1 Crossings of Geostationary Orbit by Themis
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Electric Propulsion System Scaling for Asteroid Capture-And-Return Missions
Electric propulsion system scaling for asteroid capture-and-return missions Justin M. Little⇤ and Edgar Y. Choueiri† Electric Propulsion and Plasma Dynamics Laboratory, Princeton University, Princeton, NJ, 08544 The requirements for an electric propulsion system needed to maximize the return mass of asteroid capture-and-return (ACR) missions are investigated in detail. An analytical model is presented for the mission time and mass balance of an ACR mission based on the propellant requirements of each mission phase. Edelbaum’s approximation is used for the Earth-escape phase. The asteroid rendezvous and return phases of the mission are modeled as a low-thrust optimal control problem with a lunar assist. The numerical solution to this problem is used to derive scaling laws for the propellant requirements based on the maneuver time, asteroid orbit, and propulsion system parameters. Constraining the rendezvous and return phases by the synodic period of the target asteroid, a semi- empirical equation is obtained for the optimum specific impulse and power supply. It was found analytically that the optimum power supply is one such that the mass of the propulsion system and power supply are approximately equal to the total mass of propellant used during the entire mission. Finally, it is shown that ACR missions, in general, are optimized using propulsion systems capable of processing 100 kW – 1 MW of power with specific impulses in the range 5,000 – 10,000 s, and have the potential to return asteroids on the order of 103 104 tons. − Nomenclature -
AFSPC-CO TERMINOLOGY Revised: 12 Jan 2019
AFSPC-CO TERMINOLOGY Revised: 12 Jan 2019 Term Description AEHF Advanced Extremely High Frequency AFB / AFS Air Force Base / Air Force Station AOC Air Operations Center AOI Area of Interest The point in the orbit of a heavenly body, specifically the moon, or of a man-made satellite Apogee at which it is farthest from the earth. Even CAP rockets experience apogee. Either of two points in an eccentric orbit, one (higher apsis) farthest from the center of Apsis attraction, the other (lower apsis) nearest to the center of attraction Argument of Perigee the angle in a satellites' orbit plane that is measured from the Ascending Node to the (ω) perigee along the satellite direction of travel CGO Company Grade Officer CLV Calculated Load Value, Crew Launch Vehicle COP Common Operating Picture DCO Defensive Cyber Operations DHS Department of Homeland Security DoD Department of Defense DOP Dilution of Precision Defense Satellite Communications Systems - wideband communications spacecraft for DSCS the USAF DSP Defense Satellite Program or Defense Support Program - "Eyes in the Sky" EHF Extremely High Frequency (30-300 GHz; 1mm-1cm) ELF Extremely Low Frequency (3-30 Hz; 100,000km-10,000km) EMS Electromagnetic Spectrum Equitorial Plane the plane passing through the equator EWR Early Warning Radar and Electromagnetic Wave Resistivity GBR Ground-Based Radar and Global Broadband Roaming GBS Global Broadcast Service GEO Geosynchronous Earth Orbit or Geostationary Orbit ( ~22,300 miles above Earth) GEODSS Ground-Based Electro-Optical Deep Space Surveillance -
NTI Day 9 Astronomy Michael Feeback Go To: Teachastronomy
NTI Day 9 Astronomy Michael Feeback Go to: teachastronomy.com textbook (chapter layout) Chapter 3 The Copernican Revolution Orbits Read the article and answer the following questions. Orbits You can use Newton's laws to calculate the speed that an object must reach to go into a circular orbit around a planet. The answer depends only on the mass of the planet and the distance from the planet to the desired orbit. The more massive the planet, the faster the speed. The higher above the surface, the lower the speed. For Earth, at a height just above the atmosphere, the answer is 7.8 kilometers per second, or 17,500 mph, which is why it takes a big rocket to launch a satellite! This speed is the minimum needed to keep an object in space near Earth, and is called the circular velocity. An object with a lower velocity will fall back to the surface under Earth's gravity. The same idea