0525 Wed 12 Nov 2008 satellite Sth to North

Another one of those "what was that?" queries.

This morning, best time I can give is between 0520 and 0530, from
observer's position 50:48N 0:23W, I saw what I'm almost certain was a
satellite.

I first noticed it between Leo and Cancer, and followed its path almost
due north until it disappeared behind the house roughly in the vicinity
of Polaris in what seemed less than a minute. It was brighter than
Castor and Pollux.

I can't find anything travelling South to North around that time in the
satellite passes on heavens-above. I guess in lieu of anything else I'll
have to put it down as a very fast very high aircraft, but I still
wouldn't believe that.

--
Pd

Wasn't it Pd who wrote:
Another one of those "what was that?" queries.

This morning, best time I can give is between 0520 and 0530, from
observer's position 50:48N 0:23W, I saw what I'm almost certain was a
satellite.

I first noticed it between Leo and Cancer, and followed its path almost
due north until it disappeared behind the house roughly in the vicinity
of Polaris in what seemed less than a minute. It was brighter than
Castor and Pollux.

I can't find anything travelling South to North around that time in the
satellite passes on heavens-above. I guess in lieu of anything else I'll
have to put it down as a very fast very high aircraft, but I still
wouldn't believe that.

Heavens-above relies on satellite data from USAF Space Track which may
possibly exclude top secret US military satellites.

--
Mike Williams
Gentleman of Leisure

Hi

The carte du Ciel calander shows there were 3 entries around this period

Flare Iridium 11 Mag -2 dec 81 at 5:27:01

Flare Iridium 46 Mag +1 dec 79.8 at 5:27:21

Flare Iridium 49 Mag -7.9 dec 82.4 at 5:33:07

I would think it was the last one

"Pd" wrote in message
id...
Another one of those "what was that?" queries.

This morning, best time I can give is between 0520 and 0530, from
observer's position 50:48N 0:23W, I saw what I'm almost certain was a
satellite.

I first noticed it between Leo and Cancer, and followed its path almost
due north until it disappeared behind the house roughly in the vicinity
of Polaris in what seemed less than a minute. It was brighter than
Castor and Pollux.

I can't find anything travelling South to North around that time in the
satellite passes on heavens-above. I guess in lieu of anything else I'll
have to put it down as a very fast very high aircraft, but I still
wouldn't believe that.

--
Pd

Paul Forsdick wrote:
The carte du Ciel calander shows there were 3 entries around this period
Flare Iridium 11 Mag -2 dec 81 at 5:27:01
Flare Iridium 46 Mag +1 dec 79.8 at 5:27:21

Flare Iridium 49 Mag -7.9 dec 82.4 at 5:33:07

I would think it was the last one

I think you're right. The pass is exactly the right track at the right
time. It didn't flare though. I didn't think of checking Iridium passes,
because I assumed they'd be included in the visible satellite listings.
It turns out they're not.

Thanks Paul.

"Pd" wrote in message
id...
Another one of those "what was that?" queries.

This morning, best time I can give is between 0520 and 0530, from
observer's position 50:48N 0:23W, I saw what I'm almost certain was a
satellite.

I first noticed it between Leo and Cancer, and followed its path almost
due north until it disappeared behind the house roughly in the vicinity
of Polaris in what seemed less than a minute. It was brighter than
Castor and Pollux.

I can't find anything travelling South to North around that time in the
satellite passes on heavens-above. I guess in lieu of anything else I'll
have to put it down as a very fast very high aircraft, but I still
wouldn't believe that.

--
Pd


--
Pd

Wasn't it Pd who wrote:
I think you're right. The pass is exactly the right track at the right
time. It didn't flare though. I didn't think of checking Iridium passes,
because I assumed they'd be included in the visible satellite listings.
It turns out they're not.

That's because the maximum possible magnitude of Iridium 49 when it's
not flaring is 4.9, and it's typical magnitude is 6.0. The visible
satellite listings only go down to mag 4.5.

--
Mike Williams
Gentleman of Leisure

Mike Williams wrote:

Wasn't it Pd who wrote:
I think you're right. The pass is exactly the right track at the right
time. It didn't flare though. I didn't think of checking Iridium passes,
because I assumed they'd be included in the visible satellite listings.
It turns out they're not.

