Stationkeeping controllers for Earth–Moon L1 and L2 libration points halo orbits

2021 ◽  
Vol 43 (7) ◽  
Author(s):  
Thiago César Lousada Marsola ◽  
Sandro da Silva Fernandes ◽  
José Manoel Balthazar
Keyword(s):  
Libration Points ◽  
Halo Orbits ◽  
L1 And L2

Low-Thrust Transfers to Lunar Orbits from Halo Orbits Around Lunar Libration Points L1 and L2

2020 ◽  
Vol 58 (3) ◽  
pp. 181-191
Author(s):  
M. G. Shirobokov ◽  
S. P. Trofimov
Keyword(s):  
Libration Points ◽  
Low Thrust ◽  
Halo Orbits ◽  
L1 And L2

scholarly journals Use of Libration-Point Orbits for Space Observatories

1990 ◽  
Vol 123 ◽  
pp. 391-395 ◽  
Author(s):  
Robert W. Farquhar ◽  
David W. Dunham
Keyword(s):  
Libration Point ◽  
Libration Points ◽  
Radiation Environment ◽  
The Sun ◽  
Halo Orbits ◽  
Libration Point Orbits ◽  
The Earth ◽  
Space Observatories

AbstractThe Sun-Earth libration points, L1 and L2, are located 1.5 million kilometers from the Earth towards and away from the Sun. Halo orbits about these points have significant advantages for space observatories in terms of viewing geometry, thermal and radiation environment, and delta-V expediture.

Motion Control of Electric Propulsion Spacecraft Transfers between the Libration Points L1 and L2 of the Earth–Moon System

2019 ◽  
pp. 66-74
Author(s):  
M.K. Fain ◽  
O.L. Starinova
Keyword(s):  
Electric Propulsion ◽  
Optimal Solution ◽  
Libration Points ◽  
Coordinate Frame ◽  
Control Laws ◽  
Moon System ◽  
The Earth ◽  
Nonlinear Motion ◽  
Sequential Linearization ◽  
L1 And L2

This article presents a study of nonlinear motion of an electric propulsion spacecraft. Spacecraft transfers between the libration points L1 and L2 of the Earth-Moon system are analyzed. The influence of the shaded areas and gravitational effects of the Earth, the Moon and the Sun is taken into account. The mathematical model of the transfers is described within the barycentric coordinate frame. The exact optimal solution of the problem is obtained using Pontryagin’s maximum principle formalism and the numerical solution of the boundary value problem. The method of optimizing the parameters and controls of interplanetary trajectories of the spacecraft based on the optimization of dynamic system components and on Fedorenko’s method of sequential linearization is applied in this study. This method allows limitations on composite functions with Fréchet derivatives. As the results of the simulation, the control laws and corresponding trajectories are obtained.

Low-Energy Sub-Optimal Low-Thrust Trajectories to Libration Points and Halo-Orbits

2019 ◽  
Vol 57 (5) ◽  
pp. 378-388 ◽  
Author(s):  
A. V. Ivanyukhin ◽  
V. G. Petukhov
Keyword(s):  
Libration Points ◽  
Low Energy ◽  
Low Thrust ◽  
Halo Orbits

Cislunar Periodic Orbit Constellation Assessment for Space Domain Awareness of L1 and L2 Halo Orbits

2021 ◽  
Author(s):  
Adam Wilmer ◽  
Robert A. Bettinger ◽  
Bryan Little
Keyword(s):  
Periodic Orbit ◽  
Space Domain ◽  
Halo Orbits ◽  
L1 And L2

A View of the Lexical–Grammatical Link in Young Latinos With Specific Language Impairment Using Language-Specific and Conceptual Measures

2019 ◽  
Vol 62 (6) ◽  
pp. 1775-1786 ◽  
Author(s):  
Lucía I. Méndez ◽  
Gabriela Simon-Cereijido
Keyword(s):  
Low Income ◽  
Language Impairment ◽  
Specific Language Impairment ◽  
L2 Acquisition ◽  
Cross Sectional ◽  
Specific Language ◽  
Vocabulary Skills ◽  
In The Beginning ◽  
Study Participants ◽  
L1 And L2

Purpose This study investigated the nature of the association of lexical–grammatical abilities within and across languages in Latino dual language learners (DLLs) with specific language impairment (SLI) using language-specific and bilingual measures. Method Seventy-four Spanish/English–speaking preschoolers with SLI from preschools serving low-income households participated in the study. Participants had stronger skills in Spanish (first language [L1]) and were in the initial stages of learning English (second language [L2]). The children's lexical, semantic, and grammar abilities were assessed using normative and researcher-developed tools in English and Spanish. Hierarchical linear regressions of cross-sectional data were conducted using measures of sentence repetition tasks, language-specific vocabulary, and conceptual bilingual lexical and semantic abilities in Spanish and English. Results Results indicate that language-specific vocabulary abilities support the development of grammar in L1 and L2 in this population. L1 vocabulary also contributes to L2 grammar above and beyond the contribution of L2 vocabulary skills. However, the cross-linguistic association between vocabulary in L2 and grammar skills in the stronger or more proficient language (L1) is not observed. In addition, conceptual vocabulary significantly supported grammar in L2, whereas bilingual semantic skills supported L1 grammar. Conclusions Our findings reveal that the same language-specific vocabulary abilities drive grammar development in L1 and L2 in DLLs with SLI. In the early stages of L2 acquisition, vocabulary skills in L1 also seem to contribute to grammar skills in L2 in this population. Thus, it is critical to support vocabulary development in both L1 and L2 in DLLs with SLI, particularly in the beginning stages of L2 acquisition. Clinical and educational implications are discussed.

Measuring Word Learning Ability in Sequential Bilingual Children

2010 ◽  
Vol 17 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Pui Fong Kan
Keyword(s):  
Word Learning ◽  
Learning Ability ◽  
Bilingual Children ◽  
Word Knowledge ◽  
Typically Developing ◽  
Learning Skills ◽  
Word Forms ◽  
The Individual ◽  
Novel Word Learning ◽  
L1 And L2

Abstract The purpose of this article is to look at the word learning skills in sequential bilingual children—children who learn two languages (L1 and L2) at different times in their childhood. Learning a new word is a process of learning a word form and relating this form to a concept. For bilingual children, each concept might need to map onto two word forms (in L1 and in L2). In case studies, I present 3 typically developing Hmong-English bilingual preschoolers' word learning skills in Hmong (L1) and in English (L2) during an 8-week period (4 weeks for each language). The results showed gains in novel-word knowledge in L1 and in L2 when the amount of input is equal for both languages. The individual differences in novel word learning are discussed.

Bilingual Resonance: Reactivating Text Elements Between L1 and L2

2007 ◽  
Author(s):  
Brooke Lea ◽  
Paul Van Den Broek ◽  
Jazmin Cevasco ◽  
Aaron Mitchel
Keyword(s):  
L1 And L2
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