applies to any object in orbit around a larger object. The circular velocity of the Moon around the Earth is 1 kilometer per second. The Earth orbits the Sun at an average circular velocity of 30 kilometers per second (the Earth's orbit is an ellipse, not a circle, but it's close enough to circular that this is a good approximation). At further distances from the Sun, planets have lower orbital velocities. Pluto only has an average circular velocity of about 5 kilometers per second. To launch a satellite, all you have to do is raise it above the Earth's atmosphere with a rocket and then accelerate it until it reaches a speed of 7.8 kilometers per second. -
Orbit and Spin
Orbit and Spin Overview: A whole-body activity that explores the relative sizes, distances, orbit, and spin of the Sun, Earth, and Moon. Target Grade Level: 3-5 Estimated Duration: 2 40-minute sessions Learning Goals: Students will be able to… • compare the relative sizes of the Earth, Moon, and Sun. • contrast the distance between the Earth and Moon to the distance between the Earth and Sun. • differentiate between the motions of orbit and spin. • demonstrate the spins of the Earth and the Moon, as well as the orbits of the Earth around the Sun, and the Moon around the Earth. Standards Addressed: Benchmarks (AAAS, 1993) The Physical Setting, 4A: The Universe, 4B: The Earth National Science Education Standards (NRC, 1996) Physical Science, Standard B: Position and motion of objects Earth and Space Science, Standard D: Objects in the sky, Changes in Earth and sky Table of Contents: Background Page 1 Materials and Procedure 5 What I Learned… Science Journal Page 14 Earth Picture 15 Sun Picture 16 Moon Picture 17 Earth Spin Demonstration 18 Moon Orbit Demonstration 19 Extensions and Adaptations 21 Standards Addressed, detailed 22 Background: Sun The Sun is the center of our Solar System, both literally—as all of the planets orbit around it, and figuratively—as its rays warm our planet and sustain life as we know it. The Sun is very hot compared to temperatures we usually encounter. Its mean surface temperature is about 9980° Fahrenheit (5800 Kelvin) and its interior temperature is as high as about 28 million° F (15,500,000 Kelvin). -
Up, Up, and Away by James J
www.astrosociety.org/uitc No. 34 - Spring 1996 © 1996, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112. Up, Up, and Away by James J. Secosky, Bloomfield Central School and George Musser, Astronomical Society of the Pacific Want to take a tour of space? Then just flip around the channels on cable TV. Weather Channel forecasts, CNN newscasts, ESPN sportscasts: They all depend on satellites in Earth orbit. Or call your friends on Mauritius, Madagascar, or Maui: A satellite will relay your voice. Worried about the ozone hole over Antarctica or mass graves in Bosnia? Orbital outposts are keeping watch. The challenge these days is finding something that doesn't involve satellites in one way or other. And satellites are just one perk of the Space Age. Farther afield, robotic space probes have examined all the planets except Pluto, leading to a revolution in the Earth sciences -- from studies of plate tectonics to models of global warming -- now that scientists can compare our world to its planetary siblings. Over 300 people from 26 countries have gone into space, including the 24 astronauts who went on or near the Moon. Who knows how many will go in the next hundred years? In short, space travel has become a part of our lives. But what goes on behind the scenes? It turns out that satellites and spaceships depend on some of the most basic concepts of physics. So space travel isn't just fun to think about; it is a firm grounding in many of the principles that govern our world and our universe. -
Multisatellite Determination of the Relativistic Electron Phase Space Density at Geosynchronous Orbit: Methodology and Results During Geomagnetically Quiet Times Y
