1. Space Data Actionability Metrics for SSA
AGI User's Conference
October 2005
Space Data Actionability Metrics for SSA
Center for Space Standards and Innovation
Dan Oltrogge, T.S. Kelso, S. Alfano, D. Vallado & J. Griesbach
29 June 2011

2. Contents
Review Improvement Opportunities for Space Positional Knowledge
Variety of SSA metrics for RFI, CA
Data Source Accuracy
Actionability Metrics for Data
Suitability of Data/Pairings for SSA
Conclusions

3. Opportunities for More Effective Satellite Position Estimation
Have challenges in our ability to estimate satellite position
These issues affect accuracy of predicted satellite position vs time
Want to explore SSA impacts of Improvement Opp #2, #3, #4…
Opportunity:
Affected Data Source
Affected
Orbit(s)
Opp #1: Identifying satellites correctly – mitigating cross tagging
NCT
GEO, LEO
Opp #2: Tracking satellites better, particularly through maneuvers
Opp #3: Improving orbit estimation and propagation to account for uncertainty in drag due to changes in the atmosphere (space weather, satellite attitude)
O/O + NCT
LEO
Opp #4: Making sensor tasking more effective (tasking and measurement duration/intervals)
Opp #5: Making analysis practices interoperable and more consistent

4. Space Positional Data Sources
AGI User's Conference
October 2005
Space Positional Data Sources
Data Source Generic Nomenclature:
NCT = Non-Cooperative Tracker
Examples include SSN/JSpOC, ISON, ESA
NCT sensors don’t have to interrogate or “cooperate” with satellite to determine position
O/O = Owner/Operator
e.g., SDA, indiv operators, ESA, NASA
Data Source Notional Accuracy:
Source
Sensor
Debris
Live Sats
NCT
Radar
Optical
O/O
Active Ranging

5. Variety of SSA metrics for CA, RFI
For CA, many metrics to evaluate collision risk:
Miss distance at TCA
Mahalanobis distance at TCA for both straight and bent ellipsoids
Max Probability (linearized relative motion)
Analytical True Probability (linearized relative motion)
Numerical True Probability (linearized relative motion)
Analytical True Probability (nonlinear relative motion)
Numerical True Probability (nonlinear relative motion)
Also a variety of weighted, combined metrics:
NASA has had success with “F-factor” (Newman, Frigm, et al)
Objective of F-factor is to prioritize conjunctions and alleviate operators from having to sift through long lists of potential conjunctions that nothing can be done for
RFI is also an SSA issue…
Actionability & sensitivity of RFI input data complex, but clearly significant

6. RFI Event Detection
Can define RFI as:

7. Error Growth and Unmodeled Forces
Nominal predicted trajectory drifts away from actual path if unmodeled perturbations or maneuvers exist
Error growth may or may not incorporate unmodeled forces
Iridium/Cosmos impact caused by covariance not encompassing maneuver

8. Tasking Resonance = Similar Degradation
Optical tracking relies on lighting conditions to illuminate space object during darkness at optical sensor (> astronomical twilight)
Can lead to under-sampling conditions with observations collected only in evening and early morning
Sensor
Position Error (km)

9. Orbit Sol’ns at Unknown Maneuvers
Tracking across maneuver(s)
Degrades orbit solution accuracy
Low thrust, long duration burns common at GEO
But what portion of objects are operational?
For GEO, turns out to be quite high; for GEO ±300km:
873 active sats out of 1523 (nearly 60%)

10. SSA Data Actionability Analysis
Insight gleaned by analyzing test cases where SSA threat occurs
For RFI, can develop test cases of RFI and examine impact of degrading orbit solutions, frequencies, TDOA and FDOA measurement uncertainty
Demonstrated yesterday
For CA, can develop collision test cases and examine impact of degraded orbit solutions, collision geometries, erroneous object sizes, etc
For purposes of study, adopted following SSA maneuver action thresholds:
One-in-1,000,000 triggers a warning (i.e. keep an eye on this)
One-in-100,000 triggers a meeting to discuss/plan maneuver options
One-in-10,000 causes some executive-level decision maker to give a GO or NO-GO maneuver call

11. Already Presented This Approach For RFI
10° Longitude Separation
TLE-vs-TLE
TLE-vs-SDA
SDA-vs-SDA

12. Collision Probability Sensitivity Study
Conducting literature and peer survey to assess ‘representative’ levels of accuracy for different data sources
Preliminary results excerpted from upcoming AAS paper research
Simulated direct collision (zero miss distance)
Defined “encounter angle” & characterized maximum collision probability for each combination of data types

13. Peer-Based Error Metrics for GEO
Examined all combinations of GEO data sources
VNC error metrics estimated by research aggregation and peer review

14. Actionability With Unknown Maneuvers
Tracking across maneuver(s)
Degrades orbit solution accuracy
Low thrust, long duration burns common at GEO

15. GEO “Actionability” vs Data, Encounter Angle
Preliminary
* Excerpt from Upcoming CSSI Tech Paper

16. Peer-Based Error Metrics for LEO

17. Opp #3: Improving drag modeling in orbit estimation and propagation (cont.)

18. LEO “Actionability” vs Data, Encounter Angle
Preliminary
* Excerpt from Upcoming CSSI Tech Paper

19. Conclusions Data Fusion critical for actionable SSA product
No data source can “do it all”
SDA (Owner/Operator) data only for active satellites
NCT data products affected by:
Cross-Tags
Fitting orbits thru unknown maneuvers
Sensor observation timing biases
Potential lack of priority for your mission