SORCE Daylight-Only Operations

The recent experience of the SORCE flight operations team offers an excellent example of innovative engineering using limited resources. The goal of this paper is to extend to the space operations community the lessons learned during this critical redesign in order to aid other missions facing equally daunting challenges. The end result is a mission extended well beyond its designed life continuing to return important data to the science community to extend the climate record

First Evidence of Persistent Nighttime Temperature Structures in the Neutral Thermosphere of Mars

Using two Mars years of data collected by the Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatiles EvolutioN spacecraft, we reconstruct the local solar time structure of the Martian equatorial thermosphere for the dawn and dusk sectors. The results indicate the presence of several persistent features near the dusk and dawn terminators appearing in the neutral temperature and in the O, Ar, N2, and CO2 densities. The dusk temperature features include a minimum at the terminator surrounded by two local maxima with amplitudes between 20 and 40 K. A nighttime temperature enhancement occurs at a local solar time of 4–5 hr and has an amplitude between 50 and 100 K relative to the surrounding temperatures. The observed enhancements are interpreted to be a result of either nighttime dynamical heating caused by converging and downwelling winds or of a terminator wave originating in the lower atmosphere.Plain Language SummaryNASA’s Mars Atmosphere and Volatiles EvolutioN (MAVEN) spacecraft has been collecting information about the Mars’ upper atmosphere since November 2014. In our study we examined the temperature in the upper atmosphere measured by a gas analyzer on MAVEN that periodically sniffs the air around it. By combining several years of data, we reconstructed a map of atmospheric temperatures dividing it into equatorial daytime, morning, evening, and nighttime regions. The results indicate that local patches of warm atmosphere extend about 300–600 km along the Martian equator (3–6 hr driving distance at highway speeds) on the nightside near morning and evening. One possible reason for these nighttime warm spots is the air currents in the Martian upper atmosphere. As the sun heats the dayside atmosphere, it expands and causes wind currents to blow away from the dayside region. These wind currents can extend away from the equator then return on the nightside colliding in the morning and evening regions. The resulting meeting of wind currents can heat the upper atmosphere. Warmer air escapes from the upper atmosphere faster. Because of this, these nighttime patches of warm air could have contributed to a faster escape of Martian atmospheric gases than previously believed.Key PointsPersistent neutral density and temperature enhancements are observed within 30 min of the dusk terminatorA persistent neutral density enhancement is also observed prior to the dawn terminator at around 4–5 local timeThe neutral density features are observed in all species and appear to be associated with enhancements in neutral temperaturePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146482/1/grl57932.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146482/2/grl57932_am.pd

Realistic Operational Modeling for a Spin Stabilized CubeSat: Challenges and Anticipated Control Performance

Recently, ASTRA LLC. has teamed with the Space Dynamics Laboratory of Utah State University to design a 1.5U CubeSat system for measuring electric fields. Such a system requires 2-axis control and relatively high spin-rates. The spacecraft is called the Double-probe Instrumentation for Measuring Electric-fields (DIME) SensorSat and is funded by the Air Force Research Laboratory SBIR program. In order to design and test control algorithms and verify requirements, ASTRA has developed a modeling-tool for a CubeSat 2-axis control system. First, a brief overview of the DIME SensorSat and attitude system is provided and the DIME attitude requirements are introduced. Next the operational attitude model is discussed followed by simulation results for the various operational phases of a spin-stabilized CubeSat. Finally, we present some anticipated challenges and related simulations for a spin-stabilized CubeSat

Design, Development, Implementation, and On-orbit Performance of the Dynamic Ionosphere CubeSat Experiment Mission

Funded by the NSF CubeSat and NASA ELaNa programs, the Dynamic Ionosphere CubeSat Experiment (DICE) mission consists of two 1.5U CubeSats which were launched into an eccentric low Earth orbit on October 28, 2011. Each identical spacecraft carries two Langmuir probes to measure ionospheric in-situ plasma densities, electric field probes to measure in-situ DC and AC electric fields, and a science grade magnetometer to measure in-situ DC and AC magnetic fields. Given the tight integration of these multiple sensors with the CubeSat platforms, each of the DICE spacecraft is effectively a “sensorsat” capable of comprehensive ionospheric diagnostics. The use of two identical sensor-sats at slightly different orbiting velocities in nearly identical orbits permits the de-convolution of spatial and temporal ambiguities in the observations of the ionosphere from a moving platform. In addition to demonstrating nanosat-based constellation science, the DICE mission is advancing a number of groundbreaking CubeSat technologies including miniaturized mechanisms and high-speed downlink communications

Analysis of a novel approach for determining atmospheric density from satellite drag

The dynamics and modeling of the thermosphere has been of great interest to scientists and LEO spacecraft operators since the first earth satellites were constructed. Although a great deal of data has been accumulated regarding the average conditions, or climate, of the atmosphere in this region, at the time of writing, much ongoing work remains to be done to verify or characterize crucial transient phenomena such as tides and propagating disturbances [Bruinsma 2006]. The contribution of often unmeasured in-track winds and the use of constant drag coefficients in spacecraft drag measurements [Bowman and Moe 2005] has introduced 10-15% errors into the atmospheric models which rely on this data as a source of density values. To address these in-situ measurement issues, a novel method of drag determination is proposed, modeled, and combined with a wind measurement method as well as a numerical tool for calculating the coefficient of drag of complex geometries. This analysis and error model will be applied to the Drag and Atmospheric Neutral Density Explorer (DANDE) and its instruments. DANDE is a satellite being developed at the University of Colorado and will be a low earth orbiting spacecraft with the capability to study in-situ winds, composition, and density. A method is presented here which will serve as an error analysis of the measurements and which can be extended to other in-situ missions with similar instruments. This will include the modeling of the spacecraft and its sensors, the input from the ambient environment, on-board data analysis, and gas-surface interactions causing the measured forces on the spacecraft. In the course of the analysis, it is demonstrated that DANDE will meet its required drag measurement fidelities. We also show how the presence of solar cells (raised features) on the spherical spacecraft changes the drag coefficient and calculate the overall uncertainty during solar maximum and solar minimum conditions

PRECISE HEAD TRACKING IN HEARING APPLICATIONS

The paper gives an overview about two research projects, both dealing with optical head tracking in hearing applications. As part of the project “Development of a real-time low-cost tracking system for medical and audiological problems (ELCoT)” a cost-effective single camera 3D tracking system has been developed which enables the detection of arm and head movements of human patients. Amongst others, the measuring system is designed for a new hearing test (based on the “Mainzer Kindertisch”), which analyzes the directional hearing capabilities of children in cooperation with the research project ERKI (Evaluation of acoustic sound source localization for children). As part of the research project framework “Hearing in everyday life (HALLO)” a stereo tracking system is being used for analyzing the head movement of human patients during complex acoustic events. Together with the consideration of biosignals like skin conductance the speech comprehension and listening effort of persons with reduced hearing ability, especially in situations with background noise, is evaluated. For both projects the system design, accuracy aspects and results of practical tests are discussed

Ionospheric density depletions around crustal fields at Mars and their connection to ion frictional heating

Mars' ionosphere is formed through ionization of the neutral atmosphere by solar irradiance, charge exchange, and electron impact. Observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have shown a highly dynamic ionospheric layer at Mars impacted by loss processes including ion escape, transport, and electron recombination. The crustal fields at Mars can also significantly modulate the ionosphere. We use MAVEN data to perform a statistical analysis of density depletions of ionospheric species (O+, O2+, and electrons) around crustal fields. Events mostly occur when the crustal magnetic fields are radial, outward, and with a mild preference towards east in the planetocentric coordinates. We show that events near crustal fields are typically accompanied by an increase in suprathermal electrons within the depletion, either throughout the event or as a short-lived electron beam. However, no correlation between the changes in the bulk electron densities and suprathermal electron density variations is observed. Our analysis indicates that the temperature of the major ionospheric species, O2+, increases during most of the density depletion events, which could indicate that some ionospheric density depletions around crustal fields are a result of ion frictional heating.</p