Summary and Response to the Charge
In part 1 of its charge, the CAA has been asked about the community process planned by NASA and the Roman project:
Should this community process (1) continue as is and maximize the utility of the Core Community Surveys for general astrophysics science while strictly maintain the constraint of ≥25 percent of available observing time for General Astrophysics Surveys; (2) focus the Core Community Surveys solely on cosmology and exoplanet requirements, and optimize for shortest possible surveys, thereby maximizing the time available for General Astrophysics Surveys; or (3) relax the ≥25 percent constraint to enable greater optimizations of the Core Community Surveys for general astrophysics science?
Having collected information and deliberating on the charge, the CAA is laying out 10 principles to guide NASA over the coming months as it plans and then conducts the process to finalize Roman’s observing plans. The committee believes this is a more effective response than specifying a choice based on percentages, which, as this report explained, should be based on calculations that are not currently available. The committee endorses the community collaborative process as a first step and encourages the inclusion of a competitive process arbitrated by a group of independent experts (the STAC). The committee recognizes the scientific importance of maximizing the general astrophysics return of the mission, as well as having Roman achieve the science objectives set by Astro2010 and endorsed by Astro2020. The CAA suggests that science teams provide the STAC with the required quantitative information in the form of a range of options accompanied by detailed sensitivity analysis. The STAC would use this information as input, and have broad latitude to optimize Roman’s observing plan.
In part 2 of its charge, the CAA has been asked about the competed GA program:
How should the Roman project set the balance between the fractions of time allocated to large/medium/small General Astrophysics Surveys (i.e. allocate more time to large coherent observations, or allocate more time to a multitude of smaller independent ones)? How should the Roman project set the overall number of General Astrophysics Surveys (note that increasing the number of General Astrophysics Surveys, even holding total time constant, will come at increased cost to the mission)?
For a survey instrument like Roman, there is an advantage in establishing a process during which competing survey proposals could be combined if the science objectives permit. The committee encourages consideration of a broad range of surveys, including much shorter and much longer than the nominal average of 14 days currently planned. The STAC would decide on the final selection based on the expected science return. The current limit of 30 competed proposals appears premature. The actual limit might be determined by scientific and programmatic considerations at the time of selections.