Transiting the Sun: The impact of stellar activity on X-ray and ultraviolet transits

Transits of hot Jupiters in X-rays and the ultraviolet have been shown to be both deeper and more variable than the corresponding optical transits. This variability has been attributed to hot Jupiters having extended atmospheres at these wavelengths. Using resolved images of the Sun from NASA's Solar Dynamics Observatory spanning 3.5 years of Solar Cycle 24 we simulate transit light curves of a hot Jupiter to investigate the impact of Solar like activity on our ability to reliably recover properties of the planet's atmosphere in soft X-rays (94 {\AA}), the UV (131-1700 {\AA}), and the optical (4500 {\AA}). We find that for stars with similar activity levels to the Sun, the impact of stellar activity results in the derived radius of the planet in soft X-ray/EUV to be underestimated by up-to 25% or overestimated by up-to 50% depending on whether the planet occults active regions. We also find that in up-to 70% of the X-ray light curves the planet transits over bright star spots. In the far ultraviolet (1600 & 1700 {\AA}), we find the mean recovered value of the planet-to-star radius ratio to be over-estimated by up-to 20%. For optical transits we are able to consistently recover the correct planetary radius. We also address the implications of our results for transits of WASP-12b and HD 189733b at short wavelengths.Comment: Accepted for publication in Ap

Proyecto LLAMA

In this paper we briefly describe a joint scientific and technological effort between Argentina and Brazil, whose first goal is to install and run, in the northwestern part of Argentina, a millimetre and submillimetre observational facility. In the long run, we would like to incorporate this dish to existing ones (ALMA, APEX, ASTE) in the northern extreme of Chile, to be able to carry out, for the first time in Latinamerican soil, very long base- line interferometry at mm/submm wavelengths. We also succintly mention a long term campaign that is under way in order to monitor the transparency of the atmosphere at those wavelengths. The science that can be accom- plished with this instrument, the technology transfer spin-offs related to this project, and the scientific and strategic importance of this project within both the Argentinean and Latinamerican radioastronomy is described.Fil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Mirabel Miquele, Igor Felix. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Morras, Ricardo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Abraham, Zulema. Universidade de Sao Paulo; BrasilFil: de Gouveira dal Pino, Elisabete M. de. Universidade de Sao Paulo; BrasilFil: Lepine, Jacques. Universidade de Sao Paulo; Brasi

Attitude determination with three-axis accelerometer for emergency atmospheric entry

Two algorithms are disclosed that, with the use of a 3-axis accelerometer, will be able to determine the angles of attack, sideslip and roll of a capsule-type spacecraft prior to entry (at very high altitudes, where the atmospheric density is still very low) and during entry. The invention relates to emergency situations in which no reliable attitude and attitude rate are available. Provided that the spacecraft would not attempt a guided entry without reliable attitude information, the objective of the entry system in such case would be to attempt a safe ballistic entry. A ballistic entry requires three controlled phases to be executed in sequence: First, cancel initial rates in case the spacecraft is tumbling; second, maneuver the capsule to a heat-shield-forward attitude, preferably to the trim attitude, to counteract the heat rate and heat load build up; and third, impart a ballistic bank or roll rate to null the average lift vector in order to prevent prolonged lift down situations. Being able to know the attitude, hence the attitude rate, will allow the control system (nominal or backup, automatic or manual) to cancel any initial angular rates. Also, since a heat-shield forward attitude and the trim attitude can be specified in terms of the angles of attack and sideslip, being able to determine the current attitude in terms of these angles will allow the control system to maneuver the vehicle to the desired attitude. Finally, being able to determine the roll angle will allow for the control of the roll ballistic rate during entry

Analytic Development of a Reference Profile for the First Entry in a Skip Atmospheric Entry

