GN&C Sequencing for Orion Rendezvous, Proximity Operations, and Docking

As part of the Artemis program to return humans to the lunar surface, the National Aeronautics and Space Administration is planning to use the Orion Multi- Purpose Crew Vehicle to transport crew to a small orbital platform called Gate- way in cislunar space. To facilitate this activity, Orion is required to perform Rendezvous, Proximity Operations, and Docking (RPOD) with both the Gate- way and the launch vehicle upper stage. The Orion spacecraft uses sequencing in the form of Phases, Segments, Activities, and Modes (PSAM) to configure Guidance, Navigation, & Control (GN&C) software during each portion of the mission. Significant updates to Orion PSAM definitions are required for RPOD. This paper describes the process of defining these new sequencing elements, implementing them in prototype flight software, and testing them in an integrated simulation environment. First, requirements are specified to determine the nominal and off-nominal sequencing behavior necessary to complete the mission. These requirements also specify which software functions should be fully autonomous and which functions require manual interactions from crew or ground operators. Next, the RPOD concept of operations is defined with detailed events listed in a mission timeline. Third, a state machine diagram is developed to show all PSAM states, including all possible transitions between them. After this, the PSAM states and transitions are entered into a sequencing software emulator and parameter values and modes are defined for GN&C software elements. Finally, the PSAM architecture is tested within an integrated simulation environment by connecting it with prototypes of relevant GN&C flight software elements and with detailed vehicle models. After the sequencing design has been finalized and tested, it is implemented in flight software

Information acquisition and decision making in committees: a survey

JEL Classification: D71, E52Committees, costly information acquisition, monetary policy committees, strategic voting

Stability of the Enhanced Area Law of the Entanglement Entropy

We consider a multi-dimensional continuum Schr\"odinger operator which is given by a perturbation of the negative Laplacian by a compactly supported potential. We establish both an upper and a lower bound on the bipartite entanglement entropy of the ground state of the corresponding quasi-free Fermi gas. The bounds prove that the scaling behaviour of the entanglement entropy remains a logarithmically enhanced area law as in the unperturbed case of the free Fermi gas. The central idea for the upper bound is to use a limiting absorption principle for such kinds of Schr\"odinger operators.Comment: Changes in v2: result extended from cubes to Lipschitz domains with piecewise smooth boundar

Late Maastrichtian-Early Paleocene sea level and climate changes in the Antioch Church Core (Alabama, Gulf of Mexico margin, USA): a multi-proxy approach

The Antioch Church core from central Alabama, spanning the Cretaceous-Paleogene (K-P) boundary, was investigated by a multi-proxy approach to study paleoenvironmental and sea level changes within the wellconstrained sequence stratigraphic setting of the Gulf of Mexico margin. The Antioch Church core comprises the Maastrichtian calcareous nannoplankton Zone CC25 and the Danian Zones NP1 to NP4 corresponding to the Maastrichtian planktonic foraminifera Zones CF3 and the Danian Zones P1a to P2. Facies shifts from a Maastrichtian siliciclastic to a mixed siliciclastic-carbonate depositional system during the late Danian. Sedimentary proxies indicate that depositional settings changed between littoral (foreshore) and inner and middle neritic (offshore transition zone). Four sedimentary sequences, each encompassing LST, TST, and HST were identified. Estimated water depths by using benthic foraminiferal assemblages were not exceeding 20-40 m for the Maastrichtian and 0-40 m for the Danian sequences. The succession of facies shifts within systems tracts can be very well disentangled by major and trace element data as well as by various element ratios including Zr/Rb, (Zr+Rb)/Ca, and Sr/Ca. By applying element stratigraphy, the ambiguities of the natural gamma ray log -with peaks associated either with maximum flooding surfaces or with silty lag deposits ("placer silts") during the late regressive HST- are resolved. In addition, the Zr/Rb ratio provides a good proxy for monitoring grain size distribution and sorting effects. According to the Antioch Church core data, the K-P boundary is associated with a sandstone event bed that includes ejecta spherules from the Chicxulub impact. However, the genesis of the K-P event bed, whether lowstand, tempestite- or tsunami-related, cannot be resolved from this core. In terms of clay mineralogy, the studied interval is characterized by a steady increase in smectite that parallels a decrease in kaolinite with the latter disappearing about two My after the K-P boundary during Biozone NP2. This change in the clay mineral assemblage, which is almost independent of lithology, may suggest a long-term shift from stable, tropical warm and humid climates during the latest Maastrichtian to warm climate with alternating humid and arid seasons in the middle Danian

When do bounds and domain propagation lead to the same search space

This paper explores the question of when two propagation-based constraint systems have the same behaviour, in terms of search space. We categorise the behaviour of domain and bounds propagators for primitive constraints, and provide theorems that allow us to determine propagation behaviours for conjunctions of constraints. We then show how we can use this to analyse CLP(FD) programs to determine when we can safely replace domain propagators by more efficient bounds propagators without increasing search space