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This paper estimates the size of the astrometric signatures which may be expected, and discusses prospects for using astrometry as a fundamental tool for understanding quasar nuclei.
The Space Interferometry Mission (SIM) relies on interferometry and metrology capable of measuring the change in the optical path difference with picometer accuracy.
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This paper provides a broad overview of the SIM-PlanetQuest Mission, covering: history, science objectives, key top level requirements, how the mission will be implemented (technical and programmatic), technology development status, an assessment of where the project is today, and prognosis for the future. SIM-PlanetQuest supports the U.S. President's Vision for Space Exploration and is supported by the U.S. National Academy of Sciences.
This viewgraph presentation reviews Astrometry with the Space Interferometry Mission (SIM) PlanetQuest. The topics include: 1) SIM PlanetQuest - the World's First Long- Baseline Optical Interferometer in Space; 2) National Academy of Sciences / NRC endorses SIM PlanetQuest; 3) SIM Planet Search; 4) Planetary System Architectures & Diversity; 5) SIM Search for 1~10 M(sub Earth) Planets Around Nearby Stars; 6) Deep Search of 120 nearby stars; 7) Planets around Young Stars; 8) SIM PlanetQuest Science Team; 9) Dark Halo of our Galaxy; 10) Dynamics of Galaxy Groups within 5 Mpc; 11) Probing Active Galactic Nuclei with Astrometry; 12) Snapshot Observing Mode: Astrometry for the masses; 13) SIM Technology Development is Complete; and 14) SIM Hardware, Tested for Flight.
The Space Interferometry Mission (SIM) is fundamentally a one-dimensional instrument with a 15-degree field-of-regard. Mission objectives require a global reference grid of thousands of well-understood stars with positions known to 4 microarcseconds which will be used to establish the instrument baseline vector during scientific observations. This accuracy will be achieved by frequently observing a set of stars throughout the mission and performing a global fit of the observations to determine position, proper motion and parallax for each star. Each star will be observed approximately 200 times with about 6.5 stars per single instrument field on the sky. We describe the nature of the reference grid, the candidate objects, and the results of simulations demonstrating grid performance, including estimates of the grid robustness when including effects such as instrument drift and possible contamination of the grid star sample by undetected binaries.
In this paper we will discuss the prospects for global astrometric measurements with the Space Interferometry Mission (SIM). SIM will perform four microarcsecond astrometric measurements onpoint-like objects as dim as 20th magnitude using optical interferometric techniques with a 10m baseline.
The Space Interferometry Mission Planet QuestLite (SIM-Lite) is a new mission concept to perform microarcsecond narrow-angle astrometry to search approximately 50 nearby stars for Earth-like planets, and also to perform a global astrometry. The SIM-Lite consists of two Michelson interferometers and one telescope. The main six-meter baseline science interferometer observes a target star and a set of reference stars. The four-meter baseline interferometer (Guide-1) monitors the attitude of the instrument in the direction of a target star. A new Guide-2telescope (G2T) tracks a bright star to monitor the attitude of the instrument in the other two orthogonal directions. In the current mission concept, the G2T consists of a 30 cm siderostat and a 30 cm confocal telescope, similar to other four telescopes used in the science and Guide-1interferometers. A testbed has been built to demonstrate the G2T feasibility for SIM-Lite mission. Recent results show that field-independent, star-tracking capability of the system is less than 30 (mu)as after the SIM narrow angle analysis.
The Space Interferometry Mission (SIM) will be the first in-space, long-baseline Michelson Stellar Interferometer. SIM will perform precision astrometry at the micro-arcsecond accuracy level, which will be used to characterize planetary systems around stars within about ten parsecs of Earth and address a number of other key astrophysics projects. This paper provides a broad overview of the SIM Mission. Topics covered include: the science objectives, key top level requirements, how the mission will be implemented (technical and programmatic), technology development status, who the key players are in the SIM development, an assessment of where the project is today, and prognosis for the future.
The Space Interferometry Mission (SIM) will perform astrometry to a resolution of a few micro arc seconds (after post-processing on the ground of the acquired data).
