DOCSLIB.ORG

IJEST Template

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
IJEST Template Research & Reviews: Journal of Space Science & Technology ISSN: 2321-2837 (Online), ISSN: 2321-6506 V(Print) Volume 6, Issue 2 www.stmjournals.com Diurnal Variation of VLF Radio Wave Signal Strength at 19.8 and 24 kHz Received at Khatav India (16o46ʹN, 75o53ʹE) A.K. Sharma1, C.T. More2,* 1Department of Physics, Shivaji University, Kolhapur, Maharashtra, India 2Department of Physics, Miraj Mahavidyalaya, Miraj, Maharashtra, India Abstract The period from August 2009 to July 2010 was considered as a solar minimum period. In this period, solar activity like solar X-ray flares, solar wind, coronal mass ejections were at minimum level. In this research, it is focused on detailed study of diurnal behavior of VLF field strength of the waves transmitted by VLF station NWC Australia (19.8 kHz) and VLF station NAA, America (24 kHz). This research was carried out by using VLF Field strength Monitoring System located at Khatav India (16o46ʹN, 75o53ʹE) during the period August 2009 to July 2010. This study explores how the ionosphere and VLF radio waves react to the solar radiation. In case of NWC (19.8 kHz), the signal strength recording shows diurnal variation which depends on illumination of the propagation path by the sunlight. This also shows that the signal strength varies according to the solar zenith angle during daytime. In case of VLF signal transmitted by NAA at 24 kHz, the number of sunrises and sunsets are observed in VLF signal strength due to the variations of illumination of the D-region during daytime. In both the cases, the signal strength is more stable during daytime and fluctuating during nighttime due to the presence and absence of D-region during daytime and nighttime respectively. Keywords: VLF field strength, diurnal variation, ionosphere, solar zenith angle *Author for Correspondence E-mail: [email protected] INTRODUCTION the ionosphere. That’s why these rays are used The ionosphere is made up of many gases such for communication around the globe and they as nitrogen, oxygen etc. The solar ultraviolet are also used for monitoring the ionospheric radiation interacts with the atoms present at behavior. The VLF waves reflects from the this level. This ionizing radiation collides with ionosphere, and that’s why if something oxygen molecules. The ultraviolet waves are happens in the ionosphere then the VLF radio partly absorbed by the oxygen molecules and waves reflecting from the ionosphere will be so these waves ionize the oxygen molecules affected [3–5]. [1]. Simple background cosmic radiation also The ionospheric layer breaks down into many affects continuously on the ionosphere. The layers. These layers are ionized at all times energy of cosmic radiation is not strong but except the D layer. The D layer is close to the they are constantly affecting the ionosphere. earth. It disappears during night. It is due to But, the solar radiation affects diurnally as the sufficient neutral density below 200 km. well as it affects the ionosphere during solar Due to this, electrons recombine with oxygen flares and magnetic storms [6, 7]. within a few hours [2]. So, the solar flare effects are only discrete The E region ionization decreases in small events during the day time only. During the amount during the night time. The D layer night time, VLF waves travel up to 90 km to reappears only at that time when the sun rises the E layer in the ionosphere and then reflects at the D layer height. The VLF waves travel towards earth. During the daytime the D layer along the ground as well as they reflect from is partially ionized. The VLF radio waves RRJoSST (2017) 1-12 © STM Journals 2017. All Rights Reserved Page 1 Diurnal Variation of VLF Radio Wave Signal Strength at Khatav India Sharma and More travels through the D layer and so lose some THE VLF EXPERIMENT energy in the travel way. The strength of the For the study of effect of solar activities on the signal of the VLF waves is stronger at night ionosphere, Stanford University, USA, has set time than the daytime [8]. The VLF waves up a program. This University has distributed respond in different way to different solar inexpensive SID monitors to space activity. In our study, we have recorded VLF researchers and college as well as University data since 2007 and it is observed that VLF students throughout the world [10, 11]. By radio wave signal strength is affected with the using the SID monitors and VLF loop antenna, disturbances occurred in the ionosphere and it is easy to record VLF radio waves this ionospheric disturbance can be affected on transmitted by particular VLF transmitting human life [9, 10]. station. When we use VLF radio waves for The VLF