My family and I went camping this weekend, and Saturday night presented clear weather and an excellent opportunity for some star gazing (especially since we were far away from the light pollution from our city). About 10 of us went and spent about an hour lying on our backs looking up at the sky.

We spotted a couple of shooting stars, which is always fascinating, but the highlight was spotting three satellites. Two of them followed pretty much the exact same path through the sky about a half hour apart. Then shortly later we saw another one traveling in the same path, but in the exact opposite direction.

My question is this - do we launch satellites in multiple directions, such that the above makes sense? I don't yet have very strong skills with regards to identifying stars and orientation, though I do know the path the satellites took with respect to Ursa Major. This was bugging me all weekend, because I had thought that we launch most of our satellites in the same direction to take advantage of the earth's rotation. Am I wrong here? It wouldn't be the first time for sure.

Yes; but not many. Search for "retrograde" in your quest if you are so inclined. (pun intended)

Keep trying... I'm not that skilled myself, and a star chart does help a great deal.

Mostly right. If we did it, it would be from Vandenberg, although most of those are polar orbits.
Anyway. It also depends on the direction. If it were N/S, then either direction would be equally plausible. E/W would require retrograde orbits.

While we are on the subject... I did see a N/S rocket body the other day, and it did seem to be going slightly west. Is the rotation of the Earth enough to see visually from a casual ground observation?

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A previous BAUT discussion of retrograde satellites
A wikipedia article on them

You can go to heavens-above.com/, input your location, and see what was passing overhead at the time you were looking.

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One Earth, One Sky - IYA 2009

kpesanka,

There are two broad categories of Earth orbits: Those launched eastward,
mainly to take advantage of the speed of Earth's rotation to slightly reduce
the amount of energy needed to get into orbit (or increase the payload),
and those launched into polar orbits, mainly to be able to look straight down
on any point on the Earth. US orbital launches to the east are from Cape
Canaveral in Florida; US launches into polar orbit are from Vandenberg AFB
near Santa Barbara in California. Launches from Vandenberg are toward the
south or southwest. The exact direction of any launch depends on the
orbit desired, the range of directions allowed at any particular launch site,
and the latitude of the launch site. Because Russian launch sites are at
relatively high latitudes, the International Space Station had to be put into
a relatively high-inclination orbit in order for Russian spacecraft to reach it.
That means the US Space Shuttle cannot carry as much payload to the
ISS as it would be able to do if the ISS were in an orbit with the same
inclination as the latitude of the Cape Canaveral launch site. The Shuttle
has to launch to the northeast instead of straight east.

Satellites in polar orbits go from north to south and from south to north,
and the Earth is always rotating underneath them from west to east...

A very small number of small satellites have been put into east-to-west
orbits by Israel, because that is the only direction they can launch in
without flying over other nations during the boost phase. The Israel
space launch site is at Palmachim AFB on the Mediterranian coast just
south of Tel Aviv.

-- Jeff, in Minneapolis

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"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

NEOWatcher,

Many polar satellites orbit slightly "backwards", with inclinations of something
like 103 degrees or thereabouts, in order to orbit over the Earth with a nearly
constant angle of sunlight on the ground track. Each succeeding orbit is
farther to the west by the amount needed to keep the satellite orbiting over
the noontime part of the Earth, or whatever time of day is desired.

Edit to add: This is called a Sun-synchronous orbit.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

Thanks guys!

I checked with heavens-above.com and based on the time we saw the satellites, they were most likely cosmos rockets (the timing is right such that one was going the opposite direction in a polar orbit). Glad I'm not going nuts!

I knew there were some like that, but didn't know why.
But; I was more pondering about whether a 90 degree inclination would be visibly skewed.
A quick napkin math tells me a 200mile altitude object visibly in the sky for about 10 minutes, visibly travels about 400 miles, and at my latitude had moved around 125 miles in that time. So; it could look like a retrograde satellite, No?

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Numbers are not case sensitive. (me)