when analyzing level 3 composites.
The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is scheduled to launch in 1995 as a follow-on to CZCS.
DSP Image File Format (Appendix D)
PC-SEAPAK User's Guide (Version 4.0)
SEAPAK User's Guide (VAX) (Version 2.0)
CZCS Level 1 Data Product Users' Guide
"Information on The GSFC Distributed Active Archive Center" flyer (from GSFC DAAC)
SEAPAK is a user-interactive satellite data analysis package that was developed at the NASA/Goddard Space Flight Center. The primary application of SEAPAK is for the processing and interpretation of Coastal Zone Color Scanner (CZCS) and Advanced Very High Resolution Radiometer (AVHRR) data. In addition, CZCS DSP images can be converted to the SEAPAK format using the SEAPAK package.
Two versions of the SEAPAK CZCS processing software are available from NASA Goddard Space Flight Center. PC-SEAPAK runs on PC-AT, 386, or 486 class machines. UNIX-SEAPAK operates only on SGI's Unix Workstation. Beside including most major programs in PC-SEAPAK to process CZCS and AVHRR satellite data, Unix-SEAPAK also includes programs to handle ancillary data. To obtain these programs see Software Access. DSP is image processing software package developed at the Rosenstiel School of Marine and Atmospheric Sciences of the University of Miami. DSP images can be converted to the SEAPAK format in the SEAPAK package. For information on the full applications, requirements and availability of these systems, contact:
SEAPAK: Dr. Charles McClain C.MCCLAIN (OMNET) URCHIN::MCCLAIN (NSI-Decnet) MCCLAIN@CALVAL.GSFC.NASA.GOV (Internet) DSP: Dr. Robert Evans R.EVANS (OMNET) MIAMI::EVANS (NSI-Decnet)
If you do not have ftp capability, we can send you a non-display version of PC-SEAPAK, on diskettes. This version is sent in order to minimize the number of diskettes needed and will provide you a working, non-graphical version of PC-SEAPAK. On shark.gsfc.nasa.gov, you will find several compressed files and one program to decompress those files under the directory '/pcseapak/version4'. Use 'ftp' and login as 'anonymous' (no password required), change directory to '/pcseapak/version4', and copy over these files:
UPDATES:
These update files have to be restored (in any temporary directory
using 'pkunzip') and installed (copied) IN ORDER into the SEAPAK
directory after you have installed the original PC-SEAPAK 4.0.
Download all of these files to the PC first. Then run PKUNZIP to decompress all the ZIP files. Type PKUNZIP at the DOS prompt and you will get a detailed description about how to use this command.
For example, to decompress all files in 'SEAPAK.ZIP' to the directory 'D:\SEAPAK', just type 'PKUNZIP SEAPAK.ZIP D:\SEAPAK'. All other compressed files should be decompressed the same way. It is recommended that you decompress different zip files into different directories. After all compressed files are restored, you need set up the SEAPAK environmental variable, modify SEAPAK.FIG file if necessary, run the programs SPKSETUP and INIT.
For further information, read SYSTEM ENVIRONMENT : SOFTWARE in the PC-SEAPAK User's Guide. This User's Guide is available on request. Contact the DAAC User Services Office to request a copy of the PC-SEAPAK User's Guide or to request a non-graphical version of PC-SEAPAK on diskettes. If you have any problem or need assistance with installing or using PC-SEAPAK, please call Gary Fu at 301-286-7107 or send e-mail to
Gary Fu is also involved in developing the SEADAS processing software for processing SeaWiFS data.
GSFC DAAC
GSFC DAAC
The central archive and distribution facility responsible for providing access to the entire CZCS data set is at NASA's Goddard Space Flight Center. There are several ways to access the data.
The primary means of access is through the Goddard DAAC IMS. The procedure is as follows:
Telnet daac.gsfc.nasa.gov (192.107.190.139)
username: daacims
password: gsfcdaac
First you will be asked for user information. A Search Inventory window will then appear where you will supply your search criteria and then submit your order.
In addition to Goddard, a number of academic and research institutions have been established by NASA to serve as regional browse, distribution and analysis centers for Levels 1a, 2 and 3. These distributed archives have resident copies of all Level 1a and higher data, and the necessary hardware and software required for browsing, copying and reformatting the images.
The CZCS Browse Program was designed to provide a researcher with the ability to quickly search the entire Level-2 CZCS data set and to instantly view the color-coded phytoplankton pigment fields that meet the search criteria.
This version of the browse program also provides approximately 9,000 ship (in situ) observations for comparison with the Level-2 data. Additionally, researcher-specified 'movie loops' can be generated to allow study of temporal changes.
Most of CZCS level 1 dataset currently is available from the GSFC DAAC IMS and the ESDIS IMS. It's archive at the GSFC DAAC is scheduled for completion by the late summer of 1994. The higher level products will be archived by autumn of 1994. The higher level products will be available from the GSFC DAAC IMS as they are archived. However, CZCS products that do not yet appear in the IMS inventory may be ordered by contacting the GSFC DAAC User Services Office (See Data Access).
Information is not available yet.
CZCS Coastal Zone Color Scanner
EOSDIS Earth Observing System Data and Information System
ESDIS EOSDIS Data and Information System
IFOV Instrument Field of View
IMS Information Mangement System