The Wide Field Infrared Survey Telescope (WFIRST)

James Green and Paul SchechterCo-Chairs of the Science Definition Team

Neil Gehrels: Project study scientist Kevin Grady: Project study manager

Rita Sambruna: Program scientistLia LaPiana: Program executive

Space Telescope Science InstituteJune 13, 2011

The SDT Charter

“The SDT is to provide science requirements, investigation approaches, key mission parameters, and any other scientific studies needed to support the definition of an optimized space mission concept satisfying the goals of the WFIRST mission as outlined by the Astro2010 Decadal Survey.”

The SDT Charter

“In particular, the SDT report should present assessments about how best to proceed with the WFIRST mission, covering the cases that the Euclid mission, in its current or modified form, proceeds to flight development, or that ESA does not choose Euclid in the near future.”

WFIRST Science Objectives(equally weighted – still subject to word smithing)1: Complete a statistical census of planetary systems in the Galaxy, from habitable Earth-mass planets to free floating planets, including analogs to all of the planets in our Solar System except Mercury.2: Determine the expansion history of the Universe and its growth of structure so as to test explanations of its acceleration such as Dark Energy and possible modifications to Einstein's gravity.

3: Produce a deep map of the sky at NIR wavelengths, enabling new and fundamental discoveries ranging from mapping the Galactic plane to probing the reionization epoch by identifying thousands of quasars at z>10.

Key Conclusions of the SDT1: WFIRST should include all of the science objectives and utilize

all of the techniques outlined in the decade recommendation:

A: Baryon Acoustic Oscillation SurveyB: Exo-Planet Microlensing SurveyC: Supernova Ia surveyD: Weak Lensing SurveyE: Infrared Sky Survey – including a survey of the galactic planeF: Guest Observer Program

G: Redshift Space Distortion Survey (Free)

Key Conclusions of the SDT

2: Due to the importance of the scientific questions, and the need for verification of the results, WFIRST should proceed with all of its observational capabilities intact regardless of the ESA decision on EUCLID. The actual observation program might be altered in light of EUCLID’s selection or in response to any EUCLID results prior to WFIRST’s launch.

Key Conclusions of the SDT

3: Should NASA and ESA decide to pursue a joint mission, all of the capabilities currently included in WFIRST must be included in the joint mission.

WFIRST Design Reference Mission (DRM)* used in the interim report

Off – Axis Three Mirror Anastigmat Design with field pickoffs to tailor the plate scale for imaging and spectroscopy

Supernova spectroscopy performed through insertion of prism as a “filter” in the imaging channel

* The DRM is a straw man mission concept to demonstrate the capabilities of WFIRST for purposes of the interim report. The final mission parameters and observational implementation will only be finalized after further study.

DRM Observational Capabilities Dark Energy:

BAO/RSD : 11,000 deg2/dedicated yearWeak Lensing: 2700 deg2/dedicated yearSN Ia Survey: 100 SN per z= 0.1 bin /dedicated 6 months

DRM Microlensing Capabilities• Detection to 0.1 Mearth

• Detect > 90 planets of MEarth (in 2 year orbits) per dedicated observing year

• Observe 2 square degrees in the Galactic Bulge at ≤ 15 minute sampling cadence

• Minimum continuous monitoring time span: ~60 days• Separation of ≥4 years between first and last

observing seasons

DRM Observational CapabilitiesNIR Survey:

High Latitude data collected in imaging channel during BAO survey

Galactic Plane Survey a dedicated observational plan

Exact parameters still TBD

DRM Observational Plan

Actual assigned times to each survey still in flux. Mission lifetime is 5 years.

Preliminary Mechanical Design

SpacecraftBus

TelescopeTube

TelescopePrimary Structure

SpectrometerB

SpectrometerA

TelescopeBottom Enclosure

Imager

TelescopeBack Enclosure

6/8/11 14SDT#5 Telescope

7.5

met

ers

Imager Optical Layout

Primary Mirror

SecondaryMirror

Field Stop atCassegrainFocus

F1

F2

Tertiary Mirror

Imager FocalPlane

Cold Stopand F3

6/8/11 15SDT#5 Telescope

Imager Optics

Primary Mirror

SecondaryMirror

Field Stop atCassegrainFocus

F1

F2

Tertiary Mirror

Imager FocalPlane

Cold Stop

F3

6/8/11 16SDT#5 Telescope

Spectrometer A & B Layout

Primary Mirror

SecondaryMirror

Field Stop atCassegrainFocus

F3

F2

Tertiary MirrorSpectrometer Focal Planes

Cold Stop

F1

6/8/11 17SDT#5 Telescope

Spectrometer Optics

Primary Mirror

SecondaryMirror

Field Stop atCassegrainFocus

F3

F2

Tertiary Mirror

Spectrometer Focal Planes

Cold Stop

F1

6/8/11 18SDT#5 Telescope

Possible Modifications Under Further Study

• Extend coverage further to the red (current bandpass cuts off at 2.0 m

• Add an IFU spectrometer for SN Ia work (instead of inserted prism)

• Add additional filters• Increase the field of regard to simplify

operations• Extend operational lifetime

Conclusions• WFIRST will be an exciting, powerful, and versatile

observatory that will perform the surveys needed to advance our understanding of planetary systems, cosmology, fundamental physics, and astronomy.

• It addresses the most pressing questions in astronomy that can be addressed with the technologies available today.

• It needs the full support of the community to move forward.

Sub-committee Membership(external members in italics)

Exoplanet Microlensing: Dave Bennett, Bob Brown, Scott Gaudi, Takahira Sumi, Angelle Tanner, Jay Anderson, Eamonn Kerins, Jonathan Lunine

High Latitude Survey: (Baryon acoustic oscillation, Infrared survey and weak lensing): Rachel Bean, Chuck Bennett, Chris Conselice, Jason Rhodes, Tom Roellig, Yun Wang, Ned Wright, Chris Hirata and Zeljko Ivezic

Supernovae as a probe of the expansion history: Charlie Baltay, Tod Lauer, Bob Nichol, Saul Perlmutter, Peter Garnavich, Mark Phillips, Adam Riess

Galactic Plane survey and Guest Observer program: Megan Donahue, Daniel Stern, Kem Cook, Roeland van der Marel, George Rieke, Lynne Hillenbrand