Spacecraft attitude determination accuracy from mission experience

This paper summarizes a compilation of attitude determination accuracies attained by a number of satellites supported by the Goddard Space Flight Center Flight Dynamics Facility. The compilation is designed to assist future mission planners in choosing and placing attitude hardware and selecting the attitude determination algorithms needed to achieve given accuracy requirements. The major goal of the compilation is to indicate realistic accuracies achievable using a given sensor complement based on mission experience. It is expected that the use of actual spacecraft experience will make the study especially useful for mission design. A general description of factors influencing spacecraft attitude accuracy is presented. These factors include determination algorithms, inertial reference unit characteristics, and error sources that can affect measurement accuracy. Possible techniques for mitigating errors are also included. Brief mission descriptions are presented with the attitude accuracies attained, grouped by the sensor pairs used in attitude determination. The accuracies for inactive missions represent a compendium of missions report results, and those for active missions represent measurements of attitude residuals. Both three-axis and spin stabilized missions are included. Special emphasis is given to high-accuracy sensor pairs, such as two fixed-head star trackers (FHST's) and fine Sun sensor plus FHST. Brief descriptions of sensor design and mode of operation are included. Also included are brief mission descriptions and plots summarizing the attitude accuracy attained using various sensor complements

Spacecraft attitude determination accuracy from mission experience

This document presents a compilation of the attitude accuracy attained by a number of satellites that have been supported by the Flight Dynamics Facility (FDF) at Goddard Space Flight Center (GSFC). It starts with a general description of the factors that influence spacecraft attitude accuracy. After brief descriptions of the missions supported, it presents the attitude accuracy results for currently active and older missions, including both three-axis stabilized and spin-stabilized spacecraft. The attitude accuracy results are grouped by the sensor pair used to determine the attitudes. A supplementary section is also included, containing the results of theoretical computations of the effects of variation of sensor accuracy on overall attitude accuracy

Same but Different: Distant Supervision for Predicting and Understanding Entity Linking Difficulty

Entity Linking (EL) is the task of automatically identifying entity mentions in a piece of text and resolving them to a corresponding entity in a reference knowledge base like Wikipedia. There is a large number of EL tools available for different types of documents and domains, yet EL remains a challenging task where the lack of precision on particularly ambiguous mentions often spoils the usefulness of automated disambiguation results in real applications. A priori approximations of the difficulty to link a particular entity mention can facilitate flagging of critical cases as part of semi-automated EL systems, while detecting latent factors that affect the EL performance, like corpus-specific features, can provide insights on how to improve a system based on the special characteristics of the underlying corpus. In this paper, we first introduce a consensus-based method to generate difficulty labels for entity mentions on arbitrary corpora. The difficulty labels are then exploited as training data for a supervised classification task able to predict the EL difficulty of entity mentions using a variety of features. Experiments over a corpus of news articles show that EL difficulty can be estimated with high accuracy, revealing also latent features that affect EL performance. Finally, evaluation results demonstrate the effectiveness of the proposed method to inform semi-automated EL pipelines.Comment: Preprint of paper accepted for publication in the 34th ACM/SIGAPP Symposium On Applied Computing (SAC 2019

Improved instrumental magnitude prediction expected from version 2 of the NASA SKY2000 master star catalog

The SKY2000 Master Star Catalog (MC), Version 2 and its predecessors have been designed to provide the basic astronomical input data needed for satellite acquisition and attitude determination on NASA spacecraft. Stellar positions and proper motions are the primary MC data required for operations support followed closely by the stellar brightness observed in various standard astronomical passbands. The instrumental red-magnitude prediction subsystem (REDMAG) in the MMSCAT software package computes the expected instrumental color index (CI) [sensor color correction] from an observed astronomical stellar magnitude in the MC and the characteristics of the stellar spectrum, astronomical passband, and sensor sensitivity curve. The computation is more error prone the greater the mismatch of the sensor sensitivity curve characteristics and those of the observed astronomical passbands. This paper presents the preliminary performance analysis of a typical red-sensitive CCDST during acquisition of sensor data from the two Ball CT-601 ST's onboard the Rossi X-Ray Timing Explorer (RXTE). A comparison is made of relative star positions measured in the ST FOV coordinate system with the expected results computed from the recently released Tycho Catalogue. The comparison is repeated for a group of observed stars with nearby, bright neighbors in order to determine the tracker behavior in the presence of an interfering, near neighbor (NN). The results of this analysis will be used to help define a new photoelectric photometric instrumental sensor magnitude system (S) that is based on several thousand bright star magnitudes observed with the PXTE ST's. This new system will be implemented in Version 2 of the SKY2000 MC to provide improved predicted magnitudes in the mission run catalogs

