Contact Information

Education

Employment Experience

January 2008 - Present
TAOS-II Chief Scientist
Institute for Astronomy and Astrophysics
Academia Sinica,
Taipei, Taiwan
August 2004 - December, 2007
Research Associate
Harvard College Observatory
Cambridge, MA
USA
October 2001 - July, 2004
Research Associate
University of Pennsylvania
Philadelphia, PA
USA
November 2000 - October, 2001
Post-Doctoral Physicist
University of Pennsylvania
Philadelphia, PA
USA
August 1997 - November, 2000
Post-Doctoral Research Associate
University of Sheffield
Sheffield, UK
July 1996 - July 1997
Post-Doctoral Physicist
University of California San Diego
La Jolla, CA
USA

Research Interests

I am interested in the outer Solar System, particularly the region from the Kuiper Belt out to the Oort Cloud. Kuiper Belt Objects (KBOs) smaller than about 30 km in diameter are practically invisible to direct observational surveys, as are nearly all objects expected to exist beyond 100 AU. I worked on The Taiwanese-American Occultation Survey (TAOS), which searched for occultations of distant stars by small outer Solar System objects. Such events are rare and extremely short in duration, so we monitored a large number of stars (typically 500 stars at any given time) at a high exposure rate (5 Hz). We operated the survey for seven years, and no events were found, allowing us to place the strongest upper limits to date on the surface density of Kuiper Belt objects with diameters between 500 meters and 30 km. Furthermore, we have also found no objects at distances between 100 and 1000 AU, placing the strongest upper limits to date on objects at these distances.

We have nearly completed development of a successor survey, the Transneptunian Automated Occultation Survey (TAOS II), which will be more than a factor of 100 more sensitive than TAOS. The survey is designed to monitor 10,000 stars at a rate of 20 Hz. To achieve this goal, we will use larger telescopes and custom cameras capable of the high readout rate. The three telescopes will are 1.3 m F/4 telescopes with a 2.3 sq. deg. field of view. The cameras will be mosaics of back-illuminated CMOS devices. The telescopes were installed at the San Pedro Mártir Observatory in Baja California, México in the autumn of 2017. The cameras will be delivered in the spring of 2018, and we expect to begin science operations in the summer of 2018.

I am also a member of the Outer Solar System Origins Survey (OSSOS), a large program of the Canada France Hawaii Telescope. The survey has covered 168 sq. deg. with the goal of detecting and classifying over 1,000 KBOs down to a magnitude limit of r'=24.5. I am mainly working on follow-up observation of the objects detected by OSSOS, primarily using the Subaru and Gemini North telescopes. The goal of these follow-up observations is to measure light curves and colors of the OSSOS KBOs in order to correlate surface, shape, and rotational properties with dynamical classification.

Finally, I am a member of the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP). This survey comprises three components with different combinations of sky coverage and limiting magni- tude. The wide survey will cover 1400 sq. deg. down to magnitude r'=26, the deep survey will cover 27 sq. deg. down to r'=27, and the ultradeep survey will cover 3.5 sq. deg. down to r'=28. This program is not optimized for detection of KBOs, but a preliminary analysis of 221 sq. deg. of data from the wide survey has succeeded in discovering 231 previously unknown objects, with magnitudes as faint as r' = 25.3. Both the survey and analysis are ongoing, and this work will eventually result in a very accurate measurement of the KBO size distribution for objects with magnitudes 27>r'>25.