The SIM Lite Astrometric Observatory (aka SIM Lite), a micro-arcsecond astrometry space mission, has been developed in response to NASA's indefinite deferral of the SIM PlanetQuest mission. The SIM Lite mission, while significantly more affordable than the SIM PlanetQuest mission concept, still addresses the full breadth of SIM science envisioned by two previous National Research Council (NRC) Astrophysics Decadal Surveys at the most stringent 'Goal' level of astrometric measurement performance envisioned in those surveys. Over the past two years, the project has completed the conceptual design of the SIM Lite mission using only the completed SIM technology; published a 250 page book describing the science and mission design (available at the SIM website: http://sim.jpl.nasa.gov); been subject to an independent cost and technical readiness assessment by the Aerospace Corporation; and submitted a number of information responses to the NRC Astro2010 Decadal Survey. The project also conducted an exoplanet-finding capability double blind study that clearly demonstrated the ability of the mission to survey 60 to 100 nearby sun-like dwarf stars for terrestrial, habitable zone planets in complex planetary systems. Additionally, the project has continued Engineering Risk Reduction activities by building brassboard (form, fit and function to flight) version of key instrument elements and subjecting them to flight qualification environmental and performance testing. This paper summarizes the progress over the last two years and the current state of the SIM Lite project.
The Space Interferometry Mission (SIM) will be the first space-based long baseline Michelson interferometer designed for precision astrometry. It will address a wide range of problems in stellar astrophysics and Galactic structure, delivering precision astrometry of stars down to 20 magnitude throughout the entire Galaxy. SIM uses a 10-m Michelson interferometer in Earth-trailing solar orbit to provide 4 microarcsecond (gas) precision astrometry. With a 5-year mission lifetime, SIM will be a powerful tool for discovering planets around nearby stars, through detection of the stellar reflex motion. The astrometric method complements the radial velocity technique which as already yielded many new planets, with an important benefit of directly measuring planetary masses. SIM will have a single-measurement precision of 1 microarcsecond in a frame defined by nearby reference stars, enabling searches for planets with masses as small as a few earth masses around the nearest stars. More massive planets will be detectable to much larger distances. In addition to precision astrometry SIM will also serve an important role as a technology precursor for future astrophysics missions using interferometers. Two technologies demonstrated will be high dynamic-range aperture synthesis imaging at 10-milliarcsec resolution in the optical, and fringe nulling to 10 (exp -4).
SIM is an astrometric mission that will be capable of 1 microarcsec relative astrometric accuracy in a single measurement of approx.1000 sec. The search for terrestrial planets in the habitable zone around nearby stars is one of the main science goals of the project. In 2001, NASA through the peer review process selected 10 key projects, two of which had as its goal, the search for terrestrial planets around nearby stars. The two teams, one led by G. Marcy (UC Berkeley) and one lead by M. Shao (JPL), have an extensive preparatory science program underway. This paper describes the status of this activity as well as the technology status of SIM's narrow angle astrometry capability, to reach 1 uas in a single epoch measure and its ability to average multiple epoch measurements to well below 1 uas.
The Space Interferometry Mission will be the first of a new generation of space instruments using interferometry.
The prospects for global astrometric measurements with the space interferometry mission (SIM) are discussed. The SIM mission will perform four microarcsec astrometric measurements on objects as faint as 20 mag using the optical interferometry technique with a 10 m baseline. The SIM satellite will perform narrow angle astrometry and global astrometry by means of an astrometric grid. The sensitivities of the SIM global astrometric performance and the grid accuracy versus instrumental parameters and sky coverage schemes are reported on. The problems in finding suitable astrometric grid objects to support microarcsec astrometry, and related ground-based observation programs are discussed.
The Space Interferometry Mission (SIM) will perform global astrometry (full sky), local wide-angle (15 degree) and narrow-angle (1 degree) observations to search extra-solar planets, and can calibrate stellar and galactic evolution theories. The astrometric accuracy of the SIM mission depends on spectral characteristics of the optics, detectors and targets. This paper will discuss the photometric throughput of the SIM instrument, and analyze effects of wavefront errors, optical mismatches and control biases as a function of wavelength. The color dependence models of the instrument optics including mirrors, lenses, field-stop and beam-splitter are presented. The performances of different detectors with a variety of coatings are compared. A model of the SIM fringe spectrometer is created. For early and late types of stars, brightness dependency errors are analyzed for different combinations of optics and detectors. Visibility loss due to imperfect optics is investigated in detail. Based on the models of instrument and estimated visibilities, the astrometric accuracies for various kinds of stars are evaluated. It is important to emphasize that not only light sources, mirrors, lenses, field stop and detectors are all wavelength dependent, but also fringe visibility loss, wavefront error, optics control error, etc. are all a function of wavelengths. For the first time the estimate of SIM performance is based on spectral analysis of all factors above, rather than monochromatic approximations of detected fringes, or simply adopted constants. This paper summarizes the astrometric accuracies for a wide range of stars and various combinations of optical design and detector configurations. It has been verified that SIM has astrometric accuracy of about 4 μas for targets with different spectra.
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