field strength monitoring system at communication purposes, solar activity can Khatav, India (1646' N, 7553' E) is shown in affect the VLF signal strength. Therefore, the Figure1. Experimental set up -two channel purpose of this study was to investigate how VLF field strength monitoring system is VLF radio waves are impacted by the radiation shown in Figure 2. Figures 3 (a) and (b) shows given off by the sun at various times. loop antennas. Fig. 1: Block Diagram of VLF Field Strength Monitoring System which Consists of Loop Antennas, SID Monitor, A/D Converter and Computer. Fig. 2: Experimental set up—Two Channel VLF Field Strength Monitoring System. RRJoSST (2017) 1-12 © STM Journals 2017. All Rights Reserved Page 2 Research & Reviews: Journal of Space Science & Technology Volume 6, Issue 2 ISSN: 2321-2837 (Online), ISSN: 2321-6506 (Print) Fig. 3: Loop Antenna: (a) Hexagonal Loop Antenna (b) Square Loop Antenna. By monitoring the signal strength of the VLF level of ionization of particles in the radio waves reflecting over a period of time, it ionosphere changes, then we should be aware is possible to draw many conclusions about the of the fact that the signal strength of VLF characteristics of the ionosphere. It is because radio waves will also change. of the fact that the radio waves and the ionosphere are so closely related with each THE SOLAR BASELINE EFFECT ON other. If there is a change in the VLF signal THE IONOSPHERE OF THE EARTH strength over the daytime, then it is called as During the period 2009–10, sun was relatively sudden ionospheric disturbance (SID). During calm because there was a very low level of the SID, the numbers of ionized particles SID activities in the ionosphere of the earth. If present in the ionosphere increases or due to the solar activity, there is a change in decreases and that’s why VLF radio waves to the characteristics of ionosphere then there be reflect either more or less. The reason of will be change in the signal strength of VLF the SID can be determined by comparing SID radio waves. There is 11-year cycle for solar data to GOES satellite data. GOES satellite activity which corresponds to the reversal of directly and continuously monitors the sun and sun’s magnetic field [3]. However, it is not records solar flares [11–13]. If the SID and possible to predict when individual solar flares solar flare occurs at the same time which is are going to occur, with a high level of found by using GOES satellite data, then there accuracy. During the period 2009–10, the suns is direct correlation in between ionosphere, activity was at its lowest point of the 11-year sun and the VLF radio waves. In this way, sun cycle. Hence, there were not a big number of and solar flares affect the VLF radio waves solar flares, or SIDs observed during this which is useful because indirect observations period. Hence, it was important to take of the ionosphere as well as the sun is advantage of the lowest solar activity period to possible. The collection of the VLF data by understand the sun’s baseline effect on the using SID monitor is possible from several ionosphere of the earth as well as on the VLF different locations. Thus monitoring of VLF radio waves during sun’s minimum activity waves is very useful not only in understanding level [14]. If we are able to understand what the impact of sun on VLF radio waves which has happened in the ionosphere without or relies on the ionosphere but also the minimum solar activity then could be easy to understanding of ionosphere. It is very solve the issues of the technology accuracy. important to study VLF radio wave technology Further we will be prepared to handle the and the ionosphere because the level of technology and accuracy issues when the solar ionization of particles in the ionosphere does activity are frequent or more. Around the not remain constant for a long time. When the world, more and more scientists are recording RRJoSST (2017) 1-12 © STM Journals 2017. All Rights Reserved Page 3 Diurnal Variation of VLF Radio Wave Signal Strength at Khatav India Sharma and More SID monitor data and they noticed the effect change in radio signal strength meaning that on radio communications. For this study a SID there is a change in the level of ionization in monitors was used to record VLF radio waves ionosphere. The goal of this study was to use from US navy transmitters NAA (24 kHz) and VLF radio waves as a tool to monitor the NWC (19.8 kHz) and monitors changes in the ionosphere and to observe how radiation from ionosphere [15, 16]. The SID monitors data for the sun affects the strength of VLF radio above mentioned frequency was collected waves and how the solar flare affects on the since 2007 and analysis as well as comparison ionosphere.
