The Image Mapping system (IMGMAP) is the nucleus of the NOAA-K,L,M Environmental Image Product System. IMGMAP produces three major environmental image products: Ice maps for the NAVY/NOAA Joint Ice Center (JIC), master maps, and ocean maps. These products are further processed by the IMGMAP subsystems to produce a host of derived products such as the global Vegetation Index (VI), high resolution Sea Surface Temperature (SST), snow cover, and so on. IMGMAP and its subsystems, from now on, will be referred as the Image Product System. Products generated by the Image Product System are outlined in the system overview charts presented in the following pages of this document. The primary source of input to the Image Product System is the sensor data from the Advanced Very High Resolution Radiometer (AVHRR) instrument on board the NOAA- series of polar satellites. With the advent of NOAA-K in 1993, sensor data from the Advanced Microwave Sounding Unit (AMSU) will also be integrated into the Image Product System to generate a string of microwave products.

The heart of the IMGMAP system is a generic mapping software that facilitates a variety of mapping options. The features offered by the system are not just limited to the imaging requirements of AVHRR and AMSU. Image products from other sensors, and from any kind of earth located data can be generated effortlessly and economically by making a few peripheral changes to the system. This concept is illustrated in the overview charts. It is expected that the IMGMAP system will not only satisfy research and operational needs of the NOAA/NESDIS but also serve as a 'Consolidated Mapping System'. Efforts are already underway to generate Special Sensor Microwave/Imager (SSM/I) master maps from IMGMAP. The NOAA-K,L,M Radiation Budget system is expected to use IMGMAP to produce image products.

The image product system resides on the NOAA Central Computing Facility (NCCF) National Advanced Systems (NAS) mainframe computers. A subset of the system that generates products for the Joint Ice Center is operational on the NESDIS Data Processing Services Subsystem (DPSS) computers. The DPSS version will be upgraded when the final operation capability is implemented. The

Image Product System software is written completely in VS FORTRAN. All input and output interfaces are implemented using standard FORTRAN Input/Output (I/O) routines thus ensuring portability to other computers. The software meets the Office of Satellite Data Processing and Distribution (OSDPD) software standards and guidelines.

This document describes the scope and limitations of the Image Product System. System capabilities and limitations are discussed under System Overview in Section 2. Sections 3 and 4 identify and provide a brief description of system inputs and outputs. Capabilities of the off-line system are discussed at length in Section 5. Section 6 provides a description of various algorithms used in the Image Product System.

This section presents the capabilities and limitations of the Image Product System. System overview charts presented in Figures 1 through 1.5 identify the primary source of input, the processing system, and the product generated by each system. Data flow diagrams given in Figures 2 through 2.4 describe the flow of data and identify major input files, the processing system, and major output files produced by the Image Product System. Hierarchical relationship of IMGMAP system with its subsystems is also evident from these figures. Each component of the Image Product System has a system control file; however, the JIC rotational data base subsystem is an exception to this. Through the system control file, the user chooses the attributes of the image product desired.

2.1 IMGMAP SYSTEM

2.1.1 FUNCTION

The IMGMAP system produces three major environmental image products using sensor data processed from the AVHRR and AMSU instruments.

2.1.2 SYSTEM CAPABILITIES

Various capabilities offered by the IMGMAP system are discussed under the following list of categories:

Satellites:

Morning or afternoon or both satellites can be selected for processing.

Products:

IMGMAP system produces the Joint Ice Center product, Master Maps, and Ocean

products.

Instruments/data types:

Data from all data types of AVHRR and AMSU can be processed.

Selected set of images can be produced either from a daytime or nighttime overpass or from both.

Channels:

One or more channels can be selected in any combination.

Ancillary information:

Images of selected ancillary data can be produced. These are: scan angle, satellite zenith angle, solar zenith angle, relative azimuth angle, and scan time.

Data corrections:

Computed albedos can be optionally corrected for sun angle. Likewise, limb correction or nonlinearity calibration correction can be optionally applied to computed brightness temperatures.

Calibration options:

Four calibration options are available: raw counts, radiances, albedos and brightness temperatures, and albedos and brightness temperatures using GOES look-up table. Each selected channel can be calibrated independently using any one of these four options.

Graphics options:

Graphics can be selected from lat-long grids, coastlines, land-sea tags, and filled-up spots.

Projection:

Four different types of projections are available: Unmapped, Mercator, Polar, and Linear lat-long.

Target area:

Both global and regional options are available for all projections. Global maps cover an entire longitude window between selected latitudes (one or more latitude zones) such as the entire globe from the North pole to the South pole, either of the northern or southern hemispheres, or equatorial regions.

Image resolution:

Image size is completely variable. Mapping can be performed at a user-specified resolution. If the user does not specify resolution, the program determines one that is appropriate for a given set of input parameters.

Image pixel length:

Image pixel length can be 1-byte or 2-bytes. However, images of ancillary data are always produced in 2-bytes.

Composite flag:

Images can be optionally composited with previously generated images either spatially or temporally using a 5-way composite flag. The options available are: composite based on minimum nadir angle, average, later, warmer, or colder composites.

Fill-up option:

Holes in a mapped image can be optionally filled using an average method or an adjacent method.

Satellite zenith angle cut-off option:

A cut-off option is available to process only those spots that are within a user defined threshold zenith angle.

2.1.3 LIMITATIONS

1.     Master maps from AMSU will not be available until after the launch of    NOAA-K. Additional software will have to be written for the Image     Mapping System to accommodate the AMSU 1b format which has not     yet been defined.

2.    Limb correction and nonlinearity correction are implemented as being      mutually exclusive. Only one can be selected. For sea surface     temperature applications, limb correction must not be selected as a     correction to that effect has been taken into account in the Multi-    Channel Sea Surface Temperature (MCSST) algorithms.

3.    No limits are imposed on the number of image rows. However, there    is a limit on the number of image columns. Image columns may not    exceed 23476 if using a 1-byte option for image pixel or 11738 if    using a 2-byte option. This restriction comes from the fact that the    number of image columns times the image pixel length constitutes    a logical record length; and a record length of 23476 ( half a track on    3380 disk packs) is optimal to minimize disk storage and access time.    Some minimum limits apply on the number of image columns as well;    typically, 160 bytes to accommodate the image header record. If the    minimum limit is not followed, the header record may overflow into    data records. This limitation is, generally, applicable to all image    products discussed in this manual.

2.2 VEGETATION INDEX SUBSYSTEM

2.2.1 FUNCTION

The Vegetation Index (VI) subsystem produces a vegetation index from a weekly composite of AVHRR Global Area Coverage (GAC) master maps.

2.2.2 SYSTEM CAPABILITIES

The Vegetation Index subsystem offers the following capabilities:

    1.     Number of days for composite is user-selectable.

    2.    The Vegetation Index computed is always a normalized index.         However, there is an option to do the Vegetation Index either from raw          counts or from albedos. If the albedo option is selected, there is a         provision to do it either from pre-launch coefficients ( as retrieved from         a level 1b orbit data set) or from user-defined calibration coefficients.