The role of pancreatic islands transplantation in the management of chronic conditions

Institutul Clinic Fundeni, România, București, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Diabetul zaharat reprezintă o problemă de sănătate la nivel mondial, în primul rând datorită numarului mare de pacienți (se estimează că în 2015, 1 din 11 adulți suferea de diabet așteptându-se ca până în 2040, 1 din 10 adulți să fie diabetic); în al doilea rând, mortalitatea prin diabet depașește mortalitatea sumată prin boli răspândite ca malaria, HIV/SIDA și tuberculoza; nu în ultimul rand, costurile sistemelor de sănătate pentru o persoană diabetică sunt de 2.3 ori mai mari decât pentru o persoană nondiabetică. Transplantul de insule pancreatice ca terapie în diabetul zaharat, reprezintă o metodă sigură și eficientă, care implică o intervenție chirurgicală relativ ușoara, cu o morbiditate scăzuta și o mortalitate aproape de 0, în comparație cu transplantul de pancreas integral. Rezultatele depind însa de procesul de izolare a insulelor pancreatice, un proces complex, care implică costuri ridicate. Material și metode: Între anii 2007-2012 au avut loc 20 de recoltari în bloc spleno-pancreatico-duodenale, în cadrul recoltărilor multiorgan realizate de echipa de prelevare din IC Fundeni (în 2 cazuri s-a recoltat în acest bloc și ficatul). Pancreasul recoltat s-a folosit în 2 cazuri la transplantul de pancreas integral, iar in celelalte 18 cazuri, la obținerea insulelor pancreatice. Principalul rezultat a fost formarea unor echipe naționale calificate in prelevarea pancreasului și stăpânirea tehnicii de izolare a insulelor pancreatice, fapt ce reprezintă un prim pas în implementarea clinică a unui Program Național de Transplant de Insule Pancreatice. Ca implementare clinică a acestui procedeu, s-a realizat primul allotransplant de insule pancreatice din România simultan cu transplantul de ficat la un pacient în vârsta de 40 ani, cirotic, cu diabet zaharat insulino-dependent. O altă indicație a transplantului de insule pancreatice a fost managementul pancreatitei cronice. Pancreatectomia totală urmată de autotransplant de insule pancreatice reprezintă o bună opțiune în tratarea pancreatitei cronice, în special forma cu duct îngust, care chiar și cu necesarul suplimentar de insulină exogenă, asigură un control mai eficient al diabetului prin secreția de lungă durată a insulinei și peptidului C. Rezultate: În acest scop s-a realizat un autotransplant de insule pancreatice la o pacientă cu pancreatectomie totală pentru pancreatită cronică. Indicația chirurgicală de rezecție pancreatică a fost sindromul algic permanent, refractar la antalgice majore si episoadele de pancreatită acută recurente. Concluzii: Rezultatele acestui studiu sunt promiţătoare şi situează şi România pe harta ţărilor care au ca preocupare folosirea transplantului de insule pancreatice în managementul diabetului zaharat şi al pancreatitei cronice.Background: Diabetes mellitus is a global health problem, primarily due to the large number of patients (it is estimated that 20% of patients in 2015, 1 out of 11 adults were diabetic, with one out of 10 adults being diabetic by 2040); secondly, diabetes mortality outweighs the overall mortality rate through diseases such as malaria, HIV / AIDS and tuberculosis; Last but not least, the health care costs for a diabetic person are 2.3 times higher than for a non-diabetic person. Transplantation of pancreatic islets as a therapy in diabetes is a safe and effective method involving relatively easy surgery with low morbidity and mortality close to 0, compared to full pancreas transplantation. The results depend, however, on the isolating process of the pancreatic islands, a complex process that involves high costs. Methods and materials: Between 2007-2012, there were 20 harvests in the spleno-pancreatic-duodenal block, during the multiorgan harvests made by the sampling team from IC Fundeni (in 2 cases it was harvested in this block and the liver). The harvested pancreas was used in 2 cases for whole pancreas transplantation, and in the other 18 cases, the pancreatic islets were obtained. The main result was the formation of qualified national teams in pancreas extraction and the isolation of pancreatic islands, which is a first step in the clinical implementation of a National Pancreatic Transplantation Program. As a clinical implementation of this procedure, the first allotransplant of pancreatic islets in Romania was performed simultaneously with liver transplantation in a 40 year old, cirrhotic, insulin-dependent diabetes mellitus. Another indication of pancreatic islet transplantation was the management of chronic pancreatitis. Total pancreatectomy followed by pancreatic islet transplantation is a good option in the treatment of chronic pancreatitis, particularly narrow-duct form, which even with the extra exogenous insulin requirement, provides more efficient control of diabetes by long-term secretion of insulin and peptide C. Results: For this purpose a pancreatic islet transplant was performed in a patient with total pancreatectomy for chronic pancreatitis. The surgical indication of pancreatic resection was permanent algic syndrome, refractory to major antalgics, and recurrent acute pancreatitis episodes. Conclusion: The results of this study are promising and places Romania on the map of countries that are concerned with the use of pancreatic islet transplantation in the management of diabetes mellitus and chronic pancreatitis

