What Is TeraScan?

TeraScan is an integrated system of hardware and software designed for automated reception of data from meteorological/environmental satellites and for processing the data into images and data overlays.  The data files for these images and overlays are of a special format called TeraScan Data Format (TDF) and can be displayed with the TeraScan viewer called TeraVision.  TDF files (also referred to as datasets) can also be converted to picture products in various graphics formats.  Both TDF products and picture products can be automatically distributed to any number of local or off-site destinations across the network.  

The Satellite Data that TeraScan Can Receive and Process

TeraScan is a versatile system that can be configured for the reception and processing of many different types of data from many different types of satellites, including the X-band-transmitting polar-orbiting satellites.  TeraScan can also generate products that are a mixture of data from different satellites. The types of data that TeraScan can receive and process are listed below.

X-Band Data from Polar-Orbiting Satellites
	MODIS direct broadcast data from the Terra and Aqua EOS satellites (optional  module)
	OCM data from Oceansat-1 (optional module).

	SAR data (capture only) from Radarsat-1 and ERS-2.
L-/S-Band Data from Polar-Orbiting Satellites
	AVHRR, TOVS, ATOVS, and DCS data from the NOAA TIROS-N satellites.
	SeaWiFS data from OrbView-2 (optional module).
	OLS and Special Sensor data (SSM/I, SSM/T1, and SSM/T2) from the DMSP satellites.
	MVISR data from FY-1C and FY-1D (optional module)

L-Band Data from Geostationary Satellites
	Imager and Sounder data from GOES.
	HRI data from Meteosat (optional module).
	Imager data from GMS and FY-2.
	WEFAX data from GOES, Meteosat, and GMS.

Other Data Sources
	MODIS EOS HDF from IMAPP
	NESDIS
	Archived data from SIO, Dundee, and ESA.

For information about environmental (weather) satellites, and details about the specific satellite data that TeraScan can capture and process, click here.

TeraScan Hardware

SeaSpace produces several different configurations of its TeraScan system, each geared to a particular satellite telemetry or combination of telemetries.  The hardware configuration of your particular system is documented in the drawings and parts lists provided in the TeraScan System As-Built Specifications (hardcopy documentation) that was delivered with your system. Please refer to that document for the specific configuration of your system.

For purposes of an overview discussion, the following is a general listing of the hardware for a TeraScan receiving and processing system.  To see a diagram of signal flow through the system, click here.

• Antenna for satellite signal interception.  For high-resolution data reception from geostationary satellites, a large (3.8m-diameter) fixed-direction antenna is used.  For high-resolution data reception from polar-orbiting satellites, a tracking antenna is used, its size depending on the telemetry to be received.  Tracking antennas are enclosed in a radome for protection from the weather.
• Receiver for tuning to the correct satellite signal frequency and separating the sensor data (the baseband) from the RF carrier (the latter function is known as demodulation).
• Bit synchronizer for regenerating the bit stream against noise, converting the digital data format to NRZ-L, if necessary, and extracting the clock, a timing pulse added to the signal on the satellite to enable synchronization of the reception system with the satellite transmitter.
• Frame synchronizer for dividing the continuous bit stream into meaningful data blocks called frames.
• Computer workstation with TeraScan software for scheduling and controlling data reception and for processing data into products, and displaying and distributing data and data products; can include tape drives or other storage devices for archiving data.
• Global Positioning System (GPS) antenna to supply position and time to the system.
• Uninterruptible power supply (UPS) to protect the system from power surges and to keep the system up and running in the event of a power outage.
• Interface to shipboard navigation, for shipboard systems.

SeaSpace supports TeraScan on two platforms. These are:

• Sun Solaris
• Redhat Linux

The TeraScan Software

The TeraScan software is based on the UNIX operating system and consists of:

• A special format for data files, called TeraScan Data Format (TDF).
• More than 500 command-line functions for the reception and processing of satellite data.
• A set of daemons that run continuously to manage the automated operations of TeraScan.
• A set of reference files and databases.
• A set of graphical user interfaces (GUIs) that enable the TeraScan operator to exercise many of TeraScan's capabilities via the point-and-click actions of the computer mouse.