This note shows that a feasible reference drag profile for the first entry portion of a skip entry can be generated as a polynomial expression of the velocity. The coefficients of that polynomial are found through the resolution of a system composed of m + 1 equations, where m is the degree of the drag polynomial. It has been shown that a minimum of five equations (m = 4) are required to establish the range and the initial and final conditions on velocity and flight path angle. It has been shown that at least one constraint on the trajectory can be imposed through the addition of one extra equation in the system, which must be accompanied by the increase in the degree of the drag polynomial. In order to simplify the resolution of the system of equations, the drag was considered as being a probability density function of the velocity, with the velocity as a distribution function of the drag. Combining this notion with the introduction of empirically derived constants, it has been shown that the system of equations required to generate the drag profile can be successfully reduced to a system of linear algebraic equations. For completeness, the resulting drag profiles have been flown using the feedback linearization method of differential geometric control as a guidance law with the error dynamics of a second order homogeneous equation in the form of a damped oscillator. Satisfactory results were achieved when the gains in the error dynamics were changed at a certain point along the trajectory that is dependent on the velocity and the curvature of the drag as a function of the velocity. Future work should study the capacity to update the drag profile in flight when dispersions are introduced. Also, future studies should attempt to link the first entry, as presented and controlled in this note, with a more standard control concept for the second entry, such as the Apollo entry guidance, to try to assess the overall skip entry performance. A guidance law that includes an integral feedback term, as is the case in the actual Space Shuttle entry guidance and as is proposed in Ref 29, could be tried in future studies to assess whether its use results in an improvement of the tracking performance, and to evaluate the design needs when determining the control gains

LLAMA: Leveraging Learning to Automatically Manage Algorithms

Algorithm portfolio and selection approaches have achieved remarkable improvements over single solvers. However, the implementation of such systems is often highly customised and specific to the problem domain. This makes it difficult for researchers to explore different techniques for their specific problems. We present LLAMA, a modular and extensible toolkit implemented as an R package that facilitates the exploration of a range of different portfolio techniques on any problem domain. It implements the algorithm selection approaches most commonly used in the literature and leverages the extensive library of machine learning algorithms and techniques in R. We describe the current capabilities and limitations of the toolkit and illustrate its usage on a set of example SAT problems

Sovereign Bonds and the Collective Will

The purpose of this study was to enrich the environment for llama (Lama glama) and alpaca (Vicugna pacos) in a zoo. The zoo is located in northern Sweden (Umeå, Mickelträsk). The llama herd consists of three individuals of breed qara, two males and one female and the alpaca herd consists of six individuals of breed huacaya, one male, four females and one foal. The species lived in separate enclosures, they lived outside all year round and they had a shelter for wind and rain protection. They feed on pasture and were fed hay and pellet concentrate. A behavioral-study was carried out in April 2014, a five-day study where each of the species were observed 3 h a day, 1,5 h in morning and afternoon. The behavioral of llama and alpaca were observed individually and each behavior was observed in terms of duration and frequency. The study observed if the animals had a possibility to implement their natural behaviors in their enclosures and whether they showed any abnormal- or stereotypical behaviors that can occur in captivity. The questions I wanted to answer were: (1) what behaviors are occurring, (2) Is it possible to indicate from the behaviors if the animals are doing well or not, (3) Is there a difference in behaviors in the morning and afternoon? (4) Is there a difference between the sexes? (5) What actions should be undertaken to enrich and improve the habitat for llamas and alpacas in a zoo? The results from the study show that llamas and alpacas show many normal and natural behaviors, no abnormal-or stereotypical behaviors were visible. Some behaviors were more common in morning and some in afternoon and there were differences in behaviors between the sexes. Example for some environmental enrichment for the llamas and alpacas in the zoo was to add logs, trees, shrubs and sand piles to the enclosure

Testing aptitude

Meara (2005) developed the LLAMA tests as a free, language-neutral, user-friendly suite of aptitude tests incorporating four separate elements: vocabulary learning (LLAMA_B), phonetic (implicit) memory (LLAMA_D), sound-symbol correspondence (LLAMA_E) and grammatical inferencing (LLAMA_F) based on the standardised MLAT tests (Carroll & Sapon, 1959). Recently, they have become increasingly popular in L2 acquisition research (Grañena & Long, 2013b). However, Meara has expressed concern about the wide use of these tests without validity testing (cf. Grañena 2013a). We investigated several areas relating to the LLAMA tests.1. What is the role of gender in LLAMA test performance?2. Are the LLAMA tests language neutral?3. What is the role of age?4. What is the role of formal education qualifications?5. Does playing logic puzzles affect LLAMA scores?6. What difference would changing the test timings make to scores?229 participants from a range of language backgrounds, aged 10-75 with various education levels, typologically distinct L1s, and varying levels of multilingualism were tested. A subset of participants was also tested with varying timings for the tests. The results showed that the LLAMA tests are gender and language neutral. The younger learners (10-11s) performed significantly worse than the adults in the sound/symbol correspondence task (LLAMA_E). Formal education qualifications show a significant advantage in 3 of the LLAMA subcomponents (B, E, F) but not the implicit measure (LLAMA_D). Playing logic puzzles did not improve LLAMA test scores. The timings appear to be optimal apart from LLAMA_F, which could be shortened