Campagnola S.,Yoshinodai |
Boutonnet A.,Robert Bosch GmbH |
Schoenmaekers J.,Robert Bosch GmbH |
Grebow D.J.,Jet Propulsion Laboratory |
And 2 more authors.
Journal of Guidance, Control, and Dynamics
Tisserand-leveraging transfers (TILTs) are introduced as a new method for computing low-δv orbit transfers with the help of third-body perturbations. The TILTs can mitigate the costs and risk of planetary missions by reducing the orbit insertion maneuver requirements while maintaining short flight times. TILTs connect tw flybys at the minorbody with an impulsive maneuver at an apse. Using the circular, restricted three-body problem, TILTs extend theconcept of v-infinity leveraging beyond the patched-conics domain. In this paper, a new method is presented to compute TILTs and to patch them together to design low-energy transfers. The presented solutions have transfer times similar to the high-energy solutions, yet the -δv cost is significantly reduced. For this reason, TILTs are used inthe reference endgame ofESA's new mission option to Ganymede, JUICE, which is also presented here. JUICE's lowenergy endgame halves the cost of similar high-energy endgames, which makes TILTs a mission-enabling technology for JUICE. The "lunar resonances" of SMART-1 are also explained in terms of low-thrust TILTs, suggesting future application of TILTs and low-thrust TILTs to design missions to the Moon and to other small-body destinations. ©2013 by the American Institute of Aeronautics and Astronautics, Inc. Source
Chujo T.,Yoshinodai |
Kawaguchi J.,Yoshinodai |
Kawaguchi J.,University of Tokyo
This study evaluates the transient response of large spinning membrane structures in space – especially spinning solar sails – by two different methods. A flexible sail membrane is easily deformed when a spacecraft changes its attitude, such as when using thrusters, and the control response including membrane vibration must be estimated in advance of operation. In order to estimate the motion of the membrane, numerical simulations using a multi-particle model (MPM) are conducted, where the membrane is modeled with masses, spring, and dampers. Usually, force propagation is calculated directly in this model and the position and velocity of each particle represent the membrane motion, which is referred to as a continuum analysis in this study. This method is useful for the analysis of membrane vibration because it replaces the complex dynamics with simple equations of motion. However, the computational cost is high and the calculations require a considerable amount of time. This study introduces an eigenfunction analysis to solve this problem. In this method, natural vibration modes and natural frequencies for the entire spacecraft are derived and used for dynamics computation, which reduces the computational cost dramatically compared to the conventional continuum analysis. In this study, the transient response of a spinning solar sail is analyzed using both methods, and the advantages and disadvantages are discussed. It is shown that the eigenfunction analysis provides a suitable method for acquiring approximate solutions in a very low computation time. © 2016 IAA Source
Jaumann R.,Institute of Planetary Research |
Jaumann R.,Free University of Berlin |
Schmitz N.,Institute of Planetary Research |
Koncz A.,Institute of Planetary Research |
And 24 more authors.
