8. Mission: Why Study Ascent
Debris
• STS-107 (Columbia)
February 1, 2003
• What was the
debris?
• How do we track
ascent debris in the
night?
• Why is it important?
10. Nominal Systems (NASA)
• July 24, 2014: US Patent 20140203961 A1
• “ A method is provided for analyzing debris events after a launch
of a rocket-propelled vehicle. Radar and Doppler data of the
launch of the rocket-powered vehicle is collected for a period of
time. Atmospheric conditions are determined at the time of
launch. A trajectory of the rocket-propelled vehicle is determined
during ascent.”
ARDENT:
Ascent Radar Debris
Examination Tool
http://www.google.com/patents/US20140203961
11. Nominal Systems (NASA)
• July 24, 2014: US Patent 20140203961 A1
• Columbia Disaster Conclusion
• Small briefcase sized foam insulation struck left wing
• Common ascent debris
• SRB and SRB exhaust/smoke plumes
• Main engine 𝐻2 𝑂 exhaust
• “ During the STS-107 accident investigation, radar data collected
during ascent indicated a debris event that was initially theorized to
be the root cause of the accident. This theory was investigated and
subsequently disproved by the Columbia Accident Investigation
Board (CAIB). However, the data itself and the lack of understanding
of what debris data in radar meant to the shuttle program, required
further analysis and understanding.”
http://www.google.com/patents/US20140203961
12. Nominal Systems (Lockheed)
• February 7, 2006: US Patent 6995705 B2
• “System and method for doppler track correlation for debris
tracking”
13. Nominal Systems
• Land Based C-Band Mid-Course Imaging Radar (MCR)
• “Far enough north” such that the 𝐴𝑙2 𝑂3 exhaust of SRBs would
not impede a potential debris event
• Sea Based X-Band all weather Doppler Radars
• Mirror image of C-Band MCR
• Head on view of ascent
Kent, B.M. “The NASA debris radar for characterizing static and dynamic ascent debris
events for safety of flight,” APSURSI 2012 IEEE
15. Key Performance Parameters
• This is very interesting, and could
quickly escape the scope of this
project
• How can we use what we learned
about Kalman filters to track a
simplified ascent debris model?
• Use a Kalman filter to track shuttle and
shuttle debris
• Distinguish shuttle track from SRB
debris track using gating/association
20. Shuttle Model: STS-124
• Launch date: May 31, 2008
• Simplifying Assumption
• Entire duration of launch
takes place in a plane
http://www.spaceflightnow.com/shuttle/sts124/fdf/124ascentdata.html
21. Shuttle Model: STS-124
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
Down Range Distance of Shuttle Relative to Launch Pad (RLP) vs. Time
Time Since Launch [sec]
DownRangeDistance(RLP)[miles]
0 100 200 300 400 500 600
-10
0
10
20
30
40
50
60
70
Height of Shuttle (RLP) vs. Time
Time Since Launch [sec]
Elevation[miles]
Shuttle
Shuttle
22. Shuttle Model: STS-124
0 100 200 300 400 500 600 700 800
-10
0
10
20
30
40
50
60
70
Height Vs. Down Range Distance (RLP)
Down Range Distance (RLP) [miles]
HeightofShuttle(RLP)[miles]
Shuttle
23. Solid Rocket Booster (SRB)
Model: STS-124
• No SRB trajectory data was
available for this flight, except
the time of SRB separation
• Utilize “typical” trajectory
descriptions for SRB
• (Time, Location of Separation)
• (Time, Max Altitude)
• (Time, Height Parachute)
• (Time, Location of SRB Landing)
http://upload.wikimedia.org/wikipedia/commons/4/42/Srb_splashdown.jpg
24. No SRB Data Provided
• http://www-pao.ksc.nasa.gov/kscpao/nasafact/ships.htm
• SRB hit Atlantic Ocean ~60 miles down range,
• Just so happens that at the time that the height reaches zero, the shuttle has gone
60 miles, so we assume that the DR trajectory of the SRB is the same as that of
the shuttle
• This isn’t true, for a number of reasons.
• A pair of SRBs, fully loaded with propellant, weigh about 1.4 million pounds
(635,040 kilograms) apiece. They stand 149.2 feet (45.5 meters) tall, and have a
diameter of 12 feet (3.6 meters). The boosters in use today are the largest solid
propellant motors ever developed for space flight and the first to be used on a
manned space vehicle. These boosters will propel the orbiter to a speed of 3,512
miles per hour (5,652 kilometers per hour).
