While taking pictures for a night sky timelapse video, astrophotogrpaher Babak Tafreshi got a surprise in his field of view: a tumbling satellite! He made a special video to highlight it:
Pretty neat. A lot of people aren’t even aware that satellites are visible at night at all, but really on any given night dozens of satellites can be visible passing through the sky; in fact the space station is so bright it’s actually now the third brightest object in the sky, surpassing even Venus.
The satellites come in a lot of flavors: communications, military, scientific, even old rocket boosters abandoned in orbit after their job was done. Sometimes those satellites have to maintain a specific attitude, or angle, as they orbit the Earth, but not all of them do (especially those boosters). These can tumble end over end, and so their brightness changes as we look at them. They shine by reflecting sunlight, so when we see a long booster end-on it’s fainter than when we see it from the side. As they tumble, then, they brighten and fade.
That’s what Babak caught here. I don’t know what satellite he’s seeing, but clearly from its behavior it’s tumbling as it orbits [UPDATE: Babak told me that it's been identified as a Cosmos 2364, a defunct navigation satellite, and it's most likely rotating, not tumbling, and the change in brightness is due to how sunlight is reflecting off its solar panels]. I’ve seen this myself many, many times and it’s fascinating to watch. In this time lapse it’s sped way up, of course, so it’s more stately when you see one by eye.
If you want to see satellites yourself, then I always suggest Heavens Above, which is my go-to site to find out what’s up. Just enter your latitude and longitude (you can get them from Google Maps, for example) and off you go! They’re also easy to photograph, too (check the Related Posts below for more). It’s fun, and actually pretty cool: you can get pictures of things screaming around the Earth at tens of thousands of kilometers per hour! And all you need is an inexpensive camera and a tripod.
And you don’t even need that to enjoy them. Just go outside at the right time, face the right direction, and look up. That’s all it takes.
Related posts:
- And I saw a star rising in… the WEST?
- Shooting satellites, new and old
- The Shuttle, the Station, and Orion
February 24th, 2012 at 7:35 am
Hi Phil! This is my first comment on your blog and so I’d like to say thanks for posting all this interesting stuff, beautiful videos, and doing such a great job at outreach in astronomy & astrophysics! Your blog is also interesting for professional astronomers in the making, aka PhD students!
The above video reminded me of a few months ago when I was observing at the Mercator telescope on La Palma and I went out to see X-37B, a NASA orbital test vehicle (I had the predictions from Heavens Above). It looked a lot like in the video, very bright and with a periodic light curve, and I interpreted the variability as due to rotation around its own axis ( the heat shield won’t reflect much, but the white parts will ). I wonder if that might be our candidate?
Cheers
Richard
February 24th, 2012 at 7:56 am
In other satellite-related news: a piece of space debris came down in a Brazilian village two days ago, see summary here:
http://sattrackcam.blogspot.com/2012/02/space-debris-lands-in-brazil-village.html
It’s almost certainly a spherical tank from an Ariane rocket stage launched in 1997: time and location match the reentry information for this object to a high degree.
February 24th, 2012 at 8:58 am
I once saw one zipping overhead while laying on the beach in Saudi Arabia with my girlfriend at the time. Pretty cool thing to see personally.
February 24th, 2012 at 11:08 am
i’ll always remember the first time i saw one. you watch the sky any evening for more than 10 minutes, and your eye/brain can really spot things that move, stuff that is unusual.
this first satellite i saw, it was just a dot like a star. but it was moving. so i thought it MUST be a plane. but the dot was so small, which to me meant it was very high. and it was moving SO FAST across the sky for being so high, and that’s when it hit me that it must be a satellite.
while you can almost always see satellites in the sky, you’re best best is early or late evening. in the middle of the night, the earth would be “eclipsing” any sunlight that could reflect off the SAT.
i’ve never seen a tumbling sat before though. that is beautiful.
