AGI Technology Beyond Earth Orbit

AGIAGI TechnologyBeyond Earth OrbitDr. Matt BerryDr. Vince CoppolaBob HallDr. Jim WoodburnPg 1 of 40www.agi.com

Agenda• Introduction (Woodburn)• Current/Historical Missions (Hall)• Product Enhancements (All)• Central Body Configuration (Coppola)• Light Time Delay Issues (Coppola)• Propagation Issues (Berry)• Closing (Woodburn)AGIPg 2 of 40www.agi.com

Introduction (Woodburn)• Welcome• This is an informal discussion• Introduction of the speakersAGIPg 3 of 40www.agi.com

How did we get here?• 1995 – Generic central body concept–NEAR mission to Eros• 1994 – Navigator (based on Swing-By)• 1997 – Astrogator–MAP• 2005 – Backwards propagation–Messenger• 2006 – Interplanetary improvement• 2007 – Orbit determinationContinual ImprovementAGIPg 4 of 40www.agi.com

Current/Historical Missions (Hall)• Clementine• AsiaSat 3• MAP (WMAP)• {Contour}• Wind• SOHO• ACE• Lunar Prospector• New Horizons• Messenger• STEREOAGIPg 5 of 40www.agi.com

Recent enhancements to STK(Hall)• Planetary options–Window configuration–Eclipsing bodies• Ground tracks on multiple bodies• Coverage at the poles• PDS terrain• VGT–Drawing orbits in any frame–Use of points for 3D view from/toAGIPg 6 of 40www.agi.com

Recent enhancements to Astrogator(Berry)• Multiple complete gravity fields (STK 8.1.1)• Land – Hold – Launch• Search plugin (3:30 PM talk)• Hpop pluginsAGIPg 7 of 40www.agi.com

Recent enhancements to HPOP(Coppola)• HPOP now available for any central body• Gravity field– Re-implemented in STK 8.1.1 – large degree and order– Lunar gravity fields• Tides– Simple Tide Model (Moon)– Permanent and Full tide• Solar Radiation Pressure– Reflection model plugin ODTK 5.1– Multiple eclipse bodies (e.g., Earth and Moon)AGIPg 8 of 40www.agi.com

Orbit determination (Woodburn)• Capable of OD for lunar and solar orbiters–V5.1, Fall 2007• Generalization of the central body–Orbit state–Measurement models• DSN measurement models–DSN Trk-34 tracking data format• Gravity process noise modelAGIPg 9 of 40www.agi.com

DSN measurement models• Sequential range (two way)• *Ramped Doppler (two way and three way)• Total count phase (two way and three way)• All based on complete light time solution–Moyer, “Formulation for Observed and ComputedValues of Deep Space Network Data Types forNavigation”*Live data has not been processedAGIPg 10 of 40www.agi.com

Sequential range• Ambiguous two way rangeAmbiguous RangeAGIPg 11 of 40www.agi.com

Doppler & total count phase• Counts of received cyclesFrequency ScheduleThree WayEpoch Start FreqFreq Rate….. ………. ………..….. ………. ………..….. ………. ………..….. ………. ………..….. ………. ………..Two WayCycle countingCycle countingAGIPg 12 of 40www.agi.com

Trk-34 tracking data format• Very rich format• Supports many addition types of observables• Sample tracking data (STEREO, MAP)–Sequential range–Total count phase• Currently read only–Simulation of observations to generic obs formatAGIPg 13 of 40www.agi.com

Lunar gravity• High degree and order gravity field required–Lack of a dominant term–Missions can fly at very low altitude–Recent gravity modeling improvement• Gravity field not nearly as well known as that forthe Earth–Fit span for LS–Process noise for filtersReference: Recent Gravity Models as a Result of the Lunar Prospector MissionAGIPg 14 of 40www.agi.com

Lunar gravity process noise model• Requirement drove revisit of original gravityprocess noise algorithms by Wright• Tools for model generation were reconstructedand improved–Unique coefficients for truncation at each degree–Required data added to gravity file format–Earth gravity models will also be updatedAGIPg 15 of 40www.agi.com

Sample Lunar OD results• Lunar prospector–Approximately one month of Doppler and range• (28 Feb 1999 – 31 Mar 1999)–At least one long maneuver–Altitude under 40 kmAGIPg 16 of 40www.agi.com

