plans for slr features in vievs · tu wien department of geodesy and geoinformation research area...

TU WienDepartment of Geodesy and GeoinformationResearch Area Advanced Geodesy

Plans for SLR features in VieVS

Janina Boisits

VieVS User Workshop 2017

13.09.2017


Introduction to Satellite Laser Ranging

Introduction to SLRVieVS WS 2017

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• SLR technique:

– Optical wavelengths

– Reflection of laser pulses on satellites

– Time-of-flight measurement

+ High accuracy (error budget < 20mm)

Weather dependent

CoMAtmctof

R2

http://gpsworld.com/expert-advice-laser-reflectors-to-ride-on-board-gps-iii/


Current Station Network


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Current network of active SLR stations

Stations planned in India (2), Norway (1), USA (2)

https://ilrs.cddis.eosdis.nasa.gov/network/stations/ILRS_Stations_Map.html


SLR Products


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• Observation data:

– Full rate data

– Normal point data

• Products:

– Station coordinates and velocities

– Satellite orbit determination

– ITRF contributions (origin, scale)

VLBI SLR GNSS DORIS

Celestial Frame & UT1

X - - -

Polar Motion X X X X

Scale X X (X) (X)

Geocentre / Origin

- X (X) (X)


SLR Data Formats


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• Orbits: sp3

• Station coordinates and velocities: SNX

‘

• Observation Data: FRD or NPT

• Additional formats for corrections


Range Corrections


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• Station dependent corrections:

– Eccentricity of telescope axes

– Calibration constants

– Range bias, clock bias etc.

• Range corrections:

– Ionosphere (obsolete) and troposphere (modelled)

– Relativistic effects

• Satellite dependent corrections:

– Centre-of-Mass correction

Lageos ICEsat


SLR Module in VieVS

SLR Module in VieVSVieVS WS 2017

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• Starting SLR modules via ‘vievs_slr.m’ slr_batch() calls core modules


Folder Structure


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VieVS SLR Core Modules


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SLR_init SLR_mod SLR_lsm

Orbits

Orbits

External corrections

Loading effects etc. Eccentricity

Atmosphere

CoM

Station biases

Station coordinates

Station coordinates

Observation data


Core Module SLR_init


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Orbits

Station coordinates

Station coordinates

Observation data

Orbits



Atmosphere

CoM

Station biases

Reading in data:• Observation data according to process list• Orbit files (sp3) according to process list• Station coordinates and velocities from SNX file

Reading in external corrections:• Calibration coefficients• Station biases• Eccentricity• Centre-of-Mass correction (CoM)


Core Module SLR_mod


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Orbits

Station coordinates

Station coordinates

Observation data

Orbits



Atmosphere

CoM

Station biases

Modelling station coordinates:• Loading effects etc.

(analogous to VLBI modules)

Modelling troposphericcorrections:

• Hydrostatic delay modelled (meteorological parameters)

• Non-hydrostatic delay also modelled (very small)

Applying external corrections:

• Calibration coefficients

• Station biases• Eccentricity• CoM


Core Module SLR_lsm


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Orbits

Station coordinates

Station coordinates

Observation data

Orbits



Atmosphere

CoM

Station biases

Station coordinates:• Observation data files contain

observations to one specific satellite• Selection of sufficient sessions for

good geometry• Estimated daily or weekly

Satellite orbits:• No continuous measurements• Force model and orbit integrator


Further Plans

Further PlansVieVS WS 2017

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• Implement VieVS SLR module as presented

• Full compatibility to VLBI modules

– Combination of VLBI and SLR at Normal Equation level

– Consistent parameter estimation

• Adapting VMF coefficients to optical frequencies

– Implement advanced tropospheric delay model for SLR

plans for slr features in vievs · tu wien department of geodesy and geoinformation research area...

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