1. National Aeronautics and Space Administration www.nasa.gov NAVIGATION & MISSION DESIGN BRANCH NASA GSFC code 595 Andrew Abraham Lehigh University Kenny Getzandanner Preliminary and Detailed Survey Phase of the OSIRIS-REx Mission

2. NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC OSIRIS-REx Background  Origins  Spectral Interpretation  Resource Identification  Security  Regolith Explorer 2 OSIRIS-REx = $800 Million New Frontiers class mission to study asteroid Bennu (RQ36)

3. NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Asteroid Bennu (RQ36) 2 Arecibo Observatory Mission Goals About Bennu  Type B Carbonaceous – rich in organics  500m in diameter  Eccentricity 0.204  Rotates every 4.5hrs.  Approaches Earth every 6 years  Measure Yarkovsky effect  Return organic-rich regolith to Earth  Characterize surface properties

4. 4 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Mission Timeline ll 4

5. Departure Orbit & TAG 5 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Proximity Operations 5 Survey Preliminary Detailed Ratchet Diamond Approach

6. 6 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Preliminary Survey 6 Goal: To measure the mass of the asteroid to 1% via fly-by North Pole South Pole Equatorial

7. 7 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Preliminary Survey Details 7 7 km 2 days 8 cm/s 18.5 km A B CD E F

8. 8 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Detailed Survey 8  Segment A B gets to correct RA  Segment B C has fixed RA and sweeps DEC from -40 o to 40 o  Spacecraft over viewing station for 4.8 hrs. to map entire surface  Map ±3 o DEC, at 3.8km radius, at each station’s particular RA A B C Equator Station Overflight

9. Vary Pt. B & C Loop 9 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Nested Targeters: Single Station 9 Achieve Station Overflight? Target Pt. B Vary ΔV @ A Loop Target Pt. C Vary ΔV @ A Loop B C A Current Location

10. 10 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Nested Targeters: Multiple Stations 10 Vary Pt. B & C Achieve Station Overflight? Target Pt. B Loop Target Pt. C Loop Iterate Over “n” Stations Loop

11. 11 NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Conclusion: GMAT; better than STK 11  GMAT scripting ability is key  STK GUI can’t script  Save stations to file  change file and re-run code quickly if mission changes

12. Thank You! Acknowledgements: Kenny Getzandanner Joel Parker Steve Huges

13. NAVIGATION & MISSION DESIGN BRANCH, CODE 595 NASA GSFC Baseball Diamond 13  High latitude viewing angle  Viewing geometry complements Ratchet maneuver  Points are 3.8km in radius and ±30 o RA and ±30 o DEC with 1 day time of flight