LP Position UncertaintyPosition Uncertainty (0.95P)4800.004500.004200.003900.003600.003300.00Process: SmootherSatellite(s): LPTime of First Data Point28 Feb 1999 00:00:13.000 GPSGTwo Sigmas (m)3000.002700.002400.002100.001800.001500.001200.00900.00600.00300.000.000 3000 6000 9000 12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000Minutes since 28 Feb 1999 00:00:00.000 GPSGLP 2-Sigmas Radial LP 2-Sigmas Intrack LP 2-Sigmas CrosstrackAGIPg 17 of 40www.agi.com

Doppler Residuals4.00TrackerMeasurement Residual and SigmaTime3.00Measurement Residual and Sigma2.001.000.00-1.00-2.00-3.00-4.001 3001 6001 9001 12001 15001 18001 21001 24001 27001 30001 33001 36001 39001 42001Minutes since 1 Mar 1999 00:00:00.000 GPSGAGIPg 18 of 40www.agi.com

Central Bodies (Coppola)• Celestial Bodies of the Solar System• Settings configured thru text files (*.cb)• Loaded from Install area–And Config area (if CentralBodies folder present)–And Scenario folder (if CentralBodies folder present)AGIPg 19 of 40www.agi.com

Central Bodies (cont’d)• STK Objects (Satellite, Facility, etc.) areassociated with just 1 central body• Set the central body during creation–We don’t allow modification afterward yet–We do ship an HTML utility that can do thisAGIPg 20 of 40www.agi.com

Central Bodies (cont’d)• CB used as an indicator–Some default parameter values–Pass Definition–VGT (Position Vector, Velocity Vector, etc.)–2D Graphics (STK 8.1 – now can choose CB’s)–Vehicle Attitude–Frames available for reporting–Shape for Line Of Sight obstruction in Access–Inertial/Fixed frame used for vehicle ephemeris storage–Certain graphics settingsAGIPg 21 of 40www.agi.com

CB Settings• Parent• Mu value, System Mu value• Default Gravity Field• Shape (Sphere, Oblate, Triaxial ellipsoid)• Ephemeris Source• Attitude definition• Available propagators• Special settingsAGIPg 22 of 40www.agi.com

CB Mu Values• Orbital element conversions–Uses the mu value from the *.cb file [Gm keyword]• TwoBody, J2Perturbation, J4Perturbation–Uses the mu value from the *.cb file• Propagation–mu and other values from the selected gravity file• Third Body Perturbations–Uses the System Mu value (if specified in *.cb file)AGIPg 23 of 40www.agi.com

Gravity FieldsBodyEarthMoonMarsMercuryVenusJupiterSaturnNeptuneOthersModels984111111NotesSolid/Ocean tides using IERS 2003Simple tide model (Earth, Sun)From published papersFrom published paperFrom published paperFrom published paperFrom published paperFrom published paperSimple zonal (J2, J3, J4)AGIPg 24 of 40www.agi.com

Default CB Ephemeris Settings• Sun, Moon, Earth, Mercury, Venus, Mars–JPL DE 405 file (405, 403, 200 supported)–Ignores TDT-TDB differences (2 millisec max)–Treats ICRF as J2000• Jupiter, Saturn, Uranus, Neptune, Pluto–JPL DE 405 file, ignores TDT-TDB, ICRF = J2000– Barycentric ephemeris–Mu is planetary value–System Mu is system value (used for 3 rd body perts)• Span: 1960 - 2060AGIPg 25 of 40www.agi.com

Default CB Ephemeris (cont’d)• Moons of–Mars, Jupiter, Saturn, Neptune, Pluto [no Uranus]–Use JPL SPICE files• mar033, jup204, sat077, nep016, plu006• de405–Contains planetary ephemerides too–Considers TDT – TDB difference• Span: 2000 – 2025AGIPg 26 of 40www.agi.com

Modifying CB ephemeris• EphemerisSource JplDE–Available only for major planets, Sun, Moon–ApplyTDTtoTDBCorrectionForDE No [Yes]• EphemerisSourceJplSpice–JplSpiceId ##• Ex: 5 = Jupiter barycenter, 599 = planet center–Additional *.bsp file placed in STKData/Spice directory• Also supported–Analytic (TwoBody with element drift)–External Files (*.e files)AGIPg 27 of 40www.agi.com

Default Earth Attitude• Rotation, Nutation, Precession, Pole wander, Equinoxes• Complicated – see Technical help• Nutation: NutationUpdateInterval– STK Default: 1800 secs (30 mins)– ODTK: 0.0• Nutation: IAU1980NutationMethod– STK Default: uses values interpolated from JPL DE file– ODTK: IERS1996• Modeling TEME frame: UseUpdatedEquationOfEquinox– Default: Yes• Inertial Frame: J2000AGIPg 28 of 40www.agi.com

