Домашнее чтение, перевод №2, страницы 1-3. (Некоторые готовые переводы и другие ДЗ)

AIAA 2011-1600Infotech@Aerospace 201129 - 31 March 2011, St. Louis, MissouriDebris Resistive Acoustic Grid Orbital Navy Sensor(DRAGONS)Michael D. Ramsey1, David J. Ash1, Eric M. Bunker1, Bradley D. Harden1, Tim M. Musmanno1,Christopher R. Anderson2, Hau T. Ngo2,Albert C. Sadilek3, Vincent L. Pisacane4United States Naval Academy, Annapolis, MD, 21412Frank Giovane5Virginia Tech University, Blacksburg, VA, 24060Robert Corsaro6Global Systems Group Inc., at the U. S. Naval Research Laboratory, Washington D.C., 20375Mark J. Burchell7University of Kent Center of Astrophysics & Planetary Science, Canterbury, Kent, CT2 7NH, UKandEugene G.

Stansbery8 and Jer-Chyi Liou8NASA Johnson Space Center Orbital Debris Office, Houston, TX, 77058Orbital debris has become an increasing concern for countries wishing to deploy spaceassets. Orbital debris can impact spacecraft with a relative velocity of up to 15 km persecond and micrometeoroids can travel with relative velocities up to 70 km per second.Consequently, micrometer sized particles can seriously damage spacecraft and spacecraftsubsystems. Ground based radars can only detect particles with a characteristic size greaterthan 0.5-1 cm and ranges less than 1000-2000 kilometers.

The Debris Resistive/ AcousticGrid Orbital Navy Sensor (DRAGONS) is a spacecraft instrument that will detect andmeasure the characteristics of these smaller particles. The mission objective of DRAGONS isto deploy an instrument to detect hypervelocity impacts of particles 50 microns or largerusing inexpensive and low resource technology to collect a sufficient population of data toupdate current debris models. It will provide data on the particle environment to improvedebris and micrometeoroid models and alert spacecraft controllers in real time.

An acousticsubsystem will accomplish the objective by measuring the characteristics of the waveformgenerated by an impacting particle on a spacecraft surface. Obtained simultaneously will bemeasurements of resistance changes caused by broken links of a resistive grid subsystemdeposited on the surface. These sets of observations will provide important complementaryinformation about the characteristics of impact particles, which will lead to a better debrismodel and improved assessment of the risks from space debris. Real time monitoring of thedebris field will permit spacecraft controllers to change orbit parameters to avoid reenteringintensive debris fields.1Midshipman 1/C, Aerospace Engineering Department, USNA, and AIAA Student Member (SS)Co-Investigator, Assistant Professor, Electrical Engineering Department, USNA3Co-Investigator, Aerospace Engineering Department, USNA4Principal investigator, Professor, Aerospace Engineering Department, USNA, and AIAA Fellow5Co-Investigator, Professor, Aerospace Engineering Department, Virginia Tech University6Co-Investigator, Signals Analyst, Global Systems Group Inc., at the U.

S. Naval Research Laboratory7Professor, Center of Astrophysics & Planetary Science, University of Kent8Co-Investigator, Orbital Debris Office, NASA Johnson Space Center1American Institute of Aeronautics and Astronautics2This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.I. IntroductionOII.

Mission RequirementsThe technical requirements for the DRAGONS instrument are to:a. Detect impacts of particles greater than 50 microns in diameterb. Determine the physical characteristics of the impacting particlec. Utilize minimal resources so the instrument would be a candidate for repeated missionsd. Minimize powere. Minimize massf.

Assure a mission life of at least one yearg. Collect sufficient data to update the NASA orbital debris modelThe orbital requirements for the mission to sample the region of greatest uncertainty are:2American Institute of Aeronautics and Astronautics2010200820062004200220001998199619941992199019881986198419821980197819761974197219701968196619641962196019581956Number of Objectsrbital Debris is becoming an issue of increasing concern for space missions. Low Earth, semisynchronous, andgeosynchronous altitudes contain the densest amounts of spacecraft and as a result have the most orbital debris.Low Earth orbits have the densest orbital debris due to two recent events. In January 2007, the Chinese performedan ASAT test where they destroyed one of their weather satellites.

This intercept created at least 2600 pieces oforbital debris greater than 10 cm in diameter as well as millions of micro-debris particles. In February 2009, asatellite from the Iridium constellation and a retired Russian Cosmos satellite collided and created numerous piecesof orbital debris. The Chinese ASAT test and the Iridium Cosmos collision occurred near the same orbital altitude(Chinese ASAT: mean altitude of 865 km and Iridium Cosmos: 792 km) making spacecraft launched into thisaltitude particularly vulnerable toimpacts from space debris.

