1. SDO Flight Dynamics Subsystem
Mission PDR
R. L. DeFazio
S. F. Andrews

2. Agenda FDS Driving Requirements FDS Launch & Early Orbit Operations
FDS Nominal Mission Operations
Trade Studies
Flight Dynamics System (FDS) Diagram
FDS Software Functional Diagrams
FDS Software Heritage
FDS Testing
FDS Schedule
FDS Documentation
Risks, Issues and Concerns
Backup Slides

3. FDS Driving Requirements
Launch and Early Orbit Requirements
Perform orbit determination and acquisition data generation
Plan, execute and calibrate orbit maneuvers to circularize the orbit at 102 degrees West longitude
Maneuver SDO to place it on its nominal East-West station keeping profile
Generate applicable FDS products to support spacecraft and instrument checkout
Perform star tracker alignment and calibration plus gyro and guide telescope calibration
Perform momentum management once per orbit while perigee remains at 300 km. altitude

4. FDS Driving Requirements (Continued)
Mission Orbit Requirements
Perform orbit determination and prediction
o Position accuracy: < 150 meters
o Velocity accuracy: < 10 cm./second
Generate and deliver acquisition data for all supporting networks
Perform attitude validation of the on-board attitude
o Accuracy without/guide telescope: 120 arc seconds
o Accuracy with/guide telescope: arc seconds
Perform attitude maneuver slew planning to support science planning and sensor calibration

5. FDS Driving Requirements (Continued)
Mission Orbit Requirements (Continued)
Generate FDS products required for scheduling and planning science and insuring spacecraft health and safety
Perform East-West station keeping maneuver about (2) times per year
Perform monthly momentum management maneuvers

6. Orbit Raising Diagram

7. A Week in the Life of the SDO FDS in the MOC

8. List of FDS Products for SDO
   
·                     Earth & Lunar Shadows
·                     Beta Angles
·                     Spacecraft Longitude Drift Table
·                     Apogees & Perigees
·                     Right Ascension of Ascending & Descending Nodes
·                     Predicted Attitude Dependent Ground Station Visibility (Omnis)
·                     Predicted HGA View Periods of SDO Dedicated Antennas
·                     Predicted Attitude
·                     Predicted RFI (Sun and other Spacecrafts)
·                     Predicted SDO Orbital State Vectors (Geocentric & Heliocentric)
·                     Maneuver Command File & Planning File
·                     Sensor Visibilities & Interference (e.g. sun, moon)
·                     Ground Track
·                     Propellant Usage Summary
·                     Maneuver Summary (maneuvers performed)
·                     Two-way Range (Clock Correction)
·                     Spacecraft Local Time
·                     Extended Precision Vectors (EPVs)
2-Line Elements
·                     Acquisition Data (IIRVs, SPICE Files
·                     Science Planning Aids (Instrument CalibrationProducts)

9. FDS Trade Studies Right ascension of ascending node (RAAN) trade study
Optimized RAAN at 200 degrees to minimize the number of shadowed days per year
Initial inclination was 28.5 degrees and remained deg. < IM < 30 degrees over a 10 year mission
High gain antenna viewing of SDO ground station
Evaluated unobstructed viewing of the future SDO antennas at the White Sands ground stations by HGAs
Studied several potential spacecraft models, including varied antenna boom lengths, dish diameters and solar configurations
Goal is attainable to have at least six months of unobstructed viewing from a given HGA without switching antennas or rolling the spacecraft

10. FDS Trade Studies (continued)
SDO orbit raising maneuver profiles
Generate SDO orbit raising profiles using various thruster configurations to determine feasibility
Determine the number and duration of orbit maneuvers required to raise the orbit to geosynchronous
Study attitude slew constraints for performing East-West station keeping maneuvers
Evaluate the impact of keeping the spacecraft X-axis to within 45 degrees of the sun line
Evaluate omni antenna and star tracker coverage to verify interference free operations
Omnis using +/- 70 deg. FOV provide adequate coverage with a s/c roll needed for station keeping coverage
Glint in star tracker FOV (58 deg.) can be eliminated by adjusting mounting location

11. SDO Flight Dynamics System

12. SDO Orbit Determination Process

13. SDO Orbit Maneuver Planning Process

14. SDO Product Generation Process

15. SDO Attitude Computations Process

16. SDO FDS Software Heritage

17. SDO FDS Testing
Run system tests as soon as functions of the FDS are ready
Develop an acceptance test plan that exercises all FDS functions and interfaces
Perform preliminary interface testing as soon as corresponding systems are available
Be ready for acceptance testing / formal interface testing of Release 1 (L-25 months) and Release 2 (L-18 months)
Participate in certification of the S-Band links of the SDO White Sands antennas
Participate in ground system end-to-end testing
Continue to exercise software through simulations and training until launch

18. SDO FDS Schedule

19. FDS Documentation Document Delivery Date Delivered
Inputs to Ground System DMR 9/15/ Yes
Inputs to Ops Concept Document 9/15/03 Yes
Inputs to MOC ICD By Ground System PDR In Preparation
FDS Level 4 Requirements Document By Spacecraft PDR Yes
FDS Product Development Plan Before Spacecraft PDR Yes
WHS Antenna Certification Plan By Ground System PDR Draft Ready
FDS Design Document By Spacecraft CDR Draft Ready
FDS Acceptance Test Plan By Spacecraft CDR In Preparation
FDS Operations Handbook (Final) By Launch – 1 month No

20. Risks, Issues and Concerns
None noted at this time

21. Conclusions
Flight Dynamics requirements are well understood and our design is adequate to successfully meet them.

22. Back up Materials

23. Apogees & Perigees During Orbit Raising

24. SDO FDS Hardware Complement

25. FDS Software Implementation Plans
The FDS will be a PC-based system
FDS requirements will be met using heritage COTS and GOTS software where applicable
When existing software requires modification, the mods will be spec’ed, implemented and tested under the direction on the FDS Lead Analysts. Code 583, the Mission Applications Branch, will help oversee the preparation of FDS software
If new software is required, it will be developed in the same manner as modified software
Automation approaches for the FDS such as GMSEC/AUTOFDS are being explored