2.2.3 LIMITATIONS

Number of days selected for composite may not exceed 10 days. If it does exceed 10 days, header records run out of room to store additional information.

2.3 COASTWATCH SUBSYSTEM

2.3.1 FUNCTION

The CoastWatch Subsystem extends and supplements the capabilities of IMGMAP, allowing region images generated by IMGMAP to be broken into one or more sectors for which a variety of images can be generated.

2.3.2 SYSTEM CAPABILITIES

* Sectorization: A user may specify geographical sectors with respect to a region for which images are to be generated by IMGMAP. These sectors may lay wholly or partially within the region, and sectors may overlap. For each sector, a variety of images can be generated, as can stand-alone sector graphics files. The user may request sectors at the same resolution as the region images generated by IMGMAP or that the region be subsampled.

* Channel & Ancillary Images: Channel and ancillary images for any sector, similar to those generated by IMGMAP for a region, can be generated.

* SST Images: Split, Dual & Triple Window algorithms for each of the MCSST, CPSST, and NLSST techniques for computing SSTs, in any combination, can be generated for user-defined sectors. The user may alter any or all of the algorithms by providing values for the various coefficients and constants that comprise the algorithm. The user can supply two sets of coefficients for each of the algorithms -- one set for use with pixels that are in darkness and another for pixels in daylight. SST calculations can be restricted to be performed only over water and can also be restricted to cloud-free areas.

* Ocean Reflectance: OR calculations can be performed for user-defined sectors. The coefficients and constants that comprise the algorithm can be modified by the user. OR calculations can be restricted to be performed only over water and can also be restricted to cloud-free areas. The user may specify totally different sets of coefficients for each sector.

* Cloud Masks: The user may select from among 20 user-modifiable cloud tests. The results of the cloud tests can be preserved in a cloud mask image for any sector and the user can designate particular bits in the mask to be set (or, for restoral tests, reset) depending upon the outcome of particular tests. A different bit can be specified for pixels in daylight from those in darkness. Cloud tests can be performed with or without a unit array and in a variety of modes and conditions -- all user specifiable.

* Sector Graphics: For any sector, the user can request graphics be either merged with various of the other images generated, or that graphics be placed in a stand-alone file for that sector. In the event that a stand-alone graphics file for the sector has been created sometime in the past, the user can cause that data to be merged with various of the images for that sector.

* Data Compression: For any sector the user can specify that the appropriate images for that sector be compressed. (Not all images -- e.g., cloud masks and ancillary data -- are compressible.)

2.3.3 LIMITATIONS

* The limitations listed for the IMGMAP System generally apply.

* Logical Record Length: There is a minimum length allowed for the logical record of any region file and for any sector file produced by OCNMAP of 200 bytes because the logical record length must be large enough to contain the image header.

* Region Graphics: IMGMAP map should produce images without merged graphics. Graphics information should be supplied to OCNMAP in either a single stand-alone region file or in a set of stand-alone sector files, one for each sector.

* File Limit: OCNMAP will produce at most 50 output files for any single run.

* Single-byte Pixel Images: OCNMAP cannot currently process single-byte pixel images from IMGMAP.

* Mixing Cloud Type Modes: Do not mix single-pixel cloud tests with restoral tests performed over a unit array.

2.4 GRAPHICS SUBSYSTEM

2.4.1 FUNCTION

The graphics subsystem produces selected graphics from: lat-long grids, coastlines, and land-sea tags and down-loads them to a static graphics file IMGMAP system uses the static graphics file to optionally merge graphics with image data.

2.4.2 SYSTEM CAPABILITIES

    1.     The graphics subsystem offers the same mapping options as offered        by the IMGMAP system.

    2.     Griding interval used for lat-long grids is user-selectable. If the user        does not specify one, the program uses either a 1-degree interval or a         5-degree interval depending on the mapped resolution.

    3.     The user can select Geography from one or more continents.

    4.     The level of detail required for Geography can be selected through a        WDB rank file. The current configuration selects all

ranks (see        Sections 4.2.1.2 and 4.2.1.4 ).

2.4.3 LIMITATIONS

    1.     In order to successfully merge graphics with image data, the image        pixel length has to be 2-bytes. No graphics can be merged with         1-byte pixel data. Also, the static graphics file must have the same         blocksize as that of the corresponding image file.

    2.     The land-sea tag data base, from which the land-sea tags are        retrieved, has a    resolution of 1/16th of a degree or about 7 km; as a         result, the land-sea tag    registration may be off by a few pixels if the         resolution of the target image is finer than 7 km. This can be rectified         by choosing a data base that has a better resolution than 7 km         (currently under development).

    3.     The WDB II access routine performs an extensive search to retrieve        appropriate Geography from the data base. This operation takes        considerable time for large target areas/images. Time can be saved         by selecting only those continents that are required for processing.

2.5 JIC ROTATIONAL DATA BASE SUBSYSTEM

2.5.1 FUNCTION

The JIC rotational data base system receives JIC image files produced on the DPSS computers and uploads them to a rotating data base resident on the NAS computers.

2.5.2 CAPABILITIES

    1.    The system operates in a real-time mode. The features offered by the        system are generally applicable to other applications.

    2.    The data base can stack up to eight orbits each of HRPT, LHRR, and         GHRR data types.

    3.    The system maintains a dialogue with the user through a status file.         The status file contains relevant information about various files         resident on the data base at any given time. Through the status file,        the user can select files of interest for further transmission or        processing.

2.6 OFF-LINE SYSTEM

The off-line system is invoked by a command: #PANEL after starting up the operational library (see Section 2.2). The following appears on the terminal once the command is entered.

THIS IS A MASTER CLIST FOR THE IMGMAP SYSTEM

SELECT A UTILITY OF INTEREST

1    =    #BNDCHK    -    DETERMINES TEMPERATURE AND VALUE OF A                PIXEL GIVEN POSITION OF THE PIXEL
2    =    #BREAKUP    -    CREATES INDIVIDUAL CHANNEL AND ANCILLARY                FILES FROM OUTPUT IMAGE FILE OF IMGMAP                SYSTEM
3     =    #HEADER     -     DISPLAYS HEADER INFORMATION
4     =    #IMGMAP     -     EXECUTES THE 'IMGMAP' SYSTEM
5     =    #LUKUP     -     CREATES 8 BIT LOOKUP TABLES
6     =    #MASK     -     DETERMINES PERCENTAGE

CLOUDINESS IN A                CLOUD MASK FILE
7    =    #ORBSTAT     -    DISPLAYS COMPOSITE INFORMATION
8     =    #SETRES     -    DETERMINES LAT/LONG BOUNDARIES AND
        RESOLUTION

ENTER Q IF YOU WISH TO QUIT

A description of each utility follows.

