Are there any satellites that travel in reverse, from East to West?

Question

I am about fifty miles west of Montreal. Watching the sky this evening, I saw what clearly looked like a satellite pass over, travelling from the northeast towards the southwest. It was quite bright, not as bright as Jupiter. It passed very close to Jupiter, almost occulting it, at 18h35 zulu. It faded out of sight about half way between Jupiter and Venus, as the reflection from the solar panels shifted away from my location.

I have a telescope. I know what the sky looks like. I fly. I know what is up there. This was not an airplane with landing lights on. I have seen it before. It definitely looks like a satellite, except it was moving in a westerly direction. It has always been my understanding that satellites are launched to travel from west to east, to take advantage of the rotation of the earth to help get the device up there. 

Is this always the case, or are there some that are launched to travel against the rotation of the earth? If so, what is the purpose? What advantage would this have for a satellite?

bikenbeer2000 · Accepted Answer

Many satellites are in polar orbits and some of these travel 'slightly' westwards, that is to say that their orbital inclination is a little greater than 90°. A 0° inclination is in the plane of the equator and travelling directly eastwards, 90° is perpendicular to the equator (ie. north - south or south - north) and 180° would be in the plane of the equator again, but directly westwards.
Due to the pull of the Earth's equatorial bulge, the orbits of satellites gradually twist round in the opposite direction to their orbital motion. For example, the International Space Station's orbit moves westwards at about 5° per day. Some satellites in polar orbits have inclinations just over 90° because this means that this 'twisting' of the orbit will be eastwards. For example, an inclination of about 97° would mean that the orbit would move eastwards at about 1° per day, thus keeping pace with the Sun. This is an advantage for environmental observation satellites, some of which need to look at the ground under the same conditions of illumination. Thus the satellite will always pass over at roughly the same time of day.
Looking at the Heavens Above website for Montreal yesterday http://www.heavens-above.com/allsats.asp?lat=45.500&lng=-73.583&alt=113&loc=Montreal&TZ=EST&Date=40943.9791666667&Mag=3.5 there was a satellite called Cosmo-Skymed 1 which might fit the bill, even allowing for the fact that you are not exactly in Montreal. It travelled from north to SSW between 18:30 and 18:38.
Looking at its orbital details, its inclination is 98°.
I suspect very few, if any, satellites travel directly against the rotation of the Earth, but there are number of these slightly westward travelling polar orbiters. You could always try and find a list of satellites with their orbital elements and see how large the inclinations go.

Sally · Answer

At 18.25 this evening (11.3.2016) as I saw an iridium flare there was a  satellite travelling from SE to NW.
 As I live in Israel it may have been an Israeli satellite which travel EAST  to WEST

Joseph · Answer

Yes.  Israel, for example, is forced to launch its satellites to the West over the Mediterranean Sea, because a normal launch to the East may be construed as an attack by some of its enemies.

Trix · Answer

I'm going out to look now, might be a bit late to have missed what you've observed...I'll return if anything is worth reporting, thanks :)

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Are there any satellites that travel in reverse, from East to West?

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