1. SPACE DEBRIS Roger Thompson Sr. Engineering Specialist
Abstract: Space debris is a growing concern among satellite operators because the number of objects that have the potential to destroy a satellite now number in the hundreds of thousands. The history of space debris generation, tracking, modeling, and prediction is presented. Examples of debris generating events are used to illustrate the complexity of the problem and the risk to satellite operations. Deficiencies in our ability to quantify and mitigate the risk are noted. Animations of space debris orbits over the last 40 years visually illustrate the rapidly increasing density of the space debris environment.
Roger Thompson
Sr. Engineering Specialist

2. WHAT IS SPACE DEBRIS?
Obsolete spacecraft, parts of satellites or rockets
AND
Fragments of spacecraft that have broken up or collided

3. how many breakups and COLLISIONS?
Prior to 1 August 2007, there have been 194 fragmentations and 51 anomalous events1
Most of the debris comes from propellant explosions and deliberate action
56 were deliberate
99 were accidental: 88 propulsion, 8 battery, 3 collisions
39 have unknown causes
The have been only 4 known collisions between tracked objects
1991 Cosmos 1275 debris and Cosmos 1934 (inactive)
(not discovered until 2005)
1996 Cerise active satellite and Ariane 1 Debris
2005 Thor Burner 2A debris and CZ-4 Debris
2009 Iridium 33 active satellite and Cosmos 2251 (inactive)
[1] History of On-Orbit Satellite Fragmentations 14th ed., NASA Orbital Debris Program Office, June 2008)

4. HOW DO WE KNOW ABOUT SPACE DEBRIS?
JSpOC gets approx 400,000 observations and 85,000 tracks PER DAY.
12,000 observations and 2500 tracks are uncorrelated (can’t be identified)
Graphic from USSTRATCOM Space Control and Space Surveillance Fact Sheet

5. SPACE DEBRIS COMES IN ALL SIZES
From microscopic particles
To obsolete spacecraft and rocket bodies tens of feet in length
Photographs Courtesy of NASA

6. But we can only track “large” objects
10 cm
5 cm
1 cm
3 mm
1 mm

7. How Much space debris is there?
Size Class
Quantity
Collision Risk
~10 cm or larger
Over 19,000
Catastrophic damage
Tracked and cataloged
We can try to avoid these
1 cm to ~10 cm
Over 500,000
(estimated)
Most can’t be tracked
Major to catastrophic damage
Constant daily risk to satellites
1 mm to 1 cm
Over 10,000,000
Can’t be tracked
Localized damage
3 mm = upper limit of shielding
Constant but lower risk

8. IS SMALL DEBRIS REALLY A PROBLEM?
It may be small, but it is moving at 17,000 mph!
That kind of energy can damage anything it hits

9. IS SMALL DEBRIS REALLY A PROBLEM?
Hubble Space Telescope antenna damage
Photograph Courtesy of NASA

10. IS SMALL DEBRIS REALLY A PROBLEM?
This panel, returned from the Hubble Space Telescope after 7 years in space , has 69 space debris impacts
Photograph Courtesy of NASA
1994: Shuttle window had a ½ inch crater that penetrated all but one of the layers of the window
NASA determined the cause was a 1/8 inch diameter paint chip

11. HOW CAN WE PROTECT SPACECRAFT?
For very small debris, an outer shield can protect critical components
Photograph Courtesy of NASA

12. Mass (g) aluminum sphere
HOW CAN WE PROTECT SPACECRAFT?
For very small debris, an outer shield can protect critical components
For large debris, maneuvering out of the path is the only option
At 10 km/sec typical LEO impact speed
Debris size
Mass (g) aluminum sphere
Kinetic Energy (J)
Equiv TNT (kg)
Energy similar to
1 mm
0.0014 71
0.0003
Baseball
3 mm
0.038
1,910
0.008
Bullets
1 cm
1.41
70,700
0.3
Falling anvil
5 cm
176.7
8,840,000 37
Hit by bus
10 cm
1,413.7
70,700,000
300
Large bomb

13. PREDICTING COLLISIONS
Not a yes/no result, we have to work with probabilities
Exact orbits and positions are never known
Copyright Aerospace Corporation

14. Remember those four known collisions?
1991 Cosmos 1275 debris and Cosmos 1934
Predicted miss distance meters
Probability of collision E-5 (~1 : 50,000)
1996 Cerise active satellite and Ariane 1 Debris
Predicted miss distance meters
Probability of collision E-7 (~1 : 2,000,000)
2005 Thor Burner 2A debris and CZ-4 Debris
Predicted miss distance meters
Probability of collision E-6 (~1 : 500,000)
2009 Iridium 33 active satellite and Cosmos 2251
Predicted miss distance meters
Probability of collision E-5 (~1 : 100,000)

15. WHAT HAPPENS WHEN OBJECTS COLLIDE?
First animation includes only 10 cm and greater fragments
Model predicts 1,184 fragments
Only 245 (20%) are shown in animation
Second animation includes 1 cm and greater fragments
Collision with these objects will probably destroy a satellite
Model predicts 148,062 fragments
Only 11,364 (less than 8%) are shown in animation

16. WHAT HAPPENS TO SPACE DEBRIS?
Debris in very low orbits slowly loses altitude and re-enters the atmosphere
Most of time it burns up during re-entry
Sometimes, it survives and lands back on Earth
Debris in higher orbits can remain for hundreds or thousands of years
Photograph Courtesy of NASA

17. UNCONTROLLED DEBRIS RE-ENTRY
Objects pose a risk to life and property if they survive re-entry
This tank landed 150 ft from a house
Photograph Courtesy of NASA

18. UNCONTROLLED DEBRIS RE-ENTRY
It is impossible to predict exactly where objects will land
Copyright Aerospace Corporation

19. UNCONTROLLED DEBRIS RE-ENTRY
We can calculate a probable impact zone
But it may cover thousands of square miles (28,000 for Columbia)
Initial Breakup
Catastrophic Breakup
Secondary Breakup
Main Debris field
Low Mass Debris
Jan. 1978: Soviet satellite reenters, breaks up, and lands in Canada.
spreads radioactive debris over 124,000 sq. miles

20. CONTROLLED DEBRIS RE-ENTRY
Spacecraft that are no longer needed are sometimes programmed to re-enter and impact in the ocean
Photograph Courtesy of NASA

21. IT ALL BEGAN WITH THE FIRST SATELLITE
Since the October 1957 launch of the world’s first satellite, Sputnik 1
More than 4,500 space missions have been conducted, producing over 19,000 tracked pieces of debris still in orbit.
America’s Vanguard 1 is the oldest piece of space debris
Photograph Courtesy of NASA
# Vanguard I
# Vanguard I R/B 3/17/1958
# Oldest Agena upper stage 9/29/1962
Aug 2010 added 6 debris objects from 1965 launch of a Titan 3C
Aug 2011 added a debris object from a 1970 launch
Still finding/cataloging FY-1C debris from 2007, now over 8 years after the event (20 more added Nov 2015)