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ISS, Tiangong, Satellites Over Puna
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03-01-2016, 05:18 PM
Aloha, Mr. Tom (aloha Pam!). Mahalo for the reminder, and update, Sir.[
 ]I believe we also have an eclipse coming soon (the 8th or 9th of this month?)! Trust all is well with both of you. Warmest regards. 
03-01-2016, 05:50 PM
Hello Opihikao, nice to see you back! I hope you and family are well.
Yes, there's a partial solar eclipse on March 8th (from the perspective of Hawaii that is, other places will see a total eclipse). For Hawaii it will start around 4:27pm and ends at 6:32pm with the maximum occurring at 5:37pm. At maximum, about half the sun will be eclipsed by the moon. Please remember not to look at the sun directly without some filtering device (sunglasses don't count!). Even during an eclipse you can do serious damage to your eyes by looking at the sun. If you don't have something to protect your eyes but have a pair of binoculars, then you can point the binoculars at the sun (please don't look through the binoculars directly while doing this, you will do serious damage to your eyes) and hold a piece of paper a foot or so behind the binoculars. You should get a projected image of the eclipsed sun without blinding yourself! 
03-03-2016, 08:13 AM
"Time: Thu Mar 03 5:24 AM, Visible: 5 min, Max Height: 66°, Appears: 25° above SSW, Disappears: 11° above NE."
Caught a glimpse of the ISS for about 20 seconds or so as it crossed the sky above. It really moves along at a good clip. Was curious how fast and at what height above the earth's surface it travels in it's orbit. Here is what Wikipedia says: Orbit height: 249 mi Speed on orbit: 4.76 miles/s 
03-03-2016, 08:42 AM
Speed on orbit: 4.76 miles/s
That is fast, but i believe pog and a few others could overtake on the downhill slope of it's orbit - - even with their foot off the gas! "How we spend our days is, of course, how we spend our lives." -Annie Dillard
"I'm at that stage in life where I stay out of discussions. Even if you say 1+1=5, you're right - have fun." - Keanu Reeves
03-03-2016, 07:57 PM
PM2,
"Caught a glimpse of the ISS for about 20 seconds or so as it crossed the sky above. It really moves along at a good clip." It does move surprisingly quickly, doesn't it? Maybe it's just me, but when I see it I always feel in awe knowing there are people in that bright fast-moving light. Admittedly, when you saw it, there were three less in it than a couple of days ago, but I hope you understand what I mean.
03-04-2016, 08:46 AM
"...when I see it I always feel in awe knowing there are people in that bright fast-moving light."
Exactly what I was thinking when I was watching it. That and imagining what someone who wasn't aware of what it was they were looking at might think. More from Wikipedia: "Because of the size of its reflective surface area, the ISS is the brightest man-made object in the sky excluding flares, with an approximate maximum magnitude of -4 when overhead, similar to Venus. The ISS, like many satellites..., can also produce flares of up to 8 or 16 times the brightness of Venus as sunlight glints off reflective surfaces.[291][292]" That would be fun to catch one of those moments when sunlight is reflected much more brightly. This was the first time I had seen the ISS, knowingly. Edit: grammar.
03-04-2016, 06:01 PM
PM2 (and any others interested),
The reason the ISS appears to move so quickly compared to other satellites you may have seen is it's in low earth orbit (LEO) so it's not that far away when you see it and is actually traveling very quickly (17,000 mph). Other LEO satellites would appear to move as quickly, but are much smaller than the ISS therefore much fainter, and like the ISS can only be seen shortly after sunset or before sunrise, and are hard to spot with the naked eye, if not impossible. The satellites you see at night are in much higher orbit therefore farther away and are actually moving more slowly. The higher an object is in orbit, the slower it needs to move. Basically, people are not used to seeing fast-moving LEO satellites. I might be wrong here, but I don't think flares from the ISS are easily predictable, I suspect it's because its structure is so complicated. However, there are things called Iridium flares you might want to watch for on your next early morning walk! Iridium satellites (these are LEO communication satellites) have an unusual configuration of reflective antennas. They are controlled from the ground and the flares they produce are predictable, although their flares are a fairly narrow beam so even a few miles difference in locations on Earth makes a big difference to what you can see. The flares last for a few seconds but can be incredibly bright. They look like this: https://youtu.be/uymzXNdXwmo https://youtu.be/MTGVuPr9Epg Heavens Above (http://www.heavens-above.com) is the best site I know for finding predicted flares. You'll need to set up your precise location (top right of the page) and then select Iridium Flares from the list on the left. I can't emphasize enough the need to get your location precise. You will get predictions for the next 10 days for flares you can see. The second column of the table (Brightness) will tell you how bright it will be in magnitudes. The more negative the number, the brighter it will be. Bear in mind this is a logarithmic scale, and Venus is typically about -4. So, if you get a flare prediction of, e.g., -7, that means it should appear roughly 15 times brighter than Venus. If you're interested but need more info, just let me know. ETA: Added another Iridium flare video
03-05-2016, 11:41 AM
Hey Tom, thank you for the very interesting and instructive info. Good read as I had some spare moments this afternoon. Currently on the go but should have a chance to take a look at the links tomorrow morning and see about getting predictions for Iridium flares at my precise location. Who needs Wikipedia when we have our local random astrophysicist!
03-05-2016, 04:30 PM
No problem at all, PM2. Have to admit over the last few months I've learned an awful lot about what's in orbit around the Earth given our work with NASA on orbital debris observations. It's pretty much a new field for me, but it's very interesting. As for the "local random astrophysicist", I really like that name, perhaps I should have used it for my old blog!
03-06-2016, 06:03 AM
What a great website. Went ahead and downloaded the app too. Plenty features to peruse.
Some details of an upcoming Iridium flare predicted to be visible from my location: Date: 11 March 2016 Time: 04:58:27 Brightness: -5 Altitude: 34° Azimuth: 197° Satellite: Iridium 64 Distance to satellite: 1255 km |
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