Daily Earth rotation determinations from IRIS very long baseline interferometry
Classical optical determinations of Earth rotation (UT1) require several weeks of observations to achieve an accuracy of ∼1.5 ms of time, whereas modern techniques have demonstrated an accuracy of 0.7–0.9 ms on timescales of 1–5 days l,2. Here we have probed the limits of the accuracy and time resolution of very long baseline inteferometry (VLBI) determinations of UT1 by conducting a series of 1-h observing sessions using only one baseline. Comparison of the results from the 1-h sessions with corresponding determinations from 24-h multi-baseline sessions establishes that the accuracy of the 1-h determinations is close to 0.1 ms of time. These observations were scheduled as part of the project MERIT (monitor earth rotation and intercompare techniques of observation and analysis3) intensive observing campaign.
Determination of Sub-daily Earth Rotation Parameters from VLBI Observations Summary
The work presented deals with the determination of sub-daily Earth Rotation Parameters (ERPs) from Very Long Baseline Interferometry (VLBI) observations. Monitoring and interpreting the Earth's rotation variations in general is an important task for Earth sciences, as they provide boundary which support other geophysical investigations. This holds especially for sub-daily variations of the Earth's rotation which are primarily excited by variations of the oceans. Furthermore, atmospheric impacts as well as effects of the shape of the Earth are present. VLBI observations are in particular feasible. With VLBI all five parameters of the Earth's orientation can be determined without hypothesis. Thus, VLBI derived results do not suffer from resonance effects from the modeling of artificial Earth satellites, which is the fact for ERPs derived, Although the analysis of sub-daily variations of the Earth's rotation is by no means a new scientific area of research, there is a clear need to expand the methods used. This is also obvious as further studies by other authors were performed in parallel to the results presented in this thesis. Thus, the determination and analysis of sub-daily ERPs can be considered as a vital field of research. The determination of sub-daily ERPs from VLBI observations can be divided into two areas. On the one hand, time series with a high temporal resolution, e.g., one hour, can be generated. On the other hand, an empirical model for the tidal variations of the ERPs with periods of one day and below can be determined from the VLBI observations. Both areas of research are considered within this thesis. Concerning the time series approach, special continuous VLBI campaigns are examined as they offer ideal conditions for this approach. For the analysis of these campaigns, an optimized solution scheme is implemented. This adapts the continuous character in an optimal way and avoids negative influences of the VLBI-analysis on the subsequent examination of the sub-daily ERPs. In this way, irregular variations are confirmed and further ones are detected. However, it is pointed out that these variations can be confirmed only with continuous campaigns over longer time spans. Furthermore, a temporal resolution below one hour of the sub-daily ERPs would be desirable to detect additional short periodic variations. This is not possible with the current status of VLBI observations, but, improvement is promised by future technical concepts of VLBI. The analysis methods that are applied within this thesis, will be directly applicable to …
Analogy, Supposition, and Transcendentality in Narrative Argument
Rodden writes, “How do stories persuade us? How do they ‘move’—and move us? The short answer: by analogies.” Rodden’s claim is a natural first view, also held by others. This chapter considers the extent to which this view is true and helpful in understanding how fictional narratives, taken as wholes, may be argumentative, comparing it to the two principal (though not necessarily exclusive) alternatives that have been proposed: understanding fictional narratives as exhibiting the structure of suppositional argument, or the structure of a kind of transcendental argument. Three key aspects of understanding a fictional narrative as an argument from analogy are identified. First, the argument will be relativistic or depend in an essential way upon the circumstances or intentions of the auditor or author. Second, in view of the first aspect, the argument will be loose and subjective, and accordingly less likely to yield knowledge. Third, the argument will not exhibit a distinctive structure applicable only to fictional narratives. I find that the third, and sometimes the first and second, of these same three aspects apply to understanding fictional narratives as suppositional arguments. I present considerations that point to a way of establishing that some extended fictions exhibit the structure of a kind of transcendental argument that is neither relativistic nor subjective, is knowledge-generating, and is uniquely applicable to fictional narratives. This supports literary cognitivism—the thesis that “literary fiction can be a source of knowledge in a way that depends crucially on its being fictional.”