Video: Yet another satellite tumbling toward earth

  1. Transcript of: Yet another satellite tumbling toward earth

    BRIAN WILLIAMS, anchor: Well, we have another dying satellite to look forward to. This time it's an uncontrolled German satellite called ROSAT . And our website, shown here briefly, is a great animation tonight that is more fun to watch once you learn that the path of this thing is not expected to bring it in over the US or Europe. It is expected to begin its re-entry starting Friday of this week.

updated 10/18/2011 7:18:45 PM ET 2011-10-18T23:18:45

This week will likely provide you with your very last opportunities to get a glimpse of a big German satellite, first put into orbit back in June 1990 and which has been dormant since February 1999.

The decommissioned German X-ray space observatory, called the Roentgen Satellite or ROSAT, will likely re-enter Earth’s atmosphere sometime between Oct. 22 and 24. ROSAT is currently moving around the Earth in a nearly circular orbit at an altitude of about 145 miles (236 kilometers) at an inclination of 53 degrees, which means that it is visible from virtually all inhabited regions on Earth.

Satellites become visible only when they are in sunlight and the observer is in deep twilight or darkness. This usually means shortly after dusk or before dawn. On any clear evening within a couple of hours of local sunset and with no optical aid, you can usually spot several orbiting Earth satellites moving with a steady speed across the sky like moving stars. [ Photos: Germany's ROSAT Satellite Falling to Earth ]

How to spot ROSAT
ROSAT is a relatively small satellite, so unlike the International Space Station or China's Tiangong space laboratory module, the defunct X-ray space observatory — while a naked-eye object — isn't a particularly bright object.

Astronomers measure the brightness of sky objects using the magnitude scale, in which low numbers correspond to bright objects.

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In terms of ranking, the International Space Station usually reaches a brightness of about -2 to -4 magnitude, equaling or even rivaling the planets Jupiter and Venus. The brightest stars, such as Vega or Deneb have magnitudes of zero or one. A fairly bright star like Polaris (also known as the North Star) is categorized as 2nd magnitude, while stars of medium brightness are 3rd magnitude and faint stars are considered to be 4th magnitude. Megrez, the star that joins the handle with the bowl of the Big Dipper, is a 3rd magnitude star.

Image: ROSAT satellite undergoing test.
Dornier (now Astrium Friedrichshafen)
The ROSAT satellite undergoing tests in the space simulation chamber at Dornier. 


ROSAT appears generally between third and fourth magnitude.  So, unlike the space station, which can easily be seen from a brightly-lit city, you’ll need to have access to a reasonably dark sky to see ROSAT.

In addition, because it's probably tumbling during its final days in space and because this 2.4-ton satellite is irregular in shape, ROSAT may appear to "blink" or "flicker" in brightness on its track across the sky. It might even "flare" briefly in brightness as it catches a glint of reflected sunlight and directs it toward you.

When and where to look
Ted Molczan, the moderator of the SeeSat Internet mailing list, utilized 12 sets of orbital elements obtained from the U.S. Strategic Command to derive a possible window for re-entry. His calculations suggest that ROSAT could re-enter anytime from Oct. 22 to 24.

So these are the final days to catch a glimpse of the German satellite before it makes its fiery plunge through Earth’s atmosphere. This week, ROSAT should be visible at dusk as an evening object across most of North America, as well as Europe. 

So what is the viewing schedule for your particular hometown? You can easily find out by visiting one of these two web sites:

Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they will certainly change due to the increasing decay of ROSAT's orbit. (So it is very important that you check frequently for updates.)

Another great site is this one, which provides real-time satellite tracking and shows you at any given moment during the day or night over what part of the Earth ROSAT happens to be.

Editor's note: If you snap a great image of based on the skywatching website data above and would like to share it for a possible image gallery or story, please contact managing editor Tariq Malik at

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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