Muinonen K.,University of Helsinki |
Muinonen K.,Finnish Geodetic Institute |
Parviainen H.,Institute of Astrophysics of Canarias |
Naranen J.,Finnish Geodetic Institute |
And 7 more authors.
Astronomy and Astrophysics | Year: 2011
A novel shadowing and coherent-backscattering model is utilized in the analysis of the single-scattering albedos and phase functions, local surface roughness, and regolith porosity of specific lunar mare regions imaged by the AMIE camera (Advanced Moon micro-Imager Experiment) onboard ESA SMART-1 mission. Shadowing due to the regolith particles is accounted via ray-tracing computations for densely-packed particulate media with a fractional-Brownian- motion interface with free space. The shadowing modeling allows us to derive the scattering phase function for a ∼100-μm volume element of the lunar mare regolith. The volume-element phase function is explained by coherent-backscattering modeling, where the fundamental single scatterers are the wavelength-scale particle inhomogeneities or the smallest fraction of the particles on the lunar surface. The phase function of the fundamental scatterers is expressed as a sum of two Henyey-Greenstein terms, accounting for increased backward scattering as well as increased forward scattering. Based on the modeling of the AMIE lunar photometry, we conclude that most of the lunar mare opposition effect is caused by coherent backscattering within volume elements comparable in size to typical lunar particles, with only a small contribution from shadowing effects. © 2011 ESO.
Zhang L.,Space Micro |
Nakamura H.,Space Micro |
Lee C.-G.,Space Micro |
Maeda H.,Space Micro |
And 2 more authors.
RSC Advances | Year: 2012
Increasing the synthesis scale is one of the most important issues in nanocrystal synthesis. The main difference between small and large reactors is the thermal transfer rate, which has been reported to have great effects on particle nucleation and growth. According to this viewpoint, the heating rate effects should be studied before designing the scale-up process. In this paper, CdSe quantum dots synthesis was used as a model to investigate the heating rate effects in a microreactor system capable of precisely controlling the temperature and heating rate. The results showed a high dependence of heating rate effects on synthesis parameters. The effects of nucleation and growth kinetics were also investigated. Test experiments to demonstrate the possibility of a scale-up were conducted and results showed that products synthesized by a batch reactor were comparable with microreactor products. Further investigation indicated that heating rate could affect the growth kinetics and subsequently affect the final products at 10% and 20% DDA. Based on these results, the application of a large reactor for large scale synthesis can be considered possible, otherwise a larger reactor cannot be applied and precise heating rate controlling is deemed necessary. © 2012 The Royal Society of Chemistry.
Adell P.C.,Jet Propulsion Laboratory |
Liu T.,Arizona State University |
Vermeire B.,Space Micro |
Bakkaloglu B.,Arizona State University |
Aveline D.,Jet Propulsion Laboratory
IEEE Transactions on Nuclear Science | Year: 2011
This paper presents a digitally controlled programmable point-of-load regulator for next-generation power systems. A novel digital control scheme was designed to minimize single-event effect (SEE)-induced transient effects. By effectively programming the loop transmission, the POL can trade off transient response time with SET robustness. The IC works with 1 to 5.5 V input voltage, 1-4.5V regulated output voltage, high efficiency (peak efficiency at 94%) and power of up to 5 W. The design was fabricated in the AMI i2t100 0.7 μm complimentary, metal-oxide semiconductor (CMOS) process and characterized with the Jet Propulsion Laboratory (JPL) pulsed laser system. © 2011 IEEE.
Barnaby H.J.,Arizona State University |
Vermeire B.,Space Micro |
IEEE Transactions on Nuclear Science | Year: 2015
Current gain degradation in irradiated bipolar junction transistors is primarily due to excess base current caused by enhanced carrier recombination in the emitter-base space-charge region (SCR). Radiation-induced traps at the interface between silicon and the bipolar base oxide facilitate the recombination process primarily above the sensitive emitter-base junction. This leads to an increase in surface recombination current in the SCR, which is a non-ideal component of the BJT's base current characteristic under active bias conditions. In this paper, we derive a precise analytical model for surface recombination current that captures bias dependencies typically omitted from traditional models. This improved model is validated by comparisons to these traditional approaches. © 1963-2012 IEEE.
Bao M.,Xidian University |
Li Y.-C.,Xidian University |
Li Y.-C.,Space Micro |
Xing M.-D.,Xidian University |
And 2 more authors.
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2010
The elliptic orbit module and property of motion of geosynchronous synthetic aperture radar (GEOSAR) are analyzed. The paper discusses in detail the Doppler property of the GEOSAR target in the elliptical orbit. Satellite attitude changes have significant effects on GEOSAR imaging. By deducing the Doppler parameters expression with the satellite attitude variety, it is discovered that we should enhance the measurement precision of the pitch angle and roll angle. The nonlinear motion of the satellite orbit should be taken into account in GEOSAR imaging, so that the SPECAN algorithm, RD algorithm and back-projection algorithm are compared and analyzed, and it is proved that the three imaging approaches are feasible in GEOSAR imaging. Computer simulation results validate the conclusions obtained through analysis and the imaging method.
