GOCE Satellite Expected To Crash-land Who Knows Where Today

GOCE (pronounced GO-chay) is 17 feet long and dubbed the “Ferrari of Space” because of its sleek design. It will burn up later today in Earth’s atmosphere. Credit: ESA

Get out the way! The European GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite ran out of fuel in October and it’s on the way down. Scientists at European Space Debris Office expect it to plunge through the atmosphere between 12:30 p.m. and 6 p.m. this afternoon.

The position of GOCE is tracked by GPS satellites – slight shifts in its orbit from the continuously changing gravitational pull of land and water below are used to obtain gravity field information. Credit: ESA

Since most of the Earth’s surface is ocean, that’s where GOCE’s likely to fall … but you never know. This isn’t a controlled re-entry, so there’s a small chance it could land in your backyard. A very small chance. If it does burn up over inhabited land it will be a spectacular sight even in the daytime.

Most of the 2,000-pound satellite will burn up harmlessly, but Heiner Klinkrad, head of the Space Debris Office, estimates that about 20 percent or 440 pounds (220 kg) of debris in the form of dozens of fragments will survive the plunge and reach the ground along a sizable re-entry swath.

Spread out this way, the chances of a particular piece of machinery coming down on your head is exceedingly small. But if that does happen, you’ve got options. According to a 1972 U.N. agreement called the Convention on International Liability for Damage Caused by Space Objects, you’re fully covered by the European Space Agency in case of damage to life or property.

A picture of Earth’s gravity field – the most detailed ever – from the GOCE satellite. The colors in the image represent deviations in height from -100 meters to +100 meters (-328 feet to +328 feet) from an ideal shape. Blue represents low and red/yellow high. Africa is at right and South American at left. Credit: ESA/HPF/DLR

GOCE’s currently about 90 miles up and losing 0.6 miles of altitude for every orbit it makes from friction with the atmosphere. It was launched in March 2009 on a mission to precisely map Earth’s gravity field and ocean currents and create a high-resolution map of the boundary between Earth’s crust and mantle (dense rock layer directly beneath the crust that’s some 1,800 miles thick.)

Primer on GOCE’s mission

One of the coolest things it did was create a detailed map of the “geoid” or virtual map showing the strength of gravity across the planet. Mountain ranges, composed of dense rock, have a stronger gravitational pull on the spacecraft compared to ocean waters. Every minute variation in gravity altered GOCE’s orbit a little bit here and a little bit there. Combined with data from its internal gravity-measuring gradiometers, the probe compiled the information to create a map showing a very lumpy Earth.

Frame from the live tracking widget grabbed at 10:30 a.m. when GOCE was over the Indian Ocean headed toward Antarctica. Credit: ESA

Mapping the geoid helps scientists better understand sea level changes and global ocean circulation which are in turn affected by climate change.

I’ll report back later today when GOCE bites the dust. In the meantime click HERE to track it live from your phone or computer.

Please note that it sometimes takes a minute for GOCE to show up on the tracking map.

** UPDATE 8:15 p.m. CST: According to the BBC News, GOCE has re-entered Earth’s atmosphere. It was last sighted at 4:52 p.m. CST passing just 75 miles (121 km) over Antarctica. Any debris that survived the fiery dive would have fallen anywhere from Eastern Asia across the Pacific to Antarctica. We can all breathe now!

More information can be found on Visual SAT-Flare Tracker 3D as well as on Daniel Souka’s blog. Souka is Senior Editor for Spacecraft Operations at ESOC, ESA’s European Space Operations Center in Darmstadt, Germany.

12 Responses

  1. Edward M. Boll

    Lovejoy is an awesome sight in binoculars at magnitude 5.5. Are you still looking at Comet Lemmon? At magnitude 12, it is probably still visible in a 12 inch telescope. Meanwhile I have heard that Panstaarrs L4 is dimmer than magnitude 16.

    1. astrobob

      Congrats Edward! We were out this morning checking it out too along with ISON and Encke and the new comet (faint) recently discovered by Nevski. Yep, I’m still trying to follow Lemmon. I made my last observation earlier in the week – it’s VERY faint and barely visible at mag. 13 and diffuse.

  2. RC

    Do you happen to know how much gravity changes around the world? If something weighs 100 pounds in the area of least gravity, what would it weight in the area of highest gravity? 100.5, 101? Or is it a bigger difference, like 105? 110? (10% seems like a lot).

    1. astrobob

      Great question. I can’t answer your question with precision, but since we are very small compared to the gravitational attraction of the Earth, I would think the difference would be extremely small – maybe near the limits of measurement.

      1. RC

        I was thinking that 1/2 pound (0.5% difference) would be about the most it could be, but that’s just a total guess. Maybe 0.05% is closer, or even 0.005%. I’d think it would be a measureable difference (with a precise scale and a large enough weight), after all, we’re measuring the affects of gravity on a 2000 pound machine 90miles up!

        1. astrobob

          True, but the effects we measured were in the spacecraft’s position in space, not its weight. I’m not sure how that translates.

  3. While we discuss satellites in difficulty, the Mars Orbiter Mission (MOM – Mangalyaan) just experienced a “uh-oh” moment during the 4th of the planned 6 engine burns to insert it on to its Mars journey. Hopefully, it will perform nominally during tomorrow’s next attempt.
    More about the anomaly and analysis here:
    and here:

    1. astrobob

      Thanks BC. Let’s hope it all turns out well. By the way, I see the probe is out in Duluth’s skies, moving extremely slowly near apogee. Don’t know the magnitude but it must be very faint. Heavens Above provides no brightness on this one.

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