2.6.1 #BNDCHK

Given an image file, this utility can be used to display the minimum and maximum pixel values or to display pixel values at specific pixel locations as selected by the user. Displayed parameter is in counts, albedos, temperatures or degrees depending on which image file is selected. The utility displays in numeric order a list of channels and ancillary information that was written to the file. The user can select an image of interest by entering a number corresponding to that of the image desired. Once the image is selected, the user is prompted again to select one of the options, minimum and maximum pixel values or pixel values at user-selected locations.

2.6.2 #BREAKUP

This utility breaks up image files into individual images. The utility can be used to separate channel images, ancillary images, and images of SST. Separated images will be saved into the user's catalog with the user's ID as a prefix. The user will be prompted to enter an image file name that has more than one image written to it. The utility looks into image headers and displays a list of images that were written to the file. The user will be prompted again to select images of

interest. Based on the user's selection, appropriate files are allocated, the information is separated, and written to those files.

2.6.3 #HEADER

Given an image file, the utility #HEADER displays the contents of the image header records. Options are available to display the entire header record, to display a selected range of words, or to display a specific word. In addition to display of contents, word positions and a literal description of contents are also provided.

2.6.4 #IMGMAP

Through the utility #IMGMAP, the user can create/update the IMGMAP system control file, select an orbit of interest or have the utility select a suitable one, build a production JCL stream, and submit it from foreground. As a first step, #IMGMAP builds a system control file. Once the control file is ready, orbit selection is initiated. The orbit selection is done using one of two options: Program choice, and User's choice. The User's choice is normally opted when the user wants to select a known 1b orbit for processing. To facilitate this, the utility displays an up-to-date catalog of available 1b orbits for the chosen data type and spacecraft. The Program choice determines a suitable orbit from a catalog of available 1b orbits. Once the orbit selection is done, the orbit Data Set Name (DSN) is implanted in the template JCL and a production JCL is made ready for submission.

The production JCL uses the jobname SMPGACZ1 which can be changed at any time. #IMGMAP also makes a provision to process 1b orbits that are stored to a static 1b data set. Orbits that can not be processed right away are normally stored to a static 1b data set for later processing. #IMGMAP has two key word operands that are satellite dependent. These key words are set to NG and NH,

the spacecrafts that are currently in orbit. New satellites can be added to the system by changing the spacecraft IDs.

#IMGMAP does not interact with subsystem control files. Any changes to subsystem control files are to be carried out manually. The MCSST subsystem has four control files, DAMCSST, NAMCSST, DMMCSST, NMMCSST, where the first letter stands for daytime or nighttime and the second one stands for afternoon or morning satellite. The Vegetation Index subsystem has VEGCNTL as a control file and the graphics system has WDBRNK as a control file.

2.6.5 #LUKUP

Through #LUKUP, the user can define interactively a 11-bit to 8-bit look-up table. The look-up table can be created/updated using this utility. Either albedos or temperatures or both can be defined/updated. The table has entries for 5 channels X 2047 values. When the table is created for the first time, look-up values for all 5 channels have to be specified. For successive updates, entries for any channel of interest may be updated without affecting the entries of the rest of the channels. Only the linear relationship is valid. There is no limit on the number of steps. For each step, the user defines an albedo/ temperature value followed by a corresponding 8-bit count value. At the end of the session, the look-up table can be saved to a permanent file.

2.6.6 #MASK

The utility #MASK accesses a cloud mask file supplied by the user and reports the percentage of clouds.

2.6.7 #ORBSTAT

Given an image file as input, the utility #ORBSTAT reports a history of the

composite. A list of orbits used to composite the data is reported. #ORBSTAT looks into image headers and retrieves orbital information.

2.6.8 #SETRES

Given the beginning and ending lat-longs, image size, and type of projection, the utility #SETRES computes and displays an optimum resolution (Program choice). Alternatively, given a central lat-long, image size, mapped resolution, and type of projection, #SETRES displays the beginning and ending lat-longs of the calculated target area (User's choice). The utility prompts the user to select one of two options: Program choice, and User's choice. The Program choice is to be opted to obtain a computed resolution. The User's choice returns lat-longs of the calculated target area. Since the same routines and methodology are also used within the IMGMAP system, this utility serves as a guideline to select image size and target area appropriately.

2.6.9 #SPACE

Given the number of channels and ancillary information, and the image size, the utility #SPACE estimates amount of disk space required to allocate an image file.

2.6.10 #SYSCON

Through the utility #SYSCON, the user can create/update the IMGMAP system control file and optionally store it to a permanent file. A temporary file CNTROL will be created under the user's catalog with the user's ID as a prefix. At the end of the session, the utility displays the control file and lets the user make any corrections.

#SYSCON has a few key word operands that are satellite dependent. These are the central wave numbers of channels 3,4, and 5 and equatorial crossing times for both morning and afternoon satellites. New satellites can be added to the system

by resetting these parameters

In addition to the panel described above, the off-line system has two information utilities. These are #SHOW and PLOT.

#SHOW displays an up-to-date catalog of available 1b data sets of AVHRR for a chosen data type, HRPT,LHRR, or GHRR. If no catalog is available for a chosen spacecraft or if a valid data type is not selected, the Clist exits with an error message. The catalog defaults to the NOAA-H spacecraft. Catalogs of other spacecrafts can be displayed by specifying the spacecraft ID via the key word 'SCID'. For example, the HRPT catalog of NOAA-G can be displayed with the command: #SHOW HRPT SCID(NG)

The Clist PLOT, when executed after #SHOW, retrieves earth locations from a selected level 1b data set of AVHRR and displays lat-longs of the left most FOV, nadir, and the right most FOV of every few scan lines. The Clist #SHOW displays a catalog of available 1b orbits at any given time in numerical order. The user picks a number displayed for an orbit of interest and enters the same number after the command PLOT to activate the Clist. The data set name of the selected orbit and the number of scan records in that orbit are also made available to the user. This Clist is normally used to verify if an orbit covers a user-selected target area. PLOT is also useful to verify the accuracy of earth locations provided with the 1b data set. The interval used for scan line sampling is 250. No display will be available if #SHOW is not executed prior to the execution of PLOT.

2.6.11 # CSTWTCH

#CSTWTCH initiates the Ocean Map Off-line subsystem. This, unlike the CLIST driven off-line system of Image Map, is an ISPF panel driven application. Through its use, a user can create or modify an Ocean Map control file - the file which controls the Ocean Map program's processing. If the user is familiar with ISPF/PDF, then there should be no problems using this subsystem: ISPF

consistently was a major design objective. If a problem does arise, a complete hierarchical structure of Help panels is available at anytime when the HELP command (PF1) is issued. From there, the user has complete access to the remaining HELP panels. The CoastWatch Off-line Tutorials design and function are consistent with other ISPF/PDF Help panels, as well.

This section provides a general description of various files that serve as input to the image product system. A detailed byte-level description of these files can be found in the Interface Control Document for the NOAA-K, L & M Environmental Image Products.

