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FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER. Lisa Policastri [email protected] 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

FLIGHT DYNAMICS OPERATIONS FOR THE INTERSTELLAR BOUNDARY EXPLORER

Lisa Policastri

[email protected]

AGI Users’ Conference Tour, Greenbelt, MD

12 July2010

ibex background
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

ibex orbit
IBEX Orbit

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ibex s science objectives
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?

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ibex flight operations team
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

ibex flight dynamics info
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

ibex flight dynamics group
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

ibex flight dynamics software
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

equipment
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

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operational flow stages high level
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

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planned maneuvers validate
Planned Maneuvers - Validate
  • Mother-of-all IBEX STK scenarios
    • Originally called “IBEX ATS” scenario
  • Script that reads in ATS files
  • Models spacecraft attitude

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attitude check
Attitude Check

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pre screen tracking files
Pre-screen Tracking Files
  • Grab
  • Load
  • Preview
  • Time period?
  • Correct IDs?
  • Gaps with file?
  • Missing files?

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pre processing tracking measurements odtk preview
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

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pre processing tracking measurements utdf reader
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)

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ads utdf reader
ADS UTDF Reader

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odtk configuration
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

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running odtk filter
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

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doppler residual ratios example
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

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example of histogram of residual ratios
Example of Histogram of Residual Ratios
  • Hawaii station
  • Filtered Doppler measurements (14,835 samples)

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filter 3 sigma position covariance
Filter 3-Sigma Position Covariance

Radial uncertainty is blue, in-track is red, cross-track is black

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filter 3 sigma velocity covariance
Filter 3-Sigma Velocity Covariance

Radial uncertainty is blue, in-track is red, cross-track is black

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current measurements by altitude
Current Measurements by Altitude

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running odtk smoother
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

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smoother 3 sigma position covariance
Smoother 3-Sigma Position Covariance

Radial uncertainty is blue, in-track is red, cross-track is black

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smoother 3 sigma velocity covariance
Smoother 3-Sigma Velocity Covariance

Radial uncertainty is blue, in-track is red, cross-track is black

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running filter smoother
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

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filter smoother differencing
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

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filter smoother position consistency check
Filter-Smoother Position Consistency Check
  • 3-sigma bounded
  • Radial uncertainty is blue, in-track is red, cross-track is black

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filter smoother velocity consistency check
Filter-Smoother Velocity Consistency Check
  • 3-sigma bounded
  • Radial uncertainty is blue, in-track is red, cross-track is black

www.AppliedDefense.com

ephemeris with covariance
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

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predict ephemeris delivered
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

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acquisition data types
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

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current acq data deliveries
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

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tle generator utility
TLE Generator Utility
  • Allow for easy generation of multiple TLEs from the same ephemeris file
  • Sets up satellite object with TLE for quality checking

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tle quality check example
TLE Quality Check Example
  • STK Chain “Angle Between” graph
  • TLE only valid:10 Apr 2009 23:00 to11 Apr 2009 06:30 UTC

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inp2 angle generator utility
INP2 Angle Generator Utility
  • Allow for easy generation of multiple INP2s
  • Sets up sensor objects for quality checking

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inp2 angle file quality check example
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

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example 1 nominal case
Example #1, Nominal Case

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example 2 not nominal
Example #2 (…Not Nominal)

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orbit events reports from stk
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

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tracking schedule variations
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

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additional reporting from stk
Additional Reporting from STK
  • View Periods
  • Star Tracker Outages

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long term analysis
Long-Term Analysis
  • Come to Toronto in August!

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where is fdg
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!!!!

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