1、Ob95534 O002083 TT4 = Special Copy right Notice 1994 by the American Institute of Aeronautics and Astronautics. All rights reserved. COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob9 94 = Ob95534 0003797 T78 AIAA SP-069-1994 Contemporary
2、 Models of the Orbital Envi ron ment COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob7 74 W Ob75534 OOOL778 TOY AIAA SP-069- 1994 Special Project Report Contemporary Models of the Orbital Environment Robert A. Skrivanek, Editor Abstract
3、The six papers included in this Special Report were presented at the AIAA Aerospace Sciences Meeting in January 1994. They provide state-of-the-art knowledge about ionospheric, radiation, neutral density, space debris, and thermal environments. The papers will be employed in the development of stand
4、ard models for these aspects of the orbital environment. COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob9 94 Ob95534 0003777 840 Published by American Institute of Aeronautics and Astronautics 370 LEnfant Promenade, SW, Washington, DC 2
5、0024 Copyright O 1994 American Institute of Aeronautics and Astronautics All rights reserved No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America COPYRIGHT
6、 American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob9 94 = 0675534 OOOLBOO 392 H AMA SP-069-1994 CONTENTS Foreword . . 1 Ionospheric Models The Space Radiation Environment 29 65 Neutral Density Models for Aerospace Applications 81 Orbital Debris Envi
7、ronment: An Update . Space Debris Reentry Risk Analysis . Thermal Environment in Space for Engineering Applications . 89 105 . 111 COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob9 94 m Ob95534 OOOLBOL 229 m AIAA SP-069-1994 iv COPYRIGHT
8、 American Institute of Aeronautics and AstronauticsLicensed by Information Handling ServicesAIAA SP-Ob7 74 m Ob75534 0001802 1b5 Foreword The Air Force and NASA Co-leaders of the Space Technology Interdependency Group (STIG) have noted recently that more effort is needed to encourage the application
9、 of available knowledge toward specifying and modeling the interaction and effect of the space environment on space systems. This need exists despite the significant amount of progress that has been achieved mutually by both organizations in measuring and model- ing the physical and chemical propert
10、ies of near Earth space. Our ability to measure, understand, and specify the detailed characteristics of the space environment has improved steadily since the first simplified measurements were made using research balloons and sounding rockets. The lead agencies for sponsoring and performing many of
11、 the these measure- ments have been the US Air Force and NASA. Each of these agencies has had its own requirements and priorities for obtain- ing the various specific measurements of the space environment. Through the years each has accumulated a comprehensive collection of data sets and models. Thi
12、s information, as it was being collected, analyzed, and assembled, has been used by the spacecraft design groups in government agencies and industrial concerns throughout the United States. Hundreds of military and civilian satellites, designed and built for both research and operational purposes, h
13、ave benefited from this evolving data over the last 30 years. The space environment data that was used by these satellite designers has not always been easily accessible nor easily understood. In most cases the data or models were gen- erated by scientists who were driven more by their desire to und
14、erstand particular geo- physical phenomena than they were to de- velop an engineering guide or translate a space measurement into a systems design standard. Generally speaking, the space sci - entists have been very successful. We are still surprised occasionally by a new space environment measureme
15、nt, but by and large, space scientists have provided us with an AIAA SP469-1994 excellent understanding of near Earth space that may well continue to be refined, but is not likely to change dramatically. As mentioned, the Co-leaders of the Air ForceNASA group concerned with the in- terdependency of
16、their space programs feel that more effort is needed to encourage the interaction between NASA and Air Force working level scientists and the hands-on space systems engineers in industry and government that design, build, and operate space systems. A technical meeting, at which a series of survey pa
17、pers describing the characteristics of available empirical and theoretical models in select areas of interest to the space systems community seemed to be a reasonable approach. It was decided that a well-attended, national, AIAA meet- ing, with its diverse participation that in- clude some scientist
