ToO Proposals

1. Definition

Target of Opportunity (ToO) proposals are for observations of transient and/or rare phenomena with specific or unspecific objects based on clear observational strategy, such as nearby supernovae, Gamma-Ray Burst follow-up, etc.

2. Eligibility

ToO Proposals should be submitted in the same manner as Normal Program proposals, while clarifying which Subaru instruments can be used to perform the ToO observations and how much time will be required.
Eligibility for intensive programs that involve a ToO observation is under discussion. We do not open this mode in S26A.

3. Requirement

Applicants of ToO proposals must be able to perform observations by their own teams, including remote observations. The Observatory staff is not necessarily required in their team.

4. Gemini ToO Observation

Subaru users who are eligible for Subaru-Gemini time exchange programs may also submit ToO proposals to the time-exchange program with Gemini, which will be executed at queue mode. Please refer to Subaru/Gemini page for more details.

5. Execution of ToO

When a ToO observation request is executed, the Director will make the decision to override scheduled observations. ToO observations are generally conducted in a half-night increments, except during HSC Queue mode, when observations can be undertaken in hourly increments, with the minimum observation time being 2 hours or more. PI or observers should attend the ToO observations. The telescope time of regular observers lost due to the interruption of ToO observations will be compensated by the observatory. Please also refer to the ToO Policy (English/Japanese).

updated on August 5, 2025