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

AbstractFuture space programmes pose some interesting research problems in the field of non-Keplerian dynamics, being the Moon and the cislunar space central in the proposed roadmap for the future space exploration. In these regards, the deployment of a cislunar space station on a non-Keplerian orbit in the lunar vicinity is a fundamental milestone to be achieved. The paper investigates the natural orbit-attitude dynamics and the attitude stabilisation of coupled motions for extended bodies in the Earth–Moon system. The discussion is carried out analysing the phase space of natural dynamics, constituted by both the orbital and the rotational periodic motions of a spacecraft in cislunar orbits. Floquet theory is applied to periodic orbit-attitude solutions in lunar proximity, to characterise their attitude stability properties and their attitude manifolds, which are discussed and analysed focusing on their dynamical features applicable to cislunar environment. Attitude stabilisation methods are proposed and developed, with particular attention to spin-stabilised solutions. Periodic orbit-attitude dynamics are studied to highlight possible favourable conditions that may be exploited to host a cislunar space station with a simplified control action. The focus of the analysis is dedicated to halo orbits and near-rectilinear halo orbit in the circular restricted three-body problem Earth–Moon system.

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The orbit of Pluto over a long interval of time

Symposium - International Astronomical Union ◽

10.1017/s0074180900105509 ◽

1966 ◽

Vol 25 ◽

pp. 227-229 ◽

Cited By ~ 1

Author(s):

D. Brouwer

Keyword(s):

Periodic Orbit ◽

Numerical Integration ◽

Restricted Problem ◽

Three Dimensional ◽

The Third ◽

Circular Restricted Problem ◽

Resonance Relation

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.

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

Journal of Speech Language and Hearing Research ◽

10.1044/2019_jslhr-l-18-0315 ◽

2019 ◽

Vol 62 (6) ◽

pp. 1775-1786 ◽

Cited By ~ 2

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.

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Measuring Word Learning Ability in Sequential Bilingual Children

Perspectives on Communication Disorders and Sciences in Culturally and Linguistically Diverse Populations ◽

10.1044/cds17.1.25 ◽

2010 ◽

Vol 17 (1) ◽

pp. 25-32 ◽

Cited By ~ 3

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.

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