1.1.3.3 Space Environment Monitoring (SEM) 



SEM equipment onboard the spacecraft measures the energy and trajectory 

 of incident particles. These data are transmitted to the Space 

 Disturbance Forecast Center at Boulder, Colorado, for distribution and 

 analysis . 



1.1.3.4 Command and Telemetry 



The "housekeeping" functions necessary to maintenance of correct attitude 

 and position, and monitoring spacecraft status, etc., are provided by 

 the Command and Telemetry subsystem under control of the CDA Station. 



1.1.3.5 Data Collection 



The Data Collection capability enables atmospheric and Earth-based 

 sensors within view of the spacecraft to transmit synoptic or interrogated 

 data to the CDA through the spacecraft transponder. These data are 

 relayed to the Central Distribution Facility (CDF) at Suitland, Maryland, 

 for dissemination to users. 



1.1.4 Is There a Standby Satellite? 



To serve as a backup in event of failure of either operational satellite 

 there is a third geostationary satellite in orbit at longitude 105°W 

 (located midway between the other two). The backup satellite can 

 readily be moved to either the east or west satellite position should 

 such a need arise. 



1.1.5 Will Service Interruptions Occur? 



There may be interruptions during the periods of solar eclipses. The 

 GOES satellites undergo spring and autumn eclipses during a 46-day 

 interval at the vernal and autumnal equinoxes. The eclipses vary from 

 approximately 10 minutes at the beginning and end of eclipse periods 

 to a maximum of approximately 72 minutes at the equinox. The eclipses 

 begin 23 days prior to equinox and end 23 days after equinox; i.e., 

 March 1 to April 15 and September 1 to October 15. The outages occur 

 during local midnight for the satellites' mean meridian. There will 

 also be shutdowns for periodic maintenance at the Wallops CDA station. 

 These scheduled outages will be reduced in the future as redundancy is 

 added to the Wallops Station facility. 



1.2 Description of the Data Collection Subsystem 



In consonance with the primary purpose of this brochure, the following 

 paragraphs discuss in some detail those aspects of the Data Collection 

 System that will be of particular interest to users. 



1.2.1 How Can an Organization Become a GOES/DCS User? 



An organization having a requirement for data collection, or which plans 

 to collect data using the GOES DCS capability, must formally request 

 permission to participate. Requests are processed by: National Oceanic 

 and Atmospheric Administration, National Environmental Satellite Service, 

 Washington, D.C. 20233. 



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