Measuring the Speed of Light and the Moon Distance with an Occultation of Mars by the Moon: a Citizen Astronomy Campaign
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NTIA Technical Report TR-89-241 Meteor–Burst System Communications Compatibility
NTIA REPORT 89·241 METEOR BURST SYSTEM COMMUNICATIONS COMPATIBILITY David Cohen William Grant Francis Steele U.S. DEPARTMENT OF COMMERCE Robert A. Mosbacher, Secretary Alfred C. Sikes, Assistant Secretary for Communications and Information MARCH 1989 ABSTRACT The technical and operating characteristics of meteor burst systems of importance for spectrum management appl i cati ons are i dent ifi ed. A techni ca1 assessment is included which identifies the most appropriate frequency subbands withi n the VHF spectrum to support meteor burst systems. The electromagnetic compatibility of meteor burst systems with other equipments in the VHF spectrum is determined using computerized analysis methods for both ionospheric and groundwave propagation modes. It is shown that meteor burst equipments can cause and are susceptible to groundwave interference from other VHF equipments. The report includes tables of geographical distance separations between meteor burst and other VHF equipments which satisfy interference threshold criteria. KEY WORDS Compat i bil ity Interference Meteor Bu rst Spectrum Management iii TABLE OF CONTENTS Subsection SECTION 1 INTRODUCTION BACKGROUND. ••••••••••••••••••••• .. • .. •••••••••• .. •••••••••••••••••••••••• • • • • 1 OBJECTIVES •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2 APPROACH ••••••••• e'. ••••••••••••••••••••••••••••••••••••••••••••••••••••••• 2 SECTION 2 CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS.... ••••••••••••••••••••••••••••••••••••••••••• ••• •••• •••••••• • 4 FREQUENCY USE •••••••••••••• -
A New Vla–Hipparcos Distance to Betelgeuse and Its Implications
The Astronomical Journal, 135:1430–1440, 2008 April doi:10.1088/0004-6256/135/4/1430 c 2008. The American Astronomical Society. All rights reserved. Printed in the U.S.A. A NEW VLA–HIPPARCOS DISTANCE TO BETELGEUSE AND ITS IMPLICATIONS Graham M. Harper1, Alexander Brown1, and Edward F. Guinan2 1 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA; [email protected], [email protected] 2 Department of Astronomy and Astrophysics, Villanova University, PA 19085, USA; [email protected] Received 2007 November 2; accepted 2008 February 8; published 2008 March 10 ABSTRACT The distance to the M supergiant Betelgeuse is poorly known, with the Hipparcos parallax having a significant uncertainty. For detailed numerical studies of M supergiant atmospheres and winds, accurate distances are a pre- requisite to obtaining reliable estimates for many stellar parameters. New high spatial resolution, multiwavelength, NRAO3 Very Large Array (VLA) radio positions of Betelgeuse have been obtained and then combined with Hipparcos Catalogue Intermediate Astrometric Data to derive new astrometric solutions. These new solutions indicate a smaller parallax, and hence greater distance (197 ± 45 pc), than that given in the original Hipparcos Catalogue (131 ± 30 pc) and in the revised Hipparcos reduction. They also confirm smaller proper motions in both right ascension and declination, as found by previous radio observations. We examine the consequences of the revised astrometric solution on Betelgeuse’s interaction with its local environment, on its stellar properties, and its kinematics. We find that the most likely star-formation scenario for Betelgeuse is that it is a runaway star from the Ori OB1 association and was originally a member of a high-mass multiple system within Ori OB1a. -
Measuring the Astronomical Unit from Your Backyard Two Astronomers, Using Amateur Equipment, Determined the Scale of the Solar System to Better Than 1%
Measuring the Astronomical Unit from Your Backyard Two astronomers, using amateur equipment, determined the scale of the solar system to better than 1%. So can you. By Robert J. Vanderbei and Ruslan Belikov HERE ON EARTH we measure distances in millimeters and throughout the cosmos are based in some way on distances inches, kilometers and miles. In the wider solar system, to nearby stars. Determining the astronomical unit was as a more natural standard unit is the tUlronomical unit: the central an issue for astronomy in the 18th and 19th centu· mean distance from Earth to the Sun. The astronomical ries as determining the Hubble constant - a measure of unit (a.u.) equals 149,597,870.691 kilometers plus or minus the universe's expansion rate - was in the 20th. just 30 meters, or 92,955.807.267 international miles plus or Astronomers of a century and more ago devised various minus 100 feet, measuring from the Sun's center to Earth's ingenious methods for determining the a. u. In this article center. We have learned the a. u. so extraordinarily well by we'll describe a way to do it from your backyard - or more tracking spacecraft via radio as they traverse the solar sys precisely, from any place with a fairly unobstructed view tem, and by bouncing radar Signals off solar.system bodies toward the east and west horizons - using only amateur from Earth. But we used to know it much more poorly. equipment. The method repeats a historic experiment per This was a serious problem for many brancht:s of as formed by Scottish astronomer David Gill in the late 19th tronomy; the uncertain length of the astronomical unit led century. -