# Does a Geo-Synchronous Satellite Catch a Shadow?

• ucmassahana
In summary, a geo-synchronous satellite with the same time period as the earth will not necessarily cause a full eclipse on the earth due to its small size and the angle at which sunlight converges. Even the Moon, which is larger than most satellites, does not always cause a full eclipse due to its orbit not being a perfect circle. The size and distance of a satellite play a significant role in the size and visibility of its shadow on the earth. Some satellites may throw a shadow farther than others, but due to their high altitude, they will not be visible on the ground.
ucmassahana
If a geo-synchoronise satelite(which has the same time period as that of the earth) comes in a straight line with the Sun. Does it catch the shadow on the earth? If not why?

ucmassahana said:
If a geo-synchoronise satelite(which has the same time period as that of the earth) comes in a straight line with the Sun. Does it catch the shadow on the earth? If not why?
Do a search on google for umbra and penumbra

Basically, it is too small.

Even the Moon, doesn't always cause a full eclipse - sometimes it is just slightly too far away (It's orbit isn't a perfect circle), and some sunlight gets round the edges.

The Sun is about half a degree across - so the rays of light from each limb (side) as we look at it, are not parallel - they are converging (from our viewpoint) at an angle of about half a degree.

So if you do the maths:-
For a 2 metre wide satellite...
Right angle triangle - quarter of a degree angle - 1 metre 'opposite' side (half the width of the satellite)
Tangent of 0.25 degrees = one metre / adjacent side (distance behind satellite where light rays will converge

So you'd need to be within 229 metres of the satellite to get a proper umbral shadow.

Obviously - different satellites will be different sizes to the one in my example - so some will throw a shadow quite a bit more than 229m.
However - satellites are AT LEAST tens of miles up, many are hundreds of miles above the surface - so even the largest ones won't throw a shadow anywhere near far enough for it to be seen on the ground.

Last edited:
Well, here's what it looks like with a telescope and a solar filter... http://www.badastronomy.com/bablog/2006/09/20/shuttle-and-iss-transit-the-sun/

## 1. What is a geo-synchronous satellite?

A geo-synchronous satellite is a type of satellite that orbits the Earth at the same rate as the Earth's rotation, allowing it to maintain a fixed position relative to the Earth's surface. This means that it appears to stay in the same spot in the sky, making it useful for telecommunications, weather monitoring, and other applications.

## 2. How does a geo-synchronous satellite stay in orbit?

A geo-synchronous satellite stays in orbit by balancing the forces of gravity and centrifugal force. Gravity pulls the satellite towards the Earth while centrifugal force pushes it away. By orbiting at a specific altitude and speed, these two forces cancel each other out, allowing the satellite to maintain a stable orbit.

## 3. Can a geo-synchronous satellite catch a shadow?

Yes, a geo-synchronous satellite can catch a shadow. Just like any other object in space, a geo-synchronous satellite can block the light from the sun, creating a shadow. This can happen when the satellite passes in front of the sun or when it is in the Earth's shadow during a lunar eclipse.

## 4. How big is the shadow of a geo-synchronous satellite?

The size of the shadow of a geo-synchronous satellite depends on the size and shape of the satellite, as well as its distance from the sun. The shadow can range from a few meters to several kilometers in diameter.

## 5. Can the shadow of a geo-synchronous satellite be seen from Earth?

In most cases, the shadow of a geo-synchronous satellite is too small and faint to be seen from Earth. However, during a lunar eclipse, the Earth's shadow can be seen passing over the satellite, making it briefly visible to the naked eye.

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