Satellite collision on February 10, 2009

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On February 10, 2009 , the first satellite collision occurred in Earth orbit. The two communication satellites Iridium 33 and Kosmos 2251 of the Iridium and Strela systems, operating at an altitude of almost 800 kilometers , were completely destroyed. The collision with the enormous relative speed of 11.6 km / s resulted in over 100,000 fragments that are large enough to remain in orbit for decades and cause severe damage in the event of a hit. By January 2013, 2201 larger fragments of this space debris ( radar limit size 5 to 10 cm) had been cataloged ; 380 of them had already crashed due to the braking effect of the atmosphere. The International Space Station (ISS) has already flew evasive maneuvers several times when one of these parts had sunk to the orbit height of the station and an impact could not be safely ruled out.

Details

satellite SCN active Dimensions volume Largest dimension perigee apogee Inclination
Iridium 33 24946 1997 - February 10, 2009 556 kg 3.39 m 3 25 m (horizontal, between solar cell modules) 776 km 779 km 86.4 °
Cosmos 2251 22675 1993-1995 900 kg 7.84 m 3 17 m (vertical, boom down) 776 km 800 km 74.0 °
The trajectories of Iridium 33 and Kosmos 2251 intersected at an angle of 102.2 °

For 16:56:00 UTC a close encounter of the two satellites was over northern Siberia been predicted: the service SOCRATES ( S atellite O rbital C onjunction R eports A ssessing T hreatening E ncounters in S pace) of the Center for Space Standards and Innovation ( CSSI) has been calculating and publishing possible collisions (limit distance 5 km) between satellites with other satellites or cataloged parts of space debris twice a day since 2005 on the basis of freely accessible satellite orbit elements . Due to gravity anomalies, these path elements describe the paths only approximately and become obsolete within a few revolutions. In the last report before the collision, at 15:02 UTC, the roughly estimated minimum distance during the flyby was almost 600 m. The entry was therefore only ranked 16th among the approximately 1000 entries in this report that concerned the Iridium system from 66 satellites at the time. There was no immediate cause for concern with these data.

At the predicted time, but surprisingly, communication with Iridium 33 stopped . In accordance with physical models of high-speed impacts ( NASA Standard Breakup Model , a Monte Carlo simulation ), two debris clouds were created that largely followed the old orbits. This seems to contradict physics, according to which large deflections arise in both elastic and inelastic collisions . Here, however, the kinetic energy of the material is far higher than its chemical binding energy , so that the elastic properties are insignificant for parts of the satellites that penetrate one another. Rather, the strongly interacting mass elements change into a plasma state within microseconds. As with a detonation, the surrounding material is torn apart. The momentum transfer to larger, observable fragments is relatively low.

Within a few hours, the two debris clouds expanded so that the radars of the Space Surveillance Network (SSN) could break them down into dozens of individual objects. Some fragments, in particular from Kosmos 2251, had been pushed into clearly elliptical orbits in the height range 200 to 1700 km. The concern was not only about the ISS, which at that time had an orbit height of 350 km, but also about the STS-125 service mission planned for spring 2009 to the Hubble Space Telescope (HST) at 570 km. One would be able to avoid the individually tracked fragments, but a far larger number of smaller particles was expected, which are not observable with these radars, but are nevertheless dangerous.

In order to be able to assess the risk, observations were made with two larger, more sensitive radars: with the 70 m antenna of the Goldstone Observatory and with the 37 m telescope of the Haystack Observatory . Because they were too clumsy for tracking, both were operated with a fixed orientation, with the rotation of the earth taking care of the scanning pan of the narrow antenna lobes. In order to obtain representative results, one waited a few weeks, during which the particles spread evenly along their orbit around the globe. The limit sizes of the two telescopes were 2 to 3 and 10 mm for these observations. The result of the investigations: The increase in the number of particles with decreasing particle size matched the physical models of high-speed collisions and was therefore not as steep as the size distribution of the cataloged, larger fragments indicated and led to fear.

Meanwhile, the Iridium system operator worked to remedy the effects of the loss. The routing was changed within 60 hours so that no more attempts were made to establish connections from / to the ground or between satellites via the missing satellite. By March 2 of the same year, a reserve satellite that was already in orbit was maneuvered into the gap.

Gabbard diagrams of the fragments of Iridium 33 (left) and Kosmos 2251 (right) on March 5, 2009. The apogee height (blue) and the orbit period (horizontal axis) of low-flying fragments has already decreased due to air friction.

Within 24 weeks, 1307 radar objects were cataloged, which apparently originated from this event. Measured against the mass and size of the original bodies, this number seemed rather small. Apparently most of the mass is in two large fragments, the satellite wrecks. In fact, like other satellites at this altitude, these wrecks are visible from the ground. The light curve of the Iridium wreck, occasionally with two flashes of light per period, indicates that two of the three antenna surfaces mounted below are still present.

Of the fragments included in the catalog up to January 2013 - others have already been identified - 1603 come from Kosmos 2251 and 598 from Iridium 33. Of these, 261 and 119 fragments (16 and 20%) have already crashed due to air friction, mainly in 2012. That NASA Orbital Debris Program Office estimated that by the end of the then high solar activity (≈ ~ 2016) just under 40% or around 50% of the fragments would have taken this route. The observed greater braking effect of the high atmosphere on the fragments of Iridium 33 can be explained by the consequent lightweight construction of the satellite compared to the more robust Russian model.

See also

Individual evidence

  1. ↑ a b c An update of the FY-1C, Iridium 33, and Cosmos 2251 Fragments. In: NASA : Orbital Debris Quarterly News. Vol. 17, Issue 1, January 2013, page 4.
  2. ^ Another Debris Avoidance Maneuver for the ISS. ibid , p. 3.
  3. ↑ Analytical Graphics, Inc (AGI): Flyer ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. via the Center for Space Standards and Innovation (CSSI), SOCRATES Home . @1@ 2Template: Webachiv / IABot / www.agi.com
  4. ↑ a b Thomas Sean Kelso, CSSI: Analysis of the Iridium 33-Cosmos 2251 Collision , Maui: Advanced Maui Optical and Space Surveillance Technologies Conference, 2009. ( White Paper ( Memento of the original from July 31, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Sept. 2009). Source [3] in it is apparently this video . @1@ 2Template: Webachiv / IABot / www.agi.com
  5. ↑ TS Kelso: Determining that the predicted conjunction for Iridium 33 and Cosmos 2251 was more significant than the many dozens of other Iridium conjunctions for that week is simply not possible using the TLE data. Ibid, p. 3.
  6. ^ William J. Broad: Debris Spews Into Space After Satellites Collide , The New York Times , February 11, 2009.
  7. ↑ Small Debris Observations from the Iridium 33 / Cosmos 2251 Collision. In: NASA : Orbital Debris Quarterly News. Vol. 14, Issue 2, April 2010, page 6.
  8. ^ Iridium press release , February 26, 2009.
  9. ^ Iridium press release , March 9, 2009.


Coordinates: 72 ° 31 '12 "  N , 97 ° 23' 24"  E