Abstract
NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is a space-based observatory currently under design and initial stages of fabrication, targeted to launch in the mid-2020s. The U.S. National Academy of Science’s Astro2010 decadal survey identified WFIRST as the highest-priority mission to investigate three fundamental problems in astronomy: the dark energy content of the Universe, the evolution of the high-redshift galaxy and quasar population, and the demographics of exoplanets in our own galaxy. Ball Aerospace is currently developing the mechanical/optical assembly for WFIRST’s key imager, the Wide Field Instrument. With its leading-edge mosaic of IR detectors, this imager will provide a field of view over 100 times greater than the competing instruments on the Hubble Space Telescope, thus opening an exciting new era in sky surveys from space. To achieve the mission’s ambitious science objectives, WFI must observe celestial objects over an exceptional range of brightness with extraordinary photometric precision. Ball Aerospace and Utah State University’s Space Dynamics Laboratory (SDL) are collaborating to design and build an onboard light source system capable of helping WFI meet these stringent photometric performance requirements. This Relative Calibration System (RCS) generates light matched to the wavelengths of each of the imager’s six filters, illuminating the WFI Focal Plane Assembly (FPA) with temporally stable illumination at six logarithmically-spaced signal levels. Measuring these light levels will define a detector response ratio we’ll use to define a transfer standard relating faint objects to bright ones. This talk will highlight the engineering methods we’ve employed to select the sources for use in the calibration system, some unexpected consequences of these choices, the lessons learned from the trade studies, and what challenges lie ahead in completing the RCS.
The WFI Relative Calibration System for WFIRST
NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is a space-based observatory currently under design and initial stages of fabrication, targeted to launch in the mid-2020s. The U.S. National Academy of Science’s Astro2010 decadal survey identified WFIRST as the highest-priority mission to investigate three fundamental problems in astronomy: the dark energy content of the Universe, the evolution of the high-redshift galaxy and quasar population, and the demographics of exoplanets in our own galaxy. Ball Aerospace is currently developing the mechanical/optical assembly for WFIRST’s key imager, the Wide Field Instrument. With its leading-edge mosaic of IR detectors, this imager will provide a field of view over 100 times greater than the competing instruments on the Hubble Space Telescope, thus opening an exciting new era in sky surveys from space. To achieve the mission’s ambitious science objectives, WFI must observe celestial objects over an exceptional range of brightness with extraordinary photometric precision. Ball Aerospace and Utah State University’s Space Dynamics Laboratory (SDL) are collaborating to design and build an onboard light source system capable of helping WFI meet these stringent photometric performance requirements. This Relative Calibration System (RCS) generates light matched to the wavelengths of each of the imager’s six filters, illuminating the WFI Focal Plane Assembly (FPA) with temporally stable illumination at six logarithmically-spaced signal levels. Measuring these light levels will define a detector response ratio we’ll use to define a transfer standard relating faint objects to bright ones. This talk will highlight the engineering methods we’ve employed to select the sources for use in the calibration system, some unexpected consequences of these choices, the lessons learned from the trade studies, and what challenges lie ahead in completing the RCS.