Key word	Explanation
TERRA PROGRAM
ASTER Project	ASTER is a joint satellite project between NASA and METI (Japan's Ministry of Economy, Trade and Industry).MITI is responsible for development of the ASTER sensors and operation of the ASTER Ground Data System. The ASTER Project in Japan manages sensor command and control, standard data processing, higher level data processing and analysis, and the archiving and distribution of data.
EOS Program	A program of the Earth Observing System from space EOS is an international cooperative enterprise which contributes to solving the earth's environmental problems.
ASTER	Advanced Spaceborne Thermal Emission and Reflection Radiometer. ASTER is Japan's remote sensing instrument mounted on the TERRA satellite.
ASTER GDS	ASTER Ground Data System. GDS is ASTER's ground system which commands and controls the ASTER instruments, and processes, analyzes, archives and distributes data transmitted from the ASTER instruments.ASTER GDS consists of three primary components: 1. AOS (ASTER Operation Segment)which operates the ASTER instrument. 2. SDPS (Science Data Processing Segment)which processes, analyzes, archives, and distributes scientific data, and manages the user interface. 3. CSMS (Communication and System Management Segment)which connects and controls the above operations.
Data Products	ASTER collects an average of 8 minutes of data per orbit, and transmits about 780 scenes of observation data to the ground each day. According to the EOS program policy, Japan provides the sensors, and is responsible for completing Level 1 data processing (with geometric and radiometric correction coefficients) within 24 hours. Japan has developed the high-speed mass-data processing system at the ASTER GDS. The Level 1 data processing system processes the scenes requested by users. EOS policy also states that Japan's ASTER GDS and the US's EOSDIS will each produce various standard products from the Level 1 data. Japan and the US will individually process and analyze data for semi-standard products and any special products.
EOSDIS	EOS Data Information System. EOSDIS is the system that commands and controls the spacecraft and sensors, and receives, processes, archives and distributes data from EOS sensors.
TERRA	The first of the earth-observing satellites for the EOS (Earth Observing System) program. TERRA was launched in December 1999 in a sun synchronous orbit, crossing the equator from north to south in the morning (AM), Therefore AM-1 was the former name for TERRA. NASA provides the spacecraft and three instruments: CERES, MODIS and MISR. Japan provides ASTER. Canada provides MOPITT. TERRA was launched from the US Air Force Western Test Range. Its mission period is 6 years.
ERSDAC	Earth Remote Sensing Data Analysis Center. ERSDAC is one of the organizations responsible for the ASTER Project. It is a non-profit organization under supervision of METI.
NASA	National Aeronautics and Space Administration. NASA is one of the organizations responsible for the EOS program.
DATA PRODUCTS
Standard Product	Products are offered to users based on submission of a DPR (Data Product Request). The science team guarantees its fixed accuracy. Listed below are the standard products created in Japan. 1. ASTER Level 1 product(including radiometric and geometric correction) 2. Relative Emissivity (decorrelation stretch)(2A02) 3. Relative Reflectivity (decorrelation stretch)(2A03) 4. Surface Radiance (2B01) 5. Surface Temperature (2B03) 6. Surface Emissivity (2B04)7. Surface Reflectivity (2B05)
Semi-Standard Products	Semi-standard products are produced in Japan, in accordance with the production policy of the project's working groups. DPRs from users are also accepted, however, they are not guaranteed. Listed below are the semi-standard products generated in Japan. 1. Orthographic Image (3A01) 2. Relative Digital Elevation Model (DEM)(4A01)
Special Products	In principle, DPRs from users will not be accepted. However, users can consult with the science team members who produce or are responsible for the special products that the user wishes to obtain. Accuracy will not necessarily be guaranteed. Once special products are produced, distribution to the general public is subject to the approval of the science team members who produced the products, and the science team leader.
Data Specification(SPEC)	Documents that describe data structures and formats
HDF	Hierarchical Data Format ASTER products use HDF-EOS. HDF was developed by the National Center for Supercomputing Applications (NCSA) established in the Illinois State University in the US. HDF can manage science data in various formats.
DAR	A DAR (Data Acquisition Request) is a request for acquiring data with the ASTER instrument. There is an established procedure for a user to submit a DAR, which includes specifying the observation condition for the requested geographic region and the time. This is the normal method used to acquire observation data.
DPR	A DPR (Data Product Request) is a request for a particular data product. The user confirms whether there is his/her requested product by using the product search service. In some cases, the DPR requires parameters input on the product order screen, e.g., format, distribution media, no. of data sets, etc.
EDS	Expedited Data Set.The EDS is the format in which data is transmitted to the ASTER GDS via network circuits. The EDS has a priority to be processed to products. Science users can designate and request EDS in their DAR or TOO.
Browse Image	Displays data (browse) of limited size and resolution to distinguish data type and quality easily.
Metadata	Displays the name of the person who created the data algorithm, the content of the data set, the format, and how to use the data set.
Coverage Image	Displays the position of the data on a map.
Directory Search Parameter	The parameters used to specify a group of processed data that meets the search conditions.