February 24th, 2012 at 11:17 am
Since it’s being caught by a timelapse that shows the stars moving significantly, it is tumbling *very* slowly. I would also at first think that it’s relatively high in altitude because of the amount of time needed to cross the field of view, but as the camera is nearly horizontal, the satellite is just above the horizon and the velocity vector is likely greatly foreshortened, so it’s difficult to estimate whether it’s in low earth orbit or much higher. I’d take a guess that the rate of rotation is on the order of 1 RPM, which wouldn’t catch your eye as dramatically as a faster rotation rate. I’ve seen tumblers that rotate as fast as once per second … those catch your eye as you see them go overhead.
February 24th, 2012 at 11:57 am
It’s amazing where you can see satellites. I love Denver’s thin air for just that reason. Even when I was living barely two miles from downtown, I could see satellites on most clear nights, especially in winter.
February 24th, 2012 at 12:18 pm
Thank you Phil for posting this. Based on my imaging date and information the satellite is identified by Ted Molczan of http://www.satobs.org: It is the Glonass navigation satellite Cosmos 2364 (98077A / 25593). The satellite’s angular velocity was ~0.01 deg/second. The satellite altitude was 19148 km and 23631 km from the observer as it was captured near the horizon. Its orbital period is 675.73 minutes. The flashes probably are specular reflections from the solar array, caused by rotation of the satellite, which probably no longer operates.
The timelapse is a 42-minute sequence starting around 1:40 UT, 2011 August 31. Each frame is 15 second exposure (+ 1s for intervals) and the video is 24 frames per second.
February 24th, 2012 at 1:20 pm
Babak is simply amazing!
And yes, it is cool to see tumbling satellites, specially if you have a cool pair of binoculars with you to enhance the experience.
February 24th, 2012 at 2:59 pm
The original Iridium constellation twirled its solar panels to create a flash (I think the period was 2 minutes) – this was done purely as a gimmick.
February 24th, 2012 at 4:10 pm
While the ISS is great to look at and dazzles the first time viewers, Iridium flares are twice as fun. You have to know when and where to look, but when you get it right, it’s quite a show. A brilliant flash for about 5 seconds, then a dim spot continuing on. Sometimes they line up 1 minute after each other – a special treat.
February 24th, 2012 at 5:41 pm
I do star parties 6 to 15 times a year and only see a “Tumbler” about twice a year, and I Always Flip Out. They are so much fun to see, and try to predict where the next flash will be. The first Tumbler I saw was in 97 or so, and it flashed for a second every 45 seconds or so, it was so cool when I figured out what it was.
February 25th, 2012 at 9:39 am
@ #1 Richard:
The X37-B is USAF, not NASA. And it is steady, not a flasher, so this cannot be the object you describe.
February 25th, 2012 at 1:51 pm
I love going up to the Black Rock desert in Nevada for my sky viewing pleasure. Of course, during Burning Man the sky is not quite as inky black as it is the rest of the year but still way better than here in Sacramento. While following a satellite with binoculars one time while camping out on the playa, I stumbled upon the Andromeda galaxy for the first time. It was breathtaking to me. I will have to keep an eye out for these “tumblers” when I go up in July.
February 25th, 2012 at 5:55 pm
Great clip – thanks BA & thanks Babak Tafreshi for that & for your informative comment #7 .
Question – what is that super bright yellow star – or more likely planet – seen in this clip?
February 26th, 2012 at 4:57 pm
Using the data provided by Babak Tafreshi, Google Street View & Stellarium, I’m pretty sure that’s the red giant Menkar/Alpha Ceti.
February 28th, 2012 at 5:55 am
@ ^ Syrion : Cheers for that.
March 11th, 2012 at 2:01 pm
Hi all!
Did anyone else notice another fast moving object in that video? It’s most clear in the last most-zoomed-in ‘replay’, just before the ‘credits’ (around 21 seconds into the clip).
It’s moving almost parallel to the star streaks/arcs, from just left of top-centre toward the bottom, left of centre. I would guess that it is an asteroid, and judging from the rate of motion, I’d say it was a pretty close one too.
Does anyone know which one it was, or if it was even a known one?