Click for next page ( 20


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 19
Assessment of Solar System Exploration Programs 1991 (Chapter 5) Assessment of Solar System Exploration Programs 1991 5 Detection and Study of Other Solar Systems The committee recently published its first report in this area, Strategy for the Detection and Study of Other Planetary Systems and Extrasolar Planetary Materials: 1990-2000 (SSB, 1990d). NASA has not yet had an opportunity to implement the scientific goals and objectives and related recommendation established in that strategy. This chapter therefore only summarizes the principal recommendation from the report's Executive Summary and discusses several parallel activities at the agency. Initiate, and maintain for at least a decade, systematic observational planet searches that encompass the widest feasible domain of the planetary mass versus semimajor axis exploration space. Specifically, REPORT MENU NOTICE MEMBERSHIP 1. Initiate an astrometric observational survey program designed FOREWORD to track the reflex motion of 100 or more stars in the solar neighborhood (r SUMMARY 10 parsecs) with a design goal for relative astrometric accuracy of = CHAPTER 1 10 microarcsec, sufficient in a search of adequate duration to detect and CHAPTER 2 track Uranus-mass planets in a solarlike system. CHAPTER 3 CHAPTER 4 2. Obtain and interpret a record of Doppler shifts in stellar spectral CHAPTER 5 CHAPTER 6 features due to reflex motion, at or above the current measurement CHAPTER 7 10 m/s-1 for the velocity of the orbital reflex, in a survey accuracy of CHAPTER 8 of the duration and extent specified for the astrometric survey. CHAPTER 9 REFERENCES 3. Until such systematic searches are mounted, maintain ongoing ground-based searches at their present best accuracies, and investigate and implement improvement of these accuracies if technically and financially feasible. Augment current observational studies of young stellar systems, and file:///C|/SSB_old_web/ssep91ch5.htm (1 of 4) [6/18/2004 1:58:06 PM]

OCR for page 19
Assessment of Solar System Exploration Programs 1991 (Chapter 5) of the physical properties of circumstellar-interstellar dust systems as precursors to and products of planetary systems, on a variety of spatial and spectral resolution scales. Survey a statistically meaningful number of stars of varied masses and types to detect such systems. Continue investigations of links between interstellar-circumstellar dust and isotopically "exotic" grains in solar system materials such as primitive meteorites, interplanetary dust, and comets. Important elements and objectives of this effort include collection and curation of rare interplanetary asteroidal- cometary dust particles (IDPs); laboratory identification and analysis of micron to submicron presolar dust grains preserved in these meteoritic and IDP materials; and laboratory simulation and theoretical studies of the astronomical dust cycle, including the formation and physical and chemical processing of interstellar grains in preplanetary and planet-forming environments. Improve the capability of theoretical models and computer experiments to make specific predictions regarding the observational properties of planetary systems at all stages of their evolution, and further develop models to aid in the interpretation of existing data. Encourage the following multidisciplinary activities between the responsible divisions at OSSA: participation of planetary scientists in the design and building of future observatories and facility instruments, and in the allocation of observing time at existing observational facilities; joint support for multidisciplinary scientific initiatives; and joint development of instrumentation for extrasolar observation. Pursue long-range instrumental and strategic initiatives that are conceptually applicable and potentially valuable to the investigation of extrasolar planetary materials in later stages of reconnaissance or in subsequent phases of exploration and intensive study, but that at present are technologically or theoretically too undeveloped to be of immediate utility in implementing the short- term strategy proposed in this report. Prospects for the detection of extrasolar planetary systems have also been under investigation by the Planetary Systems Science Working Group (PSSWG), chartered by the Solar System Exploration Division to explore the science strategy for detecting other planetary systems. Similar to the recommendations of COMPLEX listed above, the PSSWG has concluded that NASA should begin a concentrated, long-term effort to detect extrasolar planetary systems. The PSSWG envisions an evolutionary approach, starting with current ground-based astrometric and radial-velocity searches, which are capable of detecting Jupiter-mass planets around stars in the solar neighborhood. The next step would be major ground- or space-based instruments, using astrometry, direct imaging, interferometry, or some combination of these techniques. This effort could potentially allow detection of Uranus-mass planets around the same nearby stars, or (for imaging techniques) of relatively fine details (with a resolution of 1 to 10 AU) in the structure of preplanetary disks in the Taurus or file:///C|/SSB_old_web/ssep91ch5.htm (2 of 4) [6/18/2004 1:58:06 PM]

OCR for page 19
Assessment of Solar System Exploration Programs 1991 (Chapter 5) Ophiuchus molecular clouds. Finally, the ultimate instrument might be a lunar- based interferometer capable of detecting Earth-mass planets or extremely fine details (at scales 0.1 to 1.0 AU) in preplanetary disks. The Astrophysics Division has initiated parallel studies of the capabilities of the Large Deployable Reflector and the Space Infrared Telescope Facility to detect planetary bodies around nearby stars. Other activities in astrophysics include theoretical studies of star formation at a center established for that purpose. Last update 12/13/00 at 9:45 am Site managed by Anne Simmons, Space Studies Board file:///C|/SSB_old_web/ssep91ch5.htm (3 of 4) [6/18/2004 1:58:06 PM]