Space Science Reviews
The MASCOT Camera (MasCam) is part of the Mobile Asteroid Surface Scout (MASCOT) lander’s science payload. MASCOT has been launched to asteroid (162173) Ryugu onboard JAXA’s Hayabusa 2 asteroid sample return mission on Dec 3rd, 2014. It is scheduled to arrive at Ryugu in 2018, and return samples to Earth by 2020. MasCam was designed and built by DLR’s Institute of Planetary Research, together with Airbus-DS Germany. The scientific goals of the MasCam investigation are to provide ground truth for the orbiter’s remote sensing observations, provide context for measurements by the other lander instruments (radiometer, spectrometer and magnetometer), the orbiter sampling experiment, and characterize the geological context, compositional variations and physical properties of the surface (e.g. rock and regolith particle size distributions). During daytime, clear filter images will be acquired. During night, illumination of the dark surface is performed by an LED array, equipped with (Formula presented.) monochromatic light-emitting diodes (LEDs) working in four spectral bands. Color imaging will allow the identification of spectrally distinct surface units. Continued imaging during the surface mission phase and the acquisition of image series at different sun angles over the course of an asteroid day will contribute to the physical characterization of the surface and also allow the investigation of time-dependent processes and to determine the photometric properties of the regolith. The MasCam observations, combined with the MASCOT hyperspectral microscope (MMEGA) and radiometer (MARA) thermal observations, will cover a wide range of observational scales and serve as a strong tie point between Hayabusa 2’s remote-sensing scales ((Formula presented.)–(Formula presented.)) and sample scales ((Formula presented.)–(Formula presented.)). The descent sequence and the close-up images will reveal the surface features over a broad range of scales, allowing an assessment of the surface’s diversity and close the gap between the orbital observations and those made by the in-situ measurements. The MasCam is mounted inside the lander slightly tilted, such that the center of its 54.8° square field-of-view is directed towards the surface at an angle of 22° with respect to the surface plane. This is to ensure that both the surface close to the lander and the horizon are observable. The camera optics is designed according to the Scheimpflug principle, thus that the entire scene along the camera’s depth of field (150 mm to infinity) is in focus. The camera utilizes a (Formula presented.) pixel CMOS sensor sensitive in the 400–1000 nm wavelength range, peaking at 600–700 nm. Together with the f-16 optics, this yields a nominal ground resolution of 150 micron/px at 150 mm distance (diffraction limited). The camera flight model has undergone standard radiometric and geometric calibration both at the component and system (lander) level. MasCam relies on the use of wavelet compression to maximize data return within stringent mission downlink limits. All calibration and flight data products will be generated and archived in the Planetary Data System in PDS image format. © 2016 Springer Science+Business Media Dordrecht Source
Kikuchi T.,Yoshinodai |
Hoshino M.,Yoshinodai |
Nakayama T.,Yoshinodai |
Yamasaki N.Y.,Yoshinodai |
And 2 more authors.
Journal of Low Temperature Physics
The dielectric micro calorimeter (DMC) is a novel radiation detector utilizing a GHz resonator with dielectric thermometer (Sekiya et al. in J Low Temp Phys 167:435, 2012). The advantage of using a DMC is that the detection mechanism is based on a phonon mediation without Johnson noise and quasi-particle decay process. A large format array of DMCs can be easily multiplexed by a resonator circuit in the readout at GHz band width. We describe the design of a DMC as an X-ray photon counter. It is optimized to detect photon at 5.9 keV energy. We consider (Formula presented.)O-doped SrTiO(Formula presented.) (STO18) and Nb-doped KTa(Formula presented.)Nb(Formula presented.)O(Formula presented.) (KTN) as a candidate of dielectric thermometer. Dielectric materials which have sensitivity (Formula presented.)(= d(Formula presented.)) are also ideal for our application. We check that both STO18 and KTN have (Formula presented.) at 100 mK. If we assume a DMC resonator operating at 100 mK, we need a Q value of a resonator to be 2000 for X-ray detection. © 2016 Springer Science+Business Media New York Source
Hayashi T.,Yoshinodai |
Nagayoshi K.,Yoshinodai |
Muramatsu H.,Yoshinodai |
Yamasaki N.Y.,Yoshinodai |
And 5 more authors.
Journal of Low Temperature Physics
We report the fabrication and evaluation of the Cu/Bi bilayer absorber with electrodeposition. We designed the Cu/Bi absorber to satisfy the requirements for scanning transmission electron microscope (STEM). The residual resistivity ratios of films of Cu and Bi with electrodeposition was (Formula presented.) and (Formula presented.), respectively; these values are sufficient for the requirements of STEM. We found that the Cu/Bi bilayer absorber TES microcalorimeter experienced a pulse-shape variation and we considered that these variations were caused by the quality of the contact surface between the absorber and TES. In addition, we examined the structure of the absorber using focus ion beam analysis and STEM. The results suggest that an oxidation between the Cu and seed layer, in which the layer is an electrode for electrodeposition, yielded variations. Moreover, thermal simulation suggests that the thermal conduction between the absorber and TES caused variations. The results of this study will improve the process of Bi electrodeposition. © 2016 The Author(s) Source