(12 February 2009)—On February 10 at approximately 1656 GMT, the Iridium 33 and Cosmos 2251 communications satellites
collided over northern Siberia. The impact between the Iridium Satellite LLC-owned satellite and the 16-year-old satellite launched
by the Russian government occurred at a closing speed of well over 15,000 mph at approximately 490 miles above the face of the
Earth. The low-earth orbit (LEO) location of the collision contains many other active satellites that could be at risk from the
resulting orbital debris.
The following videos, interactive 3D Viewer files, 3D models, and high-resolution images are available to better
understand this event:
VIDEOS:
In all uses, please courtesy "Video courtesy of Analytical Graphics, Inc. (www.agi.com)."
| Satellite collision with a statistical breakup model. |
 |
This one-minute video demonstrates the approach trajectories of the two satellites prior to impact, as well as a
statistical breakup model with an example of propagated debris.
|
The breakup model is a statistical model that generates 1,000 debris samples for each satellite, numerically integrated in a
full force model in STK/Astrogator. Statistical debris models employ stochastic processes useful for rapidly characterizing a
debris event to understand where debris could go and can assist in risk analysis. While not requiring observation data to run,
this model can be refined by seeding the statistical values with data from tracked debris as it becomes available. An output of
the model is a high-precision catalog of ephemeris data. The breakup model used a Gaussian distribution of samples with a 1
km/s delta-V magnitude (sigma 1 km/s) and uniform density and mass distributions. The breakup model delta-V directions were set
to Azimuth -90 deg and an elevation of 38 deg and -38 deg (sigma 30 deg). The propagator used a JGM2 gravity field with degree
12 and order 12. The computational time to generate these models in STK is extremely rapid with the ability to calculate results
for several day propagations in less than 15 minutes on a single legacy processor. Since each piece is modeled individually,
parallel processing techniques would provide near instant data if required. Values for propagators and breakup statistics are
user controlled.
| Satellite collision with an Evolve-based, statistical break-up model |
 |
This 1-minute video demonstrates the approach trajectories of the two satellites prior to impact, as well as a statistical break-up model
with an example of propagated debris.
|
This is a 1000 object statistical sample of more than 2,600 fragments predicted using a modification of the NASA Evolve debris model. This model
abstracts structural and material fragmentation physics. Outcomes depend on the degree of contact between the two satellites, distinguishing between
portions totally involved and those outside the contact area. This depiction uses initial on-orbit masses of 685 Kg for Iridium and 900 kg for Cosmos
2251 and assumes 30% direct contact for each object. The model can also release instantaneously energy stored in unexpended propellants, although
that capability was not used in this case.
INTERACTIVE 3D VIEWER FILES:
In all uses, please courtesy "Viewer file courtesy of Analytical Graphics, Inc. (www.agi.com)."
AGI Viewer is free application that allows you to experience STK-generated content in a dynamic and interactive 3D environment.
VDFs, the AGI Viewer file format, allows you to view the collision from the position and time of your choosing.
Plus, you can cycle through a series of stored views and camera paths that the STK scenario author used to communicate the
details of the event.
3D MODELS:
In all uses, please courtesy "3D models courtesy of Analytical Graphics, Inc. (www.agi.com)."
Both STK and AGI Viewer provides users with the opportunity to incorporate 3D models of objects into an accurate virtual globe
environment. The following 3D models are in an MDL format to be used with STK and AGI Viewer.
HIGH-RESOLUTION IMAGES:
In all uses, please courtesy "Image courtesy of Analytical Graphics, Inc. (www.agi.com)."
Download the high-resolution graphics by clicking on the images below.
AGI CONTACT INFORMATION:
For additional information or to set up interviews with AGI and CSSI technical experts, please contact:
Press Contact:
Joanne Welsh
Strategic Product Marketing Manager
Analytical Graphics, Inc. Phone: 610-981-8148 (w) or 610-457-4385 (c)
E-mail:
media@agi.com;
jwelsh@agi.com
ADDITIONAL INFORMATION
To support the space community in better understanding this unprecedented satellite-to-satellite collision, AGI and CSSI have used
their software to reconstruct the event. TLEs distributed via Celestrak.com and standard STK conjunction analysis tools have powered
CSSI's SOCRATES service since 2004 for regularly performing all payloads-on-all conjunction assessment calculations. Additionally, AGI and
CSSI software has been used to help assess the possibility of additional collisions by applying breakup models for debris prediction.
Since May of 2004, CSSI has been providing free online conjunction advisory services--SOCRATES--to the satellite community,
using AGI tools, to help the space community develop a better understanding of the magnitude of the problem with satellite
close approaches in Earth orbit. Since February 2008, CSSI has worked closely with geostationary satellite operators to find
ways to improve the accuracy of the data used for these analyses in an effort to reduce the number of false alarms and thereby
reduce the risk of a potential collision. For more information, visit
http://celestrak.com/SOCRATES/.
Desktop Applications
