Engineering and QC Analysis Session Summary

R. Noomen and V. Glotov

This session addresses two general topics: (1) a variety of engineering aspects of the SLR observations, and (2) data quality control by means of orbital techniques.

Engineering

Prochazka addressed the issue of numerical noise, in particular introduced by the processing of the laser data. A comparison of SLR data fitting procedures was done, either using an integrator plus range/time bias functions, or by using a polynomial representation. He concluded that artificial effects of about 3 ps (round trip travel time) might be introduced; single-shot effects are smaller. It is smaller than 1 ps for normal points, and is negligible compared to the satellite signature effect.

Luck presented an evaluation of interpolation effects. In particular, he studied different interpolation techniques, on various targets. Depending on the exact application, large errors may be introduced here. In conclusion, predictions need to be integrated at step sizes much smaller than the normal point bin size, and interpolation should be done in x/y/z rather than azimuth/elevation/range. Cubic splines are not to be used.

Salminsh reported on an Engineering Data File system, in which a large variety of aspects of the laser station (configuration) are stored. Applications are comparison studies, to explain data anomalies, to record the system history and such. Implementation of this configuration management system is complete or in progress in Potsdam, Graz and Wettzell. Results and examples are available at www.astr.lu.lv/edf.

Q/C analysis

Gibbs reported on the time bias detection and monitoring system that is operational at Herstmonceux. It provides a rapid-turnaround option to QC passes of a variety of satellites, taken by arbitrary stations. A possible time bias is the particular parameter that can be detected by this technique.

Glotov addressed the MCC experience on weekly, operational QC analysis. He noted the differences between various QC reports, and suggested several explanations: station coordinates, rejection procedures, orbit solutions and incorrect estimations of range and time biases.

Schillak also addressed the QC analysis of the global network of stations. In particular, he solves for (a time-series of) station coordinates, which are used to monitor station performance (possible range biases), or which may be used to expand ITRF2000 with epoch coordinates and velocities of new stations.

Müller gave a presentation on the weekly network/EOP solutions, that are generated for the AWG pilot project, and the QC aspects embedded in this activity. This may focus on the latter (biases) or on products (Helmert transformations, orbit overlaps). In addition to these operational solutions, multi-year solutions are used for similar purposes.

Noomen gave an overview of the Delft QC analyses. He showed the developments in data quality, computation models and analysis strategies, and highlighted the progress in quality of the orbital solutions. The inherent uncertainty of range and time bias estimates was discussed. The system is expected to switch to a daily mode of operation shortly.