Click here for an overview of the TeraScan file system.

TeraScan Data Format

TeraScan ingests (imports) data into its own TeraScan data format (TDF). TDF is an extremely versatile file format capable of assimilating a wide variety of data types, shapes, and sizes. For example, a single dataset could contain satellite image data, random in-situ data, and 3-D model data.

TDF is self-describing; both dataset definitions and data are typically stored together in the same file. A TDF dataset can reference variables from several files using links. Links allow rapid import of non-TDF data and support lightweight dataset subsets and assemblies.

TeraScan includes a C-language programming interface to TDF. This interface accesses TDF components as named objects, hiding all unnecessary details about physical data layout.

TDF is very similar to other self-describing dataset standards such as HDF and netCDF. TDF supports conversion to and from these and other formats.

The TeraScan Reception and Processing Functions

TeraScan has more than 500 command-line functions for reception and processing of satellite data. Many of these functions are incorporated into TeraScan GUIs or are accessed indirectly by them.

All GUI-accessible functions can also be run from the command line by users who have a need or preference for command-line input. Some users may also have need for additional capabilities found in functions available only from the command line.

TeraScan has functions for:

• Ingesting raw satellite telemetry or industry-standard archive format data (e.g., NESDIS LAC and GOES and ESA SHARP).
• Importing structured ASCII or binary data.
• Sensor-specific processing; e.g., generating geophysical parameters from sensors aboard a given satellite (e.g., SST or NDVI from AVHRR, temperature soundings from NOAA HIRS and MSU).
• Automatic navigation to correct for errors due to satellite clock drift and satellite attitude and orbit changes.
• Defining area-of-interest maps using various projections and remapping and interpolating data to those maps.
• Managing datasets, retrieving and setting dataset and variable attributes, such as variable units.
• Element-by-element math, featuring multiple expressions, trigonometric and transcendental functions, access to satellite-pixel-sun angles, land masks, and neighborhood statistics.
• Statistical and convolution filtering.
• Sampling at points, along lines, along polylines, within or outside boxes, and within or outside polygons.
• Combining data via time compositing, lamination, concatenation, and assembly.
• Simple statistics, multi-variable statistics, spectral analysis, and eof analysis.
• Generating geopolitical overlays, including coastlines, latitude/longitude grids, and topography/bathymetry contours.
• Generating overlays from data in the form of contours, station plots, wind vectors, and stream plots.
• Generating annotation overlays, including color wedges and text legends.
• Generating pictures consisting of colored/enhanced imagery with embedded overlays, and for exporting the pictures in PostScript, JPEG, GIF, TIFF, MARTA-PCX, METOC-TIFF (JIF), GeoTIFF, Sun raster, PPM, and PNG.
• Exporting non-picture data in plain ASCII, in binary, or in HDF or netCDF.
• Common scripting, e.g., date and time arithmetic, real arithmetic, finding nearest files in terms of date and time.

The TeraScan Daemons

The primary TeraScan daemons that orchestrate the reception and processing of satellite data are:

tsched—Manages all the processes involved in the automatic reception of direct-broadcast satellite data: (1) updates the data reception schedule on a daily basis; (2) checks the reception schedule for upcoming satellite passes; and (3) at the appropriate time, initiates satellite data reception and subsequent archiving and post-capture processing.

gvarsched - Manages continuous GVAR capture and processing.

terapgsd - Distributes data products produced by TeraPGS.

waitd - Monitors arrival of data in specified directories and then initiates processing.

sunclock - Gets the current time from the GPS and updates the system time if needed. (See xntpd for X-band systems.)

xntpd - Synchronizes the system time with a network time server.  TeraScan X-band systems get the time from the GPS, using the daemon's ability to link to a device on a serial port.  (public domain software)

whereami - Gets the location from the GPS and updates the system location if needed (if the system is on a moving ship, for example).

ups_monitor - Monitors the UPS, logs changes in the status of the system's power source, responds with system shut-down and start-up if warranted by the power level of the UPS.

