Doomed Russian Mars probe seen from the ground

By Phil Plait | January 4, 2012 2:21 pm

In November 2011, the Russian space agency launched the much-anticipated Mars probe called Phobos-Grunt (which means "Phobos dirt" or "ground"), which would go to the Red Planet, soft-land a probe on the tiny moon Phobos, and return a sample of the surface to Earth. Unfortunately, the booster that would take it from Earth orbit into a Mars-intercept trajectory failed to fire, stranding the spacecraft in low-Earth orbit. Atmospheric drag has doomed the mission; it will most likely burn up sometime in the next two weeks.

Phobos-Grunt is visible to the naked eye as a bright star if it happens to pass overhead. Astronomer Thierry Legault, an expert in nabbing incredible images of objects in orbit (and no stranger to this blog!), traveled to Nice, France to observe it, and (as usual) got great video of it:

You can actually see detail in the probe; he provided a helpful picture to make it more clear:

The solar panels and other parts are pretty obvious.

Like UARS and ROSAT last year, Phobos-Grunt is making an uncontrolled re-entry, and it’s not entirely clear where it will fall. Odds are it’ll be over water, since the majority of Earth’s surface is ocean. The predictions I’m seeing look like it’ll be on or around January 15th. The actual location of re-entry won’t be known pretty much until the moment it comes down; it’s moving at several kilometers every second, so being off by a few minutes in the time means being off by thousands of kilometers in the location! There are a lot of variables involved too, including the orientation of the satellite (which changes the drag it feels from the atmosphere), solar activity (a solar storm can make the atmosphere puff up, speeding up the date of the spacecraft’s demise), and so on. I’ll write more information as I hear it.

In the meantime, you can check to see if Phobos-Grunt will pass over your location and you can see it; I suggest using Heavens-Above.com.

Image and video credit: Thierry Legault, used by permission. Slight edit of image done by The Bad Astronomer to compress it horizontally.

Related posts:

ESA writes off Phobos-Grunt
Phobos-Grunt scheduled to launch at 20:16 UT
Final: ROSAT came down in the Bay of Bengal
UARS official re-entry… and up next: ROSAT


Reminder: ROSAT's coming down soon

By Phil Plait | October 18, 2011 10:30 am

Last month, after the UARS satellite burned up over the Pacific, I mentioned that the German Astronomical satellite ROSAT will be burning up soon as well. It’s looking that will happen next week, with some models pointing to October 23rd. The exact time and even the date are still a bit uncertain, because it’s impossible to perfectly model the incredibly complex interaction between the satellite and the very thin atmosphere hundreds of kilometer up.

Emily Lakdawalla at The Planetary Society Blog has a nice write up of this, as does Dan Vergano at USA Today (featuring a quote by me, of all people, from that post last month). I imagine Space Weather will have info too as it comes out.

There’s a ROSAT Twitter stream with fairly up-to-date information as well. I’ll be paying attention to that carefully.

Just to be clear, I’ll state that even though more pieces of this satellite will survive re-entry than UARS did, the odds of anyone getting hit by a piece are still many thousands to one against, and of any particular person getting hit (meaning you) are trillions to one against. So while I don’t want satellites to fall from the sky every day, I’m not too concerned over this one.


UARS official re-entry… and up next: ROSAT

By Phil Plait | September 27, 2011 11:51 am

NASA has released the final update on the UARS bird that burned up in re-entry last week: it came down in the Pacific, west of the US.

The Earth’s atmosphere is not a lid over us, but gets thinner with height, so it’s hard to define exactly what it means to say that the satellite burned up at such-and-such a spot. However, at 04:01 UTC on September 24th, the satellite’s motion became dominated by the Earth’s atmosphere, and for all intents and purposes that can be called the point where it came back in… or at least, where it started. The forward motion of the satellite took the pieces along a track 500 – 1300 km (300 to 800 miles) long, which is still safely out in the ocean.

Thus ends the UARS tale.

… but we’re not quite done yet. The venerable German astronomical satellite ROSAT is due to come back down in about a month or so. Smaller than UARS — a little over 2 tons, as opposed to over 6 — ROSAT will probably have more pieces survive the ride down because its mirrors had to be shielded from heat to operate. That means the odds of it hitting someone will be slightly higher than from UARS, about 1 in 2000. Bear in mind that’s still really small odds! The chance of a specific individual getting hit are still something like only 1 in 14 trillion.

ROSAT is an X-ray satellite, designed to study high-energy radiation from astronomical sources. Years ago, I looked briefly at ROSAT data of a supernova remnant while putting together an educational activity about exploding stars. I don’t feel the same connection to the satellite as I do to, say, Hubble, but still, it’s a little sad to see it come down. However, it did provide years of outstanding service to the astronomical community, and gathered a vast amount of data about the high-energy Universe around us.