Liver transplantation in Romania

Institultul Clinic Fundeni-Clinica Chirurgie Generală și Transplant Hepatic “Dan Setlacec”, Al XI-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova și cea de-a XXXIII-a Reuniune a Chirurgilor din Moldova „Iacomi-Răzeșu” 27-30 septembrie 2011Analiza retrospectivă a 300 de transplanturi hepatice efectuate în Centrul de Chirurgie Generală și Transplant Hepatic “Dan Setlacec “.Retrospective analysis of 300 liver transplantation performed in General Surgery Center and Liver Transplantation “Dan Setlacec”

Liver retransplantation as a therapeutic method in graft dysfunctions in the immediate postoperative period

Departament Chirurgie Generală, I.C. Fundeni, București, România, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaCu toate că în ultimii ani au apărut progrese importante în domeniul hepatic, problema prevenirii apariției disfuncției și eșecului post-transplant nu a prezentat progrese semnificative. Intrucât disfuncția hepatică primară influențează dramatic evoluția grefei și a pacientului transplantat hepatic, prevenirea acestui fenomen devine obligatoriu. Creșterea penuriei de organe și a numărului persoanelor aflate pe lista de așteptare a dus la folosirea unor grefe ce depășesc criteriile normale de selecție pentru recoltare precum și transplantarea unor donatori considerați marginali. Aceste circumstanțe au adus în prim plan importanța diagnosticării și tratamentului disfuncției hepatice primare. Conceptul de disfuncție hepatică primară nu este clar definit. Există un spectru de evenimente ce definesc disfuncția hepatică postoperatorie precoce: non funcția primară (PNF), nonfuncția întârziată, funcția slabă/săracă inițială (initial poor function – IPF), non funcția inițială, insuficiența hepatică primară și disfuncția primară. Distincția între aceste entități ia în considerare gradul disfuncției hepatice, necesitatea retransplantării urgente, precum și apariția și durata acestor evenimente după transplantul hepatic.Although important progress has been made over the last few years, the problem of preventing dysfunction and post-transplant liver failure has not shown significant progress. Since primary liver dysfunction dramatically influences the progress of the graft and the liver transplant patient, prevention of this phenomenon becomes obligatory. The increase in organ shortage and the number of people on the waiting list led to the use of grafts that exceeded the normal selection criteria for harvesting as well as the transplantation of marginal donors. These circumstances have highlighted the importance of diagnosis and treatment of primary hepatic dysfunction. The concept of primary liver dysfunction is not clearly defined. There is a spectrum of events that defines early postoperative liver dysfunction: primary non-function (PNF), delayed dysfunction, initial poor function (IPF), primary hepatic failure, and primary dysfunction. The distinction between these entities takes into account the degree of hepatic dysfunction, the need for urgent retransplantation, and the occurrence and duration of these events after liver transplantation

Cumulative readings of every do not provide evidence for events and thematic roles

An argument by Kratzer (2000) based on Schein (1986, 1993) does not conclusively show that events and thematic roles are necessary ingredients of the logical representation of natural language sentences. The argument claims that cumulative readings of every can be represented only with these ingredients. But scope-splitting accounts make it possible to represent cumulative readings of every in an eventless framework. Such accounts are motivated by obligatory reconstruction effects of every and by crosslinguistic considerations. Kratzer proposes that agent but not theme occurs in the logical representation of sentences because this allows her to model subject-object asymmetries in the distribution of cumulative every. But the reason for these asymmetries seems to be that every must be c-commanded by another quantifier in order to cumulate with it, no matter what its thematic role is. So the distribution of cumulative every does not provide support for Kratzer’s proposal