The HaloSat and PolarLight CubeSat Missions for X-ray Astrophysics

TL;DR

HaloSat and PolarLight demonstrate that small CubeSats can effectively perform advanced X-ray astrophysics, including sky surveys and polarization measurements, proving their value as cost-effective space observatories.

Contribution

This paper presents two successful CubeSat missions, HaloSat and PolarLight, showcasing their capabilities in X-ray astronomy within limited size and mass constraints.

Findings

HaloSat conducted an all-sky survey of oxygen line emission.

PolarLight performed X-ray polarization measurements of bright sources.

Both missions operated successfully for multiple years, validating CubeSats as effective astrophysical platforms.

Abstract

Astronomical observations in the X-ray band are subject to atmospheric attenuation and have to be performed in the space. CubeSats offer a cost effective means for space-based X-ray astrophysics but allow only limited mass and volume. In this article, we describe two successful CubeSat-based missions, HaloSat and PolarLight, both sensitive in the keV energy range. HaloSat was a 6U CubeSat equipped with silicon drift detectors. It conducted an all-sky survey of oxygen line emission and revealed the clumpy nature of the circumgalactic medium surrounding the Milky Way. PolarLight is a dedicated X-ray polarimeter performing photoelectron tracking using a gas pixel detector in a 1U payload. It observed the brightest X-ray objects and helped constrain their magnetic field or accretion geometry. On-orbit operation of both missions for multiple years demonstrates the capability of CubeSats as an effective astronomical platforms. The rapid time scales for development and construction of the missions makes them particularly attractive for student training.