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GPI Target Duplication Policy
In general, Gemini avoids making observations that duplicate the science goals and scientific utility of other observations, given the limited resource of observing time on sky. The Gemini Science Archive (GSA) eventually provides open access to all data. Policies against target duplication using the Gemini Planet Imager (GPI) follow from these principles and apply to all observations using GPI, including Campaign targets that will be reserved in advance of the semester during which they are likely to be observed.
Additional observations of the same target that use a significantly different instrument mode, such as polarization or a different mask, are allowed. Observations may demonstrate that they are significantly different by obtaining a meaningfully different measurement that supports the scientific goals of the proposed program, for example in planet mass sensitivity. Observations for the same purpose but only in a different filter will not be permitted.
The GPI Campaign has provided a list of targets and observing mode that will be protected against duplication until the data are released in the GSA at the standard time, 18 months after observation. The exceptions are sources with known planetary companions. Given the scientific interest and utility of concentrated study, principal investigators (PIs) may propose duplicate observations of these Campaign targets. Proposals must include evidence of a companion, which may be through citation of published work or presentation of unpublished data. Multiple duplicate PI observations will not be permitted. These PI duplication conflicts will be resolved in the standard way, within National Time Allocation Committees (NTACs) and by the International TAC.
Some examples that would be considered duplication and therefore not approved:
- Searching for planets or companions in a different filter. (The rationale is that the science is substantially the same, and the instrument setup is not significantly different.)
- Searching for planets or companions to a slightly different observational depth. (The rationale is that there is little scientific gain with much deeper observations, given that the number of detectable planets is an extremely weak function of exposure time. E.g., with detectability likely ~t0.1, to be twice as likely to detect a planet as a baseline 1-hour GPI observation would require 800 hours exposure. Much shallower observations obviously provide no new information.)
Some examples that would not be considered duplication and therefore be approved:
- Using a polarimetric mode. (Although the polarimetric mode also provides images, a scientifically-justified use of polarimetry would provide additional new information beyond non-polarimetric observations.)
- Using the non-redundant aperture mask (if commissioned) or no coronagraph, compared with planned observations using the standard coronagraphic masks.
- Observations of HR8799, although it is part of the Campaign target list. (Planetary companions are known.)
The Science and Technology Advisory Committee (STAC) has reviewed and endorsed these policies. The STAC encourages the organizers and chairs of the NTAC processes to forward any questions regarding potentially duplicative targets to the Gemini Deputy Director for review ahead of national TAC meetings so that TACs can focus on science and avoid ambiguity about whether proposed targets fall under the duplication policy.