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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unpublished data.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.