Subaru Prepares for Open Use

October 23, 2000

September saw continuing engineering work at Subaru, and further test observations by IRCS and FOCAS. In addition, on September 18, the Subaru Telescope Time Allocation Committee (TAC) met for the first time to approve a number of proposals for Subaru's first period of Open Use.

The observations so far performed by Subaru and published as Press Releases or in scientific journals, were undertaken by observatory staff or members of the various instrument groups during the initial testing of the telescope and instruments. The purpose of Subaru Telescope, however, is to perform cutting-edge scientific observations by inviting proposals from astronomers from around the world, and the tireless engineering work which has been ongoing since First Light in December 1998 meant that we were able to announce the availability of Subaru in June of this year. Although all seven of Subaru's instruments have been tested on the telescope, it was decided that only IRCS and Suprime-Cam were working sufficiently well to be offered for the first semester (called S00). In addition, although Semester S00 will begin in December 2000 and run until the end of March 2001, only 36 nights were offered for Open Use operations, to allow engineering operations to continue during the same period, and permit the instrument groups to carry out their own observations; applicants were therefore restricted to requesting no more than 3 nights in any one proposal. Despite this, a total of 114 proposals were submitted, requesting 223 nights. The oversubscription factor (the number of nights requested divided by the number of nights available) was therefore 6.2! This is not unusual for a major observatory, as telescope time is very much in demand. The selection process is therefore an important part of Subaru Telescope's operations, although an inevitable consequence of the high demand is that it will be impossible to award time to many excellent proposals.

Each applicant must indicate to which of 5 categories his/her proposal is being submitted. These categories are:

  • Solar System
  • Stars and the Galaxy
  • Star Formation and the Interstellar Medium
  • External Galaxies and Active Galactic Nuclei
  • Structure Formation and Cosmology

Each proposal is then sent to 5 referees whose research interests lie in that field, and each referee assigns a score to each proposal, depending on its scientific merit. This process is known as "peer review", since each proposal is reviewed by people of similar ability as the applicant. In addition, each proposal is assessed for technical feasibility, to ensure that, for example, the target objects can be detected in the time requested.

Pie-charts of number of proposals by category and number of nights requested by category (Colors correspond to categories listed above)

The TAC consists of eight astronomers, one with expertise in each category, and three additional members with more general experience. They were sent the results from the referees and met in the Subaru Telescope Base Facility on September 18 to determine which proposals would be awarded time.

The 36 nights were awarded to a total of 26 proposals: 19 nights to 16 IRCS proposals, and 17 nights to 10 Suprime-Cam proposals. In some cases, proposals were awarded fewer nights than had been requested, if the TAC members felt that most of the scientific goals could still be completed.

Pie-charts of number of accepted proposals by category and number of nights awarded by category (Colors correspond to categories listed above)

The list of accepted proposals is available on our web site. In addition to the time awarded by the Subaru TAC, the University of Hawaii's Institute for Astronomy (IfA) is granted 15% of Subaru's observing time. All telescopes on Mauna Kea give a fraction of their time to the IfA since the University of Hawaii owns and operates the Mauna Kea Science Area where the telescopes are located. Proposals from IfA members are submitted to a separate TAC which awards its share of time, and checks are then made to ensure that there are no conflicts between proposals accepted by the two TACs.

The first visiting observers will come to Subaru Telescope in early December. By that time, we will already have made an announcement inviting applications for Semester S01A, which will begin in April 2001. The fraction of time assigned to Open Use operations will increase gradually as the performance of the telescope and instruments becomes more stable and less engineering time is needed.

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