Load more

Recommended publications
  • Starry Starry Night Part 1
    Starry Starry Night Part 1 DO NOT WRITE ON THIS PORTION OF THE TEST 1. If a lunar eclipse occurs tonight, when is the soonest a solar eclipse can occur? A) Tomorrow B) In two weeks C) In six months D) In one year 2. The visible surface of the Sun is called its A) corona B) photosphere C) chromosphere D) atmosphere 3. Which moon in the Solar System has lakes and rivers on it: A) Triton B) Charon C) Titan D) Europa 4. The sixth planet from the Sun is: A) Mars B) Jupiter C) Saturn D) Uranus 5. The orbits of the planets and dwarf planets around the Sun are in the shape of: A) An eclipse B) A circle C) An ellipse D) None of the above 6. True or False: During the summer and winter solstices, nighttime and daytime are of equal length. 7. The diameter of the observable universe is estimated to be A) 93 billion miles B) 93 billion astronomical units C) 93 billion light years D) 93 trillion miles 8. Asteroids in the same orbit as Jupiter -- in front and behind it -- are called: A) Greeks B) Centaurs C) Trojans D) Kuiper Belt Objects 9. Saturn's rings are made mostly of: A) Methane ice B) Water ice C) Ammonia ice D) Ice cream 10. The highest volcano in the Solar System is on: A) Earth B) Venus C) Mars D) Io 11. The area in the Solar System just beyond the orbit of Neptune populated by icy bodies is called A) The asteroid belt B) The Oort cloud C) The Kuiper Belt D) None of the above 12.
    [Show full text]
  • Conspicuity of High-Visibility Safety Apparel During Civil Twilight
    UMTRI-2006-13 JUNE 2006 CONSPICUITY OF HIGH-VISIBILITY SAFETY APPAREL DURING CIVIL TWILIGHT JAMES R. SAYER MARY LYNN MEFFORD CONSPICUITY OF HIGH-VISIBILITY SAFETY APPAREL DURING CIVIL TWILIGHT James R. Sayer Mary Lynn Mefford The University of Michigan Transportation Research Institute Ann Arbor, MI 48109-2150 U.S.A. Report No. UMTRI-2006-13 June 2006 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. UMTRI-2006-13 4. Title and Subtitle 5. Report Date Conspicuity of High-Visibility Safety Apparel During Civil June 2006 Twilight 6. Performing Organization Code 302753 7. Author(s) 8. Performing Organization Report No. Sayer, J.R. and Mefford, M.L. UMTRI-2006-13 9. Performing Organization Name and Address 10. Work Unit no. (TRAIS) The University of Michigan Transportation Research Institute 11. Contract or Grant No. 2901 Baxter Road Ann Arbor, Michigan 48109-2150 U.S.A. 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered The University of Michigan Industry Affiliation Program for 14. Sponsoring Agency Code Human Factors in Transportation Safety 15. Supplementary Notes The Affiliation Program currently includes Alps Automotive/Alpine Electronics, Autoliv, Avery Dennison, Bendix, BMW, Bosch, Com-Corp Industries, DaimlerChrysler, DBM Reflex, Decoma Autosystems, Denso, Federal-Mogul, Ford, GE, General Motors, Gentex, Grote Industries, Guide Corporation, Hella, Honda, Ichikoh Industries, Koito Manufacturing, Lang- Mekra North America, Magna Donnelly, Muth, Nissan, North American Lighting, Northrop Grumman, OSRAM Sylvania, Philips Lighting, Renault, Schefenacker International, Sisecam, SL Corporation, Stanley Electric, Toyota Technical Center, USA, Truck-Lite, Valeo, Visteon, 3M Personal Safety Products and 3M Traffic Safety Systems Information about the Affiliation Program is available at: http://www.umich.edu/~industry 16.