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, A10210, doi:10.1029/2004JA010895, 2005 Multisatellite determination of the relativistic electron phase space density at geosynchronous orbit: Methodology and results during geomagnetically quiet times Y. Chen, R. H. W. Friedel, and G. D. Reeves Los Alamos National Laboratory, Los Alamos, New Mexico, USA T. G. Onsager NOAA, Boulder, Colorado, USA M. F. Thomsen Los Alamos National Laboratory, Los Alamos, New Mexico, USA Received 10 November 2004; revised 20 May 2005; accepted 8 July 2005; published 20 October 2005. [1] We develop and test a methodology to determine the relativistic electron phase space density distribution in the vicinity of geostationary orbit by making use of the pitch-angle resolved energetic electron data from three Los Alamos National Laboratory geosynchronous Synchronous Orbit Particle Analyzer instruments and magnetic field measurements from two GOES satellites. Owing to the Earth’s dipole tilt and drift shell splitting for different pitch angles, each satellite samples a different range of Roederer L* throughout its orbit. We use existing empirical magnetic field models and the measured pitch-angle resolved electron spectra to determine the phase space density as a function of the three adiabatic invariants at each spacecraft. Comparing all satellite measurements provides a determination of the global phase space density gradient over the range L* 6–7. We investigate the sensitivity of this method to the choice of the magnetic field model and the fidelity of the instrument intercalibration in order to both understand and mitigate possible error sources. Results for magnetically quiet periods show that the radial slopes of the density distribution at low energy are positive, while at high energy the slopes are negative, which confirms the results from some earlier studies of this type. -
Positioning: Drift Orbit and Station Acquisition
Orbits Supplement GEOSTATIONARY ORBIT PERTURBATIONS INFLUENCE OF ASPHERICITY OF THE EARTH: The gravitational potential of the Earth is no longer µ/r, but varies with longitude. A tangential acceleration is created, depending on the longitudinal location of the satellite, with four points of stable equilibrium: two stable equilibrium points (L 75° E, 105° W) two unstable equilibrium points ( 15° W, 162° E) This tangential acceleration causes a drift of the satellite longitude. Longitudinal drift d'/dt in terms of the longitude about a point of stable equilibrium expresses as: (d/dt)2 - k cos 2 = constant Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF EARTH ASPHERICITY VARIATION IN THE LONGITUDINAL ACCELERATION OF A GEOSTATIONARY SATELLITE: Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF SUN & MOON ATTRACTION Gravitational attraction by the sun and moon causes the satellite orbital inclination to change with time. The evolution of the inclination vector is mainly a combination of variations: period 13.66 days with 0.0035° amplitude period 182.65 days with 0.023° amplitude long term drift The long term drift is given by: -4 dix/dt = H = (-3.6 sin M) 10 ° /day -4 diy/dt = K = (23.4 +.2.7 cos M) 10 °/day where M is the moon ascending node longitude: M = 12.111 -0.052954 T (T: days from 1/1/1950) 2 2 2 2 cos d = H / (H + K ); i/t = (H + K ) Depending on time within the 18 year period of M d varies from 81.1° to 98.9° i/t varies from 0.75°/year to 0.95°/year Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF SUN RADIATION PRESSURE Due to sun radiation pressure, eccentricity arises: EFFECT OF NON-ZERO ECCENTRICITY L = difference between longitude of geostationary satellite and geosynchronous satellite (24 hour period orbit with e0) With non-zero eccentricity the satellite track undergoes a periodic motion about the subsatellite point at perigee. -
Geosynchronous Orbit Determination Using Space Surveillance Network Observations and Improved Radiative Force Modeling
Geosynchronous Orbit Determination Using Space Surveillance Network Observations and Improved Radiative Force Modeling by Richard Harry Lyon B.S., Astronautical Engineering United States Air Force Academy, 2002 SUBMITTED TO THE DEPARTMENT OF AERONAUTICS AND ASTRONAUTICS IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN AERONAUTICS AND ASTRONAUTICS AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY JUNE 2004 0 2004 Massachusetts Institute of Technology. All rights reserved. Signature of Author: Department of Aeronautics and Astronautics May 14, 2004 Certified by: Dr. Pa1 J. Cefola Technical Staff, the MIT Lincoln Laboratory Lecturer, Department of Aeronautics and Astronautics Thesis Supervisor Accepted by: Edward M. Greitzer H.N. Slater Professor of Aeronautics and Astronautics MASSACHUSETTS INS E OF TECHNOLOGY Chair, Committee on Graduate Students JUL 0 1 2004 AERO LBRARIES [This page intentionally left blank.] 