18、s, as well as a large number of engineers and managers from industry and government, would provide a very appropriate forum. I had the privilege of being asked to orga- nize one technical session for the 1994 Aerospace Sciences Meeting. In this ses- sion, a small group of scientists, each well estab
19、lished and respected in his field, would present the characteristics of available on- orbit space environment models. The speakers would describe which models were appropriate under which conditions, what assumptions were made within a particular model, and the effect of these assumptions on the mod
20、els product. The session con- tained six papers and attracted an audience twice as large as expected. The consensus of the audience was that the presented mate- rial was interesting, useful to the engineering community, and that the program should be expanded to include additional types of space dat
21、a and models the following year. This publication, based on the papers in that session, is another step toward facilitating the availability of space environment data and models to the designers and builders of civilian and military space systems. While this material addresses a limited number of to
22、pics, it is comprehensive and up to date for the specific areas covered and should of use of the space systems community. V COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling Services AIAA SP-Ob9 94 Ob95534 0001803 OT1 D AIAA SP-069-1994 vi COPYRIGHT America
23、n Institute of Aeronautics and AstronauticsLicensed by Information Handling Services- AIAA SP-Ob9 94 m Ob95534 0001804 T38 AIAA SP-069-1994 IONOSPHERIC MODELS H. C. Carlson, Jr. R. W. Schunk USAF Phillips Utah State Laboratory University Hanscom AFB, MA Logan. UT Abstract We seek here to provide a f
24、rame of reference for assessing the present status of iono- spheric modeling, and for determining which models may best serve a particular user need. This choice depends not only on the geo- graphic region, and time of concern (post analysis, nowcast, forecast), but on the accu- racy required by the
25、 user, and the ionospheric parameters of greatest concern. Introduction Development of ionospheric models has been a preoccupation of scientists and engineers for some decades. The continuing interest of the engineers (communications, surveillance) has been motivated by continuing improve- ment of c
26、ommercial and military systems de- pendent on the ionosphere as a component of the total system. This in turn has generated recurring need for further accuracy and re- finement of ionospheric modeling, specifica- tion, and prediction capability, as rf systems saw recurring advances to meet ever more
27、 stringent demands. The continuing interest of scientists has been motivated by the rapid pace of discovery of different regions of the global ionosphere, controlled by very differ- ent physical processes. Furthermore, many global regions exhibit a character often driven by coupling to often very re
28、mote regions of space, by a rich complex of interactive mech- anisms. In the earliest days empirical and climatologi- cal models were adequate for many purposes. Greater accuracy was afforded, at least for over-head or nearby specification, by adding local measurement for real time scaling or calibr
29、ation of the empirical statistical model. Today this is still true for certain applications, and for some regions of the globe it is diffi- cult to improve on this approach. For many R. A. Heelis Sa. Basu University of Texas USAF Phillips at Dallas Laboratory Richardson, TX Hanscom AFB, MA purposes
30、however, particularly those involv- ing larger sectors of the global ionosphere, physical models are the only way to achieve the accuracies required by the needs of today. This is true not only as a particularly effective way of identifying mechanisms controlling ionospheric behavior, but for practi
31、cal appli- cations as well. For the latter purposes, the trend is now clearly towards models driven by real time data. To enhance operating speed, and reduce computational cost, these are often streamlined to the form of analytic or semi-empirical models. These then also form the basis of predictive
32、 models, where the challenge is to break beyond the realm of prediction by persistence. Governing processes: For even simple models, the minimum set of parameters re- quired as input to drive the model are: solar activity, geomagnetic activity, time of day (in general both universal and local time),
33、 sea- son, and latitude (in general both geomag- netic and geographic). To achieve accuracies of tens of percent or better in electron density requires periodic input of measured iono- spheric parameters, with crucial dependence on correlation distances and times. Figure 1 shows a representative mid
34、latitude ionospheric profile, demonstrating some common nominclature. F region plasma typically has chemical lifetimes of hours and is dominated by transport between production and loss; lower altitude plasma has chemical lifetimes of minutes and less, and is domi- nated by local production (solar r