    [Show full text]
  • Numerical Modelling of VLF Radio Wave Propagation Through Earth-Ionosphere Waveguide and Its Application to Sudden Ionospheric Disturbances
    Numerical Modelling of VLF Radio Wave Propagation through Earth-Ionosphere Waveguide and its application to Sudden Ionospheric istur!ances Thesis submitted for the degree of octor of Philosoph# (Science% in Ph#sics (Theoretical) of the &niversity of 'alcutta Su(a# Pal Ma#8, )*+, CERTIFICATE FROM THE SUPERVISOR This is to certify that the thesis entitled "Numerical Modelling of VLF Radio Wave Propagation through Earth-Ionosphere waveguide and its application to !udden Ionospheric Distur#ances", submitted by Mr. Sujay Pal who got his name registered on $%&$'&%$(( for the award of Ph.D. )!cience* degree of the Universit, of Calcutta. absolutely based upon his own work under the supervision of Professor !andip K. Cha0ra#arti and that neither this thesis nor any part of it has been submitted for any degree/diploma or any other academic award anywhere before. Prof. !andip K. -ha0ra#arti Senior Professor & Head Department of #strophysics & Cosmology S. N. Bose National Centre for Basic Sciences JD Block, Sector())), Salt *ake, +olkata 7---./, India TO My PARENTS i ABSTRACT Very Low Frequency (VLF) radio waves with frequency in the range 3 30 kHz ∼ propagate within the Earth-ionosphere waveguide (EIWG) for#ed $y the Earth as the %ower $oundary and the %ower ionosphere (50 100 k#) as the upper $oundary ∼ of the waveguide. These waves are generated from #an-#ade transmitters as wel% as fro# lightnings or other natura% sources( *tudy of these waves is very i#portant since they are the only tool to diagnose the %ower ionosphere( Lower part of the Earth+s ionosphere ranging &0 90 km is known as the -- ∼ region of the ionosphere( *olar Lyman-α radiation at '.'./ n# and EUV radiation in 80 '''.& n# are #ain%y responsib%e for for#ing the --region through the ∼ ionization of 123N 23O 2 during day time( The VLF propagation takes p%ace $etween the Earth+s surface and the --region at the day time.
    [Show full text]
  • Dark Model Adaptation: Semantic Image Segmentation from Daytime to Nighttime
    Dark Model Adaptation: Semantic Image Segmentation from Daytime to Nighttime Dengxin Dai1 and Luc Van Gool1;2 Abstract— This work addresses the problem of semantic also under these adverse conditions. In this work, we focus image segmentation of nighttime scenes. Although considerable on semantic object recognition for nighttime driving scenes. progress has been made in semantic image segmentation, it Robust object recognition using visible light cameras is mainly related to daytime scenarios. This paper proposes a novel method to progressive adapt the semantic models trained remains a difficult problem. This is because the structural, on daytime scenes, along with large-scale annotations therein, textural and/or color features needed for object recognition to nighttime scenes via the bridge of twilight time — the time sometimes do not exist or highly disbursed by artificial lights, between dawn and sunrise, or between sunset and dusk. The to the point where it is difficult to recognize the objects goal of the method is to alleviate the cost of human annotation even for human. The problem is further compounded by for nighttime images by transferring knowledge from standard daytime conditions. In addition to the method, a new dataset camera noise [32] and motion blur. Due to this reason, of road scenes is compiled; it consists of 35,000 images ranging there are systems using far-infrared (FIR) cameras instead from daytime to twilight time and to nighttime. Also, a subset of the widely used visible light cameras for nighttime scene of the nighttime images are densely annotated for method understanding [31], [11]. Far-infrared (FIR) cameras can be evaluation.