TheseMonthly Number of Objects in Earth Orbit by Object Type16000two events together constitute about15000Iridium-Cosmosone quarter of the estimated orbital14000Total Objectsdebris population.13000Fragmentation DebrisMission planners require the mostFY-1C ASAT Test12000Spacecraftup to date models of the space11000Mission-related Debrisenvironment. The U.S. Space10000Rocket Bodies9000Surveillance Network (US-SSN) and8000NASA Orbital Debris Office7000provide this data1. The US-SSN6000tracks orbital debris greater than 105000cm using radars and electro-optic4000systems.

NASA uses radars to detect3000particles as small as 5 mm and2000examines returning spacecraft and1000components for impacts for more0insight about the orbital debris andmicrometeoroid environment. ThisYearinformation is the basis for theFigure 1. Total orbital debris by year.current NASA orbital debrisengineering model, ORDEM2000. ORDEM2000 is a model of the space environment from altitudes of 200 to 2000km. However, with the Chinese ASAT test and Iridium Cosmos Collision producing thousands of undetectableparticles, the ORDEM2000 model would benefit from observations at 800-900 km altitudes.

Figure 1 shows theamount of orbital debris tracked by US-SSN that man has created2. The drastic increases in orbital debris are fromthe Chinese ASAT test and the Iridium -Cosmos collision.Currently, spacecraft like the International Space Station (ISS) use various methods like Whipple shields todefend themselves against orbital debris. Although the current methods to protect spacecraft from the orbital debrisenvironment have been successful, they are costly and add significant mass to the spacecraft.The objective of the DRAGONS project is to develop an instrument to detect hypervelocity impacts of particles50 microns and larger using inexpensive and low resource technology and obtain a sufficient population of data toupdate the current NASA orbital debris model.

DRAGONS has been approved by the DOD Space ExperimentsReview Board for a potential flight on an unspecified DOD spacecraft.a. Altitude of 800-900 kmb. Lifetime of 3 years or morec. Any non-equatorial inclinationAt altitudes between 800-900 km, the sample debris rate is estimated to be about 1000 particles per year persquare meter of area3. Our current estimates of the instrument characteristics are that it will have a mass of 3 kg andconsume about 2 W of power.

The data rate will be 448 kb per day and will be stored in the instrument memory andaccessed and transmitted by the communication system of the host spacecraft at the latter’s convenience.III. Systems OverviewThe overall system concept of the DRAGONS mission is illustrated in Figure 2. The DRAGONS instrumentconsists of three subsystems: a resistive grid subsystem, an acoustic subsystem, and an integrated electronicssubsystem.

The acoustic subsystem is the primary sensor system with the purpose of the resistive grid to verify thecharacteristics deduced from the acoustic subsystem. Once this verification has been established, future missionswould only need to utilize the acoustic subsystem. The transducers of the acoustic subsystem detect the waveform asthe impact wave propagates from itsHostimpact location. The differential times ofSpacecraftreceipt of 4 spatially separatedHypervelocitytransducers will permit determination ofparticlethe impact time, propagation velocity ofthe waveform, and the impact location.ImpactThe signal waveform is related to theproducesenergy transferred by the impact, whichacoustic wavescan be related to particle kinetic energyDRAGONS Panels (0.5m x 0.5m)or momentum.

The shape of thewaveform can also be used todiscriminate an impact signal fromCommsextraneous noise. The resistive gridsubsystem identifies the size of theimpact crater and provides a definiteCommandindication that a particle impact event,Requestsoccurred at the location identified. ItUSNAconsists of a series of microscopic linesHost SpacecraftAcoustic &Satelliteof resistive material deposited on theGround Station &Resistiveacoustic substrate.

When a particleTelemetry Data Mission Controlimpacts the resistive grid breaking lines,the change in resistance provides ameasure of the number of lines brokenFigure 2. DRAGONS overall mission concept.and therefore the size of the impactcrater. Preliminary testing of a Duroidboard shows that the ratio of the size of the impact crater to the diameter of the particle is about a factor of 2.4 for awide range of energies.The electronics subsystem consists of the necessary components to measure and store the acoustic waveformsand the resistive grid observations for transmission to the ground by the host spacecraft’s communication system.To achieve a surface area of 1 m2 with minimal impact to the host spacecraft, the DRAGONS instrument consists of4 independent identical panels of 0.5 x 0.5 meters in size as illustrated in Figure 3.2. Each panel consists of anacoustics subsystem, a resistive-grid subsystem, and the supporting electronics subsystem..IV.

DRAGONS SubsystemsA. Resistive Grid SubsystemAs indicated earlier, the objective of the resistive grid is to verify the characteristics inferred from the particleimpacts recorded by the acoustic system. To accomplish this, the resistive grid subsystem must be able to withstanda particle impact, measure the impact diameter to determine particle size, have long-term resistive stability, and musthave a stable or repeated resistance as its temperature changes.3American Institute of Aeronautics and AstronauticsThe resistive grid consists of a parallel set of resistive lines (1640 per grid) such that when one or more lines arebroken in an impact, the overall resistance of the grid increases, represented as a voltage change in the electronics.Each of the resistive lines is 75 microns in diameter, with spacing between lines of 75 microns.