Mathematics – Probability
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.336p&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Mathematics
Probability
Scientific paper
The paper is devoted to the actual problem of securing reliable radio communications with manned and unmanned spacecrafts using electric propulsion systems (EPS) as sustainer engines during their missions to the planets of Solar system and beyond it. The problem actuality is in that any electric propulsion (EP) is a source of interference broadband emission being within the space communication frequency range, as a rule. [1]. If for the geostationary communications satellites, equipped with low- power (1-3 kW) EP's for the orbit correction and station-keeping, the interference effect is insubstantial due to the high energetic potential of the radio line, the situation changes principally for the deep space spacecrafts. Energetic potential of the long-distance radio line is defined by the ultimate capabilities of ground transmitters and drops abruptly with the distance growth. Power of advanced sustainer EPS (as of a set of individual EP's, in the simplest case) may, in the limit, be as high as some MW, and when interference created by it reaches the pass band of onboard receiver, its real sensitivity is reduced substantially. Thus, with the growth of spacecraft distance from the Earth, real conditions may be crated which would lead to the radio communications worsening (up to its complete failure), and thus to the growth of risk and reduction of safety for the mission as it is. Under these conditions, securing of reliable communications during the entire spacecraft mission is a complex scientific problem requiring a systematic approach for its solving. Parameters and characteristics of modern lines for the long-distance space radio communications are analyzed in the paper on the basis of systematic approach. Operational characteristics of radio channels defining their main purpose are studied as systematic indications of reliability and operation quality. Such indications comprise: data transfer rate, error probability, etc. The potentially achievable characteristics of modern radio lines for securing communications with interplanet spacecrafts are assessed for the given reliability indices, defining the required safety level for the mission. EP effect is taken into account by statistical analysis for the results of joint action of the desired signal and interference created by EP upon the radio line quality indices. In this case, dynamics of EP interference characteristics variation during its lifetime is taken into account. Test data for the EP interference level within the frequency range of space communications was used for quantitative estimations. The required measurements were made by the authors on the basis of test procedure developed by them for assessing the EP self-emission under ground conditions that may be used as a base for the certification of such measurements. Analysis was made on the basis of test data obtained for the EP effect upon the radio communications reliability that is displayed by the reduction of maximum data transfer range and rate for the radio line. Results are generalized for the case of application of EPS (a set of individual EP) of arbitrary power. Parameters are assessed on the basis of analysis made for the integral mission risk, which are connected with the worsening (failure) of radio communication with interplanet spacecrafts equipped with EPS. Recommendations are given on the choice of parameters for EPS and spacecraft radio complex for securing required reliability for communications with manned and unmanned spacecrafts equipped with sustainer EPS. 1. A.P.Plokhikh, N.A.Vazhenin, G.V.Soganova "Methods for Investigating the Influence of Self-Induced Electromagnetic Emission of Electric Propulsions Upon the Sensitivity Characteristics of Onboard Radio Systems of Spacecrafts", IEPC-01- 257, 27th International Electric Propulsion Conference, October 14-19, 2001, Pasadena, CA.
Plokhikh A. P.
Soganova G. V.
Vazhenin N. A.
Volkovsky A. S.
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