35、adiation and energetic particles) and chemical recombina- tion. Quite different morphologies and physical processes distinguish between equatorial, midlatitude, near auroral, and polar cap iono- spheric conditions. For instance, the equato- rial ionosphere is characterized by strongly enhanced peak
36、electron densities roughly 10- 1 COPYRIGHT American Institute of Aeronautics and AstronauticsLicensed by Information Handling Services AIAA SP-Ob9 94 M Ob95534 0001805 974 AIAA SP-069-1994 20 degrees either side of the equator (the Appleton anomaly). These occur on many, but not all days, depending
37、on a variable equatorial electric-field-driven upward trans- port term. Midlatitude ionospheric electron densities exhibit: strong seasonal variations due in large part to changing upper atmo- spheric composition; and considerable day to day variability due largely but not solely to variable vertica
38、l transport driven by variable horizontal upper atmospheric winds and elecmc fields. Auroral ionospheric electron densities may be anomalously enhanced in the E region by particle production, and de- pleted in the F region by velocity dependent chemical loss rates. Because polar iono- spheric F regi
39、on plasma (with typical life- times of hours) commonly has anti-sunward horizontal transport velocities of order a Ws, the polar cap is characterized by large plasma densities which typically come from source regions thousands of km away. This ionospheric transport is driven by forces originating in
40、 the solar wind, and transmitted via interaction through the magnetosphere. Consequently, the character of the polar ionosphere is critically dependent on the in- terplanetary magnetic field (IMF). The IMF, particularly its vertical component, in fact dominates the polar cap ionospheric electro- dyn
41、amics and energetics, and threrby its plasma densities, thermal structure, and com- position. Despite these complexities, physical models of ionospheric electron densities, when driven by real time data, can produce real time global models with nominal accuracies of a few tens of percent, within cor
42、relation distances less than about a thousand km, and correlation times of a fraction of an hour. Approaches to modeling: Empirical or statis- tical models have been widely used over the last decade, based on a large body of mea- surements, binned by known dependent pa- rameters, and generally analy
43、tically fit. The most comprehensive of these is the International Reference Ionosphere, the RI. It provides a model of the global distribution of electron density , ion composition, and electron and ion temperature and drift. Empirical models also exist for ionospheric high latitude convection, plas
44、ma structuring, auroral particle precipitation, and field aligned currents. Physical models are very effective research tools for identifying missing physical pro- cesses and mechanisms controlling iono- spheric behavior, and for applications are generally the best way to extrapolate and in- terpola
45、te between direct measurements of de- sired parameters. Ab initio calculations grow steadily more accurate as increasingly com- prehensive global data sets and refined mod- els are iterated The model usually solves the continuity, momentum, and energy equations for the electrons and ions, as a funct
46、ion of altitude along curved magnetic field lines, to derive plasma densities, flow velocities, temperatures, and composition. Analytical models can make much of the power of physical models available to a much broader community of users than otherwise economically feasible. An extensive set of phys
47、ical model outputs is fit by sets of rela- tively simple analytic functions, tagged to key parameters, so that the “physical model data“ can be more quickly and easily accessed, us- ing a much smaller and less expensive com- puter. Real time data driven models are the next logical step, combining th
48、e above capabili- ties. These are already on line, with signifi- cantly enhanced capability scheduled for the near future, based on ground based active and passive radio sensors and satellite in situ and remote sensors. User needs: A major model selection crite- rion is user or system requirement. W
49、hat ac- curacy is needed, for which ionospheric pa- rameters, over what sector of the globe, for what time frame, and with what turnaround time. For system applications, the nature of the rf system for which the ionosphere must be specified is a crucial consideration. An HF communication system is concerned with the bottomside ionosphere, where photo- chemistry is important, and the height and magnitude of the peak electron density, de- texminexi by the balance between photochem- istry and vertical transport. The ionospheric span of concern can exceed transcontinental distances. A trans
