Micronuclear Sequences Associated with Assembly Graphs

This paper investigates given an assembly graph, find the possible micronuclear sequences in terms of MDSs and IESs; which represent Hamiltonian polygonal paths. We will consider the orientations of the assembly graph and Hamiltonian polygonal path. To obtain a micronuclear sequence of this path, we will compare orientation of the Hamiltonian polygonal path with respect to the orientation of the assembly graph. We concentrate on two assembly graphs with two 4-valent vertices. These Hamiltonian polygonal paths influence the type of smoothings performed. There are two types of smoothings parallel and non-parallel smoothing. We consider a micronuclear sequence after one smoothing of a vertex

CHAMP Orbit Determination with GPS Phase-Connected Precise Point Positioning

A completely geometric approach for precise orbit determination (POD) of low earth orbiters (LEOs) is presented, which does not rely on dynamic models, but only data from a GPS receiver onboard a LEO and the International GPS Service (IGS) GPS orbit and clock products. Initial processing of CHAMP receiver data indicated measurement anomalies requiring additional pre-processing. The excis-ing of outliers becomes a significant concern in the processing, given that this re-sults in significant gaps in datasets. Intermediate processing results indicate that orbit comparison precision approaching 30 cm r.m.s. in each position component is attainable. However, these results are severely impacted by the near ubiquitous data gaps in the preprocessed measurements. However, initial analysis of recent data indicates quality datasets capable of providing near-decimetre-level precision

Analysis of NOAA-Generated Tropospheric Refraction Corrections for the Next Generation Nationwide DGPS Service

The U.S. Coast Guard has begun the modernization of its Nationwide Differential GPS (NDGPS) beacon network. One potential component of modernization is to provide the information necessary for long baseline, centimetrelevel, differential carrier phase processing. In order to achieve these results, improved handling of atmospheric refraction of the incoming GPS signals must be achieved. The utility of the NOAA tropospheric delays in position determination was accomplished by supplying the NOAA zenith delay estimates to an in-house ionospheric-free relative GPS processor. Results indicate that the most significant improvement is observed in upcomponent bias reduction of a few centimeters to more than four decimeters.La "U.S. Coast Guard” ha iniciado la modernizaciôn de su red de balizas del GPS Diferencial a nivel nacional (NDGPS). Una componente potencial de esta modernizaciôn es proporcionar la informaciôn necesaria para el procesado de lîneas base largas, de la fase portadora diferencial, a nivel de centfmetro. Para lograr estos resultados se debe alcanzar un mejoramiento en la manipulaciôn de la refracciôn atmosférica de las sehales GPS entrantes. La utilidad de los retrasos troposféricos de la NOAA en la determinaciôn de las posiciones fue llevada a cabo proporcionando a la NOAA estimaciones de retrasos cenitales para un procesador GPS interno relativamente no ionosférico. Los resultados indican que la mejora mâs significativa se observa en la reducciôn de bias (distorsiones) de componentes ascendentes, que van desde algunos centimetros hasta mâs de cuatro decimetros.L"'U.S. Coast Guard” a entrepris de moderniser son réseau de balises NDGPS (GPS différentiel au niveau national). Une composante potentielle de cette modernisation consiste à fournir les informations nécessaires au traitement de longues lignes de base, de la phase porteuse différentielle, au centimètre près. Pour obtenir ces résultats, il est indispensable de parvenir à améliorer la gestion de la réfraction atmosphérique des signaux GPS entrant. L’utilité des retards de la NOAA dans la détermination de la position troposphérique a été menée à bien en fournissant à la NOAA des estimations de retard, au zénith, pour un processeur GPS interne relativement non ionosphérique. Les résultats montrent que l ’amélioration la plus significative est observée dans la réduction des erreurs des composantes en amont, qui vont de l ’ordre de quelques centimètres à plus de quatre décimètres

Global Navigation Satellite System Performance in Cislunar Space for Cubesat Form Factors

