Upper Atmospheric Densities Derived from Starshine
UPPERUPPER ATMOSPHERICATMOSPHERIC DENSITIESDENSITIES DERIVEDDERIVED FROMFROM STARSHINESTARSHINE SPACECRAFTSPACECRAFT ORBITSORBITS R. G. Moore1, J. Lean2, J. M. Picone2, S. Knowles3, A. Hedin2, and J. Emmert2 1. 3855 Sierra Vista Road, Monument CO 80132 2. Naval Research Laboratory, Washington DC 20375 3. Raytheon Company, Lexington MA 02421
Motivation - improved density model for orbit tracking Starshine Orbits - cycle 23 max Spacecraft Drag - independent data for model validation Starshine vs NRLMSIS – model density comparison UpperUpper AtmosphereAtmosphere DensityDensity CausesCauses SpacecraftSpacecraft DragDrag
2 drag acceleration = 0.5 ρ v Cd A/ M ρ atmospheric density velocity relative to local v environment
Cd drag coefficient, M mass A cross sectional area perpendicular to velocity vector
three Starshine Spacecraft with spherical geometry and known mass have been launched into circular low-Earth orbits
9,000 resident space objects larger than 15 cm PropertiesProperties ofof StarshineStarshine SpacecraftSpacecraft
Starshine Launch Re- Initial Eccen- Inclination Mass Diameter CD Inverse Space- entry Altitude tricity (degree) (kg) (cm) Ballistic craft (km) Coefficient (cm2 gm-1) 1 1999 2000 385 0.001 51.6 39 48 2.1 0.097 05-27 02-18 (19”) 2 2001 2002 370 0.002 51.6 38 48 2.1 0.100 12-05 05-01 (19”) 3 2001 2003 475 0.001 67 90 94 2.1 0.162 09-29 01-21 (37”) SolarSolar ActivityActivity AltersAlters TemperatureTemperature andand CompositionComposition atat StarshineStarshine AltitudesAltitudes Temperature Primary Constituents
solar min – dashed solar max - solid
F10.7=70,
USSPACECOM orbit parameters derived from General Perturbation theory: six Kozai mean elements • inclination • right ascension of ascending node • argument of perigree
• eccentricity -3
• mean motion 10 • mean anomaly plus drag (Bstar) provided by Dr T. Kelso, http://www.celestrak.com AtmosphericAtmospheric DensityDensity DerivedDerived fromfrom TLEsTLEs µ instantaneous change in dn = 3 n1/ 3 −2 / 3 BFρv3dt mean motion with time 2 change in mean motion µ n − n ≅ 3 n1/ 3 −2 / 3 Bρ Fv3dt between two successive ρ2 1 2 E E ∫ TLE epochs 2 / 3 density average between 2 µ two successive TLE epochs E = ()n2 − n1 3 Bn1/ 3 Fv3dt E ∫
n = mean motion, t = time ρ = mass density where ρE and nE are effective B = inverse ballistic coef values between two successive = C A/M d TLE epochs: µ = GM, gravitational parameter ρ Fρv3dt v = spacecraft velocity ∫ 2 = F = wind factor ⎛ rω ⎞ E 3 ≅ ⎜1− cos()i ⎟ Fv dt ⎝ v ⎠ ∫ StarshineStarshine OrbitsOrbits areare AssumedAssumed CircularCircular for circular orbits Fv3dt = Fv3 (t − t ) ρ∫ 2 1 dn µ 2 / 3 gravitational ≅ 2 constant density at TLE epoch 3 dt Bn1/ 3v3 F wind factor derivative of speed mean motion inverse ballistic mean motion coefficient
height and speed are approximately constant during Starshine orbits so 3 3 ∫ Fv dt ≅ Fv ()t2 − t1 QuantitiesQuantities forfor DragDrag CalculationsCalculations
3 obtained from TLE’s directly
obtained from SPG4 with TLE inputs obtained from SPG4 and TLE’s TotalTotal MassMass DensitiesDensities DerivedDerived fromfrom DragDrag onon StarshineStarshine SpacecraftSpacecraft StarshineStarshine TotalTotal MassMass DensitiesDensities andand USUS StandardStandard AtmosphereAtmosphere (1976)(1976)
Densities from Starshine drag: • higher than USSA76 at altitudes above 200 km • lower than USSA76 at altitudes below 200 km
