Why do some satelites have lights?

Originally posted by apc
And I dont remember where I read it, but I think I remember that some/most satellites do have some form of illumination, only it is off until remotely activated to aid in locating for repair.

Yeah, but the lights are generally tiny and can only be seen from a short ways off. Nothing that can be seen from the ground.

Think I found out why...great site BTW at...

www.satobs.org...

"Many satellites do not have a constant brightness, they give off flashes at (usually) regular times. This flashing behavior is caused by the rotation of the satellite around its rotation axis. The satellite's metallic surfaces act as mirrors for the sun (specular reflection). Objects with a diffusely reflecting surface will also show varying brightness since the observer will see a changing amount of light reflecting area of the rocket as it tumbles about in its orbit"

Here's one.

I've posted it in a couple of threads before.
It's an Iridium Satellite. Flashing at a -8 Magnitude..
The whole trail lasted about 20 seconds..
I took it last year.



Go here to find out exactly when and where to look in your area.

Heavens Above

cmdrkeenkid

It's 9:40 pm. Heres how I see things (excuse the simple graphics)


o
...o
.....o Ursa Major

o
..........o
.....o

...........-----1 fist------




..................................I
..................................I
...........................4.5 fists down
..................................I
..................................I

..................................* flashing object at 20-25 degrees


Also spied another (about half as bright/flashing) due west 2nd object in a series of three lights in a slight arc

[edit on 7-6-2005 by gman55]

[edit on 7-6-2005 by gman55]

[edit on 7-6-2005 by gman55]

I'll go home and take a photo at 9:40 My time..
And post it here for you..

Thats about 95 minutes from now..

Originally posted by gman55
It's 9:40 pm. Heres how I see things (excuse the simple graphics)

Still sounds like one of Saturn, Venus, or Capella to me.

Also spied another (about half as bright/flashing) due west 2nd object in a series of three lights in a slight arc

Procyon is about due west and low on the horizon.

I just spent the past couple hours at the observatory... I didn't see anything out of the ordinary. Neither did the other O staff.

We should clairfy the difference between flashing, or blinking objects that retain the same color and blinking objects that seem to go from red, green, blue, etc. The original question was concerning the color changing ones, if you will, and the top two candidates would be an airplane or a star.


How to check:
If it's an airplane, you will know it. In 3 minutes time it will move almost completely across the horizon.

If it's a star, take a look and note it's distance relative to other stars close by. Come back in an hour or two; if it's still in the same position, it's a star.



Note: A planet viewable with the naked eye is extremely unlikely to exhibit atmospheric distortion to the point of blinking different colors. We can, with great certainty, dismiss a planet as being the possible candidate.

Thought I should post again.
No pic, too cloudy..
I'l try again tomorrow.

Originally posted by backtoreality
We should clairfy the difference between flashing, or blinking objects that retain the same color and blinking objects that seem to go from red, green, blue, etc. The original question was concerning the color changing ones, if you will, and the top two candidates would be an airplane or a star.


If it's a star, take a look and note it's distance relative to other stars close by. Come back in an hour or two; if it's still in the same position, it's a star.



Note: A planet viewable with the naked eye is extremely unlikely to exhibit atmospheric distortion to the point of blinking different colors. We can, with great certainty, dismiss a planet as being the possible candidate.

I agree thats its not a planet. It does slowly go over the horizon (about 1-1/2 hours from time it's visible.

BTW it is only visible during the warm months, so this leads me to believe that I'm looking at a flashing/rotating satellite.

If it is in the sky for 1 1/2 hours, it's definitely not an airplane or satellite. Satellites move across the sky at about the same rate as an airplane at high altitude.

Again, the thing to take note of is the objects movement in relation to the stars immediately around it. That will tell you once and for all what it is.

p.s. That is a great pic of the iridium satellite. I used to track them, the ISS, MIR, Space Shuttle and other objects using the Heavens Above site. Anyone interested, check it out. Great stuff.

Originally posted by backtoreality
Note: A planet viewable with the naked eye is extremely unlikely to exhibit atmospheric distortion to the point of blinking different colors. We can, with great certainty, dismiss a planet as being the possible candidate.

That all depends on your skies... I've seen Venus, Mars, Jupiter, and Saturn all scintillate quite a bit when low on the horizon. And look where Saturn and Venus are right now.

Originally posted by backtoreality
If it is in the sky for 1 1/2 hours, it's definitely not an airplane or satellite. Satellites move across the sky at about the same rate as an airplane at high altitude.

What about a circular equatorial geosynchronous orbit? Would that not appear to hover in the same place?

Originally posted by gman55
What about a circular equatorial geosynchronous orbit? Would that not appear to hover in the same place?

Maybe you missed what I said previously in the thread: "Geosynchronous satellites are over the equator and are also about 20,000 miles up. There's no way they can be seen. "

But aside from that, yes, it does stay in the same spot in the sky.

Okie Dokie...but I'm not giving up! I'll find some way to document this object. Every so often my wife comes out with me and ask's me "What the hell is that!" (SNL reference)

Originally posted by cmdrkeenkid
That all depends on your skies... I've seen Venus, Mars, Jupiter, and Saturn all scintillate quite a bit when low on the horizon. And look where Saturn and Venus are right now.

I agree with you cmd.... It was stated the the obeject was changing colors from red to blue to green (i think we the combinations). For that to happen to a planet, even at 100% humidity would be extremely rare.

By the way, what are your thoughts on the object given the info?

Originally posted by backtoreality
By the way, what are your thoughts on the object given the info?

I'm sticking with Saturn, Venus or Capella... I don't see another option but one of those three.

Satellites do not have lights.

Telescopes have varying degrees of optical correctness and can lead to bogus or changing colors as the light from the object moves across the field of view.

Factor in atmospheric crud and you have your answer....

Originally posted by UofCinLA
Telescopes have varying degrees of optical correctness and can lead to bogus or changing colors as the light from the object moves across the field of view.

Yes I agree...but I can see these objects with just my eyes. I might have crud in them!