Stellar Imager (SI) mission concept

Abstract

The Stellar Imager (SI) is envisioned as a space-based, UV-optical interferometer composed of 10 or more onemeter class elements distributed with a maximum baseline of 0.5 km. It is designed to image stars and binaries with sufficient resolution to enable long-term studies of stellar magnetic activity patterns, for comparison with those on the sun. It will also support asteroseismology (acoustic imaging) to probe stellar internal structure, differential rotation, and large-scale circulations.SI will enable us to understand the various effects of the magnetic fields of stars, the dynamos that generate these fields, and the internal structure and dynamics of the stars. The ultimate goal of the mission is to achieve the best-possible forecasting of solar activity as a driver of climate and space weather on time scales ranging from months up to decades, and an understanding of the impact of stellar magnetic activity on life in the Universe. In this paper we describe the scientific goals of the mission, the performance requirements needed to address these goals, the "enabling technology" development efforts being pursued, and the design concepts now under study for the full mission and a possible pathfinder mission.

MAXIM science and technology

“…The principal disadvantages are a) the limitation to energies below 0.5keV, b) the monochromatic nature of the response which precludes any spectroscopy, and c) the positional tolerance of the mirrors is λ x /10, which is a fraction of a nanometer. The idea is to reproduce in the x-ray an architecture that is similar to the Stellar Imager concept (Carpenter, 2003).…”

X-Ray Interferometry

“…Stability requirement for each of the degrees of freedom is presented in Table I. The idea is to reproduce in the X-ray an architecture that is similar to the Stellar Imager concept (Carpenter et al, 2003). Multilayer mirrors are placed on multiple spacecraft as shown in Figure 27.…”

Scalable Sensing, Estimation, and Control Architecture for Large Spacecraft Formations

“…Although several designs are currently under review, a TPF design by Lockheed Martin is composed of four, possibly six, free flying spacecraft which will function as an infrared interferometer. The stellar imager (SI) [3] mission postulates that stellar activity is key to understanding life in the universe. Specifically, SI is a large, spacebased UV optical sparse aperture telescope/Fizeau interferometer designed to study the sun.…”

“…Interferometry missions are especially challenging due to the high tolerance requirements. Such missions are currently slated to employ a multiple resolution control architecture: conventional thrusters and RF range and bearing sensors are to be used for coarse spacecraft control, and laser sensors and adaptive optics will provide fine optical path control [1,3]. The autonomous formation flying sensor (AFF) has been identified as a key component for coarse control of spacecraft formations [4,5].…”

“…Typical single spacecraft systems are allowed to drift with respect to an external frame, as it is not crucial (and would be fuel expensive) to reposition the satellite with respect to a model-based reference track. Multiple satellite missions can similarly relax the positioning of the formation in an external reference frame over small time horizons, but each individual spacecraft must control its relative position with respect to the fleet (and minimize fuel) for mission performance and safety [1][2][3]. Moreover, sensitivity of these factors grows with the number of spacecraft in the system.…”