Testing and characterization of the TESS CCDs

Abstract

The Transiting Exoplanet Survey Satellite (TESS) is an Explorer-class mission dedicated to finding planets around bright, nearby stars so that more detailed follow-up studies can be done. TESS is due to launch in 2017 and careful characterization of the detectors will need to be completed on ground before then to ensure that the cameras will be within their photometric requirement of 60ppm/hr. TESS will fly MIT-Lincoln Laboratories CCID-80s as the main scientific detector for its four cameras. They are 100µm deep depletion devices which have low dark current noise levels and can operate at low light levels at room temperature. They also each have a frame store region, which reduces smearing during readout and allows for near continuous integration. This paper describes the hardware and methodology that were developed for testing and characterizing individual CCID-80s. A dark system with no stimuli was used to measure the dark current. Fe 55 and Cd 109 X-ray sources were used to establish gain at low signal levels and its temperature dependence. An LED system that generates a programmable series of pulses was used in conjunction with an integrating sphere to measure pixel response non-uniformity (PRNU) and gain at higher signal levels. The same LED system was used with a pinhole system to evaluate the linearity and charge conservation capability of the CCID-80s.

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

“…Using the known energies of the X-ray peaks (K α = 22.1 keV, K β = 25.0 keV), and the conversion of eV/e − for Silicon [5], we fit a line to the peaks whose slope gives the gain conversion factor [6]. The gain measured is 6.99 ±0.01 e − /ADU [2,9]. The gain measurements are verified by calculating the mean variance from the photon transfer measurements.…”

“…For the QE measurements, we use a single flight-grade engineering CCD with pre-flight electronics, and the output from the CCD is obtained in a FITS-format file with the pixels reconstructed such that the four outputs are placed adjacent to each other. In addition, there are 10 virtual rows, 10 smear rows and 10 buffer rows, and 11 virtual underclock and 11 virtual overclock columns [9].…”

“…Figure 4: Schematic of the CCID-80 device showing the imaging array and frame-store regions, and readout directions for the four sectors A, B, C, and D. The imaging array is has 2048 x 2048 pixels with 512 columns allocated to each of the four sectorsA, B, C, and D. In addition, there are 10 virtual rows, 10 smear rows and 10 buffer rows, and 11 virtual underclock and 11 virtual overclock columns [Thayer et al, 2016]. …”

CCD imagers for the Transiting Exoplanet Survey Satellite from benchtop to space environment

“…The excellent wafer production quality produced clean imagery even with modest cooling at a probe station, as shown in Figure 10. Companion package and mosaic-level testing with lab and flight-like electronics was also done at MIT Kavli (Krishnamurthy et al 2016;Thayer et al 2016;Villasenor et al 2017).…”

The TESS camera: modeling and measurements with deep depletion devices

“…Given the complexity of the optical system and the inherent uncertainties in modeling the as-built optical PSF, the effects of these other considerations would be difficult to distinguish. Additional characterization of the TESS CCDs is ongoing 25 .…”