3.1 Level 1B Orbit Data Set

Level 1B data consists of instrument raw data , calibration, and earth location information. For AVHRR, three types of 1B data sets are available: the GHRR, LHRR, and HRPT. The LHRR and HRPT, which are commonly known as Local Area Coverage (LAC), provide an average data resolution of 1.1 km. The GHRR data give an average resolution of 4.0 km. The AVHRR instrument makes observations in five different spectral ranges. The channelization of the AVHRR is as follows:

    Channel 1            0.58-0.68 m m        Visible
    Channel 2            0.725-0.11 m m        Reflected IR
    Channel 3            3.55-3.93 m m        Thermal IR
    Channel 4            10.3-11.3 m m        Thermal IR
    Channel 5            11.5-12.0 m m        Thermal IR

Channels 1 and 2 are used to discern clouds, land-water boundaries, snow and ice extent. Channels 3, 4, and 5 are used to measure cloud distribution and to determine cloud or surface temperatures. In addition to this, channels can be combined to produce VI, snow cover, SST, and so on. Since all five channels are window channels, the AVHRR sensor data is widely used to study surface properties. For a technical description on specific characteristics of the AVHRR instrument, the user is encouraged to consult 'NOAA Technical Memorandum NESS 95 (Schwalb, 1978)'. The user may also refer to 'NOAA polar orbiter data User's Guide (Kidwell, 1985) ' for a detailed format description of level 1B data

sets.

With the advent of NOAA-K, one additional infrared channel will be added to operate at 1.6 m m. When this channel becomes available, it will be known as channel 3a and the current channel 3 will be known as 3b. These two channels operate in a time-shared mode with channel 3a providing daytime coverage and channel 3b providing nighttime coverage.

3.2 AMSU

Sensor data from the Advanced Microwave Sounding Unit (AMSU) will be available after the launch of NOAA-K. The sounding unit consists of two instruments: AMSU-A and AMSU-B. The primary purpose of AMSU is to provide microwave sounding capability. However, both AMSU-A and AMSU-B have some channels that operate at window frequencies. These channels will be used to generate master maps of AMSU data. The following table provides a list of AMSU window channels and their central frequencies.

    INSTRUMENT    Channels        Central Frequency (GHz)

    AMSU-A        1,2,3,15        23.8,31.4,50.3,89.0
    AMSU-B        16,17            89.0,157.0

More details on instrument characteristics and sensor data formats will be provided when the instrument data format has been defined.

3.3 System Control Files

The Image Product System has three control files: the IMGMAP system control file, the VI subsystem control file, and the CoastWatch subsystem control file.

Using these control files, the user can choose the attributes of the desired image product.

3.3.1 IMGMAP System Control File

The following options are exercised through the IMGMAP system control file:

Job Processing flag        
Satellite            
Products            
Data types            
Day/night option         
Channels (day)        
Channels (night)        
Ancillary images (day)    
Ancillary images (night)    
Data corrections        
Calibration options        
Graphics            
Projection            
Target area                                 
Image resolution        
Image pixel length        
Composite flag        
Fill-up option            
Central wave numbers and equ. crossing times of morning satellite
Central wave numbers and equ. crossing times of afternoon satellite
Block size of image file
Satellite zenith cut off

IMGMAP system control file can be created/updated interactively with the help of

the Clist #SYSCON (see Section 5.2.10 of this manual) . A description of these options follows. The term 'bit flag' used in this and the following Sections refers to a binary digit which assumes only two valid values 1 or 0. A flag value of 1 is used to select an option. The order in which these bit flags are described here is the same as what is used to create the file.

Job processing flag:

The Job processing flag must be set to 'ON' state ( flag value=1) at all times in order to run the system. No processing gets done if the flag is in 'OFF' state (flag value=0). The 'OFF' state is normally used to shut down the system temporarily (or even permanently) when the product generated by the system is no longer needed. This feature is useful to generate seasonal products, that is, products over specific target areas during specific seasons.

Satellite:

Two bit flags control the type of satellite selected for processing, morning or afternoon. If data from both the satellites are required, both flags must be turned "on" (flag value=1).

Products:

The IMGMAP system produces three different products: Ice maps for the JIC, master maps, and ocean maps. Since the system makes some decisions based on the product Identification (ID), it is important to specify the right ID that corresponds to the product being generated. ID=1 is used for JIC product, 2 for master maps, and 3 for ocean applications. For example, if it is evident from the ID that the product is master maps, lat-long information specified in the system control file is ignored as master maps, by definition, is a global product. Likewise, lat-long information is also ignored for JIC product since the product is meant to provide coverage over the polar caps whose lower latitude cut-off is defined in a

seasonal adjustment file.

Data types:

There are five bit flags available to select data types from which the data are to be processed. Currently, any data type or a combination of data types may be selected from GHRR, LHRR, and HRPT by setting the corresponding bit flags to 1.

Day/night option:

Two bit flags are set up to select either daytime or nighttime coverage over the chosen target area. If both flags are set to 1, all those orbits that cover the target area will be processed regardless of daytime or nighttime. However, if either daytime or nighttime coverage is selected, the system processes only those orbits that provide the selected coverage.

Channels (day/night):

Five bit flags are available to select one or more channels of AVHRR for processing. Daytime and nighttime channels are selected independent of each other.

Ancillaries (day/night):

Five bit flags are available to select ancillary information from scan angle, satellite zenith angle, solar zenith angle, relative azimuth angle, and scan time.
Daytime and nighttime ancillary maps can be selected independent of each other.

Data corrections:

Three bit flags are available to perform one or more data corrections from sun normalization, limb correction or non-linearity correction. (see Section 6.7)

Calibration options:

Four calibration options are available for each of the selected channels. These are raw counts (flag value=0), radiances (flag value=1), albedos and brightness temperatures (flag value=2), and albedos and brightness temperatures using GOES look-up table ( flag value=3). Section 6.1 provides more details on the calibration process.

Graphics:

Four bit flags are set up to select overlay graphics from filled-up spots, lat-long grids, coastlines, and land-sea tags. Whenever a pixel represents a filled spot (as opposed to the original data value), a bit will be optionally illuminated in the graphics portion of that pixel to indicate that it is a filled-up spot. The other graphics information is optionally merged from a static graphics file created by the graphics subsystem.

Projection:

Any one of the four projections can be selected from unmapped (flag value=0), mercator (flag value=1), polar stereograph (flag value=2), and linear lat-long projection (flag value=3). See Sections 5.1.2 and 6.3 for more details.

Target area:

A target area is defined by specifying either a central lat-long location or the beginning and ending lat-longs of a geographical area considered for processing. For both master maps and JIC product filler values are used in place of target area. For ocean applications, a global option is also available to produce global maps. These maps could cover the entire globe from the North pole to the South pole, either of the northern or southern hemispheres, or the equatorial regions. The conventions used to define the target area are discussed in Section 5.1.1.

