Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
4-13 SATELLITE ACQUISITION AND TRACKING An essential operation in communicating by satellite is the acquisition (locating) of the satellite by the earth terminal antenna and the subsequent tracking of the satellite. Initial acquisition depends upon an exact knowledge of the position of the satellite. In combination with the geographic location of the earth terminal, knowing the position of the satellite enables you to compute accurate antenna pointing information. The degree of difficulty in locating and tracking a satellite is determined largely by what type orbit the satellite is in. The locating and tracking of a synchronous satellite is relatively simple. This is because the satellite appears to be stationary. Locating a near-synchronous satellite is also relatively simple because of the slow relative motion of the satellite However, the movement of a near-synchronous satellite is enough that accurate tracking is required to keep the narrow beam antenna pointed toward the satellite. Satellites in medium altitude circular orbits or in elliptical orbits are more difficult to acquire and to track because of the rapid changes in position. Orbital Prediction To acquire and track a satellite in space, the earth terminal antennas must be provided with very accurate pointing information. Antenna pointing information is based upon the orbital prediction of the satellite. This information is derived from an EPHEMERIS table. This table provides the coordinates of a satellite or a celestial body at specific times during a given period. After you know the ephemeris data of a satellite, you can predict for any given location the apparent track of the satellite as viewed from that location. The constants defining an orbit are initially obtained by the process of tracking. At the time of launch, the rocket is tracked by radar from lift-off to orbit and then until it passes out of sight. Tracking data obtained in this way is sufficient for making rough predictions of the orbit. These predictions are made rapidly with a computer and sent to tracking stations all over the world. These other tracking stations watch for the satellite during its first trip and record additional data. During the first week of orbiting, tracking stations all around the world are obtaining progressively more accurate data concerning the Satellite. This data is put into a computer where corrections of earlier estimates of the orbit are made. Once the initial predictions are complete and the satellite link becomes operational, very little change in these calculations is made. The orbits of a satellite will change slightly over a period of time; however, these changes are so gradual that predictions will be accurate enough to be used for weeks or even months without further corrections. When the orbits are known precisely, an ephemeris can be calculated for each satellite of the system. Antenna Pointing Antenna pointing instructions for each satellite must be computed separately for each ground station location. A satellite that bears due south of station A at an elevation of 25 degrees may simultaneously bear due southeast of station B at an elevation of 30 degrees. Antenna pointing instructions are determined by taking into consideration the orbital prediction and the latitude and longitude of each ground station. To establish radio contact with a satellite, the ground station needs to know the bearing and elevation of a satellite. This allows the antenna to be properly pointed.

Electrical News
EEVblog #657 – Maker Faire 2014 Interviews
Some interviews from the 2014 Sydney Mini Maker Faire at...
The Internet of Things Versus Slumlords
Smart thermostats are not only for the well-to-do. One group...
IBM Watson Speeds Drug Research
IBM Watson moves from supplying known answers to tough questions...
Samsung Funds III-V FinFETs in US Lab
Samsung is funding Penn State researchers working to fabricate III-V...
LG, Samsung Debut Smartwatches, Apple Lurks
LG's G Watch R and Samsung's Gear S do little...
Imagination Takes On Raspberry Pi
Imagination Technologies has developed its own version of Raspberry Pi,...
California Smartphone Kill-Switch Law: What It Means
Do you understand the consequences of California's new smartphone anti-theft...
9 Insights From Hot Interconnects
Facebook described its network switch, while experts picked apart flaws...
Microchip in Pursuit of CSR
Microchip confirmed Thursday that it has had preliminary mutual discussions...
Are There Marsquakes on Mars?
A 2016 mission will investigate the stuff under the surface...
Friday Quiz: Forgotten T&M Companies
Remember the names of these test-equipment companies? Most are long...
Rohm Opens MEMS Foundry Operation
Rohm Co. Ltd. created a foundry business at the six-inch...
Touch Taiwan: Display Vendors' 10 Bold Forecasts
Display suppliers are in the know. The companies exhibiting at...
Power Week: RF Charging Startup & Dialog Semi Team Up for Over-the-Air Power
This week, "over-the-air" power got a boost when RF charging...
9 Notorious Automotive Electronics Recalls
It's been a banner year so far for automotive recalls,...
Indoor Navigation: The Next Big Thing
Custom system-on-chip from parent company mCube enables Ten Degrees to...
New UART to WIFI chipset will unleash low cost Internet of Things
WiFi infrastructure is everywhere which makes easier to make network...
Data Centers May Ride on ASICs
Firebox, a research prototype in the works at UC Berkeley,...
Product Compatibility Is a Constant Dilemma
Because most new products are based on previous ones, engineers...
White Goods Consolidation Drives Power Deals
The power semiconductor industry has seen two key announcements this...

Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +