Smallsats for METOP: Design definition, heritage and performance

The results of a study by MMS for BNSC and the UK Meteorological Office into the potential use of Smallsats to support METOP are reported. A risk of degradation or failure of a mission critical instrument during the METOP lifetime has been identified. The scenario proposed uses a Smallsat flying in formation with METOP to replace a failed instrument with data being returned to METOP via an inter-satellite link. An assessment of small launcher and small platform availability and instrument interface requirements indicates that such a scenario is feasible. Minor modifications to METOP and a relative pointing correction during ground processing would be required. It is concluded that a Smallsat could provide a significant improvement to METOP programme reliability with low design and cost risk. Scenario attractiveness depends upon whether a critical instrument failure would justify replacement.     

Scheduling algorithms for rapid imaging using agile Cubesat constellations

Distributed Space Missions such as formation flight and constellations, are being recognized as important Earth Observation solutions to increase measurement samples over space and time. Cubesats are increasing in size (27U, ～40?kg in development) with increasing capabilities to host imager payloads. Given the precise attitude control systems emerging in the commercial market, Cubesats now have the ability to slew and capture images within short notice. We propose a modular framework that combines orbital mechanics, attitude control and scheduling optimization to plan the time-varying, full-body orientation of agile Cubesats in a constellation such that they maximize the number of observed images and observation time, within the constraints of Cubesat hardware specifications. The attitude control strategy combines bang-bang and PD control, with constraints such as power consumption, response time, and stability factored into the optimality computations and a possible extension to PID control to account for disturbances. Schedule optimization is performed using dynamic programming with two levels of heuristics, verified and improved upon using mixed integer linear programming. The automated scheduler is expected to run on ground station resources and the resultant schedules uplinked to the satellites for execution, however it can be adapted for onboard scheduling, contingent on Cubesat hardware and software upgrades. The framework is generalizable over small steerable spacecraft, sensor specifications, imaging objectives and regions of interest, and is demonstrated using multiple 20?kg satellites in Low Earth Orbit for two case studies – rapid imaging of Landsat’s land and coastal images and extended imaging of global, warm water coral reefs. The proposed algorithm captures up to 161% more Landsat images than nadir-pointing sensors with the same field of view, on a 2-satellite constellation over a 12-h simulation. Integer programming was able to verify that optimality of the dynamic programming solution for single satellites was within 10%, and find up to 5% more optimal solutions. The optimality gap for constellations was found to be 22% at worst, but the dynamic programming schedules were found at nearly four orders of magnitude better computational speed than integer programming. The algorithm can include cloud cover predictions, ground downlink windows or any other spatial, temporal or angular constraints into the orbital module and be integrated into planning tools for agile constellations.     

Study of the radiation fields in LEO with the Space Application of Timepix Radiation Monitor (SATRAM)

We present the analysis of data taken by the Space Application of Timepix Radiation Monitor (SATRAM). It is centred on a Timepix detector (300?$\mathrm{\mu }$m thick silicon sensor, pixel pitch 55?$\mathrm{\mu }$m, 256?×?256 pixels). It was flown on Proba-V, an Earth observing satellite of the European Space Agency (ESA) from an altitude of 820?km on a sun-synchronous orbit, launched on May 7, 2013. A Monte Carlo simulation was conducted to determine the detector response to electrons (0.5–7?MeV) and protons (10–400?MeV) in an omnidirectional field taking into account the shielding of the detector housing and the satellite. With the help of the simulation, a strategy was developed to separate electrons, protons and ions in the data. The measured dose rate and stopping power distribution are presented as well as SATRAM’s capability to measure some of the stronger events in Earth’s magnetosphere. The stopping power, the cluster height and the shape of the particle tracks in the sensor were used to separate electrons, protons and ions. The results are presented as well. Finally, the pitch angles for a short period of time were extracted from the data and corrected with the angular response determined by the simulation.     

Demographics of principal investigators involved in NASA-funded research

This report presents the findings of a study of 2875 principal investigators identified through a database maintained by NASA's Office of Space Science and Applications. It was found that there will be a major ‘retirement wave’ involving the loss of approximately 1200 of these experienced scientists within the next 15 years. A manpower crisis can apparently only be averted by reversing the exodus from space science that occurred after the end of the Apollo programme.     

A new view of the galactic plane with EXOSAT

A new X-ray image of the galactic plane has been produced using the 45 arcmin square field of view of the Medium Energy Instrument on EXOSAT. This image shows a total of 64 sources including 18 new ones which include the first observation of persistent emission from the globular cluster bursters Terzan 1 and Terzan 5. The most important discovery from this image is a 2° wide ridge of diffuse emission symmetrical about the plane and extending from the galactic centre to 1=±40°. The spectrum of this emission appears to be hard ( 1.2) with no significant absorption.     

Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.     

Three dimensional spatial memory and learning in real and virtual environments

Human orientation and spatial cognition partlydepends on our ability to remember sets ofvisual landmarks and imagine their relationshipto us from a different viewpoint. We normallymake large body rotations only about a singleaxis which is aligned with gravity. However,astronauts who try to recognize environmentsrotated in 3 dimensions report that theirterrestrial ability to imagine the relativeorientation of remembered landmarks does noteasily generalize. The ability of humansubjects to learn to mentally rotate a simplearray of six objects around them was studied in1-G laboratory experiments. Subjects weretested in a cubic chamber (n = 73) and aequivalent virtual environment (n = 24),analogous to the interior of a space stationnode module. A picture of an object waspresented at the center of each wall. Subjectshad to memorize the spatial relationships amongthe six objects and learn to predict thedirection to a specific object if their bodywere in a specified 3D orientation. Percentcorrect learning curves and response times weremeasured. Most subjects achieved high accuracyfrom a given viewpoint within 20 trials,regardless of roll orientation, and learned asecond view direction with equal or greaterease. Performance of the subject group thatused a head mounted display/head tracker wasqualitatively similar to that of the secondgroup tested in a physical node simulator. Body position with respect to gravity had asignificant but minor effect on performance ofeach group, suggesting that results may alsoapply to weightless situations. A correlationwas found between task performance measures andconventional paper-and-pencil tests of fieldindependence and 2&3 dimensional figurerotation ability.     

The MESSENGER Science Operations Center

The MESSENGER Science Operations Center (SOC) is an integrated set of subsystems and personnel whose purpose is to obtain, provide, and preserve the scientific measurements and analysis that fulfill the objectives of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The SOC has two main functional areas. The first is to facilitate science instrument planning and operational activities, including related spacecraft guidance and control operations, and to work closely with the Mission Operations Center to implement those plans. The second functional area, data management and analysis, involves the receipt of science-related telemetry, reformatting and cataloging this telemetry and related ancillary information, retaining the science data for use by the MESSENGER Science Team, and preparing data archives for delivery to the Planetary Data System; and the provision of operational assistance to the instrument and science teams in executing their algorithms and generating higher-level data products.     

Potential of laser-induced ablation for future space applications

This paper surveys recent and current advancements of laser-induced ablation technology for space-based applications and discusses ways of bringing such applications to fruition. Laser ablation is achieved by illuminating a given material with a laser light source. The high surface power densities provided by the laser enable the illuminated material to sublimate and ablate. Possible applications include the deflection of Near Earth Objects – asteroids and comets – from an Earth-impacting event, the vaporisation of space structures and debris, the mineral and material extraction of asteroids and/or as an energy source for future propulsion systems. This paper will discuss each application and the technological advancements that are required to make laser-induced ablation a practical process for use within the space arena. Particular improvements include the efficiency of high power lasers, the collimation of the laser beam (including beam quality) and the power conversion process. These key technological improvements are seen as strategic and merit greater political and commercial support.