2 Geosynchronous Orbit Determination Using Space Surveillance Network Observations and Improved Radiative Force Modeling by Richard Harry Lyon Submitted to the Department of Aeronautics and Astronautics on May 14, 2004 in Partial Fulfillment of the Requirements for the Degree of Master of Science in Aeronautics and Astronautics ABSTRACT Correct modeling of the space environment, including radiative forces, is an important aspect of space situational awareness for geostationary (GEO) spacecraft. Solar radiation pressure has traditionally been modeled using a rotationally-invariant sphere with uniform optical properties. This study is intended to improve orbit determination accuracy for 3-axis stabilized GEO spacecraft via an improved radiative force model. The macro-model approach, developed earlier at NASA GSFC for the Tracking and Data Relay Satellites (TDRSS), models the spacecraft area and reflectivity properties using an assembly of flat plates to represent the spacecraft components. -
An Introduction to Rockets -Or- Never Leave Geeks Unsupervised
An Introduction to Rockets -or- Never Leave Geeks Unsupervised Kevin Mellett 27 Apr 2006 2 What is a Rocket? • A propulsion system that contains both oxidizer and fuel • NOT a jet, which requires air for O2 3 A Brief History • 400 BC – Steam Bird • 100 BC – Hero Engine • 100 AD – Gunpowder Invented in China – Celebrations – Religious Ceremonies – Bamboo Misfires? 4 A Brief History • Chinese Invent Fire Arrows 13th c – First True Rockets •16th c Wan-Hu – 47 Rockets 5 A Brief History •13th –16th c Improvements in Technology – English Improved Gunpowder – French Improved Guidance by Shooting Through a Tube “Bazooka Style” – Germans Invented “Step Rockets” (Staging) 6 A Brief History • 1687 Newton Publishes Principia Mathematica 7 Newton’s Third Law MOMENTUM is the key concept of rocketry 8 A Brief History • 1903 KonstantineTsiolkovsky Publishes the “Rocket Equation” – Proposes Liquid Fuel ⎛ Mi ⎞ V = Ve*ln⎜ ⎟ ⎝ Mf ⎠ 9 A Brief History • Goddard Flies the First Liquid Fueled Rocket on 16 Mar 1926 – Theorized Rockets Would Work in a Vacuum – NY Times: Goddard “…lacks the basic physics ladeled out in our high schools…” 10 A Brief History • Germans at Peenemunde – Oberth and von Braun lead development of the V-2 – Amazing achievement, but too late to change the tide of WWII – After WWII, USSR and USA took German Engineers and Hardware 11 Mission Requirements • Launch On Need – No Time for Complex Pre-Launch Preps – Long Shelf Life • Commercial / Government – Risk Tolerance –R&D Costs 12 Mission Requirements • Payload Mass and Orbital Objectives – How much do you need, and where do you want it? Both drive energy requirements. -
Richard Dalbello Vice President, Legal and Government Affairs Intelsat General
Commercial Management of the Space Environment Richard DalBello Vice President, Legal and Government Affairs Intelsat General The commercial satellite industry has billions of dollars of assets in space and relies on this unique environment for the development and growth of its business. As a result, safety and the sustainment of the space environment are two of the satellite industry‘s highest priorities. In this paper I would like to provide a quick survey of past and current industry space traffic control practices and to discuss a few key initiatives that the industry is developing in this area. Background The commercial satellite industry has been providing essential space services for almost as long as humans have been exploring space. Over the decades, this industry has played an active role in developing technology, worked collaboratively to set standards, and partnered with government to develop successful international regulatory regimes. Success in both commercial and government space programs has meant that new demands are being placed on the space environment. This has resulted in orbital crowding, an increase in space debris, and greater demand for limited frequency resources. The successful management of these issues will require a strong partnership between government and industry and the careful, experience-based expansion of international law and diplomacy. Throughout the years, the satellite industry has never taken for granted the remarkable environment in which it works. Industry has invested heavily in technology and sought out the best and brightest minds to allow the full, but sustainable exploitation of the space environment. Where problems have arisen, such as space debris or electronic interference, industry has taken 1 the initiative to deploy new technologies and adopt new practices to minimize negative consequences. -
