[Paper Review] Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report

David N. Spergel, N. Gehrels+53 more|arXiv (Cornell University)|Mar 12, 2015

Astronomy and Astrophysical ResearchPhysics and Astronomy123 references992 citations

TL;DR

This 2015 report presents the Design Reference Mission (DRM) for the Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA), a space observatory leveraging a 2.4-meter Hubble-quality telescope to conduct wide-field infrared surveys. It enables breakthrough science in dark energy, exoplanet demographics via microlensing, and general astrophysics through a wide-field instrument and an on-axis coronagraph for direct imaging of exoplanets.

ABSTRACT

This report describes the 2014 study by the Science Definition Team (SDT) of the Wide-Field Infrared Survey Telescope (WFIRST) mission. It is a space observatory that will address the most compelling scientific problems in dark energy, exoplanets and general astrophysics using a 2.4-m telescope with a wide-field infrared instrument and an optical coronagraph. The Astro2010 Decadal Survey recommended a Wide Field Infrared Survey Telescope as its top priority for a new large space mission. As conceived by the decadal survey, WFIRST would carry out a dark energy science program, a microlensing program to determine the demographics of exoplanets, and a general observing program utilizing its ultra wide field. In October 2012, NASA chartered a Science Definition Team (SDT) to produce, in collaboration with the WFIRST Study Office at GSFC and the Program Office at JPL, a Design Reference Mission (DRM) for an implementation of WFIRST using one of the 2.4-m, Hubble-quality telescope assemblies recently made available to NASA. This DRM builds on the work of the earlier WFIRST SDT, reported by Green et al. (2012) and the previous WFIRST-2.4 DRM, reported by Spergel et. (2013). The 2.4-m primary mirror enables a mission with greater sensitivity and higher angular resolution than the 1.3-m and 1.1-m designs considered previously, increasing both the science return of the primary surveys and the capabilities of WFIRST as a Guest Observer facility. The addition of an on-axis coronagraphic instrument to the baseline design enables imaging and spectroscopic studies of planets around nearby stars.

Motivation & Objective

• To develop a comprehensive mission design for WFIRST-AFTA based on a 2.4-meter telescope recently made available to NASA.
• To address the top-priority scientific goals identified in the 2010 Astro2010 Decadal Survey, including dark energy, exoplanet demographics, and general astrophysics.
• To enhance science return by leveraging the higher sensitivity and angular resolution of a 2.4-meter mirror compared to smaller designs.
• To integrate a coronagraphic instrument for direct imaging and spectroscopy of exoplanets around nearby stars.
• To establish a robust, multi-phase mission architecture that supports both guaranteed time and guest observer programs.

Proposed method

• Utilize a 2.4-meter primary mirror to achieve high angular resolution and sensitivity, surpassing previous 1.3-meter and 1.1-meter designs.
• Implement a wide-field infrared instrument (WFI) capable of surveying large sky areas with high efficiency for dark energy and general astrophysics studies.
• Integrate an on-axis coronagraphic instrument to enable direct imaging and spectroscopy of exoplanets around nearby stars.
• Design the mission to support three core programs: dark energy science, microlensing exoplanet surveys, and a general observing program.
• Leverage existing hardware and engineering designs from the WFIRST Study Office at GSFC and the Program Office at JPL to ensure mission feasibility and cost efficiency.
• Base the DRM on prior studies, including the 2012 Green et al. report and the 2013 Spergel et al. WFIRST-2.4 DRM, to ensure scientific and technical continuity.

Experimental results

Research questions

• RQ1 How can a 2.4-meter telescope optimize scientific return in dark energy, exoplanet detection, and general astrophysics compared to smaller aperture designs?
• RQ2 What is the optimal configuration of a wide-field infrared instrument and coronagraph to enable high-precision surveys and direct exoplanet imaging?
• RQ3 How can the mission architecture support both guaranteed time and guest observer programs effectively?
• RQ4 What are the technical and cost implications of using a 2.4-meter telescope for a wide-field survey mission?
• RQ5 How does the inclusion of a coronagraph enhance the mission’s capability for studying exoplanet atmospheres and systems?

Key findings

• The 2.4-meter telescope provides significantly improved angular resolution and sensitivity over previous 1.3-meter and 1.1-meter designs, enhancing science return across all mission programs.
• The wide-field infrared instrument enables deep, wide-area surveys essential for constraining dark energy through weak gravitational lensing and baryon acoustic oscillations.
• The on-axis coronagraphic instrument enables direct imaging and spectroscopy of exoplanets around nearby stars, expanding the mission’s exoplanet science capabilities.
• The mission design supports a comprehensive Guest Observer program, ensuring broad scientific access beyond the core surveys.
• The DRM integrates existing hardware and engineering frameworks, reducing technical risk and supporting a cost-effective implementation.
• The final design satisfies the top-priority recommendations of the Astro2010 Decadal Survey, positioning WFIRST-AFTA as a cornerstone mission for U.S. astrophysics.