Preliminary analysis of effect of random segment errors on coronagraph performance

Stahl, Mark T.; Stahl, H. Philip; Shaklan, Stuart

doi:10.1117/12.2190160

Cited by 19 publications

(23 citation statements)

References 8 publications

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“…Previous research has suggested that 10 minute stability at the 10 picometer level is necessary for the detection of Earth-like planets around 5th to 6th magnitude stars (Stahl et al 2013(Stahl et al , 2015. The analysis presented here shows that the combination of a limiting magnitude of m V = 5 to m V = 6 and σ 10 = 10 minutes may be overly optimistic.…”

Section: Stable Case: Increased Discovery Spacementioning

confidence: 64%

“…Predictive control ) could also improve performance at resonance frequencies. For example, JWST has a 20 nm RMS segment "rocking" mode at ∼40 Hz (Stahl et al 2015). The results above show care must be taken to specify the full PSD envelope of OPD disturbances, otherwise the actual limiting magnitude may be much brighter than expected.…”

Section: Discussionmentioning

confidence: 90%

“…Different means of sensing segment motion to picometer levels have been proposed: edge sensors, wavefront sensing using the target star, or internal metrology (Feinberg et al 2017). Wavefront sensing using target starlight minimizes calibration errors between sensors and the science image; however, photon noise limits wavefront sensing (and science observations) to bright nearby stars Stahl et al 2013Stahl et al , 2015. Contrast depends on wavefront sensing and control, which in turn requires sufficient flux for effective wavefront sensing.…”

mentioning

confidence: 99%

“…(Bronowicki 2006). Stahl et al (2015) finds a 0.25 minute wavefront sensing cadence is required for a 12 m telescope observing a m V =5 star, with a stability ten times longer ( 2.5 minutes) to ensure control system performance (see also ; Stahl et al (2013)). Depending on the coronagraph, the wavefront error requirement can be significantly relaxed for lower spatial order modes, such as global tilt or focus (Ruane et al 2017).…”

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confidence: 99%

See 3 more Smart Citations

Laser Guide Star for Large Segmented-aperture Space Telescopes. I. Implications for Terrestrial Exoplanet Detection and Observatory Stability

Douglas¹,

Males²,

Clark³

et al. 2019

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Precision wavefront control on future segmented-aperture space telescopes presents significant challenges, particularly in the context of high-contrast exoplanet direct imaging. We present a new wavefront control architecture that translates the ground-based artificial guide star concept to space with a laser source aboard a second spacecraft, formation flying within the telescope field-of-view. We describe the motivating problem of mirror segment motion and develop wavefront sensing requirements as a function of guide star magnitude and segment motion power spectrum. Several sample cases with different values for transmitter power, pointing jitter, and wavelength are presented to illustrate the advantages and challenges of having a non-stellar-magnitude noise limited wavefront sensor for space telescopes. These notional designs allow increased control authority, potentially relaxing spacecraft stability requirements by two orders of magnitude, and increasing terrestrial exoplanet discovery space by allowing high-contrast observations of stars of arbitrary brightness.

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Section: Stable Case: Increased Discovery Spacementioning

confidence: 64%

Section: Discussionmentioning

confidence: 90%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Laser Guide Star for Large Segmented-aperture Space Telescopes. I. Implications for Terrestrial Exoplanet Detection and Observatory Stability

Douglas¹,

Males²,

Clark³

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Current methods for error budget are simulations of end-toend propagation through the optical system, with variations of factors that are known to impact the contrast: segment phasing errors, segment surface quality, local or global vibrations, resonant modes on the segments, quasi-static aberrations due to thermal drift, and so on. 27,28 Because of the large number of factors that affect contrast, a multitude of cases need to be tested. Because of the computational burden involved, these studies can be dauntingly slow.…”

Section: Introductionmentioning

confidence: 99%

Pair-based Analytical model for Segmented Telescopes Imaging from Space for sensitivity analysis

Leboulleux

Sauvage

Pueyo

et al. 2018

J. Astron. Telesc. Instrum. Syst.

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The imaging and spectroscopy of habitable worlds will require large-aperture space-based telescopes, to increase the collecting area and the angular resolution. These large telescopes will necessarily use segmented primaries to fit in a rocket. However, these massively segmented mirrors make high-contrast performance very difficult to achieve and stabilize, compared to more common monolithic primaries. Despite space telescopes operating in a friendlier environment than ground-based telescopes, remaining vibrations and resonant modes on the segments can still deteriorate the performance.In this context, we present the Pair-based Analytical model for Segmented Telescopes Imaging from Space (PASTIS) that enables the establishment of a comprehensive error budget, both in term of segment alignment and stability. Using this model, one may evaluate the influence of the segment cophasing and surface quality evolution on the final images and contrasts, and set up requirements for any given mission. One can also identify the dominant modes of a given geometry for a given coronagraphic instrument and design the feedback control systems accordingly.In this paper, we first develop and validate this analytical model by comparing its outputs to the images and contrasts predicted by an end-to-end simulation. We show that the contrasts predicted using PASTIS are accurate enough compared to the end-to-end propagation results, at the exo-Earth detection level. Second, we develop a method for a fast and efficient error budget in term of segment manufacturing and alignment that takes into account the disparities of the segment effects on the final performance. This technique is then applied on a specific aperture to provide static and quasi-static requirements on each segment for local piston and 45 • -astigmatism aberrations. Finally we discuss potential application of this new technique to future missions.

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Experimental validation of coronagraphic focal-plane wavefront sensing for future segmented space telescopes

Leboulleux

Sauvage

Soummer

et al. 2020

A&A

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Context. Direct imaging of Earth-like planets from space requires dedicated observatories, combining large segmented apertures with instruments and techniques such as coronagraphs, wavefront sensors, and wavefront control in order to reach the high contrast of 1010 that is required. The complexity of these systems would be increased by the segmentation of the primary mirror, which allows for the larger diameters necessary to image Earth-like planets but also introduces specific patterns in the image due to the pupil shape and segmentation and making high-contrast imaging more challenging. Among these defects, the phasing errors of the primary mirror are a strong limitation to the performance. Aims. In this paper, we focus on the wavefront sensing of segment phasing errors for a high-contrast system, using the COronagraphic Focal plane wave-Front Estimation for Exoplanet detection (COFFEE) technique. Methods. We implemented and tested COFFEE on the High-contrast imaging for Complex Aperture Telescopes (HiCAT) testbed, in a configuration without any coronagraph and with a classical Lyot coronagraph, to reconstruct errors applied on a 37 segment mirror. We analysed the quality and limitations of the reconstructions. Results. We demonstrate that COFFEE is able to estimate correctly the phasing errors of a segmented telescope for piston, tip, and tilt aberrations of typically 100 nm RMS. We also identified the limitations of COFFEE for the reconstruction of low-order wavefront modes, which are highly filtered by the coronagraph. This is illustrated using two focal plane mask sizes on HiCAT. We discuss possible solutions, both in the hardware system and in the COFFEE optimizer, to mitigate these issues.

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Preliminary analysis of effect of random segment errors on coronagraph performance

Cited by 19 publications

References 8 publications

Laser Guide Star for Large Segmented-aperture Space Telescopes. I. Implications for Terrestrial Exoplanet Detection and Observatory Stability

Laser Guide Star for Large Segmented-aperture Space Telescopes. I. Implications for Terrestrial Exoplanet Detection and Observatory Stability

Pair-based Analytical model for Segmented Telescopes Imaging from Space for sensitivity analysis

Experimental validation of coronagraphic focal-plane wavefront sensing for future segmented space telescopes

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