The 4MOST Operation System: instrument and science optimization; MPE software and management contribution
Th. Boller, H. Böhringer, T. Dwelly
Following an ESO call for proposals a consortium lead by AIP Potsdam proposed the building of the 4MOST fiber spectrograph comprising 1600 low resolution and 800 high resolution fibers feeding 3 spectrograph units. The main consortium goal in the application of this instrument is the spectroscopy of interesting targets of the GAIA and eROSITA sky surveys. The role of MPE within the consortium is the design of the survey operations concept and the construction of the survey operation software. For the preparation phase of the project a survey simulator software system has been built at MPE which performs the handling of prioritized target input catalogues from various science groups, allocates these targets to sky tiles and spectroscopic fibers in each tile, and evaluates the successful observations of the objects depending on instrument throughput and statistically simulated observing conditions. Mock catalogues of AGN and of galaxy clusters (the latter draw from a full analytical cosmological simulation) have been fed into the simulator together with catalogues from 5 other core science programs. It was shown that spectra of 1.4 Million galaxies in about 55 000 galaxy clusters and about 700 000 AGN can be harvested in the 5 year survey. Overall it was shown that the operations software can handle the 7 core science projects in such a way that success of all projects can be achieved simultaneously. This successful multiplexing in the survey operation is a new achievement in the performance of such sky surveys.
The high-capacity 4MOST Multi-Object Spectrograph accepted as an instrument for the ESO VISTA Telescope will enable us to obtain more than 25 Million object spectra in a 5 year survey. Among the core science programs of the 4MOST Survey is the massive spectroscopic follow-up of X-ray luminous galaxy clusters and AGN to be discovered in the eROSITA Survey. These survey data will provide important new insights into the evolution of black holes through cosmic history, the astrophysics of AGN, the large scale structure traced by AGN and galaxy clusters, and allow tests of cosmological model parameters with the eROSITA galaxy cluster population to much higher precision than without redshift data. Other Design Reference Surveys study the three-dimensional velocity space of Galactic stars and the chemical properties of all type of Galactic stars.
One important tasks of MPE is to define the design and implementation of the Operation System (OpSys) for the 4MOST project. The 4MOST OpSys has several roles, firstly to optimise the design of the instrument, secondly to devise a survey strategy for the wide field design reference surveys that are proposed for 4MOST, and thirdly to verify that 4MOST, as designed, can indeed achieve its primary science goals. We are defining the overall structure of the OpSys, together with details of some important subsystems. We are presently working out the results from the OpSys which illustrate clearly the value of having a functioning OpSys facility during its scientifically useful lifetime at the telescope, as well as during commissioning and survey phase 2 preparation period.
The Operation System is the collection of tools and procedures that together enable all 4MOST Phase 1 and 2 activities. The 4MOST Operations System (OpSys) will be the system driving all 4MOST survey planning functions (Phase 1) during its scientifically useful lifetime at the telescope, as well as during commissioning and survey phase 2 preparation period. The OpSys also provides survey simulation tools that will be used to predict survey outcomes, to optimize the survey strategy, and to prepare for the real survey.
The major components of the OpSys are the 4MOST Facility Simulator (4FS), the Exposure Time Calculator (ETC), the Observer Support Software (OSS), and the Survey Progress Monitor (SPM) described in the following. The figure illustrates the basic OpSys components.
Proceedings of the SPIE, Volume 8448, id. 84480X-84480X-7 (2012).