Image resolution:

The image resolution is specified in terms of number of image rows, number of image columns followed by the mapped resolution. In cases where the resolution is computed internally, the resolution parameter specified in the system control file is ignored. See Section 5.1.2 for more details.

Image pixel length:

The image pixel length can be 1-byte (8-bits) or 2-bytes (16-bits). If at least one of the graphics is selected, image pixel length has to be 2-bytes to accommodate graphics.

Composite flag:

Any one of five available options can be selected: 'no composite' (flag value=0), composite based on minimum nadir angle (flag value=1), average pixel ( flag value=2), later pixel (flag value=3), warmer pixel (flag value=4), and colder pixel (flag value=5). (Also see Section 5.1.4.)

Fill-up option:

Any one of three options can be selected to fill holes in mapped images no fill-up (flag value=0), fill-up with average values ( flag value=1), and fill-up with adjacent pixel values (flag value=2). Also see Sections 5.1.3 and 6.9.

Central wave numbers and equatorial crossing times:

Three central wave numbers are required (one for each channel) for channels 3,4, and 5 of AVHRR for data calibration purposes. Equator crossing times during ascending and descending portions of the orbit are also required to make a determination on whether or not a pass provides daytime coverage or nighttime

coverage over the chosen target area. Two sets of these parameters are required, one for each satellite, morning and afternoon. (See Sections 6.1 and 6.6)

Block Size of image file:

The block size (size of the physical record) used for the output image file must be known to the system to perform I/O successfully. Also see Section 2.1.3.

Satellite zenith cut-off:

A cut-off angle may be specified to discard the edges of AVHRR scans and process only the middle portion of the scan. For sea surface temperature applications, an angle of 53 degrees is normally used.

3.3.2 VI Subsystem Control File

Through the VI subsystem control file, the following options can be selected:

Number of days for composite
Calibration flag
Calibration coefficients
DCBs
VI computation flag

The VI subsystem control file can be updated manually. A description of these options follows:

Number of days for composite:

The daily master maps (only the daytime maps) of AVHRR GAC are normally composited for a period of one week before the VI is computed and made into a

product. However, the composite period can be defined through the VI subsystem control file. The number of days selected for composite may not exceed 10 days.

Calibration flag:

The calibration flag, in this context, is a bit flag. If it is set to 'OFF' (flag value=0), the system uses pre-launch calibration values, the slope and intercept values of channels 1 and 2 obtained from a 1B orbit data set, to compute albedos. Otherwise, the system uses user-defined calibration values.

Calibration coefficients:

The user-defined calibration coefficients are defined in terms of slopes and intercepts for channels 1 and 2.

DCBs:

The Data Control Blocks of the weekly composite file and the VI file are defined for logical record length and block size parameters.

VI computation flag:

The VI computation flag is a bit flag. When it is 'OFF' (flag value=0), the system uses raw counts to compute VI. Otherwise, it computes albedos using pre-launch or user-defined coefficients and further computes VI from albedos.

3.3.3 CoastWatch Subsystem Control File

The main CoastWatch processor is the program OCNMAP and it can be configured to perform the particular tasks desired by a user through the use of a control file. Such a control file can be constructed using the CoastWatch Off-line Subsystem, the use of which is described in detail in the CoastWatch Off-line

Subsystem User's Manual. The Image Product Interface Control Document describes the format of the file. In the remainder of this section we describe the information items stored in the control file's records.

CoastWatch (OCNMAP) Control File

HEADER RECORD

This record is to contain 80 bytes of header information, the content of which is yet to be specified.

GENERAL REGION INFORMATION

SATELLITE ID

The ID of the satellite to which this control file applies. (E.g., NOAA-11 has 'NH' for a satellite ID.)

SST & SZ CUT OFF ANGLE, SST CLOUDY FLAG and LANSST FLAG

The satellite and solar zenith angle cutoffs for SST computations and 2 flags that indicate: (1) whether SST are to be computed for cloud covered pixels, and (2) whether they are to be computed over land. Note that for the first to make sense, at least 1 cloud test must be active, and for the second, land-sea tags must be available either in a region graphics file or in the existing sector graphics files.

CLOUD MASK PROCESSING FLAG, CLOUD MASK SOLZEN CUT OFF ANGLE, UNIT ARRAY SIZE AND UNIT ARRAY SKIP AMOUNT, PRIMARY SST CLOUD TEST, SST TYPE FLAGS.

The Cloud Mask Processing Flag enables or disables cloud testing. If set to '0', no cloud testing will be performed regardless of the settings in the

remainder of the control file. The solar zenith angle cutoff will limit daytime cloud testing to those pixels having solar zenith angles below the given cutoff. Pixels having solar zenith angles greater than the cutoff will be evaluated using tests that have been specified for night only or for both day and night. The unit array is a square matrix of pixels (usually 2x2, but
possibly 3x3 or 4x4) that are tested as a group for the presence of cloud. If the test indicates cloud cover, the mask bit for each pixel covered by the unit array is set. In the case of restoral tests, the mask bit for each pixel covered by the unit array will be reset (i.e., turned off) if the test indicates a clear condition. The way the program moves the unit array between tests is determined by the skip amount. The program moves the unit array across the image (west to east) by the number of columns specified by the skip amount Then the unit array is returned to the west side of the image but now down by a number of rows equal to the skip amount, and the process is repeated. The skip amount may vary between 1 and the size of the unit array. If the skip amount chosen is less than the unit array size some overlap will occur and many pixels will be included in more than one unit array, resulting in redundant calculations and hence longer run times. In general, the larger the unit array and the smaller the skip amount the more computationally intensive will be the run. See the documentation on cloud testing for more information. The primary SST Cloud Test identifies the SST algorithm to be used for the Unreasonable SST Cloud Test. The SST type flags identify the SSTs to be used in the SST Intercomparison Test. As usual, the flags are ordered such that the first 3 represent MCSST algorithms, the second group of three represent CPSST algorithms, and the third represent NLSST. In all three groups, the Split Window Algorithm's flag precedes that for the Dual Window, which, in turn, precedes the one for the Triple Window Algorithm.

OCEAN REFLECTANCE PROCESSING FLAG, CUTOFF ANGLES AND OPTIONS TO COMPUTE UNDER CLOUD OR OVER LAND

The processing flag can be used to turn off Ocean Reflectance Processing. The cutoff angles give limits to a pixel's solar and satellite zenith angels above which OR will not be computed. Options to compute OR for cloud covered pixels and for ones on land. Again, the first makes sense only if at least 1

cloud test has been activated and the second only if land/sea tags are available in the graphics data supplied to OCNMAP.

CASCADE ORDER OF FIELD DATA

Gives the preferred order for searching out field data. If (possibly missing) field data is to be simulated by one of the SST algorithms, the SST option should be either last (i.e., least preferred) or the only option selected.

* The field data capability is not implemented.

