SCALA upgrade: development of a light source for sub-percent calibration uncertainties

Küsters, D.; Bastian-Querner, Benjamin; Aldering, G.; Blot, Summer; Boone, K.; Copin, Y.; Hebecker, D.; Karg, T.; Kowalski, M.; Lombardo, Simona; Nordin, J.; Rubin, D.

doi:10.1117/12.2561602

Cited by 5 publications

(8 citation statements)

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“…The measurement setup and the results are discussed in more detail in an accompanying article. 5,6 The detailed sensor design and the ongoing sensor performance validation will be published in forthcoming publications.…”

Section: Sensor and Mosaic Assemblymentioning

confidence: 99%

Design of the ULTRASAT UV camera

Asif,

Barschke,

Bastian-Querner

et al. 2021

Preprint

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The Ultraviolet Transient Astronomical Satellite (ULTRASAT) is a scientific UV space telescope that will operate in geostationary orbit. The mission, targeted to launch in 2024, is led by the Weizmann Institute of Science (WIS) in Israel and the Israel Space Agency (ISA). Deutsches Elektronen Synchrotron (DESY) in Germany is tasked with the development of the UV-sensitive camera at the heart of the telescope. The camera's total sensitive area of ≈ 90 mm × 90 mm is built up by four back-side illuminated CMOS sensors, which image a field of view of ≈ 200 deg 2 . Each sensor has 22.4 megapixels. The Schmidt design of the telescope locates the detector inside the optical path, limiting the overall size of the assembly. As a result, the readout electronics is located in a remote unit outside the telescope. The short focal length of the telescope requires an accurate positioning of the sensors within ±50 µm along the optical axis, with a flatness of ±10 µm. While the telescope will be at around 295 K during operations, the sensors are required to be cooled to 200 K for dark current reduction. At the same time, the ability to heat the sensors to 343 K is required for decontamination. In this paper, we present the preliminary design of the UV sensitive ULTRASAT camera.

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Section: Sensor and Mosaic Assemblymentioning

confidence: 99%

Design of the ULTRASAT UV camera

Asif,

Barschke,

Bastian-Querner

et al. 2021

Preprint

Self Cite

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“…For a detailed description of the double monochromator and the calculation of the system's wavelength, see. 3 The beam leaving the double monochromator is collimated using a Thorlabs off-axis parabolic mirror (M3). To account for astigmatism from the double monochromator, we use a cylindrical mirror (M4) and redirect the beam into the attenuator setup with a flat mirror (M5).…”

Section: Laboratory Setupmentioning

confidence: 99%

“…The light spot is always fully contained within the collecting area A c of the diode or the pixel array of the test sensor. A more detailed description about the setup and its characteristics can be found in Küsters et al 3…”

Section: Laboratory Setupmentioning

confidence: 99%

“…Using a high-resolution encoder mounted to the grating turret, we measure the grating angles, which allows us to predict the wavelength of the light passing the monochromator system. 3 To verify the predicted wavelength or model wavelength, we compare the measured wavelength of emission lines in the spectra of low-pressure gas lamps to the NIST database. 4 To find the "right" wavelength in the NIST database, we use a loaned Fourier transform spectrometer from Thorlabs (OSA201C, resolution of ≤ 20 pm for wavelength ≤ 1 µm) to assign the emission lines of our lamps to the NIST database.…”

Section: System Performancementioning

confidence: 99%

“…Furthermore, this study aims to verify whether the test sensors satisfy the ULTRASAT performance requirement for noise characteristics at the operating temperature of 200 K. The measurements rely on an updated high-precision photometric calibration setup. 3 The characterization encompasses a comprehensive test of sensor gain, linearity, dark current as well as quantum yield and quantum efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Sensor characterization for the ULTRASAT space telescope

Bastian-Querner,

Kaipachery,

Küsters

et al. 2021

Preprint

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The Ultraviolet Transient Astronomical Satellite (ULTRASAT) is a scientific space mission carrying an astronomical telescope. The mission is led by the Weizmann Institute of Science (WIS) in Israel and the Israel Space Agency (ISA), while the camera in the focal plane is designed and built by Deutsches Elektronen Synchrotron (DESY) in Germany. Two key science goals of the mission are the detection of counterparts to gravitational wave sources and supernovae. 1 The launch to geostationary orbit is planned for 2024. The telescope with a field-ofview of ≈ 200 deg 2 , is optimized to work in the near-ultraviolet (NUV) band between 220 and 280 nm. The focal plane array is composed of four 22.4-megapixel, backside-illuminated (BSI) CMOS sensors with a total active area of 90 × 90 mm 2 . 2 Prior to sensor production, smaller test sensors have been tested to support critical design decisions for the final flight sensor. These test sensors share the design of epitaxial layer and anti-reflective coatings (ARC) with the flight sensors. Here, we present a characterization of these test sensors. Dark current and read noise are characterized as a function of the device temperature. A temperature-independent noise level is attributed to on-die infrared emission and the read-out electronics' self-heating. We utilize a high-precision photometric calibration setup 3 to obtain the test sensors' quantum efficiency (QE) relative to PTB/NIST-calibrated transfer standards (220-1100 nm), the quantum yield for λ < 300 nm, the non-linearity of the system, and the conversion gain. The uncertainties are discussed in the context of the newest results on the setup's performance parameters. From three ARC options, Tstd, T1 and T2, the latter optimizes out-of-band rejection and peaks in the mid of the ULTRASAT operational waveband (max. QE ≈ 80 % at 245 nm) . We recommend ARC option T2 for the final ULTRASAT UV sensor.

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The Spectroscopic Classification of Astronomical Transients (SCAT) Survey: Overview, Pipeline Description, Initial Results, and Future Plans

Tucker¹,

Shappee²,

Huber³

et al. 2022

PASP

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We present the Spectroscopic Classification of Astronomical Transients (SCAT) survey, which is dedicated to spectrophotometric observations of transient objects such as supernovae and tidal disruption events. SCAT uses the SuperNova Integral-Field Spectrograph (SNIFS) on the University of Hawai’i 2.2 m (UH2.2m) telescope. SNIFS was designed specifically for accurate transient spectrophotometry, including absolute flux calibration and host-galaxy removal. We describe the data reduction and calibration pipeline including spectral extraction, telluric correction, atmospheric characterization, nightly photometricity, and spectrophotometric precision. We achieve ≲5% spectrophotometry across the full optical wavelength range (3500–9000 Å) under photometric conditions. The inclusion of photometry from the SNIFS multi-filter mosaic imager allows for decent spectrophotometric calibration (10%–20%) even under unfavorable weather/atmospheric conditions. SCAT obtained ≈640 spectra of transients over the first 3 yr of operations, including supernovae of all types, active galactic nuclei, cataclysmic variables, and rare transients such as superluminous supernovae and tidal disruption events. These observations will provide the community with benchmark spectrophotometry to constrain the next generation of hydrodynamic and radiative transfer models.

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SCALA upgrade: development of a light source for sub-percent calibration uncertainties

Cited by 5 publications

References 0 publications

Design of the ULTRASAT UV camera

Design of the ULTRASAT UV camera

Sensor characterization for the ULTRASAT space telescope

The Spectroscopic Classification of Astronomical Transients (SCAT) Survey: Overview, Pipeline Description, Initial Results, and Future Plans

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