    [Show full text]
  • Daytime and Nighttime Polar Cloud and Snow Identification Using MODIS Data Qing Trepte SAIC, Hampton, VA USA Patrick Minnis Atmo
    Daytime and Nighttime Polar Cloud and Snow Identification Using MODIS Data Qing Trepte SAIC, Hampton, VA USA Patrick Minnis Atmospheric Sciences, NASA Langley Research Center, Hampton, VA USA Robert F. Arduini SAIC, Hampton, VA USA Extended Abstract for SPIE 3rd International Asia-Pacific Environmental Remote Sensing Symposium 2002: Remote Sensing of the Atmosphere, Ocean, Environment, and Space Hangzhou, China October 23-27, 2002 Daytime and nighttime polar cloud and snow identification using MODIS data Qing Z. Trepte*a, Patrick Minnisb, Robert F. Arduinia aScience Applications International Corp.; bAtmospheric Sciences, NASA Langley Research Center ABSTRACT The Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra, with its high horizontal resolution and frequent sampling over Arctic and Antarctic regions, provides unique data sets to study clouds and the surface energy balance over snow and ice surfaces. This paper describes a polar cloud mask using MODIS data. The daytime cloud and snow identification methods were developed using theoretical snow bi-directional reflectance models for the MODIS 1.6 and 3.75-µm channels. The model-based polar cloud mask minimizes the need for empirically adjusting the thresholds for a given set of conditions and reduces the error accrued from using single-value thresholds. During night, the MODIS brightness temperature differences (BTD) for 3.75 - 11, 3.75 - 12, 8.55 - 11, and 6.7 - 11 µm are used to detect clouds while snow and ice maps are used to determine snow and ice surfaces. At twilight, the combination of the 1.6-µm reflectance and the 3.75 - 11-µm BTD are used to detect clouds.
    [Show full text]
  • Propagation Analysis of a 900 Mhz Spread Spectrum Centralized Traffic Signal Control System
    PROPAGATION ANALYSIS OF A 900 MH Z SPREAD SPECTRUM CENTRALIZED TRAFFIC SIGNAL CONTROL SYSTEM Brian L. Urban, AS, BS, EIT Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS May 2006 APPROVED: Perry McNeill, Major Professor Michael Kozak, Committee Member Shuping Wang, Committee Member Bernard Vokoun, Committee Member Vijay Vaidyanathan, Departmental Program Coordinator Albert B. Grubbs, Chair of the Department of Engineering Technology Oscar Garcia, Dean of the College of Engineering Sandra L. Terrell, Dean of the Robert B. Toulouse School of Graduate Studies Urban, Brian L., Propagation analysis of a 900 MHz spread spectrum centralized traffic signal control system. Master of Science (Engineering Technology), May 2006, 88 pp., 20 tables, 27 illustrations, references, 25 titles. The objective of this research is to investigate different propagation models to determine if specified models accurately predict received signal levels for short path 900 MHz spread spectrum radio systems. The City of Denton, Texas provided data and physical facilities used in the course of this study. The literature review indicates that propagation models have not been studied specifically for short path spread spectrum radio systems. This work should provide guidelines and be a useful example for planning and implementing such radio systems. The propagation model involves the following considerations: analysis of intervening terrain, path length, and fixed system gains and losses. Copyright 2006 by Brian L. Urban ii ACKNOWLEDGEMENTS I acknowledge the following people for their efforts and contributions to my thesis. It would not have been completed without them. Special thanks to the author’s thesis advisor, Dr.
