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Register a new userConcept study of a small Compton polarimeter to fly on a CubeSat
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Application of cubesats in astronomical observations has been getting more and more mature in recent years. Here we report a concept study of a small Compton polarimeter to fly on a cubesat for observing polarization of soft gamma-rays from a black-hole X-ray binary, Cygnus X-1. Polarization states provide very useful diagnostics on the emission mechanism and the origin of those gamma rays. In our study, we conducted Monte Carlo simulations to decide the basic design of this small polarimeter. Silicon detectors and cerium bromide scintillators were employed in this study. We estimated its on-axis Compton efficiency at different energies and its data telemetry requirement when flying in a low earth orbit. Our results indicate that it is feasible to achieve high signal-to-noise ratio for observing Cyg X-1 with such a small instrument. Based on this study, we will proceed to have a more realistic design and look for opportunities of a cubesat space mission.
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HaloSat is a small satellite (CubeSat) designed to map soft X-ray oxygen line emission across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. The goal of HaloSat is to help determine if hot gas gravitationally bound to individual galaxies makes a significant contribution to the cosmological baryon budget. HaloSat was deployed from the International Space Station in July 2018 and began routine science operations in October 2018. We describe the goals and design of the mission, the on-orbit performance of the science instrument, and initial observations.
We describe a new implementation of a broad-band soft X-ray polarimeter, substantially based on a previous design. This implementation, the Pioneer Soft X-ray Polarimeter (PiSoX) is a SmallSat, designed for NASAs call for Astrophysics Pioneers, small missions that could be CubeSats, balloon experiments, or SmallSats. As in the REDSoX Polarimeter, the grating arrangement is designed optimally for the purpose of polarimetry with broad-band focussing optics by matching the dispersion of the spectrometer channels to laterally graded multilayers (LGMLs). The system can achieve polarization modulation factors over 90%. For PiSoX, the optics are lightweight Si mirrors in a one-bounce parabolic configuration. High efficiency, blazed gratings from opposite sectors are oriented to disperse to a LGML forming a channel covering the wavelength range from 35 to 75 Angstroms (165 - 350 eV). Upon satellite rotation, the intensities of the dispersed spectra, after reflection and polarizing by the LGMLs, give the three Stokes parameters needed to determine a sources linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe examples of the potential scientific return from instruments based on this design.
One of the primary objectives of small satellites is to reduce the costs associated with spacecraft development and operations as compared to traditional spacecraft missions. Small satellite missions are generally able to reduce mission planning, hardware, integration, and operational costs; however, small satellite missions struggle with reducing software development and testing costs. This paper presents the case study of the NASA Operational Simulator for Small Satellites (NOS3), a software-only simulation framework that was developed for the Simulation-to-Flight 1 (STF-1) 3U CubeSat mission. The general approach is to develop software simulators for the various hardware flight components (e.g., electrical power system, antenna deployment system, etc.) to create a completely virtual representation of the actual spacecraft system. In addition, NOS3 conveniently packages together a set of open-source software packages including the 42 dynamics simulator, the spacecraft software development framework (core Flight System), and a command and control system (COSMOS). This results in a flexible and easily deployable simulation environment that can be utilized to support software development, testing, training, and mission operations. The NOS3 environment contributed to the success of STF-1 mission in several ways, such as reducing the missions reliance on hardware, increasing available test resources, and supporting training and risk reduction targeted testing of critical software behaviors on the simulated platform. The NOS3 has been released as open-source and is available at www.nos3.org.
The design of a CubeSat telescope for academic research purposes must balance complicated optical and structural designs with cost to maximize performance in extreme environments. Increasing the CubeSat size (eg. 6U to 12U) will increase the potential optical performance, but the cost will increase in kind. Recent developments in diamond-turning have increased the accessibility of aspheric aluminum mirrors, enabling a cost-effective regime of well-corrected nanosatellite telescopes. We present an all-aluminum versatile CubeSat telescope (VCT) platform that optimizes performance, cost, and schedule at a relatively large 95 mm aperture and 0.4 degree diffraction limited full field of view stablized by MEMS fine-steering modules. This study features a new design tool that permits easy characterization of performance degradation as a function of spacecraft thermal and structural disturbances. We will present details including the trade between on- and off-axis implementations of the VCT, thermal stability requirements and finite-element analysis, and launch survival considerations. The VCT is suitable for a range of CubeSat borne applications, which provides an affordable platform for astronomy, Earth-imaging, and optical communications.
In this work we present an active Compton scattering polarimeter as a focal plane instrument able to extend the X-ray polarimetry towards hard X-rays. Other authors have already studied various instrument design by means of Monte Carlo simulations, in this work we will show for the first time the experimental measurements of tagging efficiency aimed to evaluate the polarimeter sensitivity as a function of energy. We performed a characterization of different scattering materials by measuring the tagging efficiency that was used as an input to the Monte Carlo simulation. Then we calculated the sensitivity to polarization of a design based on the laboratory set-up. Despite the geometry tested is not optimized for a realistic focal plane instrument, we demonstrated the feasibility of polarimetry with a low energy threshold of 20 keV. Moreover we evaluated a Minimum Detectable Polarization of 10% for a 10 mCrab source in 100 ks between 20 and 80 keV in the focal plane of one multilayer optics module of NuSTAR. The configuration used consisted of a doped p-terphenyl scatterer 3 cm long and 0.7 cm of diameter coupled with a 0.2 cm thick LaBr3 absorber.
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