• At approximately two minutes after the Space Shuttle lifts off from the launch
pad, the twin SRBs have expended their fuel. The boosters separate from the
orbiter and its external tank at an altitude of approximately 30.3 statute miles
(26.3 nautical miles/48.7 kilometers) above the Earth's surface. After separation,
momentum will propel the SRBs for another 70 seconds to an altitude of 44.5
statute miles (38.6 nautical miles/71.6 kilometers) before they begin their long
tumble back to Earth.
25. 0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
Down Range Distance of Shuttle & SRB Relative to Launch Pad (RLP) vs. Time
Time Since Launch [sec]
DownRangeDistance(RLP)[miles]
Shuttle
SRB
0 100 200 300 400 500 600
-10
0
10
20
30
40
50
60
70
Height of Shuttle and SRB (RLP) vs. Time
Time Since Launch [sec]
Elevation[miles]
Shuttle
SRB
Shuttle and SRB Trajectories
26. Scope: Overview
• Overview
• Contact Models
• Tracker Considerations
• Tracking Shuttle, SORV
• Radar 1
• Radar 2
• Simulated Considerations
• Gating
• Gating and Association
• Simulated Data Results
• No gating, or association in time
• No gating, or association in 2D spatial
• Gating and association
• Conclusions
31. 0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
RadialDistance(RTR)[miles]
Radial Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle
Measured: Shuttle
Tracked: Shuttle
0 100 200 300 400 500 600
-60
-40
-20
0
20
40
60
Time since Launch [sec]
AzimuthalAngle[deg]
Azimuthal Angle (RTR) of Shuttle vs. Time
Truth: Shuttle
Measured: Shuttle
Tracked: Shuttle
0 100 200 300 400 500 600
-4
-2
0
2
4
6
8
10
12
14
16
Time since Launch [sec]
ElevationAngle[deg]
Elevation Angle (RTR) of Shuttle vs. Time
Truth: Shuttle
Measured: Shuttle
Tracked: Shuttle
Tracking: Shuttle, SORV
Radar 2: (xo,yo,zo)=(300,-300,0) [miles]
32. Tracking: Shuttle SORV
0 100 200 300 400 500 600
-800
-600
-400
-200
0
200
400
600
800
Time since Launch [sec]
XDistance(RTR)[miles]
X Distance of Shuttle Relative to Radar (RTR) vs. Time
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
YDistance(RTR)[miles]
Y Distance of Shuttle Relative to Radar (RTR) vs. Time
0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
Time since Launch [sec]ZDistance(RTR)[miles]
Z Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle
Measured: Shuttle
Tracked Polar: Shuttle
Truth: Shuttle
Measured: Shuttle
Tracked Polar: Shuttle
Truth: Shuttle
Measured: Shuttle
Tracked Polar: Shuttle
Radar 2: (xo,yo,zo)=(300,-300,0) [miles]
33. Shuttle and SRB Trajectories
• The radar receives serial measurements
• Without gating and association, it cannot distinguish between
shuttle and SRB
• What would happen if the radar tried to track the data
without gating and association?
34. 0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
RadialDistance(RTR)[miles]
Radial Distance Relative to Radar (RTR) of Shuttle and SRB vs. Time
Truth: Shuttle + SRB Rx Data
Measured: Shuttle + SRB Rx Data
Tracked: Shuttle + SRB
0 100 200 300 400 500 600
0
10
20
30
40
50
60
70
80
90
Time since Launch [sec]
AzimuthalAngle[deg]
Azimuthal Angle (RTR) of Shuttle and SRB vs. Time
Truth: Shuttle + SRB Rx Data
Measured: Shuttle + SRB Rx Data
Tracked: Shuttle + SRB
0 100 200 300 400 500 600
-5
0
5
10
15
20
25
30
35
Time since Launch [sec]
ElevationAngle[deg]
Elevation Angle (RTR) of Shuttle and SRB vs Time
Truth: Shuttle + SRB Rx Data
Measured: Shuttle + SRB Rx Data
Tracked: Shuttle + SRB
Tracking: Shuttle and SRB
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
35. 0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
XDistance(RTR)[miles]
X Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
YDistance(RTR)[miles]
Y Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
Time since Launch [sec]
ZDistance(RTR)[miles]
Z Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
Tracking: Shuttle and SRB,
Cartesian
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
36. Tracking Shuttle and SRB:
Gating
• Perhaps utilizing a gate alone would solve our problem?
