Small satellites with MEMS x-ray telescopes for x-ray astronomy and solar system exploration

Toward a new era of X-ray astronomy, next generation X-ray optics are indispensable. To meet a demand for telescopes lighter than the foil optics but with a better angular resolution less than 1 arcmin, we are developing micropore X-ray optics based on micromaching technologies. Using sidewalls of micropores through a thin silicon wafer, this type can be the lightest X-ray telescope ever achieved. Two new Japanese missions ORBIS and GEOX will carry this optics. ORBIS is a small X-ray astronomy mission to monitor supermassive blackholes, while GEO-X is a small exploration mission of the Earth's magnetosphere. Both missions need a ultra light-weight (<1 kg) telescope with moderately good angular resolution (<10 arcmin) at an extremely short focal length (<30 cm). We plan to demonstrate this optics in these two missions around 2020, aiming at future other astronomy and exploration missions

Photoinduced Structural Phase Transitions in Polyacene

There exist two types of structural instability in polyacene: double bonds in a cis pattern and those in a trans pattern. They are isoenergetic but spectroscopically distinct. We demonstrate optical characterization and manipulation of Peierls-distorted polyacene employing both correlated and uncorrelated Hamiltonians. We clarify the phase boundaries of the cis- and trans-distorted isomers, elucidate their optical-conductivity spectra, and then explore their photoresponses. There occurs a photoinduced transformation in the polyacene structure, but it is one-way switching: The trans configuration is well convertible into the cis one, whereas the reverse conversion is much less feasible. Even the weakest light irradiation can cause a transition of uncorrelated electrons, while correlated electrons have a transition threshold against light irradiation.Comment: 14 pages with 15 figures embedde

The Comet Interceptor Mission

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum ΔV capability of 600 ms−1. Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule

Genetic optimization for the orbit maintenance of libration point orbits with applications to EQUULEUS and LUMIO

Many Earth-Moon libration point orbits are being evaluated as candidates for future space missions, ranging from lunar gateways and possibly inhabited assets in the vicinity of the Moon to science missions in resonant synodic orbits, as in the cases of EQUULEUS and LUMIO CubeSat missions. The problem of libration point orbit maintenance is investigated here using the Target Point Approach, which leads to a closed LQR formulation of the station-keeping Delta-v once a set of parameters is specified. These parameters strongly depend on the orbit type. In view of the dramatic variety of stability property featured by halo orbits, these parameters must be fine-tuned with ad-hoc Monte-Carlo simulations or via a trial and error procedure. In this paper, a genetic algorithm is used to optimize the parameters of the target point approach for halo orbits with period ranging from 7 to 14 days and to provide a unified framework for orbit maintenance analysis of halo orbits. Numerical simulations in a high-fidelity ephemeris model show reductions in the station-keeping Delta-v budget for libration point orbits compared to previous results found in the literature