space flight center multiwavelength refraction modeling

$: Space Flight Center Multiwavelength Refraction Modeling$
GoddardGoddardSpaceSpaceFlightFlightCenterCenter

Multiwavelength Multiwavelength RefractionRefractionModeling ImprovementsModeling Improvements

forforLaser Ranging ObservationsLaser Ranging Observations

Glynn Glynn HulleyHulley(1)(1), , Erricos Erricos C. C. PavlisPavlis(1)(1)

V. B. MendesV. B. Mendes(2)(2) and D. E. and D. E. PavlisPavlis(3)(3)

(1)(1)JCET/UMBC - NASA/GSFCJCET/UMBC - NASA/GSFC(2)(2) FCUL, FCUL, LisboaLisboa, Portugal, Portugal

(3)(3) Raytheon ITSS - NASA/GSFC Raytheon ITSS - NASA/GSFC

14th International Workshop on Laser Ranging 14th International Workshop on Laser Ranging June 7-11, 2004, San Fernando, SpainJune 7-11, 2004, San Fernando, Spain

06/7-11/0406/7-11/04 Erricos C. Pavlis/JCET/NASA/926Erricos C. Pavlis/JCET/NASA/926 22

GoddardGoddardSpaceSpaceFlightFlightCenterCenterIntroductionIntroduction

•• UMBC/JCET is PI for AIRS instrument onUMBC/JCET is PI for AIRS instrument onNASANASA’’s AQUA spacecraft of EOS programs AQUA spacecraft of EOS program

•• When the mission is declared operationalWhen the mission is declared operational(real soon!!!), it will provide quick access to(real soon!!!), it will provide quick access toglobal fields of temperature, water vapor,global fields of temperature, water vapor,and other geophysical environmentaland other geophysical environmentalparameters daily in rapid modeparameters daily in rapid mode

•• Such data can be used for improvedSuch data can be used for improvedatmospheric delay modeling (e.g. gradients)atmospheric delay modeling (e.g. gradients)


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS on AQUAAIRS on AQUA



AIRS Products - TemperatureAIRS Products - Temperature October 10, 2003October 10, 2003



AIRS Products - Water VaporAIRS Products - Water VaporOctober 10, 2003October 10, 2003



AIRS Products - CoverageAIRS Products - Coverage October 10, 2003October 10, 2003


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS ProductsAIRS Products


GoddardGoddardSpaceSpaceFlightFlightCenterCenterNew Zenith Delay ModelNew Zenith Delay Model



New ZD Model PerformanceNew ZD Model Performance


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS Data IAIRS Data I

N-S and E-W Refractivity Gradients at altitudeFor each AIRS “granule” these fields are generated and processed at amaximum of 28 levels. The contribution from levels above the 10 km altitudecan be neglected at the moment.


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS Data IIAIRS Data II

Total Horizontal DelayTotal East-West and North-South gradient coefficients are integrated through alllayers of data to produce a quantitative picture of the total effect (left). Gradientprofiles at four different azimuth angles and for an 80° elevation direction.


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS Data IIIAIRS Data III

Land Granule CaseIgnoring horizontal gradients is most likely the largest error in ray-tracingtechniques at low elevation angles, but they also correct a small bias for near-zenith directions. We can see from the figures on the right, that the delay isgreatest in the north-south direction (azimuths 180° and 360°).


GoddardGoddardSpaceSpaceFlightFlightCenterCenterAIRS Data VIAIRS Data VI

Ocean Granule CaseThe increase of the delay at low elevations is mainly due to a decrease intemperature from the equator to the poles as can be seen in left figures. In this“ocean” case, the temperature gradients are greatest over the ocean where thelatitude of the granule runs from -38° to -17° . Notice the doubling of theerrors at 10° elevation between the “land” and the “ocean” example cases.


GoddardGoddardSpaceSpaceFlightFlightCenterCenterH - Gradient ComputationH - Gradient Computation

ßß The system that we are developing in placeThe system that we are developing in placeretrieves the AIRS and ancillary data, severalretrieves the AIRS and ancillary data, severaltimes a day around ILRS sitestimes a day around ILRS sites

ßß The data are preprocessed and converted toThe data are preprocessed and converted toquantities useful in the derivation of the localquantities useful in the derivation of the localgradientsgradients’’ functions (G functions (GNSNS and G and GEWEW))

ßß The gradient formulation to be adopted isThe gradient formulation to be adopted isunder investigation, including the possibility ofunder investigation, including the possibility ofan altogether brand new one.an altogether brand new one.


GoddardGoddardSpaceSpaceFlightFlightCenterCenterH - Gradient FormulationH - Gradient Formulation

A possible (currently used) model for adoption is oneA possible (currently used) model for adoption is onesimilar to what was used in prior studies with VLBI data:similar to what was used in prior studies with VLBI data:

but other approaches are being examined and in the computations webut other approaches are being examined and in the computations weadopted the [adopted the [Mendes and Mendes and PavlisPavlis, 2004, 2004] refractivity formula.] refractivity formula.

)sin()()cos()( fefe ⋅⋅+⋅⋅= azewaznsaz mLmLL

Ú ⋅⋅—= -H

nsns dhhNL0

610 Ú ⋅⋅—= -H

ewew dhhNL0

610

0032.0)tan()sin(

1)(

+⋅=

eeeazm

V


GoddardGoddardSpaceSpaceFlightFlightCenterCenterSummarySummary

ßß We are able to utilize existent AIRS data to generateWe are able to utilize existent AIRS data to generatefields with delays due to horizontal gradients.fields with delays due to horizontal gradients.ßß JCET is developing an automated procedure toJCET is developing an automated procedure to

generate these fields for all ILRS sites on angenerate these fields for all ILRS sites on anoperational basis.operational basis.ßß We are investigating 3-D ray-tracing algorithmsWe are investigating 3-D ray-tracing algorithms

using these fields to compute directly the total delay,using these fields to compute directly the total delay,thus avoiding the use of mapping functions entirely.thus avoiding the use of mapping functions entirely.



AIRS on AQUAAIRS on AQUA““First Light over the MedFirst Light over the Med””

Visible channel



AIRS on AQUAAIRS on AQUA““First Light over the MedFirst Light over the Med””

11 µm channel

space flight center multiwavelength refraction modeling

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