The TeraScan Reference Data

The TeraScan software includes numerous reference files and databases which supply the information that TeraScan needs to run all of its operations. These include:

• Orbital elements, required for satellite tracking
• Satellite-definition files
• Sensor-definition files, including calibration data
• Two geopolitical boundary databases (the Digital Chart of the World and the World Database II) and a topography/bathymetry database (ETOP05)
• Climatology databases, required for processing NOAA TOVS data, DMSP Special Sensor data, and SeaWiFS data
• List of ARGOS DCS platforms with their location and calibration data
• Color palette and enhancement look-up tables
• SeaWIFS color-processing table

TeraScan Modules

The TeraScan software is packaged into eight separately licensed modules, described below. Modules 2 through 8 are optional modules, each of which adds a specialized functionality to the Baseline Module. The optional modules work in conjunction with the Baseline Module, and installation of the Baseline Module must precede installation of any of the optional modules.

The Baseline Module provides the capability for processing any of the following telemetries: HRPT from NOAA TIROS; GVAR from GOES; SVISSR from GMS; RTD from DMSP satellites; WEFAX from GOES, GMS, and Meteosat; and archived data from SIO, Dundee, and ESA. This module also includes the TDF data and image visualization program (TeraVision), the automatic product-generation and distribution system (TeraPGS), and the Software Development Kit.

2—Data Capture Module

The Data Capture Module provides the capability for automatic reception of direct-broadcast satellite data, and is applicable to any of the telemetries listed under the Baseline Module as well as the telemetries listed under the other optional modules listed below, plus SAR data from Radarsat-1 and ERS-2 satellites.

The Data Capture Module implements the pass-capture scheduler daemon (tsched) and the scheduling capabilities of the TeraCapCon GUI.  Although TeraCapCon is included in the Baseline Module where it can be used for viewing pass coverage for polar-orbiting satellites, the Data Capture license is required to enable TeraCapCon’s scheduling capability.

3—SeaWiFS Module

The SeaWiFS Package provides the capability for decryption and for color processingof SeaWiFS data from OrbView-2. The TeraScan SeaWiFS processing module is based on NASA’s SEADAS module and is updated regularly to match the latest SEADAS functionality.

The MODIS Module provides the capability for color processing of MODIS data from the EOS satellites (Terra-1 and Aqua-1).

The OCM Module provides the capability for processing OCM data from the Oceansat-1 satellite.

6—FY-1C/D Module

The FY-1C/D Module provides the software for reception and processing of MVISR data from the FY-1C and FY-1D satellites.

7—MKU Interface (MKUI) Module

The MKUI Module provides the software and interfacing hardware for decryption and ingestion of PDUS telemetry from the Meteosat satellites.

This module includes:

• The software for PDUS decryption.
• The MKUI (Meteosat Key Unit Interface) and connecting cables. The MKUI is a case with power supply that houses the MKU and provides the interface between the TeraScan system and the MKU, the decryption device for PDUS telemetry.  Note: The MKU is available through EUMETSAT, not SeaSpace.
• The MKUI Installation and Operations Manual.

8—RSD44A Module

The RSD44A Module provides the software and hardware for remotely controlling key-address switching on the KG44A decryption device.  Note: The KG44A is a U.S. Government-controlled device and is not available from SeaSpace.

This module includes:

• The software for controlling remote switching.
• The RSD44A (Remote Switching Device for the KG44A) and connecting cables. The RSD44A is a unit that interfaces the TeraScan system with the KG44A to enable TeraScan to automatically set key addresses on the KG44A between passes of DMSP satellites.
• The RSD44A Installation and Operations Manual.

Last Update: $Date: 2002/09/10 20:28:33 $