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IntroductionSimilar to terrestrial applications, dual-frequency GPS receivers offer numerous advantages over single-frequency receivers in space applications. Even though the basic navigation requirements of many spacecraft can well be met by single-frequency receivers, the second frequency is of great interest for scientific missions and a key to ultimate accuracy in absolute and relative navigation (Yunck 2004). It allows the direct elimination of ionospheric path delays and thus gives full access to the accuracy of carrier-phase based measurements. GPS tracking of low Earth satellites has dramatically improved our knowledge of the Earth's gravity field (Reigber et al. 2004) and GPS based radio occultation measurements are an indispensable source of information for ionospheric and tropospheric research (Kursinski et al. 1997). In carrier-phase differential GPS (CDGPS), dual-frequency measurements enable a reliable resolution of integer ambiguities even at large baselines and non-negligible differential ionospheric delays (Kroes et al. 2005).Abstract This report provides a detailed performance analysis of three semicodeless dual-frequency GPS receivers for use in low Earth orbit (LEO). The test set comprises the IGOR receiver, which represents a follow-on of the flight-proven BlackJack receiver, as well as two geodetic receivers (NovAtel OEM4-G2 and Septentrio PolaRx2), which are entirely based on commercialoff-the-shelf technology (COTS). All three receivers are considered for upcoming flight projects or experiments and have undergone at least a preliminary environmental qualification program. Using extensive signal simulator tests, the cold start signal acquisition, tracking sensitivity, differential code biases, raw measurement accuracy, and navigation accuracy of each receiver have been assessed. All tests are based on a common scenario that is representative of an actual space mission and provides a realistic simulation of the signal dynamics and quality on a scientific LEO satellite. Compared to the other receivers, the IGOR instrument exhibits a superior tracking sensitivity and is thus best suited for occultation measurements with low tangent point altitudes. The OEM4-G2 and PolaRx2 receivers are likewise shown to properly track dual-frequency GPS signals and normal signal levels and to provide accurate code and carrier phase measurements. Given their limited resource requirements, these receivers appear well suited for precise orbit determination applications and ionospheric sounding onboard of microsatellites with tight mission budgets.

This article contains a synthesis of academic intervention studies conducted between 1970 and 2012 with adolescents who were incarcerated in residential juvenile correctional facilities. Literacy, mathematics, written expression, and multicomponent interventions were included if they measured effects on at least one academic outcome measure. Of the 16 studies synthesized, 7 studies employed an experimental or quasi-experimental design, 4 used a single-case design, and 5 used a single-group design. Because the results are restricted due to methodological limitations and a general lack of research in this area, we discuss the existing gaps in the literature and explore initial findings using these 16 studies. Results suggest the potential of implementing explicit, targeted, academic interventions that have previously shown promise with adolescents in the general school setting (e.g., peermediated instruction). Implications and guidance for future research regarding effective delivery of evidence-based practices for adolescents in the incarcerated setting are discussed.

Content analyses of journals in the field of LD provide a means of surveying research and publication trends, the knowledge of which may inform policy and practice related to future research agendas. As the first decade of the current millennium was particularly contentious for the field of LD, we felt that a content review would be timely. In this paper, the content of three refereed LD journals—Journal of Learning Disabilities, Learning Disabilities Research & Practice, and Learning Disabilities Quarterly—was analyzed. Articles from 2001–2010 (n = 841) were systematically coded to capture article type, area of interest, population of interest, sample characteristics, and inclusion of students with LD. Results indicate that across the decade, (a) 68% of articles reported empirical research; (b) empirical research trended up; (c) publication of intervention research remained steady; (d) the most common foci were literacy and the non‐academic characteristics of individuals with LD; and (e) inclusion of participants labeled as having a LD declined. We discuss trends, possible explanations, and implications, highlighting areas for future research.