Starship Asterisk*

Geostationary Satellites Beyond the Alps

Explanation: Why don't those stars move? Stars in the sky will typically appear to rise and set as the Earth turns. Those far to the north or south will appear to circle the pole. If you look closely at the above time-lapse movie, however, there are points of light that appear stationary. These objects are not stars but human-launched robotic spacecraft that remain fixed high above the Earth's equator. Called geostationary satellites, they don't fall down because they do orbit the Earth -- they just orbit at exactly the same speed that the Earth rotates. The orbital distance where this is possible is much farther than the International Space Station but much closer than the Moon. The video was taken from one of the highest revolving restaurants in the world located on the Mittelallalin in the Swiss Alps. In the foreground is a mountain known as the Allalinhorn. An even closer inspection will show that the geostationary satellites flash with glints of reflected sunlight. The satellites also all appear on a single line -- actually the projection of the Earth's equator onto the sky.

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I've looked, cleaned the dust off my laptop screen, looked again... where are those geostationary satellites? I can't see them. Am I not seeing the trees for the forest?

Why are all(? or rather: so many of) those satellites on one line?

I understand that Earth actually wobbled after the recent huge Japan earthquake. Did satellite operators have to realign their satellites to maintain geosynchronous orbit?

oerz wrote:Why are all(? or rather: so many of) those satellites on one line?

APOD wrote:human-launched robotic spacecraft that remain fixed high above the Earth's equator. ...

The satellites also all appear on a single line -- actually the projection of the Earth's equator onto the sky.

afd wrote:I've looked, cleaned the dust off my laptop screen, looked again... where are those geostationary satellites? I can't see them. Am I not seeing the trees for the forest?

While watching the video, mentally draw a line from about an inch below the top-left corner to about half way down the right side. Once you start to look at that line, you'll see the satellites. The easiest ones to see are all along the left half of that line.

Rob

K1NS wrote:I understand that Earth actually wobbled after the recent huge Japan earthquake. Did satellite operators have to realign their satellites to maintain geosynchronous orbit? :?:

It didn't move enough to have any effect.

Actually, however, satellite operators have to actively keep their satellites in place, as various perturbations slowly move them from their geostationary (or geosynchronous- the two are different) orbits. End-of-life for geostationary satellites (and most other satellites as well) is when they run out of propellant, and can no longer be maintained in their design orbit.

Saw 'em, thanks to the note on location. Saw one way off the line, and was a bit confused Then the video ended and it remained. Dust on my screen!

I love the feeling of flying provided... if we really rotated that fast would we fly off into outer space?

emc wrote:
... if we really rotated that fast would we fly off into outer space?

Yes.

No ordinary star, planet, moon or asteroid can rotate faster than about once per hour
... otherwise, centrifugal force would tear them apart.

Thanks for the answer Mr. Art

I still love the feeling the movie provides of flying thru space. It's hard to tell we're flying real time.

Another point besides the flying off into space thing is that it would make an astronomer's job exponentially more difficult.

One night some years ago, I was lying in my sleeping bag on the floor of the Grand Canyon, middle of the night, and realized there was a flashing object above me. It looked just like a star but rather than a steady light, it flashed briefly about every 35 seconds (based on middle-of-the-night counting, one one thousand, two one thousand etc). Could that have been a geostationary satellite? Is there one located over Arizona? I have always wondered about it.

DeborahT wrote:One night some years ago, I was lying in my sleeping bag on the floor of the Grand Canyon, middle of the night, and realized there was a flashing object above me. It looked just like a star but rather than a steady light, it flashed briefly about every 35 seconds (based on middle-of-the-night counting, one one thousand, two one thousand etc). Could that have been a geostationary satellite? Is there one located over Arizona? I have always wondered about it.

Geostationary satellites must be over the equator, so there aren't any over Arizona. There is a ring of them all the way around the Earth, so you can see many from Arizona, but they will all be in the southern sky.

Geostationary satellites can produce flares, which are fairly brief increases in brightness because of the chance alignment of some structure like their solar panels or antenna, the Sun, and the observer. I'm not aware of any that flash. That is typical of lower satellites which are rotating or tumbling. But those would be seen to move... although in some cases the amount of motion could be very small over just a few minutes.

And we come to depend so much on these satellites that the communications world would almost come to craw without them!

If i can be a nitpicker, orbiting sattellites are actually falling down, but the Earth surface is also falling down, at the same rate. Ice cold one, please !

I can see nothing at all - just the light grey background - there is no image or video there. I thought it may be a very large file but have waited 5 mins and still nothing appears - I have 8Mbs broadband - nothing has taken this long to load. I've never had this problem with the APOD page in the past. I have Adblock Plus but it says it is blocking nothing on the page. I have right-clicked in the centre where the image would normally be and no menu comes up - there's nothing there. Any ideas? Thanks

ta152h0 wrote:If i can be a nitpicker, orbiting sattellites are actually falling down, but the Earth surface is also falling down, at the same rate. Ice cold one, please !

Actually I like mine at room temperature1 Easier on my stomach!

orin stepanek wrote:And we come to depend so much on these satellites that the communications world would almost come to craw without them!

We still depend on each other... the satellites just make it possible to depend on more "others". It's a good thing!

Instead of saying:

"Called geostationary satellites, they don't fall down because they do orbit the Earth -- they just orbit at exactly the same speed that the Earth rotates."

I might have said:

"Called geostationary satellites, they don't appear to move because they orbit the Earth at a speed that gives the appearance of standing still in the sky."

Hmmm?

I am impressed with this APOD but I still think it is easier to leave a still camera shutter open for 30 minutes and then see what is not streaked. With my luck aearthquake hits at that time....or not !

Thanks for the tip about where to look for the geostationary satellites.

I'm trying to identify the background constellations, but I'm flummoxed. Can somebody help me get oriented?

Anthony Barreiro wrote:Thanks for the tip about where to look for the geostationary satellites.

I'm trying to identify the background constellations, but I'm flummoxed. Can somebody help me get oriented?

I marked a few references in the first frames of the video, some geosats positions are also marked ( click on image to see it magnified):




In really there are many geosats in a strip that extend of upper left until Orion (click on image to see it magnified):

(For reference Gamma Sextantis are marked with a green circle, all other green simbols are geosats)



Normally the geostas have low magnitude so you can see it at naked eye and even with small telescopes. But in some times in the year ( just before or after Equinoxes) occur the "Geosats Flare Season". It occurs cause the Sun is in (or near) the plane of the geosats belt (Celestial Equator) illuminating the reflective surfaces and solar panels on all the geosats on the night side of the Earth and this light is reflected to the Earth's surface on the night side.

Michael Kunze register this event (in the case of the geosats of the movie probably they were about to enter the Earth's shadow).

Huckadarn, thank you so much. It looks like this was your first apod post -- you're off to a great start!