Roman Virtual Lecture Series: History of the Roman Observatory Design, and Current Build Status

- WFIRST (widefield infrared survey telescope, prior mission name) was creation of 2010 NWNH Decadal
- Based on JDEM “Omega”, Microlensing Planet Finder, and NIR Surveyor mission concepts
- All were three mirror anastigmat near IR staring concepts
- JDEM Omega was hardware starting point, but needed to be slightly modified to accommodate continuous viewing periods of the galactic bulge for microlensing
- Multiple different surveys rolled into one mission
- Imaging, imaging spectroscopy, and precision photometry are all required among the surveys
- Cooler than HST optics are required for 2.0um red limit
- HST is background limited near room temperature and 1.7um red limit
- Mission concepts through 2011 were 1.5m on axis or 1.3m off-axis apertures
- 2.4m aperture (NRO transferred to NASA, we were directed to us, in 2012)
- Larger primary mirror has 3x area and 0.5x PSF size, ~20x discovery potential
- Realized best design has undersampled PSF with survey strategy to recover full sampling, best compromise of sampling vs wide area coverage
- Concept evolved significantly with our understanding of the existing optics
- Started with “use as is”; evolved over time towards current concept
- Overall design has been very stable after early evolution described here
- Renamed in 2020 after Nancy Grace Roman; progressing toward launch readiness in Oct2026