SOLAR WEATHER

and

GEOSYNCHRONOUS SATELLITES

TechNote 002

June 16, 2000

SUN OUTAGES:

All of us who are responsible for managing successful satellite uplinks are reminded to be aware of possible "sun outages" which may cause temporary interruptions in satellite transmission services for periods of up to seven to eight minutes per day. This natural phenomenon occurs in the Spring and Fall and can affect both uplink and downlink ground stations. Interruptions in service may occur when the satellite ground station, the transmitting satellite and the sun are in complete alignment. The time of day during which this alignment occurs for a particular ground station is predicable.

If you have questions about a satellite transmission which you have planned during these outage periods, and you are concerned about possible interference during your transmission, you may contact ADEC or you may call the appropriate satellite carrier directly.

SATELLITES CARRIER TELEPHONE NUMBER

____________________

GALAXY & SBS PanAmSat (800) 321-3959

(Hughes Communications)

TELSTAR Loral Skynet (800) 242-2422

GSTAR, SATCOM,

SPACENET & GE GTE Spacenet (800) 772-2363

ANIK Telesat Canada (800) 265 3074

(519) 364-2221

The satellite carriers provide technical assistance on their websites which may be helpful in determining if transmission difficulties may be encountered. Some of the following sites require the user to register (no cost) and/or to download operational programs.

CARRIER SUN OUTAGE WEBSITE

PanAmSat <http://www.panamsat.com/sat/sun.html>

(This site provides a detailed description of the causes of sun outages.)

GE Americom <http://www.geamericom.com/tools/license.html>

(Registration is required prior to accessing webpage)

Loral Skynet <http://www.loralskynet.com/tech_resources/tools_us.asp>

(Requires downloading of program)

In order to determine if transmission interference is probable, you will need to provide the date and time of day for the transmission, the name of the satellite you will be using and the location of your satellite ground station.

SOLAR FLARES (Sun Spots):

Earth has experienced the effects of increased solar activity since the occurrence of two AX-Class@ solar flares (the most powerful class) on June 6th of this year. The geomagnetic storms resulting from these solar disturbances sent ionized gas clouds and electromagnetic energy towards earth at 1.6 million miles per hour. Solar activity varies in intensity on an eleven year cycle and peaked this year. The Space Environment Center in Boulder, Colorado, advised that sunspot clusters could be active through June 24th.

Geomagnetic storms can adversely effect electric power grids, disrupt terrestrial electronic telecommunications and cause disorientation or failure of communications satellites. During this period of maximum solar activity, ADEC recommends that program providers which are using satellites check with the satellite operator or with ADEC for information regarding the effects of solar activity on transmission quality.