An increased Cislunar traffic is expected by the end of this decade stemming from NASA’s Artermis program. Given the prioritization limitations of the Deep-Space Network (DSN) for ranging and tracking of increased deep- space assets, a more viable, and cost effective, independent navigation capability is needed. NASA’s 2015 Navigator Global Positioning System (GPS) deployed on the Magnetospheric Multi-Scale (MMS) spacecraft has validated the feasibility of acquiring weak GPS signals at distances up to 25 Earth Radii (~150,000km) or about 40% of the Cislunar trajectory. NASA plans to upgrade the flight proven MSS Navigator GPS for the future Lunar Gateway. Concurrently, the European Space Agency has confirmed the feasibility of an interoperable GPS and Galileo receiver at Lunar altitudes for a low acquisition and tracking threshold “Weak HEO” receiver for a Cubesat platform. This engineering analysis sets out to explore: (1) the smallest Global Navigation Satellite Systems (GNSS) receiver antenna that can ensure a positive carrier and code link for a Lunar bound Cubesat; (2) the position dilution of precision (PDOP) profile of this Lunar bound space vehicle; and (3) the expected improvement of the PDOP during the Moon Transfer Orbit (MTO) for an interoperable GNSS receiver, specifically Beidou. For the designed carrier-to-noise acquisition and tracking threshold of 15 dBHz, the Eb/N0 link was assured for a helix antenna with a minimum diameter of 130 mm and length of 200 mm for the GPS L1 frequency at a data rate of 50 bps. The Galileo E5a, E5b would require a larger diameter antenna at 760 mm at 448 bps data rate while Beidou requires a 350 mm diameter antenna for a 100 bps data rate to close their respectively. Utilizing the 130 mm diameter, 200 mm length helix antenna on a Lunar MTO, the preliminary assessment indicated that the GNSS PDOP calculated from valid carrier links increases from 20 when the vehicle is within the GNSS service volume to several 100th or 1000th at 60.3 Earth Radii. Due to their similar constellation altitude geometry, the Galileo E5b PDOP growth profile is similar to that of the GPS L1. The Beidou system however has a much lower PDOP growth. This difference is attributed to the set of Beidou Geosynchronous space vehicles (SV)s that have greater angular separation to the SV- receiver line-of-sight (LoS). For an interoperable GNSS receiver that can track the GPS, Galileo, and Beidou lower bound and upper bound frequencies simultaneously, the increased number of valid signals reduces the PDOP growth below 200. This engineering analysis re-affirms the potential of utilizing existing GNSS infrastructure for onboard navigation in Cislunar space, in particular, a helical antenna that can be accommodated on a Cubesat form factor

Active megadetachment beneath the western United States

Geodetic data, interpreted in light of seismic imaging, seismicity, xenolith studies, and the late Quaternary geologic history of the northern Great Basin, suggest that a subcontinental-scale extensional detachment is localized near the Moho. To first order, seismic yielding in the upper crust at any given latitude in this region occurs via an M7 earthquake every 100 years. Here we develop the hypothesis that since 1996, the region has undergone a cycle of strain accumulation and release similar to “slow slip events” observed on subduction megathrusts, but yielding occurred on a subhorizontal surface 5–10 times larger in the slip direction, and at temperatures >800°C. Net slip was variable, ranging from 5 to 10 mm over most of the region. Strain energy with moment magnitude equivalent to an M7 earthquake was released along this “megadetachment,” primarily between 2000.0 and 2005.5. Slip initiated in late 1998 to mid-1999 in northeastern Nevada and is best expressed in late 2003 during a magma injection event at Moho depth beneath the Sierra Nevada, accompanied by more rapid eastward relative displacement across the entire region. The event ended in the east at 2004.0 and in the remainder of the network at about 2005.5. Strain energy thus appears to have been transmitted from the Cordilleran interior toward the plate boundary, from high gravitational potential to low, via yielding on the megadetachment. The size and kinematic function of the proposed structure, in light of various proxies for lithospheric thickness, imply that the subcrustal lithosphere beneath Nevada is a strong, thin plate, even though it resides in a high heat flow tectonic regime. A strong lowermost crust and upper mantle is consistent with patterns of postseismic relaxation in the southern Great Basin, deformation microstructures and low water content in dunite xenoliths in young lavas in central Nevada, and high-temperature microstructures in analog surface exposures of deformed lower crust. Large-scale decoupling between crust and upper mantle is consistent with the broad distribution of strain in the upper crust versus the more localized distribution in the subcrustal lithosphere, as inferred by such proxies as low P wave velocity and mafic magmatism

Study on cycle-slip detection and repair methods for a single dual-frequency global positioning system (GPS) receiver

In this work, we assessed the performance of the cycle-slip detection methods: Turbo Edit (TE), Melbourne-Wübbena wide-lane ambiguity (MWWL) and forward and backward moving window averaging (FBMWA). The TE and MWWL methods were combined with ionospheric total electron content rate (TECR), and the FBMWA with second-order time-difference phase ionosphere residual (STPIR) and TECR. Under different scenarios, 10 Global Positioning System (GPS) datasets were used to assess the performance of the methods for cycle-slip detection. The MWWL-TECR delivered the best performance in detecting cycle-slips for 1 s data. The relative comparisons show that the FBMWA-TECR method performed slightly better than its original version, FBMWA-STPIR, detecting 100% and 73%, respectively. For data with a sample rate of 5 s, the FBMWA-TECR performed better than MWWL-TECR. However, the FBMWA is suitable only for post-processing, which refers to applications where the data are processed after the fact

The Canadian Ocean Mapping Research and Education Network (COMREN)

In Canada, ocean, river, lake and coastal mapping knowledge, capacity building and know-how are strengthened through a network of members from academic institutions and one nonprofit organization. This note highlights the Canadian Ocean Mapping Research and Education Network (COMREN), its purpose and its membership