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FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER

FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER . Lisa Policastri Lisa@AppliedDefense.com AGI Users’ Conference Tour, Greenbelt, MD 12 July 2010. IBEX Background. NASA Small Explorer Program (SMEX) Southwest Research Institute, principal investigator

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FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER

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  1. FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER Lisa Policastri Lisa@AppliedDefense.com AGI Users’ Conference Tour, Greenbelt, MD 12 July2010

  2. IBEX Background • NASA Small Explorer Program (SMEX) • Southwest Research Institute, principal investigator • Launched from Kwajalein Atoll on 19 October 2008 • Launched on Pegasus with STAR-27 SRM • Highly elliptical orbit, approximate: • Apogee altitude of 48 Re • Perigee altitude of 7,000 km • Period of 8 days • Operational lifetime of at least two years • Three orbit-raising maneuvers to achieve mission orbit • Spinning spacecraft, sun-pointed • Tracked by Universal Space Network (USN) + APL www.AppliedDefense.com

  3. IBEX Orbit www.AppliedDefense.com

  4. IBEX’s Science Objectives • IBEX's sole, focused science objective is to discover the global interaction between the solar wind and the interstellar medium • IBEX achieves this objective by taking a set of global energetic neutral atom (ENA) images that answer four fundamental science questions: • What is the global strength and structure of the termination shock? • How are energetic protons accelerated at the termination shock? • What are the global properties of the solar wind flow beyond the termination shock and in the heliotail? • How does the interstellar flow interact with the heliosphere beyond the heliopause? www.AppliedDefense.com

  5. IBEX Flight Operations Team • Mission Operations Center (MOC) at Orbital Sciences in Virginia • Flight Dynamics (FDG) operations at Applied Defense Solutions in Maryland • Program Management at Southwest Research Institute in Texas www.AppliedDefense.com

  6. IBEX Flight Dynamics Info • Flight dynamics operations at ADS • Three tracking contacts every orbit • One attitude maneuver every orbit • Orbit determination after each contact • Product delivery requirements per orbit • Acquisition files: TLEs and INP2s… • Ephemeris predicts… • Ground station view periods • Star tracker outage predictions • Orbit events information • And more! www.AppliedDefense.com

  7. IBEX Flight Dynamics Group • Lisa Policastri (FD lead) • Ryan Lebois • John Carrico • Marissa Intelisano • Craig Nickel • Mike Loucks (Space Exploration Engineering) • FDG activities 40 hours per week total max! • Must have efficient & reliable tools & software!!! www.AppliedDefense.com

  8. IBEX Flight Dynamics Software • Satellite Tool Kit (STK) 8.1.3 • Astrogator + Professional Edition + Integration + Attitude • Recently added STK/Communications! • Orbit Determination Tool Kit (ODTK) 5.1.2 • Microsoft Excel 2007 • WSFTP 2007 • Scripts & Utilities (custom workflows) AGI software + custom workflows supports all flight dynamics operational needs for IBEX www.AppliedDefense.com

  9. Equipment • Desktop • Antec Quad-Core Xeon Processor • Configured for all flight dynamics activities • Backed up to ADS secure server • Network Connection • SFTP • e-mail • Blackberry • Modem • Communicating with friends at the MOC • Backup laptop • Dell Precision M4300 Laptop www.AppliedDefense.com

  10. Operational Flow Stages “High Level” ODTK STK Utilities • Data Products: • Definitive Ephemeris with Covariance • Predict Ephemeris with Covariance • TLEs & INP2s • View period predicts • Star tracker outage predicts • Orbit events files • Long-term analysis Planned Maneuvers QC Tracking Measurements www.AppliedDefense.com

  11. Planned Maneuvers - Validate • Mother-of-all IBEX STK scenarios • Originally called “IBEX ATS” scenario • Script that reads in ATS files • Models spacecraft attitude www.AppliedDefense.com

  12. Attitude Check www.AppliedDefense.com

  13. Pre-screen Tracking Files • Grab • Load • Preview • Time period? • Correct IDs? • Gaps with file? • Missing files? www.AppliedDefense.com

