Campbell Scientific TX312 High Data Rate GOES Transmitter - Manual (Page 9)

TX312 Transmitter
2. GOES System
2.1 Orbit
The TX312 transmitter sends data via Geostationary Operational
Environmental Satellites (GOES). GOES satellites have orbits that coincide
with the Earth's rotation, allowing each satellite to remain above a specific
region. This allows a user to point the GOES antenna at a fixed position in the
sky.
There are two satellites, GOES East and GOES West. GOES East is located at
75° West longitude and GOES West is located 135° West longitude. Both
satellites are located over the equator. Within the United States, odd numbered
channels are assigned to GOES East. Only even numbered channels are
assigned to GOES West. Channels used outside the United States are assigned
to either spacecraft.
2.2 NESDIS and Transmit
−Windows
GOES is managed by the National Environmental Satellite Data Information
Service (NESDIS). NESDIS assigns the platform ID, uplink channel number,
and self-timed or random transmit windows. Self-timed windows allow data
transmission only during a predetermined time frame (typically one minute or
less, every one, three, or four hours). The self-timed data is erased from the
transmitter's buffer after each transmission, random data is not. Random
windows are for critical applications (e.g., flood reporting) and allow
transmission immediately after a threshold has been exceeded. The
transmission is then randomly repeated to ensure it is received. A combination
of self-timed and random transmission can be executed by the TX312.
2.3 Data Retrieval
Data retrieval via the TX312 and the GOES system is illustrated in Figure 2-1.
The DAPS User Interface Manual, provided by NOAA/ NESDIS, describes the
process of retrieving the data from the NESDIS ground station. The data are in
the form of 3-byte ASCII (see Appendix B for a computer program that
converts the data to decimal). You can also retrieve data directly from the
NESDIS ground station via the DOMSAT satellite downlink. DOMSAT is
only practical for organizations with many GOES users; contact NESDIS for
more information (see Appendix A).
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