Testing Einstein with STK

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Testing Einstein with STK

• Brandon Owens
• W.W. Hansen Experimental Physics Laboratory
• Stanford University

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Presentation Overview

• Background on GP-B
• The GP-B Video the Making of the GP-B Video
• The GP-B STK Scenario Overview
• STKs Role in Mission Planning
• STKs Role in Situational Awareness Educational
  Outreach
• Acknowledgements

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Gravity Probe B The Relativity Mission

• GP-Bs mission is to test Einsteins General
  Theory of Relativity which asserts that massive
  bodies (such as the Earth) warp drag space-time

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Gravity Probe B The Relativity Mission (contd)

• The experimental concept for GP-B was originally
  envisioned in 1959 brought to life over 43
  years of research development

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Gravity Probe B The Relativity Mission (contd)

• Eight superlatives
• Roundest spheres
• Most perfect gyroscopes
• Most sensitive star-tracking telescope
• Lowest, most stable magnetic field
• Largest flight dewar
• Drag-free orbit
• SQUID readout ultra sensitive magnetometer
• Very Long Baseline Interferometry for most
  precise measurement
  of guide star proper motion

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The Making of the Gravity Probe-B Video

• STK tools made animation easy
• No graphics background required!
• Windows Movie Maker was used to splice animations
  with real-life video

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The GP-B Scenario

• The GP-B scenario runs Version 4.4 on a Unix
  machine has been used to track
• GP-B, its antennas, telescope, laser reflector
• HPOP propagation
• Delta II launch vehicle
• 14 Environmental Targets
• 9 Chains/ 5 Constellations
• 7 Ground Stations
• 6 DSN Satellites 3 DSN Ground Stations
• SPICE propagation performed on PC with STK 6.0
• 5 TDRS Satellites
• 44 Satellite Laser Ranging Sites

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STKs Role in Command Communications Scheduling

• STK was used to determine
• RF communications opportunities and constraints
• TDRS/GN View Periods
• DSN Blackout Periods
• Science and attitude control schedules
• Guide Star View Periods
• South Atlantic Anomaly Passes
• Satellite laser ranging opportunities

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STK Data Generation Processing
S/C Command File
Commands Telemetry
CmdGen
Command Script
View Periods
TDRS Satellites
GREAS
Report Files
Commands Telemetry
Schedules
TISI
Ground Stations
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TISI
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So, How Accurate was STK?

• Once GP-B went into Drag Free mode, our ground
  station and environmental target view periods
  changed by only a few hundredths of a second
• The DSN was satisfied with our blackout period
  predictions
• Guide Star view times within seconds of telescope
  telemetry data
• During a launch, the vehicle articulations synced
  up perfectly with real life

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STK as a Situational Awareness Tool

• STKs wide range of capabilities made it a
  wonderful software package to have during
  anomalies
• During anomalies, engineers usually want new
  obscure information in order to
• Test a theory on what caused the anomaly
• Understand the conditions present during the
  anomaly
• Predict future effects and/or recurrences of the
  anomaly
• STK has the capability perform many special
  purpose calculations quickly
• You dont always have to Re-invent the wheel
• You can get a lot of information in a short time

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STK as a Situational Awareness Tool (contd)

• Examples of situations where we needed STK to
  quickly generate data
• During an unanticipated attitude excursion of
  over 100 we used STK to identify new
  communication opportunities with the satellite
• After a flight computer reboot we used STK to
  verify that the on-board ephemeris data was not
  corrupted
• Several performance degradations occurred in our
  comm system throughout the mission and STK
  features (such as cone angles and elevation
  masks) were adjusted to calibrate out these
  effects in our schedule predictions

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Situational Awareness Display

• Excellent tool for flight controllers to make
  sense out of telemetry
• THE way to explain GP-B operations to outsiders

US Senator Ted Stevens, then NASA Administrator
Sean OKeefe, and me
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IS EINSTEIN RIGHT?

• STAY TUNED!
• The final results of GP-Bwill be published in 2007

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Acknowledgements

• This presentation was made possible by the
  contributions of several terrific people at GP-B
• Francis Everitt, GP-B Principle Investigator
• Brad Parkinson, GP-B Co-Principle Investigator
• Ron Sharbaugh, MOC Software Manager
• Greg Picard, Mission Planning Lead
• Jason Newquist, Mission Planning
• Gaylord Green, GP-B Program Manager
• Tom Langenstein, GP-B Deputy Program Manager

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Questions?