  14. Pre-Processing Tracking Measurements: ODTK Preview • Measurements are preprocessed in ODTK • Displayed summary information about each measurement file • Tracking station identification • Start and stop times of the measurements • Number of valid measurements in the file • Warning if the measurements are: • Out of order, then run ODTK “Sort UTDF Observation File” Utility • Not valid www.AppliedDefense.com

  15. Pre-Processing Tracking Measurements: UTDF Reader • Read binary measurement files in the UTDF format. • “Tracking and Acquisition Handbook for the Spaceflight Tracking and Data Network,” • Displayed about measurements: • Ground station identification codes • Record date and time • Tracking mode: program track or auto-track • Doppler is valid or invalid • Allows editing of data in binary files, if records showed to be mis-tagged or out of order. • Allows exporting of information • Auto-track records (angle measurements) • Doppler measurements • STK Sensor Pointing files (auto-track) www.AppliedDefense.com

  16. ADS UTDF Reader www.AppliedDefense.com

  17. ODTK Configuration • Continuous ODTK scenario • Ground stations geodetics • Biases and bias sigma estimates • For each measurement type • For each station • From measurement statistics • Refined over time as needed www.AppliedDefense.com

  18. Running ODTK Filter • Run ODTK Filter • ODTK Static Product Builder: custom graph & report product list • Histograms of residual ratios per station, per measurement type • Measurement Residuals per station, per measurement type, +/- 3 sigma • Measurement Residuals all stations, per measurement type, +/- 3 sigma • Residual Ratios (normalized residuals), per measurement type • Position uncertainty • Velocity uncertainty • Measurements locations along orbit as a function of spacecraft altitude • Measurements locations along orbit as a function of spacecraft true anomaly • Measurement summary • Results in histograms, residuals, and residual ratios are examined to determine if the Gauss-Markov parameters needed adjustment www.AppliedDefense.com

  19. Doppler Residual Ratios Example • Bias Sigma, half-life, and white noise sigma adjusted if: • Too much “white space” in the residual ratios graph • Histograms were not showing Gaussian distributions • Measurements with residuals outside of +/-3 sigma were not accepted by filter www.AppliedDefense.com

  20. Example of Histogram of Residual Ratios • Hawaii station • Filtered Doppler measurements (14,835 samples) www.AppliedDefense.com

  21. Filter 3-Sigma Position Covariance Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  22. Filter 3-Sigma Velocity Covariance Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  23. Current Measurements by Altitude www.AppliedDefense.com

  24. Running ODTK Smoother • Each successful filter run followed by corresponding smoother run • Smoother refines the state & covariance from the filter • Provides improved orbit accuracy with a smoothed ephemeris & covariance • Solves for maneuvers • Products generated after each smoother run • Smoothed position uncertainty • Smoothed velocity uncertainty • Maneuver summary reports www.AppliedDefense.com

  25. Smoother 3-Sigma Position Covariance Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  26. Smoother 3-Sigma Velocity Covariance Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  27. Running Filter & Smoother • Modified State Diff tool installed w/ ODTK • Automates file naming and storage • Automates pointing to various files for: • Smoother (rough file) • Static Product Builder • .Filrun • .Smtrun • .Difrun www.AppliedDefense.com

  28. Filter-Smoother Differencing • Position and velocity consistency tests are an important quality check • If differences in the filtered and smoothed ephemeris solutions were outside of three sigma, go back and re-examine data • Differencing process is handled by the ODTK “State Difference” utility • Position and Velocity Consistency graphs are generated www.AppliedDefense.com

  29. Filter-Smoother Position Consistency Check • 3-sigma bounded • Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  30. Filter-Smoother Velocity Consistency Check • 3-sigma bounded • Radial uncertainty is blue, in-track is red, cross-track is black www.AppliedDefense.com

