The Black Hole Explorer: Preliminary Antenna Design

TL;DR

The paper proposes a lightweight, high-efficiency spaceborne antenna design for the Black Hole Explorer mission, enabling high-resolution mm/sub-mm VLBI observations to study black hole photon rings.

Contribution

It introduces a novel antenna design balancing aperture size, weight, and performance for space-VLBI black hole imaging.

Findings

Designed a 3.5 m aperture antenna with 40 μm surface rms.

Selected a dual reflector Gregorian optical design.

Utilized CFRP sandwich construction for lightweight structure.

Abstract

We present the basic design of a large, light weight, spaceborne antenna for the Black Hole Explorer (BHEX) space Very Long Baseline Interferometry (space-VLBI) mission, achieving high efficiency operation at mm/sub-mm wavelengths. An introductory overview of the mission and its science background are provided. The BHEX mission targets fundamental black hole physics enabled by the detection of the finely structured image feature around black holes known as the photon ring, theoretically expected due to light orbiting the black hole before reaching the observer. Interferometer baselines much longer than an earth diameter are necessary to attain the spatial resolution required to detect the photon ring, leading to a space component. The science goals require high sensitivity observations at mm/sub-mm wavelengths, placing stringent constraints on antenna performance. The design approach described, seeks to balance the antenna aperture, volume and mass constraints of the NASA Explorers mission opportunity profile and the desired high performance. A 3.5 m aperture with a 40 $\mu$m surface rms is targeted. Currently, a symmetric, dual reflector, axially displaced ellipse (Gregorian ring focus) optical design and metallized carbon fiber reinforced plastic (CFRP) sandwich construction have been chosen to deliver high efficiency and light weight. Further exploration of design choices and parameter space and reflector shaping studies are in progress