Default Moon Attitude• Interpolates Euler angles from JPL DE file–405, 403 have lunar libration data, not 200• JPL Lunar Recommendation–Use 403 for attitude and ephemeris–LP gravity fields built using these models• Supports IAU2000 frame definition too• Inertial frame: constant rotation from J2000–Mean Of Epoch at J2000 Epoch–Defined using IAU2000 frame definitionAGIPg 29 of 40www.agi.com

Default Attitude for other CB’s• IAU2000 Frame definition• Models– Right Ascension and Declination of Fixed Z axis– Rotation about Fixed Z axis• Fourier series, with secular drift terms• Coefficients contained in *.rot file– Same directory as *.cb file• Fixed, Inertial, True of Epoch/Date, Mean of Epoch/Date• Inertial frame: constant rotation from J2000– Mean of Epoch at J2000 epochAGIPg 30 of 40www.agi.com

Attitude Reference• "Report of the IAU/IAG Working Group onCartographic Coordinates and RotationalElements of the Planets and Satellites: 2000",Celestial Mechanics 82: 83-110, 2002.–Corrected and updated in 2005. (“…Satellites: 2003”)–Also contains size and shape information• True Of Epoch/Date–Ignores Rotation about Fixed Z axis• Mean of Epoch/Date–Ignores Fourier series terms in True of Epoch/DateAGIPg 31 of 40www.agi.com

Adding new CB’s• Create NewCbName.cb file• Edit settings appropriately– Start with a good example: Io, Ceres– DON’T use Earth, Sun, Moon as starting point– Really, DON’T use any major planet either to start• Create NewCbName folder– Put in *.cb file (and any *.rot, *.grv files too)• Place folder in CentralBodies directory• If using SPICE, add *.bsp file to STKData/Spice• Restart STK/ODTKAGIPg 32 of 40www.agi.com

Eclipse and Obstruction (LOS)• STK Objects use CB for eclipse/obstruction– Satellites can specify the eclipsing body list• Additional obstructing bodies– Specify each body as Access Constraint• Lighting in the 3D Graphics Window– Doesn’t consider eclipse– Ex.: Io appears lit while located in shadow of Jupiter• Sensor projection– Doesn’t consider obstruction– Projects to object’s CB surface (thru any other CB if need be)AGIPg 33 of 40www.agi.com

Access and Light Time Delay• Signal Sense– Transmit (default) or Receive• Clock Host– Transmit Times or Receive Times– These are the times reported by the tool• Coverage– Normally, grid point is clock host, receiving signal• Aberration– None, Total, Annual• LTD document (pdf) available from HelpAGIPg 34 of 40www.agi.com

LTD Issues• Graphics display True positions, not LTD–Except for location of Sun• Sensors projections do not account for LTD• Example: Sensor on Mars, pointed at Earth–Must choose pointing sense: Transmit or Receive–At a time of Sensor access, both Mars and Earth aredrawn at the same time, not the delayed time–Display near Earth won’t agree with computationsAGIPg 35 of 40www.agi.com

LTD in Chains• Chains models multi-hop Access–A à B à C à D etc.• Only approximately LTD compliant–Doesn’t apply a consistent clock base–We invalidate the Chain if the LTD of any hop but thelast is too “large”• Customer support à if you need LTD compliance–HTML Tool can helpAGIPg 36 of 40www.agi.com

Interplanetary Propagation (Berry)• Choice of origin–Switching cb’s–Use appropriate 3 rd bodies–Include proper ‘indirect’ terms• Matching JPL (Apophis)–Sun-centered–Use all 3 rd bodies–General relativity–Account for TDT / TDB differencesAGIPg 37 of 40www.agi.com

HPOP in STK vs.ODTK• ODTK’s Earth.cb settings– Nutation Method, Nutation Update Interval• Gauss-Markov processes– STK/HPOP supports propagation• Hidden: No GUI or report– STK/ASTG doesn’t support this• Multiple eclipse bodies– Can’t configure yet in STK/HPOP• Hidden: No Gui (STK 8.2!)– Can configure in STK/ASTG• 3 rd Body mu values– ODTK uses CB file value only (not configurable)• Astro Consistency doc in ODTK Help (HPOP/ASTG)AGIPg 38 of 40www.agi.com

Future direction (Woodburn)• HPOP – ASTG merge• Additional DSN measurement models• Mars GRAM• Additional SPICE integration• What else should we be doing?AGIPg 39 of 40www.agi.com

Questions / Comments?AGIPg 40 of 40www.agi.com