Image credits: NASA; German Aerospace Center (DLR)


UARS down over the Pacific ocean

By Phil Plait | September 24, 2011 9:02 am

NASA has confirmed that the Upper Atmosphere Research Satellites, UARS, burned up over the Pacific Ocean last night, September 24, between 03:23 and 04:09 a.m. UTC (11:23 p.m. and 12:09 Eastern US time). I have no other reliable information on it, but I expect we’ll get more updates soon. There were lots of reports last night of it falling over Canada, but those were mistakes or hoaxes. Apparently some people were fooled by meteors, Chinese lanterns, and possibly even the planet Jupiter. That’s happened before.

If I find photos or such I’ll try to post them, but I’ve heard no reports of witnesses, and I’ll be away this afternoon for my TEDxBoulder talk, so if any pictures turn up I may not be able to get to them. I imagine SpaceWeather will post any if they crop up.

Thus ends that saga. If you’re curious, you can read about the history of the UARS and what we learned from its 15 year mission to investigate our planet’s atmosphere.

Related posts:

UARS update 5: new predicted re-entry tonight at 05:10 UTC +/- 2 hrs
UARS update 3: new predicted re-entry tonight at 03:16 UTC +/- 5 hrs
UARS update 2: new predicted re-entry at 00:58 UTC
Update: satellite *might* fall on Friday at 22:00 UTC +/- 9 hours
NASA satellite due to burn up some time in the next few days

MORE ABOUT: re-entry, satellite, UARS

UARS update 5: new predicted re-entry tonight at 05:10 UTC +/- 2 hrs

By Phil Plait | September 23, 2011 8:35 pm

The Center for Orbital and Reentry Debris Studies has updated their predicted re-entry time for NASA’s UARS satellite. It is now 9/24 (tonight!) at 05:10 UTC (01:10 Eastern US time), which puts it over the southern Indian ocean:

See Related posts below for information and background. Note the uncertainty is once again smaller, at +/- 2 hours!

Related posts:

-UARS update 3: new predicted re-entry tonight at 03:16 UTC +/- 5 hrs
UARS update 2: new predicted re-entry at 00:58 UTC
Update: satellite *might* fall on Friday at 22:00 UTC +/- 9 hours
NASA satellite due to burn up some time in the next few days

MORE ABOUT: re-entry, satellite, UARS

UARS update 3: new predicted re-entry tonight at 03:16 UTC +/- 5 hrs

By Phil Plait | September 23, 2011 11:07 am

[UPDATE to the update (22:00 UTC): a new prediction just came out: tonight, September 23/24, at 04:04 UTC (midnight Eastern US time). The uncertainty is down to +/- 3 hours, and the location is the middle of the Pacific. Clicking the links below to CORDS or the image itself will take you to the most current prediction.]

The Center for Orbital and Reentry Debris Studies has updated their predicted re-entry time for NASA’s UARS satellite. It is now 9/24 (tonight!) at 03:16 UTC, which puts it over the Sahara:

Note that again this is later than the last estimate. As the satellite has gotten lower, aerodynamic drag — the wind blowing on it, tenuous as it is — has changed its orientation, creating less drag, slowing the descent.

Please note that the time is still uncertain, though now it’s only +/- 5 hours. Still, that’s a wide swath of Earth in that range, so we’re still not sure where it’ll burn up.

Check the Related posts links below for more info on the satellite, why it’s coming down, and how to read that map. Again, the danger from this is pretty minimal. You may note that the three predictions we’ve had have put re-entry over the ocean or otherwise largely uninhabited areas, and that’s not a coincidence: most of the Earth is like that! That’s why the odds of someone getting hit are so low.

I’m sure we’ll get another update or two in the next few hours, so stay tuned. You can also check the CORDS site for updates, and the NASA page as well.

Related posts:

UARS update 2: new predicted re-entry at 00:58 UTC
Update: satellite *might* fall on Friday at 22:00 UTC +/- 9 hours
NASA satellite due to burn up some time in the next few days

MORE ABOUT: re-entry, satellite, UARS

UARS update 2: new predicted re-entry at 00:58 UTC

By Phil Plait | September 22, 2011 9:07 pm

The Center for Orbital and Reentry Debris Studies has updated their predicted re-entry time for NASA’s UARS satellite. It is now three hours later than before: 9/24 at 00:58 UTC, which puts it in the middle of the south Pacific:

Mind you, the uncertainty on this is still +/- 7 hours, so we’re a long way from knowing just where it will come down.

