Global Navigation Satellite System Receiver for Atmospheric Sounding Level 1B
Entry ID: gov.noaa.class.GRAS

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Abstract: ABSTRACT: The Global Navigation Satellite System (GNSS) Receiver for Atmospheric Sounding (GRAS) is a European GNSS receiver on board MetOp-A that operates as an atmospheric sounder. GRAS uses radio occultation to measure vertical profiles of atmospheric temperature and humidity by tracking signals received from a constellation of GNSS satellites while they are setting or rising behind the Earth's ... View entire text

Purpose: PURPOSE: The main objectives are to provide stratospheric and tropospheric temperature and humidity profiles that will be assimilated into Numerical Weather Prediction (NWP) models. In addition GRAS provides navigation solutions of the MetOp satellite position along its orbit.
Related URL
Description: Download options for GRAS Level 1b data archived and distributed at CLASS.
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Geographic Coverage
Spatial coordinates   
  N: 90.0   S: -90.0   E: 180.0   W: -180.0

Data Set Citation
Dataset Originator/Creator: EUMETSAT > European Meteorological Satellite Organization
Dataset Title: Global Navigation Satellite System Receiver for Atmospheric Sounding Level 1B
Dataset Release Date: 2007-09-14
Online Resource:
Temporal Coverage
Start Date: 2007-09-14
Quality ATTRIBUTE ACCURACY REPORT: The expected number of occultations per day is greater than 500. Expected bending angle error is less than 1.0 micro rad or 0.4% (whichever is larger). Expected sampling rate is 50 Hz (closed-loop) and 1 kHz (open loop).

LOGICAL CONSISTENCY REPORT: For GRAS Level 1b profiles, the core validation process is based on a one dimension ... View entire text
Access Constraints ACCESS CONSTRAINTS: Pre-operational MetOp data is available upon request. To request access to this data, send an email to indicating your affiliation and need for this pre-operational data. CLASS personnel will contact you with access instructions.

DISTRIBUTION LIABILITY: Disclaimer - While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
Use Constraints None
Ancillary Keywords
Data Set Progress
Data Center
Comprehensive Large Array-data Stewardship System, NOAA, U.S. Department of Commerce Supplemental Info
Data Center URL:
Dataset ID: ______GRAS ____

Data Center Personnel
Email: info at
Contact Address:
151 Patton Avenue
City: Asheville
Province or State: NC
Postal Code: 28801-5001
Country: USA
Distribution Format: EPS Native Format
Fees: FTP is free. Optical disks = $25.00, magnetic tape = $100 + service and handling
Phone: 301-817-4418
Email: james.g.yoe at
Contact Address:
NSOF Room 1235, E/OSD 4231 Suitland Road
City: Suitland
Province or State: MD
Postal Code: 20746
Country: USA
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Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2009-09-01
Last DIF Revision Date: 2011-11-29
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