Flight dynamics operations for the interstellar boundary explorer
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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

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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?

www.AppliedDefense.com


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

www.AppliedDefense.com


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

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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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Smoother definitive predict ephemeris with covariance

Smoother Definitive & Predict Ephemeris with Covariance

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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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