    [Show full text]
  • VLF Radio Observations and Modeling
    INDIAN CENTRE FOR SPACE PHYSICS ANNUAL REPORT (2013-2014) TABLE OF CONTENTS Report of the Governing Body 3 Governing Body of the Centre 4 Members of the Research Advisory Council 4 Academic Council Members 4 In-Charge, Academic Affairs 4 Dean (Academic) and Finance Officer 4 Administrative Officer 4 Public Information Officer 5 In Charge of the Departments 5 Faculty Members 5 Honorary Faculty Members 5 Project Scientists 5 Post-Doctoral Fellows 5 Senior Research Fellows 5 Junior Research Fellows 6 ICTP Senior Research Fellow 6 Visiting Research Scholars 6 Engineers / Laboratory Staff 6 Office Staff 6 Security Staff 6 Research Facilities at the Head Quarter 7 Facilities at other branches of the Centre 7 Brief Profiles of the Scientists of the Centre 7 Research Work Published or Accepted for Publication 10 Books and In Books 14 Members of Scientific Societies/Committees 15 Ph.D. degree Received 15 Ph.D. Thesis Submitted 15 Course of lectures offered by ICSP members 15 Participation in National/International Conferences & Symposia 16 Workshops / Seminars / Conferences etc. organized 17 Visits abroad from the Centre 17 Major Visitors to the Centre 17 Collaborative Research and Project Work 17 M.Sc. projects guided by ICSP members 18 Summary of the Research Activities of the Scientists at the Centre 19 The ionospheric and earthquake research centre (IERC) 38 Activities of the Indian Centre for Space Physics, Malda Branch 40 Auditors Report to the Members 42 Published by: Indian Centre for Space Physics, Chalantika 43, Garia Station Road, Garia, Kolkata 700084 EPABX +91-33-2436-6003 and +91-33-2462-2153 Extension Numbers: Department of Ionospheric Science: 21 Department of Astrochemistry/Astrobiology: 22 Accounts: 23 Seminar Room: 24 Computer room: 25 Department of High Energy Radiation: 26 X-ray Laboratory: 27 Fax: +91-33-2462-2153 E-mail: [email protected] Website: http://csp.res.in Front Cover: Superposed photos of the earth taken from a camera on board a balloon borne mission and the sky at Ionospheric and Earthquake Research Center of ICSP taken by Mr.
    [Show full text]
  • Federal Communications Commission § 73.1730
    Federal Communications Commission § 73.1730 writing, is signed by the licensees of ing daytime and until local sunset if the stations affected thereby and filed located west of the Class A station on in triplicate by each licensee with the the channel, or until local sunset at FCC in Washington, DC prior to the the Class A station if located east of time of the time of the proposed that station. Operation is also per- change. If time is of the essence, the mitted during nighttime hours not actual departure in operating schedule used by the Class A station or other may precede the actual filing of writ- stations on the channel. ten agreement, provided appropriate (b) No authorization will be granted notice is sent to the FCC. for: (d) If the license of an AM station au- (1) A new limited time station; thorized to share time does not specify (2) A limited time station operating the hours of operation, the station may on a changed frequency; be operated for the transmission of reg- (3) A limited time station with a new ular programs during the experimental transmitter site materially closer to period provided an agreement thereto the 0.1 mV/m contour of a co-channel is reached with the other stations with U.S. Class A station; or which the broadcast day is shared: And (4) Modification of the operating fa- further provided, Such operation is not cilities of a limited time station result- in conflict with § 73.72 (Operating dur- ing in increased radiation toward any ing the experimental period).
    [Show full text]
  • The Effectiveness of Daytime Running Lights for Passenger Vehicles
    DOT HS 811 029 September 2008 The Effectiveness of Daytime Running Lights For Passenger Vehicles This report is free of charge from the NHTSA Web site at www.nhtsa.dot.gov This publication is distributed by the U.S. Department of Transportation, National Highway Traffic Safety Administration, in the interest of information exchange. The opinions, findings and conclusions expressed in this publication are those of the author(s) and not necessarily those of the Department of Transportation or the National Highway Traffic Safety Administration. The United States Government assumes no liability for its content or use thereof. If trade or manufacturers’ names or products are mentioned, it is because they are considered essential to the object of the publication and should not be construed as an endorsement. The United States Government does not endorse products or manufacturers. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. DOT HS 811 029 4. Title and Subtitle 5. Report Date The Effectiveness of Daytime Running Lights for Passenger Vehicles September 2008 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Jing-Shiarn Wang 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Office of Regulatory Analysis and Evaluation 11. Contract or Grant No. National Center for Statistics and Analysis National Highway Traffic Safety Administration Washington, DC 20590 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Department of Transportation National Highway Traffic Safety Administration NHTSA Technical Report 1200 New Jersey Avenue SE. 14. Sponsoring Agency Code Washington, DC 20590 15.
