IBEX Mission Planning and Operations

1. IBEX Mission Planning and Operations Mike Loucks Space Exploration Engineering loucks@see.com 360-378-7168

2. Interstellar boundary explorer science objectives • Discover the global interaction between the solar wind and the interstellar medium

3. The IBEX orbit • Science above the Geotail • Dump data at low altitudes • Orbit highly perturbed by Lunar gravity • Must avoid: • Re-entry • Long shadows

4. The IBEX flight dynamics team: thing 1, thing 2: ODTK and STK

5. IBEX spacecraft • Spinner • Integrated Propulsion System for Orbit Raising • +/- Z Thrusters

6. IBEX orbit raising

7. IBEX flight dynamics requirements: mission analysis • For a given launch date, identify a final orbit that: • Has a desirable perigee history over 6 months • Above 7000 most of the time • Below 30,000 most of the time • Has no shadow durations that are excessive • ½ Penumbra + umbra duration < 4.0 hours • Target back to this orbit for range of +/- 3 sigma SRM dispersions for a given launch day

8. Prelaunch mission analysis: STK/Astrogator • 2-year Perigee Altitude History

9. Prelaunch mission analysis: STK/Astrogator • Nominal Screened Orbit: 2-year Shadow History

10. IBEX ascent: correcting launch errors 3 Sigma Low, Nominal, 3 Sigma High SRM Burns

11. Mission analysis: planning and operations Monte Carlos • LEOPS Monte Carlo • Start with Nominal Covariance and state vector from baseline OD process • Each successive maneuver targeted, saved and then errors introduced along with statistical state errors based on covariance • Product of this process is nominal state vector at end of LEOPS and covariance • Long-term Monte Carlo • Start with Covariance from LEOPS Monte Carlo and state vector • Single state run • Hyper-cube scan • Full Monte Carlo (10,000 runs) based on covariance

12. IBEX nominal orbit raising plan

13. Operations, post AM1: requirements changed! • Radiation concerns cause nominal perigee altitude to be adjusted. Desire to stay between 1 and 3 Re. • Aim for 5 year lifetime (without maneuvers) if possible • Re-Plan final orbit “On the fly” • 4 laptop computers running Excel/STK monte-carlos

14. Operations: post AM1 orbit raising plan Catalog “A”, P4 Altitude Raised by Moon at A4

15. Operations: post PM1 • 10% under-burn • Neutralizes Lunar perturbations at A4 • Requires extra DV at AM2, and burn in excess of 600 sec • AM2 moved up 1 rev, AM3 added

16. Operations: post PM1 • AM2 Plan • Max burn planned for 600 sec • Discovered that 614 sec burn (114 m/sec) DV gives viable new Catalog orbit (found another one)! • Any burn within +5% or -10% also works • Performance within this range and: We’re done!

17. Operations: final ascent

18. Operations: final orbit

19. Final catalog: shadow event durations

20. AGI technology and IBEX • STK/Astrogator • All pre-mission planning and operations performed with Astrogator and MS Excel. • Thousands of monte-carlo runs • Orbit Determination Tool Kit • All pre-mission and operational navigation planning performed with ODTK • All operational tracking and maneuver reconstruction performed with ODTK and scripting tool • Debugging and characterization of hardware in real time ops

21. Results • STK and ODTK complete navigation solution brought in post-PDR • Scripting interface allowed rapid prototyping and development • Stability and flexibility of platform allowed risk mitigation via monte-carlo analysis. • Physics-based ODTK solution allowed debugging of hardware

22. Summary • Mission duration extended x2 during operations • Completely re-planned ascent and final orbit during ops • Pre-launch training with all tools very important • Flexibility of tools and personnel was key