With only gating, the tracker
would mix up the shuttle and
the SRB tracks!
37. Gating and Association
• Utilizing an EKF gating and association in Cartesian
coordinates could be implemented, due to time constraints, a
3DEKF with gating and association was not implemented
• Association of trajectories crossing with significant parallel
component is increasingly difficult with noise present
• How can we implement association without this added
complexity?
38. Gating and Association
• Let’s take a look at what our shuttle and SRB data looks like in
Height, Range space
0 200 400 600 800 1000 1200
0
20
40
60
80
100
120
140
160
180
200
Height Vs. Down Range Distance of Shuttle and SRB (RTR)
Down Range Distance (RTR) [miles]
Height(RTR)[miles]
Truth: Shuttle + SRB
Measured Shuttle +SRB
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
Non-overlapping data,
perhaps association will be
easier in this domain?
39. Gating and Association
• Let’s use a 2DRV filter without gating:
0 200 400 600 800 1000 1200
0
50
100
150
200
250
300
350
400
450
500
Height Vs. Down Range Distance of Shuttle and SRB (RTR)
Down Range Distance (RTR) [miles]
Height(RTR)[miles]
Truth: Shuttle + SRB
Measured Shuttle +SRB
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
Had to use very small η,
cannot recover from
continual “zero
measurments”
40. 0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
Time since Launch [sec]
ZDistance(RTR)[miles]
Z Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
YDistance(RTR)[miles]
Y Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
0 100 200 300 400 500 600
-5
0
5
10
15
20
25
30
35
Time since Launch [sec]
AzimuthalAngle(RTR)[miles]
Azimuthal Angle of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Tracked Polar: Shuttle +SRB
Gating and Association
• Perhaps we could gate/associate Z, Y, and Phi?
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
41. 0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
Time since Launch [sec]
ZDistance(RTR)[miles]
Z Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
YDistance(RTR)[miles]
Y Distance of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
0 100 200 300 400 500 600
-5
0
5
10
15
20
25
30
35
Time since Launch [sec]
AzimuthalAngle(RTR)[miles]
Azimuthal Angle of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
Gating and Association
• Perhaps we could gate/associate Z, Y, and Phi?
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
42. Gating and Association
𝑥 = 𝑅 cos ϕ sin 𝜃
𝜃 = acos
𝑦
𝑅 cos ϕ
𝑅 =
𝑧
sin ϕ
𝑦
𝑧
ϕ
If we can track in y, z, and ϕ, we have solved the tracking problem.
43. Gating and Association
• Perhaps we could gate/associate Z, Y, and Phi?
Radar 1: (xo,yo,zo)=(0,-50,0) [miles]
0 100 200 300 400 500 600
0
20
40
60
80
100
120
140
160
180
200
Time since Launch [sec]
ZDistance(RTR)[miles]
Z Distance of Shuttle Relative to Radar (RTR) vs. Time
0 100 200 300 400 500 600
0
100
200
300
400
500
600
700
800
900
1000
Time since Launch [sec]
YDistance(RTR)[miles]
Y Distance of Shuttle Relative to Radar (RTR) vs. Time
0 100 200 300 400 500 600
-5
0
5
10
15
20
25
30
35
Time since Launch [sec]
ElevationAngle(RTR)[miles]
Elevation Angle of Shuttle Relative to Radar (RTR) vs. Time
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
Gated Track 2
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
Truth: Shuttle + SRB
Measured: Shuttle + SRB
Gated Track 1
Gated Measured Data
Gated Track 2
45. Well… Not Really.
• Clearly we made some gross simplifications to the reality of
the situation
• We did not use a Doppler radar
• We assumed point sources rather than tumbling debris with a
time dependent radar cross section
• We didn’t consider the plethora of fuel which is released during
the SRB separation…
• Even in making such simplifications, we didn’t get superb
tracks
• We gained a first experience with gating and association, and
the difficulties which come along with associating tracks
46. Conclusions
• Tracking shuttle debris is an extremely important application
of modern radar tracking
• Different radars are used in viewing shuttle debris cross range
as compared to down range
• It is rather simple to discuss and understand why gating and
association is important, it is quite another to implement it.
