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

Journal of Astronomical Instrumentation

article

V. Kudriashov¹  M. Martin-Neira²  E. Lia²  J. Michalski³  P. Kant³  D. Trofimowicz³  M. Belloni²  P. Jankovic²  P. Waller²  M. Brandt⁴ 

[1] Department of Astrophysics/IMAPP, Radboud University Nijmegen;ESTEC - ESA;SpaceForest;RPG Radiometer Physics GmbH

关键词: Space technology;    breadboard;    frequency transfer;    phase noise cancellation;    local oscillators;    radio interferometry;    Very Long Baseline Interferometry;    VLBI;    space VLBI;    orbiting VLBI;   

DOI  :  10.1142/S2251171721500100

学科分类：天文学(综合)

来源: World Scientific Publishing Co. Pte. Ltd.

【 摘 要 】

Black hole imaging challenges the third-generation space VLBI, the Very Long Baseline Interferometry, to operate on a 500GHz band. The coherent integration time needed here is 450s though the available space oscillators cannot offer more than 10s. 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/τ phase noise trend since the frequency transfer timescale of interest is shorter than 0.2s. This trend continues into longer integration times, as proven by the longest tests spanning over a few hours. The Allan Deviation between derived 103.2GHz oscillators is 1.1×10−14/τ within 10ms<τ<1000s that degrades twice towards the longest delay of 0.2s. The worst case satisfies the requirement with a margin of 11 times. The obtained coherence in the range of 0.997−0.9998 is beneficial for space VLBI at 557GHz. The result is of special interest to future science missions for black hole imaging from space.

【 授权许可】

Unknown