Szatkowski J.,Unite Launch Alliance |
Czajkowski D.R.,Space Micro
AIAA SPACE 2013 Conference and Exposition | Year: 2013
United Launch Alliance (ULA) EELV launch vehicles have a long history of providing high-value payload accommodations for a variety of customer spacecraft and missions, including planetary missions. Rideshare - the approach of sharing available performance margin with a primary spacecraft, provides satellite developers the opportunity to get their spacecraft to orbit and beyond in a cost effective and reliable manner. Hosted experiments provide another opportunity to fly nonseparating systems on the upper stage through disposal/reentry that may take up to 5 years to complete. This opportunity of hosted experiments allows for data gathering in the space environment and/or for raising technology readiness levels. This paper will give a brief overview of the rideshare capabilities that are available with current status. This includes the results from the NROL-36 launch of 8 PPODs in Sep of 2012. This presentation will focus on Rideshare delivery options for CubeSats/SmallSats and Hosted Experiments, with emphasis on support for command/ control, sequencing, data collection, and data transport to ground stations for experiment data products.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2010
Micro-Space proposes to develop a low mass, automated form of the classic navigator's bubble sextant, with no moving parts, for rapid localization and reliable navigation on the Moon and Mars. Day, night, near side and far side lunar operations will all be handled. Exploration of the Moon (or Mars) without navigation aids comparable to those now common on Earth is a daunting, and generally unacceptable concept. Since neither body has a significant magnetic field, even a compass is useless. Creating and sustaining a GPS type satellite constellation will not occur soon. But the self contained, automated system Micro-Space proposes is an excellent substitute. It can be installed on top of an astronaut's helmet, or atop a vehicle, in extended EVA. With exploration extended into terrain where a vehicle is likely to become immobilized, but access by a walking human is practical, vast areas of currently unknown territory can be examined at very close range. But an hour's trek into convoluted terrain can leave the trekker seriously disoriented, and subject to human course decisions which could prove fatal. The helmet mount system will provide continuous EVA crew localization for emergency walk back to a safe haven, even if that path crosses unexplored territory. Fixed asset or notable planetary feature localization will also be straightforward at any point in the EVA. The proposed optical navigation system uses production, solid state camera modules for Solar, Earth Shine, and Celestial sight readings, all with an accurate artificial horizon. But the accuracy required is produced by Micro-Space proprietary "Sub Pixel" processing techniques. Lunar localization accuracy will exceed ¼ mile. With the excellent directional reference also produced, this information will make visual identification of relevant terrain features easy.
Space Micro | Date: 2016-01-12
Colorant dispersions for use in surface coating compositions; Organic pigments; Tints for architectural paints and pigmented coatings for interior and exterior use; all of the aforementioned being environmentally friendly; Specifically, colorants applied to grass, lawn, or turfs in residential, commercial, or sports turf applications. Decorative painting services; Painting and applying coatings to building interiors and building exteriors; Painting contractor services; Specifically colorants being applied to grass, lawn, or turfs in residential, commercial, or sports turf applications; all of the foregoing being environmentally friendly.
Lam Q.M.,LexerdTek Corporation |
Jacox M.,Space Micro
AIAA Guidance, Navigation, and Control (GNC) Conference | Year: 2013
It is well known to the estimation community that the values of the process noise covariance matrix, Q (as a function of gyros' noise parameters and filter update cycle time), and measurement noise covariance matrix, R (e.g., star tracker accuracy), primarily dictate the performance of the Extended Kalman Filter (EKF). The theoretical formulations of these two matrices are mathematically straightforward. Nevertheless, getting them to be tuned at the right values to reflect optimal or suboptimal performance for a certain operating condition is a completely different story. As a matter of fact, many of designers tend to consider this particular tuning is really a matter of art rather than science. In reality, selecting proper values for Q and R has been traditionally done in an ad-hoc manner. This paper provides a new look into the roles of the process noise and measurement noise matrices for the spacecraft attitude estimation problem as the design benchmark. This includes an interesting situation where the theoretical values of Q and R, derived as a function of gyro and star tracker noise parameters, are exactly matched with the noise characteristics employed on the sensor model side. However, the filter still exhibits poor attitude estimation performance, as measured against an attitude knowledge requirement, while subject to a high rate slew profile. A simulation based tuning methodology is developed to optimize the filter performance and bring the attitude estimation back to within the required attitude knowledge requirement bound. Lessons learned from this tuning strategy are drawn to derive guidelines and rules of thumbs for accuracy enhancement optimization.