    [Show full text]
  • Digital Daylight Observations of the Planets with Small Telescopes
    EPSC Abstracts Vol. 8, EPSC2013-795, 2013 European Planetary Science Congress 2013 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2013 Digital daylight observations of the planets with small telescopes Emmanouel (Manos) I. Kardasis (1) (1) Hellenic Amateur Astronomy Association , Athens-Greece [email protected] / Tel.00306945335808 ) Abstract the planetary imaging methodology with the sun above the horizon and some observational results. Planetary atmospheres are extremely dynamical, showing a variety of phenomena at different spatial 2. Methodology and temporal scales, therefore continuous monitoring is required. Amateur astronomers have The basic steps of digital planetary observations are provided a great amount of observations in the presented at [6]. Though, there are some special astronomical community. Some of which are difficulties in DDO, which will be presented along unique made under difficult observational with some solutions: conditions. When the planets are close to the sun, observations can only be made either in twilight or 1. Telescope base alignment. in broad daylight. The use of digital technology in recent years has made feasible daytime planetary 2. Filters observing programs. In this work we present the methodology and some results of digital daylight 3. Position of the planet in the sky observations (DDO) of planets obtained with a small telescope (11inches, 0.28 m). This work may 4. Finding the planet motivate more observers to digitally observe the planets during the day especially when this can be 5. Planetary viewing on the pc screen / important and unique. Focusing 1. Introduction 6. Camera settings Amateur astronomers worldwide continuously 7. Reflections & Thermal heating capturing many interesting hi-resolution images of the ever changing planetary atmospheres.
    [Show full text]
  • HF Radio Propagation
    Introduction to HF Radio Propagation 1. The Ionosphere 1.1 The Regions of the Ionosphere In a region extending from a height of about 50 km to over 500 km, most of the molecules of the atmosphere are ionised by radiation from the Sun. This region is called the ionosphere (see Figure 1.1). Ionisation is the process in which electrons, which are negatively charged, are removed from neutral atoms or molecules to leave positively charged ions and free electrons. It is the ions that give their name to the ionosphere, but it is the much lighter and more freely moving electrons which are important in terms of HF (high frequency) radio propagation. The free electrons in the ionosphere cause HF radio waves to be refracted (bent) and eventually reflected back to earth. The greater the density of electrons, the higher the frequencies that can be reflected. During the day there may be four regions present called the D, E, F1 and F2 regions. Their approximate height ranges are: • D region 50 to 90 km; • E region 90 to 140 km; • F1 region 140 to 210 km; • F2 region over 210 km. At certain times during the solar cycle the F1 region may not be distinct from the F2 region with the two merging to form an F region. At night the D, E and F1 regions become very much depleted of free electrons, leaving only the F2 region available for communications. Only the E, F1 and F2 regions refract HF waves. The D region is very important though, because while it does not refract HF radio waves, it does absorb or attenuate them (see Section 1.5).
    [Show full text]
  • Time and Frequency Users' Manual
    ,>'.)*• r>rJfl HKra mitt* >\ « i If I * I IT I . Ip I * .aference nbs Publi- cations / % ^m \ NBS TECHNICAL NOTE 695 U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards Time and Frequency Users' Manual 100 .U5753 No. 695 1977 NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, a technical (3) basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essen- tial services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics
    [Show full text]