Inventory Search Parameter	This specifies the data unit that meets the search conditions.
GDS SEGMENTS
CSMS	Communication and System Management Segment (CSMS). CSMS consists of GSMS and ADN (explained below).
GSMS	Ground System Management Subsystem. GSMS controls, supervises and adjusts the GDS system, and communicates with the SMC.
ADN	ASTER Data Network. ADN supports the basic internal and external communication and networks of the ASTER GDS.
AOS	ASTER Operation Segment. AOS consists of the ICC and IST (explained below).
ICC	Instrument Control Center. The ICC establishes unit operation programs, by supervising and analyzing conditions of units. The ICC has detailed internal subsystems consisting of the Instrument Control and Operation Subsystem-1 (ICOS1) and the Instrument Analysis Support Subsystem (IASS).
IST	Instrument Support Terminal. The IST supports the final decision for operation plans made by the SSSG.
SDPS	Science Data Processing Segment. The SDPS consists of the IMS, DADS, PGS, SISS and DRS (explained below).
IMS	Information Management System. The IMS offers a centralized access to users, while managing user registration information, receiving DARs and DPRs, and searching for products.
DADS	Data Archive and Distribution System. The DADS archives and distributes products and other valid data.
PGS	Product Generation System. The PGS creates products and checks their quality. The PGS subsystems include the Data Processing Subsystem (DPS) and the Data Analysis Subsystem (DAS).
SISS	Software Implementation Support System. The SISS allows science users to develop algorithms and to generate special products.
REMOTE SENSING
Remote Sensing	Earth observation from space by man-made satellites.
Spatial Resolution	Spatial resolution is a scope on the land corresponding to one pixel of a detector. The higher the spatial resolutions, the smaller the object that can be detected; however, the observation width becomes narrower and data processing takes more time.
Geometric Resolution	The shortest distance between two reflecting point-objects that can be separated and discerned on the geometric resolution image.
Polar Orbit	Orbits where orbit inclination is near or equal to 90 degrees. Satellites located in a polar orbit can view the entire globe. Many earth observing satellites, including LANDSAT, SPOT, ERS-1 and JERS-1, use a polar orbit.
Orbit Control	Controlling satellites to keep flying on the designated orbit. When a satellite flies in low earth orbit (LEO), it gradually descends due to air drag. It is necessary to push the satellite back to the original orbit by activating station-keeping thrusters. Geostationary satellites do not descend due to air drag, however, they do de-orbit from their designated stationary position because the gravitational field of the earth is not uniform and because the gravitational pull of the sun and the moon alters their orbit. In a similar way, geostationary satellites are pushed back to their original position by activating station-keeping thrusters.
Attitude Control	The process of controlling satellites to maintain their intended attitude. Satellite attitude is calculated by either earth sensors, sun sensors or star sensors. If a satellite is off its designated attitude, it is pushed back to the original attitude by activating attitude-control thrusters. Attitude control is an important function that directly affects photographic performance when observing the Earth.
Controlling Direction of Observation Instrument	The direction of observation instruments can be changed by sending commands to the instruments.
Thermal Control	The process of controlling the temperature of all onboard equipment, such as observation instruments, and ensuring that it remains within the thermal limit. The system works with passive control using surface reflectance, heat pipes, and radiators. Active control utilizes coolers and heaters.Thermal control maximizes the performance and the long life of the observation instruments.
Power Control	Power Control generates the necessary power for onboard equipment (including observation instruments), transforms the power to the designated voltage, then transmits it. Generally, power generated by solar cells is used, supplemented by onboard batteries for when the spacecraft is in the earth's shadow. To protect the rest of the unit during a short circuit, a protective procedure is activated which isolates the troubled circuit from the other circuits. This protective procedure is an important function that ensures photographic production during Earth observation.
Command Control	Commands for operations to onboard equipment, such as observation instruments, are given from Command Control. The process uses both stored and real-time commands. Stored commands are temporarily stored in the satellite control computer and executed at the programmed time. Real-time commands are executed as soon as received.
Telemetry Control	Controls the transmission of data for the operational status of onboard equipment, including observation instruments, temperature data at various spots on the satellite, and image data, from the satellite to the ground.
Communication Control	Controls commands for communication between the ground and the satellite. It also controls the transmission of telemetry.
Toxic Waste	An earth environmental problem that extends across borders.
USER
Unregistered User	Unregistered users can read basic information regarding the ASTER GDS and TERRA by viewing general references. Products search services and guidance search services are also offered to unregistered users. A part of data acquisition services, such as checking the status of data acquisition, are also available.
Registered User	Users registered with the ASTER GDS. These include the General User the Science User the Science Computing Facility User (explained below).
General User	General users can receive distribution services for products archived at ASTER GDS.
Science User	Science users can submit requests for observation data acquisition, in addition to services offered to general users. Science users can access the maximum resources allotted in order to acquire observation data.
Science Computing Facility User	Science computing facility users can use ASTER GDS science computing facilities. They can perform image processing and develop algorithms at the computing facility or remotely.

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