Archive for July, 2009

THE SPACE ENVIRONMENT DEFINITIONS AND EFFECTS

Tuesday, July 28th, 2009

1) Perturbation-irregularity in the motion of a satellite caused by an outside force, creates degradation of signal or total loss of communications
a)Lunar/Solar effects, earth triaxiality, solar winds

2) Solar Conjunction-A phenomenon that occurs when the earth, satellite and sun are in alignment. The earth terminal antenna is pointing directly at, or very near the sun. Communications can be degraded for 2 to 15 minutes total communications blackout can last for up to 5 minutes.

3) Van Allen Radiation Belts-The dynamo action of the Earth generates a magnetic field known as the Magnetosphere. Energetic particles from the Sun’s Solar Wind leak into the Magnetosphere and become concentrated in an area known as the Plasmasphere.

SPACE ENVIRONMENT

Thursday, July 9th, 2009

 The earth’s atmosphere limits the lowest altitude at which a satellite can be placed into orbit.  Satellites launched from earth must pass through the atmosphere in order to attain the proper orbit.  The lowest altitude for a satellite in circular orbit is about 93 miles, but without propulsion, the satellite would quickly lose speed and fall back to earth.

 The earth’s atmosphere is divided into five regions:  troposphere, stratosphere, mesosphere, thermosphere, and exosphere.  The lines between these regions are not distinct, blending into each other so fluctuations occur in size depending on the time of the day, seasons, and solar activity.  A brief description of each region is below:

COMMON CHARACTERISTICS OF SATCOM REQUIREMENTS

Wednesday, July 1st, 2009

Customers do not differentiate between the types of communications services they need by dividing them between high capacity and low capacity, military or commercial. He is concerned with doing business and having the communications resources he or she needs when they need them in order to accomplish the task at hand. To ensure that the customer will have the right information at their disposal, a common set of system characteristics are needed to support business operations.