An optical test bench for the precision characterization of absolute quantum efficiency for the TESS CCD detectors

Abstract

The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright stars with Ic ≲13. TESS has been selected by NASA for launch in 2018 as an Astrophysics Explorer mission, and is expected to discover a thousand or more planets that are smaller in size than Neptune. TESS will employ four wide-field optical charge-coupled device (CCD) cameras with a band-pass of 650 nm -1050 nm to detect temporary drops in brightness of stars due to planetary transits. The 1050 nm limit is set by the quantum efficiency (QE) of the CCDs. The detector assembly consists of four back-illuminated MIT Lincoln Laboratory CCID-80 devices. Each CCID-80 device consists of 2048x2048 imaging array and 2048x2048 frame store regions. Very precise on-ground calibration and characterization of CCD detectors will significantly assist in the analysis of the science data obtained in space. The characterization of the absolute QE of the CCD detectors is a crucial part of the characterization process because QE affects the performance of the CCD significantly over the redder wavelengths at which TESS will be operating. An optical test bench with significantly high photometric stability has been developed to perform precise QE measurements. The design of the test setup along with key hardware, methodology, and results from the test campaign are presented.

Bolometric corrections of stellar oscillation amplitudes as observed by the Kepler, CoRoT, and TESS missions

“…The conductive straps have a wavelengthdependent reflectively which takes effect in the IR (above ∼800 nm) where photons can pass through the entire silicon layer of the CCD. This effectively increase the QE, hence the SRF (Figure 1), of the pixels affected by the straps with an intensity rise of 0.5 − 14% over wavelengths from 825 − 1050 nm (see Krishnamurthy et al 2017). For more information on the conducting (and other types of) straps we refer to the TESS Instrument Handbook (Vanderspek et al 2018).…”

“…• The QE of the TESS CCDs is mildly sensitive to temperature (see Krishnamurthy et al 2017). While this is likely a negligible effect it could introduce a systematic change in the bolometric correction with a change in the CCD temperature, e.g., when the Earth is in/near the FOV.…”

A detector characterization setup for testing performance under space environmental conditions

“…Therefore, to quickly and efficiently assess sensor performance, automated opto-electronic test benches are a fundamental tool. Such systems [9][10][11][12][13][14] usually consist of a defined light source that allows for stimulating the devices under test with a defined (spectral) irradiance, an optical element for beam forming and projecting targets, a mounting fixture, as well as a data acquisition system. Depending on the device under test, cooling may be necessary, which can be implemented as part of the test dewar 12,13 or as part of the device under test.…”

“…Such systems [9][10][11][12][13][14] usually consist of a defined light source that allows for stimulating the devices under test with a defined (spectral) irradiance, an optical element for beam forming and projecting targets, a mounting fixture, as well as a data acquisition system. Depending on the device under test, cooling may be necessary, which can be implemented as part of the test dewar 12,13 or as part of the device under test. 9,10 While components and entire test benches are commercially available for many standard applications, comprehensive testing according to the EMVA Standard 1288 for the characterization of image sensors and cameras 15 requires a flexible setup that needs to be capable of switching between a monochromatic light source for determining responsivity, temporal noise, linearity, non-uniformity, and pixel defects, a spectral light source for determining responsivity as a function of wavelength, and no light source for determining dark currents.…”

A low-cost ultraviolet-to-infrared absolute quantum efficiency characterization system of detectors

“…Coles et al (2017) 3 present their QE measurement system for the CCD sensors for the Vera-Rubin Observatory. Krishnamurthy et al (2019) 4 present their QE measurement system developed for the Transiting Exoplanet Survey Satellite (TESS) CCD detectors. Bastian-Querner et al (2021) 5 present their sensor characterization system for the ULTRASAT space telescope.…”