ILRS DATA FORMATS AND PROCEDURES WORKING GROUP

REFRACTION STUDY GROUP

Formed:

25 April 2000, at ILRS meeting in Nice

Team Leader:

Stefan Riepl, Wettzell Fundamental Geodetic Station, BKG

Members (draft preliminary list of possibles):

Rueger(UNSW), Mendes (UNB), Eanes (CSR), Govind (AUSLIG), Yan
(SHAO), Brunner (TUG), Herring (MIT), Gurtner (NEWG), Noomen (AWG)

CHARTER

Considering that the current standard model developed by Marini and Murray for applying atmospheric propagation delay corrections to SLR observations is believed to be uncertain by up to 1 cm in the zenith delay term; and considering that it is tuned to particular wavelengths which do not encompass all the wavelengths which might be used in practice,

1. Assess the adequacy and accuracy of the Marini and Murray model for SLR at the 1 mm level, for all elevations above 15 degrees and all wavelengths from 355 nm to 1570 nm and perhaps beyond.
2. If necessary, define a new model and/or set of procedures which will satisfy these requirements, and verify it experimentally.
3. Define optimumschemes for the collection and pre-processing of meteorological and any other necessary data to be used as input to the model/procedure, and assess the impact of the absence of any such data which may be difficult or expensive to collect.
4. Prepare a formal recommendation to the ILRS, including a standard algorithm and set of recommended practices, for adoption by the stations and analysis centres.

Timetable:

1. A report on charter item 1 is to presented to the DF&P Working Group at the Matera meeting in October 2000.
2. If this report indicates that revision is necessary, present a formal recommendation to ILRS at the ILRS Governing Board meeting subsequent to the Matera meeting.

Notes:

a. It might be desirable to extend the region of applicability to elevations lower than 15 degrees.
b. The input data to the model/procedure might include wide-area meteorological measurements, measurement types not currently used (temperature, pressure and humidity at the station), water vapour assessments from nearby IGS GPS receivers, and so on. However, considerations of cost and practicality must be borne in mind.
c. A feasible approach might be to solve for certain terms in the SLR analysis process, such as a zenith delay, while keeping the mapping function and station instrumentation relatively simple.

John McK.Luck
Coordinator, ILRS Data Formats and Procedures Working Group
26 April 2000.

ILRS DATA FORMATS & PROCEDURES WG

REFRACTION STUDY GROUP

Chairperson:Stefan Riepl,Wettzell, BKG

Formed:

Tuesday 25 April 2000

Possible Members:

Herring (MIT), Rueger (UNSW), Govind (AUSLIG), Yan (SHAO), Mendes (UNB), Eanes (CSR), Brunner (TUG), Ciddor (NML)
Ex-officio from ILRS: Gurtner (NEWG), Noomen (AWG)

Rationale:

Marini & Murray model may have errors up to 10 mm at zenith;

Marini & Murray is tuned to small wavelength band.

CHARTER

1. Assess adequacy of M&M at 1 mm level in wavelength band 355 to 1570 nm and elevations above e.g. 15 degrees. Report at Matera Workshop, October 16-20, 2000.

2. If necessary, define a new model and/or procedures, and verify experimentally.

3. Define optimum schemes for collection & processing of meteorological and related input data, and assess impact of their absence due to expense or difficulty.

4. Formal recommendation to ILRS at meeting subsequent to Matera, including a standard algorithm and set of practices for adoption by stations and analysis centres.

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