GRAPHICS SOURCE AND REGION STAND ALONE GRAPHIC DATA SET NAME

The Graphics source flag indicates whether or from whence comes the graphics information. If a region graphics file is the source of the graphics information, the name of the DDCARD defining the region graphics file should be entered. (For the PC version, the actual file name should be entered.)

NUMBER OF SECTORS SELECTED

Gives the total number of sectors defined by the user.

SST PROCESSING FLAGS

One flag to activate any of the possible SSTs. The flags are given the usual order: MCSST/SPLIT/DUAL/TRIPLE CPSST... NLSST...

SST COEFFICIENTS

The SST coefficients come in three varieties: MCSST, CPSST and NLSST. The algorithms are defined in terms of these coefficients elsewhere in this document.

MCSST COEFFICIENTS

CPSST COEFFICIENTS

NLSST COEFFICIENTS

CLOUD TEST DATA

Twenty cloud tests have been specified for OCNMAP. Room has been left for a total of 24, however, more could be easily added. For each a set of controls and a collection of parameters are to be specified by the user as follows:

PROCESSING FLAG, TEST TYPE FLAG, DAY/NIGHT OPTION, DAY BIT ASSOCIATION, NIGHT BIT ASSOCIATION, DATA SAMPLING OPTION, N VALUE AND CLOUD ID.

The processing flag activates the associated cloud test. The type flag is used to indicate whether it is a restoral test. Most of the tests are looking for cloud cover and are said to pass if it is found. Restoral tests on the other hand are looking for the absence of cloud and are said to pass in the event the area is judged to be clear The day/night option indicates whether the test is to be performed in daylight, darkness, or both. The day and night bit associations respectively indicate which bits in the cloud mask should be set or, in the case of restoral tests, reset in the event the test passes. The sampling option indicates how, if at all, the unit array is to be used for this test. The value of N specifies the value of N for the N-or-More option. Finally, the Cloud ID identifies the test to OCNMAP so that the order of cloud tests in the control file is immaterial.

CLOUD TEST PARAMETERS

Each of these algorithms is defined in terms of its coefficients in Section 6.13.

SECTOR DEFINITIONS

A set of records is to be provided for each of the sectors as follows:

SECTOR NAME, BLOCK SIZE, PROCESSING FLAG, SUBSAMPLE AMOUNT AND COMPRESSION FLAG

The sector name is left to the discretion of the user. The block size refers to the size of an uncompressed sector image, but is currently unused by OCNMAP. The processing flag allows processing for the individual sector to be turned on or off.The subsample amount indicates by what amount the data in the region file is to be subsampled. The user may choose to take every pixel in some portion of a region, or every other or every third -- subsampling amounts 1, 2 or 3 respectively.

STARTING AND ENDING ROW AND COLUMN

This refers to the starting and ending row and columns in the region file and should always indicate exactly which rows and columns are to be the first and last to be included in the sector image. For example if we wished to create a 512 x 512 sector image of a region that was 1024 x 1024 we might start with row and column 1 and end with row and column 1023. In this case row 1 would be the first row from the region included in the sector and row 1023 would be the last.

OCEAN REFLECTANCE COEFFICIENTS

The Ocean Reflectance Algorithm is defined in terms of its coefficients in Section 6.12.

STAND ALONE GRAPHICS DATA SET NAME FOR SECTOR, MERGE GRAPHIC OPTION, GRAPHICS OPTION

The data set name for the stand-alone graphics file is for documentation purposes only -- the DDNAME associate with the file is computed by OCNMAP dependent upon the ordinal number of the sector. The merge graphics option allows the user to specify that graphics be merged with the sector images. Graphics should only be merged with compressed files. If the source of the graphics data is a stand-alone sector graphics file, it too should be in compressed form. The graphics

option indicates which of the graphics data (fill-flag, lat/lon grids, coast lines, and land/sea tags) is to be transferred to the sector output.

FLAGS FOR DIFFERENT MAPS

Here the user indicates which of the available maps are desired for the sector being defined. Any combination of maps is allowed with the only restriction being that, over all sectors, a total of no more that 50 maps be selected.

*    The first 9 flags are broken into 3 groups of 3 flags for the MCSST,     CPSST and NLSST. Within each group the order is Split, Dual and    Triple Window.

*    The next 5 flags correspond to the 5 AVHRR channels. The first     corresponds to Channel 1, the second to Channel 2 and so on.

*    The next 5 flags correspond to the ancillary data associated with the     AVHRR in the usual order, i.e., Scan Angle, Satellite Zenith Angle,
    Solar Zenith Angle, Relative Azimuth Angle, and Scan Time.

*    Finally there is one flag each for the Cloud Mask, Ocean Reflectance and     Graphics.

3.4 JIC Look-up Table

IMGMAP provides four options for calibration (refer to Tables 2.1.1.1 and 2.2.2.2, 'Interface Control Document for the NOAA-K, L & M Environmental Image Products (SMSRC, 1990)'. Out of these, options 2 and 3 are used to produce albedos and brightness temperatures. Option 2 maps computed parameters to 11-bit data quantities and option 3 maps them to 8-bit data quantities. Option 2 is typically used with 2-byte image pixels and option 3 with 1-byte pixels. However, the accuracy offered by option 3 may not be adequate for some applications. In

order to take advantage of better accuracy offered by option 2 and, at the same time, produce pixels in 1-byte, the user may define a look-up table to reduce 11-bit quantities over a desired temperature range to corresponding 8-bits . The JIC look-up table is used in this context to reduce 11-bit quantities to 8-bits. When the user selects option 2 for calibration and further specifies pixel length as 1, the system automatically looks for a look-up table to convert 11-bit quantities in 8-bits. This table is specific to JIC applications; however, similar tables may be used in place of the JIC look-up table to handle other applications.

The JIC look-up table has 5-partitions, one for each channel. Each partition has a corresponding 8-bit value for each 11-bit value in the table. The table can be created/updated interactively using the Clist #LUKUP (refer to section 5.2.5 ).

3.5 JIC Seasonal Adjustment File

The JIC seasonal adjustment file contains seasonally adjusted latitude boundaries of JIC target areas for each month of the year. IMGMAP accesses this file to define proper latitude boundaries for both northern and southern hemispheres. The file can be updated manually as frequently as necessary.

3.6 Look-up Table for Scan Angle, Satellite Zenith Angle, and the Secant of      Satellite Zenith Angle.        

The look-up table for scan angle, satellite zenith angle, and the secant of satellite zenith angle contains angles for GHRR and LHRR/HRPT scans and is used by IMGMAP whenever such ancillary data is necessary.

3.7 Intermediate File

The intermediate file is used internally by IMGMAP both as an input and an output file. It has no utility to the user. The file stores mapped (I,J) values, selected channel and ancillary data. The Intermediate file is allocated as a temporary file in the IMGMAP execution Job Control Language (JCL) and remains only for the life of the job. At the end of the job, the file is deleted. The file grows dynamically as more space becomes necessary to hold intermediate data.

