Roman space telescope coronagraph: engineering design and operating concept

Poberezhskiy, Ilya; Luchik, T. S.; Zhao, Feng; Frerking, M. A.; Basinger, Scott A.; Cady, Eric; Colavita, M. M.; Creager, Brandon; Fathpour, Nanaz; Goullioud, Renaud; Groff, Tyler D.; Morrissey, Patrick; Kempenaar, Joshua; Kern, Brian; Koch, T.; Krist, John; Mok, Fai; Muliere, David; Nemati, Bijan; Riggs, A. J. Eldorado; Seo, Byoung-Joon; Shreckengost, Belinda; Steeves, John; Tang, Hong

doi:10.1117/12.2563480

Cited by 21 publications

(20 citation statements)

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“…The Roman Space Telescope will downlink images for HOWFSC processing to the ground. 63 This offers effectively unlimited computational power and increases algorithm flexibility because new software can be developed and tested directly on the target hardware without risk to the spacecraft. However, ground-in-the-loop processing is limited by the need to interact with the spacecraft over large distances.…”

Section: Alternativesmentioning

confidence: 99%

“…Computations may also be accelerated by separating the HOWFSC processor from the main telescope optics payload. The Roman Space Telescope will downlink images for HOWFSC processing to the ground 63 . This offers effectively unlimited computational power and increases algorithm flexibility because new software can be developed and tested directly on the target hardware without risk to the spacecraft.…”

Section: Radiation-hardened Processors and Alternativesmentioning

confidence: 99%

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Computational complexities of image plane algorithms for high contrast imaging in space telescopes

Pogorelyuk

Haughwout

Belsten

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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Future planned space telescopes, such as the IR/O/UV Large Telescope, recommended by Astro2020 will be used to directly image exo-Earths. They will employ high-order wavefront sensing and control (HOWFSC) to correct static and slow wavefront errors in the image plane to achieve contrasts better than 10 9 . Our work evaluates the computational requirements for HOWFSC algorithms and compares these to the capabilities of processors that are expected to be available during mission development. We find that HOWFSC creates unprecedented requirements for space-based computational power, such as the ∼10 13 floating-point operations necessary to generate the dark hole, based on the Large UV/Optical/IR (LUVOIR) study. In our worst-case estimates, maintaining an LUVOIR-size dark hole at 10 10 contrast might require up to several orders of magnitude more computational throughput than available on the most advanced radiation-hardened processor.

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Section: Alternativesmentioning

confidence: 99%

Section: Radiation-hardened Processors and Alternativesmentioning

confidence: 99%

Computational complexities of image plane algorithms for high contrast imaging in space telescopes

Pogorelyuk

Haughwout

Belsten

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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“…This can be achieved by applying small DM probes while observing the target star. Since the science images will be downlinked to Earth roughly once a day, 25 they can be used, in conjunction with the known DM probes, to compute the DM correction that will be uplinked for the next period of the observation. Such a dark hole maintenance approach would be suitable to be tested on Roman in ground-in-the-loop operation mode.…”

Section: Modal Pairwise Probingmentioning

confidence: 99%

Dark hole maintenance with modal pairwise probing in numerical simulations of Roman coronagraph instrument

Pogorelyuk

Krist

Nemati

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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We propose an efficient approach for focal-plane wavefront estimation for highcontrast imaging. It is designed for very low photon flux regimes with the Roman Space Telescope Coronagraph Instrument in mind. During days-long exposures of Roman, the starlight wavefront will drift due to the thermal instabilities of the optical tube assembly (OTA) and deformable mirror (DM) actuators. To correct the drift in high-order spatial wavefront modes, Roman will periodically be pointed to a bright reference star to sense the speckles in the dark hole (the high-contrast region of the image) and correct them. However, this maneuver decreases observation time by several hours a day and may lead to wavefront instability by causing structural and thermal stresses on the OTA. Instead, we propose maintaining the dark hole using the DM to modulate (probe) the speckles while observing the target star. Our proposed algorithm can then be used to directly estimate the DM commands that would create such speckles, rather than first estimating the electric field of the speckles. Applying the opposite commands on the DM reduces the intensity of the speckles without slewing to the reference star. Further, we analyze this dark-hole maintenance approach using data from Roman Observing Scenario 9 (OS9) simulations while assuming that the high-order wavefront control on Roman will be carried out from the Earth (ground-in-the-loop). In our simulations of Roman's Hybrid Lyot Coronagraph, the high-order wavefront errors were sensed and corrected while observing a dim target, 47 UMa. Despite the DM probes, the photon flux in the dark hole remained close to that in OS9 and well below detector noise. In terms of planet-detectability, dark hole maintenance kept the postprocessing contrast within 10% of OS9's, even after pointing the telescope at the target star for 6 days. The OTA stability that dark hole maintenance provides compared to slewing the telescope potentially outweighs the small negative impact it has on the contrast.

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“…for space-based coronagraphs, as e.g. considered for the Roman Space Telescope [40]. It remains to be seen if such behavior holds true for slightly larger bandwidth regimes (20%, or even 25%), which would mean that SLM-based coronagraphs can be used with any of the most common astronomical imaging filters from the ground.…”

Section: % Bandwidthmentioning

confidence: 99%

Active focal-plane coronagraphy with liquid-crystal spatial-light modulators: broadband contrast performance in the visible

Kühn¹,

Patapis

2022

Appl. Opt.

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The technological progress in spatial-light modulator (SLM) technology has made it possible to use those devices as programmable active focal-plane phase coronagraphic masks, opening the door to novel versatile and adaptive high-contrast imaging observation strategies. However, the scalar nature of the SLM-induced phase response is a potential hurdle when applying the approach to wideband light, as is typical in astronomical imaging. For the first time, to our knowledge, we present laboratory results with broadband light (up to ∼ 12 % bandwidth) for two commercially available SLM devices used as active focal-plane phase masks in the visible regime (640 nm). It is shown that under ideal or realistic telescope aperture conditions, the contrast performance is negligibly affected in this bandwidth regime, reaching a sufficient level for ground-based high-contrast imaging, which is typically dominated by atmospheric residuals.

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Roman space telescope coronagraph: engineering design and operating concept

Cited by 21 publications

References 0 publications

Computational complexities of image plane algorithms for high contrast imaging in space telescopes

Computational complexities of image plane algorithms for high contrast imaging in space telescopes

Dark hole maintenance with modal pairwise probing in numerical simulations of Roman coronagraph instrument

Active focal-plane coronagraphy with liquid-crystal spatial-light modulators: broadband contrast performance in the visible

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