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Integrity – Service – Excellence
Headquarters U.S. Air Force
Satellite Anomaly Assessment
Lt Col Kelly Doser AF Director of Weather
AF/A3O-W 23 April 2012
Joseph Mazur
Paul O’Brien Aerospace Corporation
1
Surface degradation from radiation
Solar array arc
discharge
Electromagnetic pulse from vehicle discharge
(on surface, behind thin shielding, or deep inside)
Single event effects in microelectronics
Spacecraft components become radioactive
False stars in star tracker CCDs
1101 0101
Solar array power
decrease due to
radiation damage
Before After
Before
During exposure to
multi-MeV protons
Electronics degrade due
to total radiation dose
Induced
Voltage
Time
Major Space Environment Hazards
1
10
100
1000
0
50
100
RBSP
SA
MP
EX
LIC
A
Charg
ing E
vents
L ~ Equatorial Radial Distance (RE)
HEO
GPS
CR
RE
S M
EP
-SE
U A
nom
alie
s
0
CR
RE
S V
TC
W A
nom
alie
s
Inner
Belt
Slot
Outer Belt
5
10
15
1 2 3 4 5 6 7 8
SEEs
Internal
Charging
Surface
Charging
(Dose behind 82.5 mils Al)
Plasma
Sheet
Magnetic Latitude in LEO (deg) 0 45 55 60 63 66 68 69
GEO
Surface charging and resulting ESD
• spacecraft or surface potential elevated
• 2000-0800 local time in the plasma sheet
• regions of intense field-aligned currents
• observed, but not explained, at very low L
Locations of Operational
Space Environment Hazards
Internal charging and resulting electrostatic discharges (ESD)
• broad range of L values
• corresponding to the outer belt
• where penetrating electron fluxes are high
Single Event Effects (SEEs)
• inner (proton) belt and higher L shells with solar particle event
• quiet-times from galactic cosmic rays
HEO
GEO
For orbits such as HEO, solar energetic particles are important sources of heavy ions that can cause single event effects
For awareness in HEO, the timing of the GEO environment is good information but not sufficient for anomaly diagnosis
However, the trapped electrons and protons in the Van Allen belts dominate the total dose hazard
Space is Not One Place: January
2012 SEP Events
Anomalies Attributed to the Space
Environment
5
Two anomaly studies attributed to space environment:
• Koons et al. Aerospace Report No.TR-99(1670)-1
• Unpublished (2009)
Databases differ
• coverage in time/space vehicles
• most frequent attributions (SEE or ESD)
However, two conclusions clear:
• Anomalies occur at all times
• Vehicle charging and single-event effects are the most frequently cited causes
Environment Hazards Versus Solar Cycle
6
Solar cycle
SEE
environment
(from solar
particle events)
Proxy for
surface
charging
Internal
charging
environment at
GEO
SEE from solar energetic particles is the only hazard whose probability strongly depends on solar cycle
Vehicle charging (and single events from the inner van Allen belt & galactic cosmic rays) can occur at any time
Hazard Visualization
Very different impact regions
Solar Proton Event in Progress
Anomaly at
L < 2
History of
GCR SEE?
Investigate SEE
Anomaly at
L >3
YES YES
YES
NO NO
NO
NO
START
Alt < 2000 km
YES
NO
Investigate SEE SEE Unlikely
Anomaly at
L < 3
NO
POES
P35MEV Slot
Index > 0
YES YES
POES
P35MEV Slot
Index > 0
In ESAA In SAA
YES YES
YES
NO NO
NO
YES
NO
Single Event Effects Flow Chart
Surface Charging:
• Kp, AE
• Field-Aligned Current intensity (LEO)
• Electron temperature
SEE:
• 20-50 MeV proton flux
• (heavy ions would be nice, too)
Internal Charging:
• 0.3-2 MeV electron flux
Total Dose:
• 1-20 MeV proton flux
Initial Global Specification Targets
I n t e g r i t y - S e r v i c e - E x c e l l e n c e
Headquarters U.S. Air Force
10
Questions?
Operations
Research &
Development
Acquisition
Customers
Rising Sun Over Pyramid (painting) – Paul Greco, 2009