3.8 Nonlinear Look-up Table

The nonlinear look-up table contains additive corrections to be applied to brightness temperatures in order to correct them for nonlinearity in calibration. The look-up table is set up as a function of brightness temperature and blackbody temperature. Separate look-up tables are available for AVHRR channels 4 and 5, and for each satellite. IMGMAP refers to these tables when correction for nonlinearity is selected by the user. These tables need to be replaced with new ones as new satellites are added to the system.

3.9 Graphics File

The Graphics file is generated by the graphics subsystem. IMGMAP refers to the graphics file when at least one graphics plane is selected for overlay. The file contains graphics for lat-long grids, coastlines, and land-sea tags.

3.10 World Data Bank Geography Files

The graphics subsystem uses World Data Bank II Geography files as input to produce coastlines as one of the graphics. The data base is organized by continent and rank (geographical features) and has a set of 16 files. Geography Routines for World Data Bank II (Kidwell)' may be consulted for more details.

3.11 World Data Bank Rank File

The World Data Bank Rank file governs which ranks of the World Data Bank II geography files are to be included in the graphics file. There are 12 ranks under coastlines, islands and lakes, 11 ranks under rivers, 3 ranks under international boundaries, and 1 rank under provincial international boundaries. The rank file has a bit flag associated with each rank. The bit flag assumes a value of 1 or 0 to indicate whether a particular rank is selected or not. ['Geography Routines for World Data Bank II (Kidwell)' for a detailed description of each rank. Currently, the file has all ranks selected.] The rank attributes may be changed manually by editing the file.

3.12 Land-sea Tag File

The land-sea tag file is used by the graphics subsystem as input to optionally produce land-sea tags as one of the graphics. The data base has land-sea tags at 1/16th degree resolution to determine if a particular lat-long is land or sea. The flag assumes a value of 1to indicate land and a value of 0 to indicate sea.

3.13 JCL Card Input

The conventional JCL card input is only used in the graphics subsystem to define necessary input parameters to generate graphic overlays. This input can be defined interactively using the Clist #IMGMAP.

3.14 Orbit Name File

The orbit name file is used by the JIC Rotational Data Base Subsystem as an input. This file contains the name of the level 1B data set most recently made available to the IMGMAP system from GAC/LAC/HRPT data. Separate orbit name

files are available for each data type.

3.15 Status File

The status file is used by the JIC rotational data base subsystem both as input and output. The file contains housekeeping information and status information about the eight most recent orbits that have been processed by the IMGMAP system. The user can browse this file to display status information on the terminal. Separate control files are available for each data type. The JIC user interacts with this file to store information about the orbits that have already been accessed.

3.16 GAC/LAC/HRPT Data File

The data file is used by the JIC rotational data base subsystem as input. The file contains the Data Set Names (DSN) of JIC image files in the rotating data base. Separate data files are available for each data type. The GAC data file has 32 entries, and the LAC and HRPT data files have 8 entries apiece.

3.17 Hold File

The hold file is used by the JIC rotational data base subsystem as input. Hold files are copies of JIC image files produced by the IMGMAP system on the DPSS computers. Hold files reside on the NAS computers. The Rotational Data Base Subsystem uploads hold files to appropriate locations on the data base. Separate hold files are available for each data type.

3.18 Field Files

The SST field files contain field temperatures at 14 km resolution. These files are used by the MCSST subsystem to detect gross clouds through the dynamic gross cloud test. There are currently eight field files across the coastal United States. These are the Gulf of Mexico, Washington/Oregon, California coast, North Atlantic, South Atlantic, Gulf of Alaska, Bering and Chukchi sea, and Gulf of California.

3.19 Weekly Composite Files

The weekly composite files are used by the VI subsystem both as input and output. There are two files, one for each hemisphere. Each file contains a composite of the daytime hemisphere AVHRR Master Map files over the number of days specified in the VI subsystem control file. Once these days have elapsed, the VI subsystem uses the weekly composite files to produce the VI product.

3.20 Sector Graphics Files

OCNMAP can use graphics output from one of its previous runs to reduce I/O and to simplify processing if the same sector is going to be processed more than once. During preliminary processing, a graphics file for the entire region is created by the Image Products Graphics Subsystem and is then used by OCNMAP to create separate, compressed graphics files for each sector. Subsequent runs of OCNMAP sector image requiring merged graphics.

3.21 The visible Cloud Threshold Table (VCTT)

The VCTT is used by the Dynamic Reflected IR Cloud Threshold Test (DRIT) which is read into an array by the subroutine CLDSET in the initialization module. The data set consists of bi-directional reflectance values derived from radiance measurements form one of the visible channels of AVHRR and channel 20 to the HIRS-2 instrument for a cloud-free atmosphere over ocean. They are stored in the

data set as functions of the solar zenith angle, the satellite zenith angle and relative azimuth angle.

This section provides a description of output files produced by the Image Product System. A detailed description of these files can be found in the Interface Control Document for the NOAA-K, L & M Environmental Image Products.

4.1 Image Files

The Image Product System produces three types of image files: the IMGMAP output file, the VI image file, and sector images from the CoastWatch subsystem.

The IMGMAP output file contains images for selected channels and ancillaries for one of the three major products, the JIC product, master maps, or ocean products. The JIC rotational data base subsystem uploads JIC image files to a rotational data base; the VI subsystem uses master maps to produce the VI image file; and the CoastWatch subsystem uses the Ocean Product image file to produce sector imgages of channel and ancillary data, SSTs, Ocean Reflectance and cloud masks. The JIC-GAC image files and master maps are produced in polar projection at 1/64th grid into 1024X1024 images, the LAC/HRPT image files at 1/128th grid into 2048X2048 images. For ocean products, resolution, map size, and projection are not pre-fixed.

Currently, the JIC operational files contain channels 1 and 4 from daytime overpass and channel 4 from nighttime overpass. No ancillary information is produced for JIC product. The master map operational files contain all channels and ancillary information (except satellite zenith angle) from daytime overpass. No visible channels and solar zenith angle are produced from nighttime overpass. Data processed from all orbits of GHRR over a period of 24-hours are accumulated and stored to a set of 4 primary files, each representing either daytime or nighttime for Northern or Southern hemisphere. At the end of the day, these files are copied to a set of 4 daily master map files. The daily daytime files are further routed to the VI subsystem for a weekly composite, and a VI product

at the end of the composite period.

The JIC rotational data base contains JIC images from the eight most recent orbits processed by the IMGMAP system.

There are two VI files, one for each hemisphere. Each file contains an index for the entire hemisphere. The resolution of the VI is the same as that of the master map.

The CoastWatch subsystem produces image files that are similar to the output file of IMGMAP except that they may be compressed. Except for uncompressed sector graphics files, they have identically formatted headers (however, some of the spare bytes have been put to use). The channel and ancillary images, the SSTs and Ocean Reflectance are analogous to the images created by IMGMAP. The CoastWatch subsystem, however, never puts more that one image into an output data set.