Starshine 1,2 & 3 orbits occurred during overall high solar activity NRL’sNRL’s TimeTime--DependentDependent UpperUpper AtmosphereAtmosphere DensityDensity SpecificationSpecification ModelModel calculates upper atmosphere total mass density, composition and temperature, for specified altitude, latitude, longitude, local time, day of year and solar activity NRLMSIS-00 Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Model (2000) • enhanced, revised model within MSIS framework - Hedin, 1987, 1991 • extended database for model formulation - total mass densities from satellite - excluding Starshine accelerometers and orbit determinations - temperatures from incoherent scatter radar -O2 densities from solar UV occultation • solar/geomagnetic inputs
-F10.7, F10.7 A, Ap Picone et al., Phys. Chem. of Earth, 2000 ComparisonComparison ofof StarshineStarshine andand NRLMSISNRLMSIS TotalTotal MassMass DensitiesDensities
• NRLMSIS model is 2 evaluated around one complete Starshine orbit 1 3 • orbit-average model density is compared with Starshine drag value Starshine 2 & 3 show similar differences with NRLMSIS NRLMSISNRLMSIS TotalTotal MassMass DensityDensity VariationsVariations DuringDuring SingleSingle StarshineStarshine OrbitsOrbits
Starshine location around orbit input to NRLMSIS model, with specified day- of-year and solar activity
density calculated by NRLMSIS model StarshineStarshine andand NRLMSISNRLMSIS DifferencesDifferences –– relatedrelated toto solarsolar indicesindices
SOHO EIT EUV/304 Å 30JUL99 14AUG99 Starshine 1 when NRLMSIS densities lead Starshine densities, F10.7 coronal index leads chromospheric index (derived from ratios of core-to-wing emission in solar Ca II K and Mg II h&k exponential Fraunhofer lines) fall off differences between NRLMSIS and Starshine densities track differences between F10.7 and chromospheric indices ReformulatingReformulating NRLMSISNRLMSIS UpperUpper AtmosphereAtmosphere DensityDensity ModelModel
CurrentCurrent Version:Version: NRLMSISNRLMSIS--0000 F10.7, [F10.7]81 -- proxies for EUV radiation AP -- proxy for geomagnetic effect of solar wind Picone et al., Phys. Chem. of the Earth, Part C, 2000, Picone et al., JGR, in preparation FutureFuture Version:Version: NRLMSISNRLMSIS--SOLCSOLC ICHROM, [ICHROM]81 -- proxies for EUV radiation AP -- proxy for geomagnetic effect of solar wind
NRLMSIS has been reformulated using a new solar irradiance index - improvements will be assessed by comparisons with Starshine drag SUMMARY:SUMMARY: UpperUpper AtmosphericAtmospheric DensitiesDensities DerivedDerived FromFrom StarshineStarshine SpacecraftSpacecraft OrbitsOrbits mass densities at 130-470 km derived from USSPACECOM TLEs along Starshine 1,2,3 orbits densities have solar EUV induced 27-day variations superimposed on exponential fall-off with altitude Starshine and NRLMSIS-00 densities agree to within 20%
… differences between chromospheric and F10.7 proxies may account for some of the differences NRLMSIS has been reformulated with a new solar EUV proxy … NRLMSIS-SOLC Starshine 4, 5 are in progress … model validation during 11-year solar cycle … comparisons with TIMED irradiance & density StarshineStarshine SpacecraftSpacecraft SeriesSeries trackingtracking Starshine 1, STS-96, mid-1999, 385 km, 39 kg thethe 1111--yearyear Starshine 3, Kodiak, Sept 2001, 471 km, 90 kg solarsolar activityactivity Starshine 2, STS-108, Dec 2001, 387 km, 38 kg cyclecycle Starshine 4,5, TBD 385 km
TIMED:TIMED: GUVIGUVI atmosphericatmospheric densitiesdensities SEESEE solarsolar EUVEUV irradiancesirradiances