Global navigation satellite system Receiver for Atmospheric Sounding Data Assessment

Federal Geographic Data Committee (FGDC) Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Reference_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: Unknown

Publication_Date: Unknown

Title: Global navigation satellite system Receiver for Atmospheric Sounding Data Assessment

Description:

Abstract:

The entire GRAS (Global Navigation Satellite System Receiver for Atmospheric Sounding) instrument weighs about 30 kg and comprises three antenna-receivers positioned separately on MetOp. One of the antennae, the GVA antenna, points in the velocity direction of the satellite, another, the GAVA antenna points in the anti-velocity direction, and the smaller GZA antenna points zenith. The GVA and GAVA antennae are both rectangle-shaped, covered by a single layer of insulation. They carry 18 elements, each targeted to look tangentially through the Earth's atmosphere to receive radio signals from the constellation of navigation satellites. The GVA observes rising occultations and the GAVA observes setting ones. Together, they can connect to up to 12 satellites at any one time (two by the GVA chain, two by the GAVA chain and eight by the GZA for navigation. Therefore, four occultation measurements can be made in parallel, two on each side). Because of the positioning of the GAVA antenna on the MetOp satellite, it is deployed after launch to prevent its field of view being obscured by the ASCAT instrument. The smaller GZA antenna is used to determine the precise position of MetOp by continuously tracking other GPS satellites. Source: ESA - AOES Medialab GRAS is a dual-frequency GPS high-performance instrument with semi-codeless operating capabilities. The codeless capability is mandatory in order to mitigate the anti-spoofing (encryption of the precise code), which prevents civilian users from benefiting from the P-code on the L2 frequency. The instrument provides carrier, code phase and signal amplitude measurements. The second GPS frequency (L2) is used for ionospheric correction of the signals. GRAS features twelve dual-frequency channels, four for rising and setting occultations and eight for navigation. The navigation channels provide the position of the Metop satellite in real-time. Carrier and code phase data are also provided for the processing of the precise orbit determination of Metop (position and velocity) necessary for the ground processing of the occultation data and in particular the effects on the Doppler caused by the GPS signal passing through the atmosphere and the troposphere. A ground network of GPS receiver tracking stations is used for determining the actual orbits of the GPS satellites. This ground network can operate in differential mode in order to cancel clock error variations. - The GRAS instrument consists of the following elements: Source: eoportal

Purpose:

Not Available

Supplemental_Information:

Not Available

Status:

Progress: Complete

Maintenance_and_Update_Frequency: As needed

Spatial_Domain:

Description_of_Geographic_Extent:

Bounding_Coordinates:

West_Bounding_Coordinate: -180.0

East_Bounding_Coordinate: 180.0

North_Bounding_Coordinate: 90.0

South_Bounding_Coordinate: -90.0

Keywords:

Theme:

Theme_Keyword_Thesaurus: GCMD SCIENCE PARAMETERS

Theme_Keyword_Thesaurus: GCMD PLATFORM

Theme_Keyword_Thesaurus: GCMD INSTRUMENT

Theme_Keyword_Thesaurus: ISO TOPIC CATEGORY

Theme_Keyword: EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC TEMPERATURE

Theme_Keyword: EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC WATER VAPOR > HUMIDITY

Theme_Keyword: METOP > METEOROLOGICAL OPERATIONAL SATELITE

Theme_Keyword: METOP-A > METEOROLOGICAL OPERATIONAL SATELLITE - A

Theme_Keyword: GRAS > GLOBAL NAVIGATION SATELLITE SYSTEM RECEIVER FOR ATMOSPHERIC SOUNDING

Theme_Keyword: CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

Theme_Keyword: GEOSCIENTIFIC INFORMATION

Access_Constraints: Access to Data during Commissioning Users should note that until the entry into operational service, the priority is given to commissioning activities. The early access to EPS data is therefore provided on a best effort basis, without full service commitment. This implies that schedule changes might occur at any time and that dissemination might be interrupted due to other commissioning activities. Data delivered during commissioning are not considered to be validated data. The data disseminated via EUMETCast will be access controlled. Source : EUMETSAT

Use_Constraints:

Disclaimer - Status of instrument and processing quality (August 2007) Data quality assessment is ongoing, so while the data are acceptable for this stage of commissioning no guarantee of quality will yet be given. Please note: Only the so-called key fields have been tested for acceptable values. These key fields are found in the MDR-1B (see the Products Guide) of the GRAS product. Source: EUMETSAT

Browse_Graphic:

Browse_Graphic_File_Name: http://esamultimedia.esa.int/images/metop/gras_occultation_principle.jpg

Browse_Graphic_File_Description:

Credits: ESA - AOES Medialab

Browse_Graphic_File_Type:

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

Not Available

Logical_Consistency_Report:

Not Available

Completeness_Report:

Not Available

Lineage:

Process_Step:

Process_Description:

Not Available

Process_Date: Unknown

Spatial_Reference_Information:

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: EUMETSAT > European Meteorological Satellite Organisation

Contact_Person: EUMETSAT USER SERVICE

Contact_Position: DATA CENTER CONTACT

Contact_Address:

Address_Type: Mailing and Physical Address

Address: Am Kavalleriesand 31

City: Darmstadt

State_or_Province: Hessen

Postal_Code: D-64295

Country: Germany

Contact_Voice_Telephone: +49 6151 807345

Contact_Facsimile_Telephone: +49 6151 807538

Resource_Description: GRAS_ESA_01

Distribution_Liability:

Not Available

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: Not Available

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address:

Network_Resource_Name:

http://www.eumetsat.de/

Access_Instructions:

DATA CENTER URL

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address:

Network_Resource_Name:

http://www.eumetsat.int/Home/Main/Satellites/Groun...

Access_Instructions:

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address:

Network_Resource_Name:

http://garf.grassaf.org/

Access_Instructions:

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address:

Network_Resource_Name:

http://oiswww.eumetsat.org/WEBOPS/eps-pg/GRAS/GRAS...

Access_Instructions:

Fees: Not Available

Metadata_Reference_Information:

Metadata_Date: 20070914

Metadata_Review_Date: 20110315

Metadata_Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: TYLER B. STEVENS

Contact_Position: DIF AUTHOR

Contact_Address:

Address_Type: Mailing and Physical Address

Address: NASA Goddard Space Flight Center

Address: Global Change Master Directory

City: Greenbelt

State_or_Province: MD

Postal_Code: 20771

Country: USA

Contact_Voice_Telephone: (301) 614-6898

Contact_Facsimile_Telephone: 301-614-5268

Contact_Electronic_Mail_Address: Tyler.B.Stevens@nasa.gov

Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata

Metadata_Standard_Version: FGDC-STD-001-1998

Metadata_Time_Convention: local time