4.2 Cloud Mask File

CoastWatch can produce cloud masks for any sector. The output file has a header that is formatted exactly like any image file header. The cloud mask data for each pixel is stored in one byte, each bit of which corresponds to one or more cloud tests. The particular correspondence in effect is determined by the user via the control file.

4.3 The Transfer File

The transfer file is created by OCNMAP to inform subsequent processors regarding the quality of the various sectors that were produced so that decisions can be made as to whether the file transfer to the end users should take place. The transfer file indicates the number of active sectors that were defined in the

control file and for each sector image produced, the percentage of non-zero pixels.

4.4 Interface Controls for the Image Product System

The CoastWatch subsystem uses and produces a great many files. The actual names of the data sets involved are a matter for the operations staff and may vary with time. The CoastWatch program, OCNMAP, is concerned mainly with the DDNAME associated, in the JCL, with any particular data set. The DDNAMEs used are provided in Table 4.4.

Table 4.3 Interface Controls of the Image Product System
_____________________________________________________________
System        File            I/O     DSN
_____________________________________________________________

IMGMAP    Level 1B orbit data set
        (AVHRR and AMSU)    I    -                         System control file        I     NSS.PSASAIMP.IMAGV.DATA
            JIC-GHRR                     (JICGCNTL)
            JIC-LHRR                     (JICLCNTL)
            JIC-HRPT                     (JICLCNTL)
            MASTER MAPS                 (MASGCNTL)
             OCEAN PRODUCTS                 TBD    
        JIC look-up table        I     NSS.PSASAIMP.IMAGV.JICLUT
        JIC seasonal adj. file    I     NSS.PSASAIMP.IMAGV.DATA(JICSAF)
        Look-up table for scan
        angle, satellite zenith
        angle, secant of satellite
        zenith angle            I     NSS.PSANAVMP.LUKUP.ANGLES
        Intermediate file         I/O    -
        Nonlinear look-up table    I     NSS.PSATAVST.OCEAN.DATA
            NOAA-10 CHANNEL 4                (N10LKUP4)
            NOAA-10 CHANNEL 5                (N10LKUP5)                     NOAA-11 CHANNEL 4                (N11LKUP4)
            NOAA-11 CHANNEL 5                (N11LKUP5)
        Graphics file            I     TBD
        JIC image files        O
             GHRR QUADRANT FILES (1-4) :
            Northern Hemisphere-Daytime          NSS.PSANAVMP.HOLD.GJICQ1
            Southern Hemisphere-Daytime        NSS.PSANAVMP.HOLD.GJICQ2
            Northern Hemisphere-Nighttime        NSS.PSANAVMP.HOLD.GJICQ3
            Southern Hemisphere-Nighttime    NSS.PSANAVMP.HOLD.GJICQ4
            LHRR IMAGE FILE            NSS.PSANAVMP.HOLD.LJIC
            HRPT IMAGE FILE            NSS.PSANAVMP.HOLD.HJIC

VI         VI subsystem control file    I     NSS.PSASAIMP.IMAGV.DATA
                                    (VEGCNTL)                  Master maps files        I    
             Northern Hemisphere-Daytime          NSS.PSANAVMP.COMPST.MASMAP1
            Southern Hemisphere-Daytime        NSS.PSANAVMP.COMPST.MASMAP2
        Weekly composite files    I/O
             Northern Hemisphere              NSS.PSANAVMP.COMPST.WEEKLY1
            Southern Hemisphere            NSS.PSANAVMP.COMPST.WEEKLY2

         VI FILES            O
             Northern Hemisphere              NSS.PSANAVMP.COMPST.VEGINDX1
            Southern Hemisphere            NSS.PSANAVMP.COMPST.VEGINDX2
GRAPHICS    JCL card input        I    -
        WDB rank file        I     NSS.PSASAIMP.IMAGV.DATA
                                    (WDBRNK)                  Land-sea tag file        I     NSS.PSATAVST.LSTAGS.TEMPHIGH
        WDB II Geography files    I     WDB II Operational files
        Graphics file            O     TBD
JIC         Orbit name file        I     NSS.PSANAVMP.ONAME
Rotational         GHRR                    .GJIC
DB             LHRR                    .LJIC
            HRPT                    .HJIC    
        Status file            I/O     COM.PSANAVMP.RSTATUS
            GHRR                    .GJIC
            LHRR                    .LJIC
            HRPT                    .HJIC    

_____________________________________________________________
System        File            I/O     DSN
_____________________________________________________________

        Data file            I     NSS.PSASAIMP.IMAGV.DATA
            GHRR                    (ROTGAC)
            LHRR                    (ROTLAC)
            HRPT                    (ROTHRP)    
        Hold files            I     Same as above
        Rot. DB files            O
             GHRR files                  COM.PSANAVMP.ORBITm.GJICQn
            (32 files)                    (m=1 to 8; n=1 to 4)
            LHRR files                  COM.PSANAVMPORBITm.LJIC
            (4 files)                    (m=1 to 4)                       HRPT files                  COM.PSANAVMPORBITm.LJIC
            (4 files)                    (m=1 to 4)
______________________________________________________________________________________

Description     I/O    DDNAME

Debug file    I    DEBUG
Options file     I    OPTIONS
Region image file (from IMGMAP)     I    REGDSN
Region graphics file (from graphics      I    GRAPHS
subsystem) Field file, 14km resolution
I FLD14 Field file, 3.5km resolution
I FLD3P5 Field file, 50km resolution
I FLD50 Control file, morning satellite
I AMCNTL Control file, afternoon satellite
I PMCNTL Visable cloud threshold table
I VISTHD Transfer file I XFERFI

Channel y image file for ith sector    O    SiCy
i = 01 or 02 or 03 ... or 10, etc. 1 <= y <= 5
Ancillary y image file for ith     O    SiAy
sector i = 01 or 02 or 03 ... or 10, etc. 1 <= y <= 5
MCSST image for for ith sector     O    SiMCj
i = 01 or 02 or 03 ... or 10, etc. j = 1 --> split window
= 2 --> dual window = 3 --> triple window
CPSST image for for ith sector     O    SiCPj
i = 01 or 02 or 03 ... or 10, etc. j = 1 --> split window
= 2 --> dual window = 3 --> triple window
NLSST image for for ith sector     O    SiNLj
i = 01 or 02 or 03 ... or 10, etc. j = 1 --> split window
= 2 --> dual window = 3 --> triple window
Ocean Reflectance for ith sector     O    SiOR
i = 01 or 02 or 03 ... or 10, etc. Graphics for ith sector     O    SiGPH
i = 01 or 02 or 03 ... or 10, etc. Cloud Mask for ith sector     O    SiMSK
i = 01 or 02 or 03 ... or 10, etc.