For more details, please read this earlier post (and you might as well read this one as well for the background info).

MORE ABOUT: re-entry, satellite, UARS

Update: satellite *might* fall on Friday at 22:00 UTC +/- 9 hours

By Phil Plait | September 22, 2011 11:40 am

NASA’s UARS satellite will almost certainly plunge back to Earth sometime Friday, September 23. The exact time is still not known, but the window for re-entry is centered at 22:00 UTC (6:00 p.m. Eastern US time) with a 9 hour uncertainty on either side. The Center for Orbital and Reentry Debris Studies puts the satellite off the west coast of South America at that time:

However, this is still very preliminary! In other words, if you live in that area, don’t panic (in fact, odds are you shouldn’t panic at all). The uncertainty is still pretty big, because it’s very difficult to pin down just when and where a satellite will come down. The +/- 9 hour window is a pretty clear indication of that. Atmospheric conditions play a big role, as does the fact that the satellite is tumbling; that means the amount of drag from our air that it feels as it orbits changes constantly, making the exact moment of re-entry too hard to determine this far out. As time goes on, it’ll get more precise.

The map shows several things. At the currently predicted re-entry time, the satellite is just west of Peru. The orange circle around it marks the area where re-entry would be visible. The blue track is the orbital position of the satellite over the Earth before the predicted re-entry, and the yellow after it; both are marked with tick marks at 5-minute intervals. The track moves across the Earth because the Earth is rotating under the satellite! That changes the apparent ground track. The white line marks the day-night boundary, so it’ll be late afternoon locally at the predicted re-entry location.

As of 07:00 Eastern US time, NASA was reporting UARS’s orbit being slightly elliptical at 185 x 195 km (115 x 120 miles). That’s very low, as you’d expect for a satellite about to come down. NASA has provided an RSS feed for updates if you want to stay on top of this, but I’ll note the CORDS site appears to be more current. They also have a nice discussion of how and why satellites come back down.

I’ll update this post as I hear news, but if there’s a significant change in the time or status, I’ll put up a new post.

MORE ABOUT: satellite, UARS

NASA satellite due to burn up some time in the next few days

By Phil Plait | September 21, 2011 6:27 am

[UPDATE: Alan Boyle at Cosmic Log is reporting that the satellite will definitely come down on Friday, though NASA is not sure yet exactly when and where.]

[UPDATE 2: Emily Lakdawalla at The Planetary Society blog has lots of detailed info now.]

By now you’ve probably heard that NASA’s Upper Atmospheric Research Satellite (UARS, pronounced YOO-arz, though in my head it’s always "You arse!") will burn up in our atmosphere some time between Thursday and Saturday. The satellite was decommissioned in 2005 and they used the remaining fuel to lower the orbit. It’s been slowly getting lower since then, but recently reached the part of our air where it slows and drops dramatically. As you can see from this plot (click to embiggen), it’s dropped from about 375 km to 200 in just the last few months, and down it’ll come later this week.

No one knows where or when it will hit, since the final flight path will depend on changing atmospheric conditions, orientation of the satellite, and so on. Most of the 6 ton satellite will burn up, but some two dozen or so pieces are expected to survive re-entry.

Speaking of which: I’m seeing some concern over people getting hit by this thing. The odds of that are extremely low. It’s possible — NASA rates the odds at about 1 in 3200 — but highly unlikely. Mind you, those are the odds of anyone getting hit by debris. The odds of a specific person, say me, getting hit are far lower — if I’m doing this math correctly, you’d multiply that number by the population of the Earth, nearly seven billion people. So the odds of me (or you, or pick someone) specifically getting hit are about 1 in 20 trillion. Pretty long odds.

In the meantime, on September, 15th, "amateur" astronomer Thierry Legault was able to capture video of the satellite while it passed over his location:

Cool, eh? You can see the rotation; it’s tumbling, apparently. Out of power, it can’t keep the correct attitude, and over time something has caused it to spin. Maybe it was a collision, or maybe it’s from other subtle but persistent forces over the years (solar wind, light pressure, drag through our tenuous upper atmosphere, slow fuel leak, what have you). Here are some stills from Thierry’s video to make that more clear:

Pretty cool. So stay tuned. I’ll update with more info when I get it; we’ll know the re-entry time and location much better as the week progresses. <a href="I’ll be tweeting about it as well as soon as I find anything out.

Credits: Orbit plot: Jonathan McDowell; UARS images: Thierry LeGault.

Related posts:

YouTube video where I explain a satellite re-entry
BREAKING: SpySat successfully hit by missile
The return of Stardust
Spy sat to come home… not too secretly


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