Laboratory Demonstration of the Local Oscillator Concept for the Event Horizon Imager

Black hole imaging challenges the third-generation space VLBI, the Very Long Baseline Interferometry, to operate on a 500[Formula: see text]GHz band. The coherent integration time needed here is 450[Formula: see text]s though the available space oscillators cannot offer more than 10[Formula: see text]s. Self-calibration methods might solve this issue in an interferometer formed by three antenna/satellite systems, but the need for the third satellite increases the mission costs. A frequency transfer is of special interest to alleviate both performance and cost issues. A concept of two-way optical frequency transfer is examined to investigate its suitability to enable space-to-space interferometry, in particular, to image the “shadows” of black holes from space. The concept, promising on paper, has been demonstrated by tests. The laboratory test set-up is presented and the verification of the temporal stability using standard analysis tool as TimePod has been passed. The resulting Allan Deviation is dominated by the 1/[Formula: see text] phase noise trend since the frequency transfer timescale of interest is shorter than 0.2[Formula: see text]s. This trend continues into longer integration times, as proven by the longest tests spanning over a few hours. The Allan Deviation between derived 103.2[Formula: see text]GHz oscillators is [Formula: see text]/[Formula: see text] within 10[Formula: see text][Formula: see text][Formula: see text]s that degrades twice towards the longest delay of 0.2[Formula: see text]s. The worst case satisfies the requirement with a margin of 11 times. The obtained coherence in the range of 0.997[Formula: see text]0.9998 is beneficial for space VLBI at 557[Formula: see text]GHz. The result is of special interest to future science missions for black hole imaging from space.

Autofocusing Optimal Search Algorithm for a Telescope System

Focus accuracy affects the quality of the astronomical observations. Auto-focusing is necessary for imaging systems designed for astronomical observations. The automatic focus system searches for the best focus position by using a proposed search algorithm. The search algorithm uses the image’s focus levels as its objective function in the search process. This paper aims to study the performance of several search algorithms to select a suitable one. The proper search algorithm will be used to develop an automatic focus system for Kottamia Astronomical Observatory (KAO). The optimal search algorithm is selected by applying several search algorithms into five sequences of star-clusters observations. Then, their performance is evaluated based on two criteria, which are accuracy and number of steps. The experimental results show that the Binary search is the optimal search algorithm.

IDeF-X HD: A CMOS ASIC for the Readout of Cd(Zn)Te Detectors for Space-Borne Applications

IDeF-X HD is a 32-channel analog front-end with self-triggering capability optimized for the readout of [Formula: see text] pixels CdTe or CdZnTe pixelated detectors to build a low power micro-gamma camera. IDeF-X HD has been designed in the standard AMS CMOS 0.35[Formula: see text][Formula: see text]m process technology. Its power consumption is 800[Formula: see text][Formula: see text]W per channel. The energy range of the ASIC can be extended to 1.1[Formula: see text]MeV thanks to the in-channel adjustable gain stage. When no detector is connected to the chip and without input current, a 33 electrons rms ENC level is achieved after shaping with 10.7[Formula: see text][Formula: see text]s peaking time. Spectroscopy measurements have been performed with CdTe Schottky detectors. We measured an energy resolution of 4.2[Formula: see text]keV FWHM at 667[Formula: see text]keV ([Formula: see text]Cs) on a single-pixel configuration. Meanwhile, we also measured 562[Formula: see text]eV and 666[Formula: see text]eV FWHM at 14[Formula: see text]keV and 60[Formula: see text]keV, respectively ([Formula: see text]Am) with a 256 small pixel array and a low detection threshold of 1.2[Formula: see text]keV. Since IDeF-X HD is intended for space-borne applications in astrophysics, we evaluated its radiation tolerance and its sensitivity to single event effects. We demonstrated that the ASIC remained fully functional without significant degradation of its performances after 200 krad and that no single event latch-up was detected putting the linear energy transfer threshold above 110[Formula: see text]MeV/(mg/cm2). Good noise performance and radiation tolerance make the chip well suited for X-rays energy discrimination and high energy resolution. The chip is space qualified and flies on board of the solar orbiter ESA mission launched in 2020.