Abstract

Strategy of the Taiwan-America Occultation Survey (TAOS)

W.P. Chen, C. Lemme, and the TAOS Team
presented by W.P. Chen

Die praktische Durchführung des Projektes "TAOS" zur Beobachtung von Kuipergürtelobjekten durch Sternbedeckungen wird präsentiert.
Die Instrumentierung und die Beobachtungsstandorte in Taiwan werden vorgestellt.
Die automatische, photometrische Überwachung von etwa 3000 Hintergrundsternen wird eine extrem hohe Datenrate liefern, die hohe Anforderungen an die Datenerfassungssoftware stellt.

Understanding the formation of the sun and the planetary system remains one of the fundamental questions in astrophysics. Cometary nuclei --- the remnant icy bodies of planet formation, located at the outer edge of the solar system --- are relatively poorly studied because of their small sizes and thus faintness.

These small objects bear imprints of not only the formation, but also the dynamical history of the solar system. Impacts by these celestial objects have played a vital role in shaping the early atmospheric, geological, or even biological evolution of planets. Yet up until recently their number as well as distribution within the solar system can only be inferred on theoretical grounds.

Discovery since 1992 of some one hundred odd objects in the Edgeworth-Kuiper belt, beyond the orbit of Neptune, makes the existence of such a belt zone no longer hypothetical, and presents one of the major breakthroughs in modern planetary science. The Kuiper belt objects (KBOs) identified so far, however, are limited only to the largest members, with diameter greater than 100-200 km. Smaller bodies are still much too faint to image directly even with the currently largest telescopes.

The Taiwan-America Occultation Survey (TAOS) project is setting up an array of small telescopes to conduct a census of the KBOs down to a few km size. Several thousand background stars will be monitored continuously to detect chance occultations by the KBOs. Initially three wide-field (f/1.9; 0.5 m aperture) telescopes equipped with 2K squared CCD cameras will be placed along a 7 km east-west baseline in central mountain range of Taiwan at an elevation above 3000 m. More telescopes in the north-south extension may later be added so as to estimate the size distribution of the KBOs and their spatial distribution along the ecliptic plane.

The robot telescopes will operate in a coincidence mode so the sequence and timing of a real occultation event can be recorded and distinguished agaist false detections. The Lawrence Livermore National Laboratory in the USA, the National Central University, and the Academia Sinica, both from Taiwan, each contributes one telescope system. The collaboration includes also researchers from UC-Berkeley, NASA/Ames, Australia, and Korea.

Our experiment provides the only means to study the numerous, small members of the cometary population, thus completing the census of the solar system objects from large to small. A great number of scientific byproducts, notably variable stars, will also derive from the huge TAOS database, some 10,000 giga-bytes worth of photometrical measurements per year sampled at 5 Hz.

Prof. Wen Ping Chen, Graduate Institute of Astronomy, National Central University, Taiwan
Address: Chung-Li 32054, Taiwan E-Mail: wchen@outflows.phy.ncu.edu.tw Internet: http://www.astro.ncu.edu.tw
Telephone: +886 3 422 3424 Fax: +886 3 4262304

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