  31. Ephemeris with Covariance • Each ODTK filter run & smoother run produced ephemeris files • With 6 x 6 position & velocity covariance • STK .e file format • Contain definitive and predict points • Smoother ephemeris files contain: • Definitive ephemeris from filter restart point until time of the last measurement • Four orbits of predictions • Smoother ephemeris files imported into STK • Spacecraft position graphically displayed • Position covariance ellipsoids displayed in 3-D • Compare differences in solutions • Graph the angle between spacecraft position • Look for covariance in ground station FOV www.AppliedDefense.com

  32. Smoother Definitive & Predict Ephemeris with Covariance www.AppliedDefense.com

  33. Predict Ephemeris Delivered • Smoother (or filter) ephemeris files used for generating the official delivery of predicted ephemeris • State at last measurement used in STK/Astrogator for initial state • Prediction files needed for scheduling ground station contacts • Prediction files used to create acquisition data for the ground stations • INP2 angle files • TLEs • SPICE www.AppliedDefense.com

  34. Acquisition Data Types • TLEs primary (initially) • Selected years ago for pointing antennas • Tested for a typical nominal operations cases • INP2 angle files • Contain azimuth & elevation angles at specified time steps over a period of time • Highly elliptical orbits • STK Access Custom report style • SPICE predict ephemeris for APL station • IIRV for NASA stations www.AppliedDefense.com

  35. Current Acq Data Deliveries • Always deliver a TLE and INP2 file set • INP2 near perigee (270 to 110 degrees true anomaly) every 1 second • INP2 for all other locations, every 5 sec • All Q/C against predicted ephemeris • TLE only valid when angle from the ground station between the predict ephemeris and the TLE is less than 0.2 degrees • INP2 must match with original ephemeris to within 0.2 degrees from the ground stations • Deliver IIRV to NASA when needed for NASA Ground Network contacts www.AppliedDefense.com

  36. TLE Generator Utility • Allow for easy generation of multiple TLEs from the same ephemeris file • Sets up satellite object with TLE for quality checking www.AppliedDefense.com

  37. TLE Quality Check Example • STK Chain “Angle Between” graph • TLE only valid:10 Apr 2009 23:00 to11 Apr 2009 06:30 UTC www.AppliedDefense.com

  38. INP2 Angle Generator Utility • Allow for easy generation of multiple INP2s • Sets up sensor objects for quality checking www.AppliedDefense.com

  39. INP2 Angle File Quality Check Example • Angle between ground station sensor boresight & satellite • Alaska INP2: 10 Apr 2009 23:00 to 11 Apr 2009 06:30 UTC www.AppliedDefense.com

  40. Example #1, Nominal Case www.AppliedDefense.com

  41. Example #2 (…Not Nominal) www.AppliedDefense.com

  42. Orbit Events Reports from STK • IBEX Crossing Times Report • At what time does each integer Re altitude occur? • Astrogator Stop & Continue for each Re integer • Astrogator Summary Report • Convert to txt format • Needed for scheduling contact times and attitude/ Sun repointing maneuvers • IBEX Apogee & Perigee Times Report • At what time does IBEX go through Apogee & Perigee? • STK satellite Apogee and Perigee Times custom report • Needed for scheduling contacts and science www.AppliedDefense.com

  43. Tracking Schedule Variations • Varies uniquely for each orbit • Based on both the visibility times and when the ground stations are available • If contacts were simply not possible near perigee, the orbit uncertainty will increase dramatically • Antenna nulls www.AppliedDefense.com

  44. Additional Reporting from STK • View Periods • Star Tracker Outages www.AppliedDefense.com

  45. Long-Term Analysis • Come to Toronto in August! www.AppliedDefense.com

  46. Where is FDG? • The FDG configuration is mobile (Thanks Jason)! • Besides the ADS MOR and Orbital MOC: • Southwest airlines flight #2892 on March 18 2009 • “Superprom 16”, Baldwin MD • Red Sky Grill/Hooters, Laurel MD • Point Mugu CA (NAVSOC) • My parents’ house, Baltimore MD • Mountain View CA (NASA Ames) • BWI Airport • Spaceflight Mechanics Meeting 2009, Savannah GA • Greene Turtle, Laurel MD • Las Vegas Airport • Game Sports Bar, Fulton MD • Many many hotels!!!! www.AppliedDefense.com

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