That's because the maximum possible magnitude of Iridium 49 when it's
not flaring is 4.9, and it's typical magnitude is 6.0. The visible
satellite listings only go down to mag 4.5.

Good answer. I guess it must've been very close to flaring then, because
the whole time I saw it, it was brighter than Castor, Pollux and Regulus
so I guess an apparent magnitude of at the very least 2.

I've seen plenty of Iridium flares. Before and after the flare, the
satellite is, as you say, very dim and in fact I've only been able to
discern it a few degrees either side, whereas this was bright for a
hundred degrees or so.

--
Pd

Wasn't it Pd who wrote:
Mike Williams wrote:

Wasn't it Pd who wrote:
I think you're right. The pass is exactly the right track at the right
time. It didn't flare though. I didn't think of checking Iridium passes,
because I assumed they'd be included in the visible satellite listings.
It turns out they're not.

That's because the maximum possible magnitude of Iridium 49 when it's
not flaring is 4.9, and it's typical magnitude is 6.0. The visible
satellite listings only go down to mag 4.5.

Good answer. I guess it must've been very close to flaring then, because
the whole time I saw it, it was brighter than Castor, Pollux and Regulus
so I guess an apparent magnitude of at the very least 2.

I've seen plenty of Iridium flares. Before and after the flare, the
satellite is, as you say, very dim and in fact I've only been able to
discern it a few degrees either side, whereas this was bright for a
hundred degrees or so.

I don't think Iridiums can "be very close to flaring" for more than a
few seconds.

As the Iridium moves along its orbit, the "flare centre" moves along the
ground at a speed somewhere in the order of 5 miles per second. For a
flare that's mag -8 at the flare centre to appear to peak at mag 2 from
your location, you need to be about 30 miles from the "flare centre". I
can't see any way that could produce an effect where you'd see anything
like a constant mag 2.

I still suspect that it was something that's not in the Heavens-Above
database. Either an unlisted secret US spy satellite or an aircraft.

--
Mike Williams
Gentleman of Leisure

Hi carte du Ciel showed Iridium 76 was at -3.6 mag and 80.6 degrees at 5;28
today as well
"Mike Williams" wrote in message
...
Wasn't it Pd who wrote:
Mike Williams wrote:

Wasn't it Pd who wrote:
I think you're right. The pass is exactly the right track at the right
time. It didn't flare though. I didn't think of checking Iridium
passes,
because I assumed they'd be included in the visible satellite listings.
It turns out they're not.

That's because the maximum possible magnitude of Iridium 49 when it's
not flaring is 4.9, and it's typical magnitude is 6.0. The visible
satellite listings only go down to mag 4.5.

Good answer. I guess it must've been very close to flaring then, because
the whole time I saw it, it was brighter than Castor, Pollux and Regulus
so I guess an apparent magnitude of at the very least 2.

I've seen plenty of Iridium flares. Before and after the flare, the
satellite is, as you say, very dim and in fact I've only been able to
discern it a few degrees either side, whereas this was bright for a
hundred degrees or so.

I don't think Iridiums can "be very close to flaring" for more than a few
seconds.

As the Iridium moves along its orbit, the "flare centre" moves along the
ground at a speed somewhere in the order of 5 miles per second. For a
flare that's mag -8 at the flare centre to appear to peak at mag 2 from
your location, you need to be about 30 miles from the "flare centre". I
can't see any way that could produce an effect where you'd see anything
like a constant mag 2.

I still suspect that it was something that's not in the Heavens-Above
database. Either an unlisted secret US spy satellite or an aircraft.

--
Mike Williams
Gentleman of Leisure

Wasn't it Paul Forsdick who wrote:

Hi carte du Ciel showed Iridium 76 was at -3.6 mag and 80.6 degrees at 5;28
today as well

Iridium *flares* can be -3.6. In fact they can be up to -8. But they
only get that bright for a second or two. The Iridium satellites are
high (about double the height of Low Earth Orbit) and not particularly
large, so they're quite dim.

I also suspect that your Carte du Ciel database might not be quite up to
date or perhaps the predictions you are reporting are for a different
location. Flare predictions are sensitive to modest changes in orbit
elements and observer's location. Heavens-Above grabs the latest orbit
data every day, but doesn't report that pass as being visible from
Worthing. H-A reckons that the ground track of I-76 passed about 280
miles to the West of Worthing at 5:39.

--
Mike Williams
Gentleman of Leisure