Theoretically, as long as you have three satellites in geosynchronous
orbit, spaced equally apart, every point on earth will have satellite
reception.
Of course, this assumes you are on the surface of the earth and have
no overhead obstructions. For instance, you won't get satellite
reception in a building, in a cave, or even in some deep
ravines/gorges/valleys.
But as long as you have line-of-sight view of the horizon, you should
have at least one satellite able to send you data.
You do have to be more specific, though. What kind of satellites are
we talking about? GPS sats? TV sats? etc? Depending on your
specific application, there are different methods of determining
strength, how they align, etc.
For instance, many satellites use the TDRS (telemetry data relay
station) satellites to allign themselves as well as communicate to the
ground. So, a satellite talks to another satellite which in turn
talks to the ground. This is true with many communications
satellites.
Many satellites also have earth, sun, and star sensors. Star sensors
have constellation maps saved in their ROM, which allows them to
determine their position relative to earth based on the star patterns
around them. Sun sensors, well, detect the sun, which is pretty easy
considering it is the brightest thing around the sat. Earth sensors
detect the earth's horizon based on the difference between the cold of
space and the relative warmth of the earth. Based on inputs from
these three sources combined with the exact time (which tells it where
it SHOULD be), the satellite can detect its exact location (accurate
to the order of meters) and perform milli-Newton thruster burns to get
where it wants to go.
In terms of determining what satellites are in view, corwin02 gave you
an awesome website. Note, however, that there are thousands more
satellites in orbit which are not represented on this site. Some for
security concerns, others because there are way too many to list.
If you want to determine which GPS satellites are in view and their
respective strengths, you simply need a GPS receiver capable of this.
They cost about $100.
As far as a "satellite finder", to find every single satellite out
there, they aren't commercially available. Besides, they're useless
because of the wide variety of frequencies and just the shear number
of sats out there. The sat finder would always find something.
Imagine trying to use a metal detector at a auto-junkyard. Same idea.
If you give more clarification as to what exactly you are looking for,
perhaps I can be of more assistance. |