Analysis of Transfer Maneuvers from Initial
Revista Mexicana de Astronom´ıa y Astrof´ısica, 52, 283–295 (2016) ANALYSIS OF TRANSFER MANEUVERS FROM INITIAL CIRCULAR ORBIT TO A FINAL CIRCULAR OR ELLIPTIC ORBIT M. A. Sharaf1 and A. S. Saad2,3 Received March 14 2016; accepted May 16 2016 RESUMEN Presentamos un an´alisis de las maniobras de transferencia de una ´orbita circu- lar a una ´orbita final el´ıptica o circular. Desarrollamos este an´alisis para estudiar el problema de las transferencias impulsivas en las misiones espaciales. Consideramos maniobras planas usando ecuaciones reci´enobtenidas; con estas ecuaciones se com- paran las maniobras circulares y el´ıpticas. Esta comparaci´on es importante para el dise˜no´optimo de misiones espaciales, y permite obtener mapeos ´utiles para mostrar cu´al es la mejor maniobra. Al respecto, desarrollamos este tipo de comparaciones mediante 10 resultados, y los mostramos gr´aficamente. ABSTRACT In the present paper an analysis of the transfer maneuvers from initial circu- lar orbit to a final circular or elliptic orbit was developed to study the problem of impulsive transfers for space missions. It considers planar maneuvers using newly derived equations. With these equations, comparisons of circular and elliptic ma- neuvers are made. This comparison is important for the mission designers to obtain useful mappings showing where one maneuver is better than the other. In this as- pect, we developed this comparison throughout ten results, together with some graphs to show their meaning. Key Words: celestial mechanics — methods: analytical — space vehicles 1. INTRODUCTION The large amount of information from interplanetary missions, such as Pioneer (Dyer et al. -
GEO, MEO, and LEO How Orbital Altitude Impacts Network Performance in Satellite Data Services
GEO, MEO, AND LEO How orbital altitude impacts network performance in satellite data services COMMUNICATION OVER SATELLITE “An entire multi-orbit is now well accepted as a key enabler across the telecommunications industry. Satellite networks can supplement existing infrastructure by providing global reach satellite ecosystem is where terrestrial networks are unavailable or not feasible. opening up above us, But not all satellite networks are created equal. Providers offer different solutions driving new opportunities depending on the orbits available to them, and so understanding how the distance for high-performance from Earth affects performance is crucial for decision making when selecting a satellite service. The following pages give an overview of the three main orbit gigabit connectivity and classes, along with some of the principal trade-offs between them. broadband services.” Stewart Sanders Executive Vice President of Key terms Technology at SES GEO – Geostationary Earth Orbit. NGSO – Non-Geostationary Orbit. NGSO is divided into MEO and LEO. MEO – Medium Earth Orbit. LEO – Low Earth Orbit. HTS – High Throughput Satellites designed for communication. Latency – the delay in data transmission from one communication endpoint to another. Latency-critical applications include video conferencing, mobile data backhaul, and cloud-based business collaboration tools. SD-WAN – Software-Defined Wide Area Networking. Based on policies controlled by the user, SD-WAN optimises network performance by steering application traffic over the most suitable access technology and with the appropriate Quality of Service (QoS). Figure 1: Schematic of orbital altitudes and coverage areas GEOSTATIONARY EARTH ORBIT Altitude 36,000km GEO satellites match the rotation of the Earth as they travel, and so remain above the same point on the ground.