P. W. Bousquet

Bio: P. W. Bousquet is an academic researcher from Centre National D'Etudes Spatiales. The author has contributed to research in topics: Spacecraft & Asteroid. The author has an hindex of 5, co-authored 18 publications receiving 259 citations.

MASCOT—The Mobile Asteroid Surface Scout Onboard the Hayabusa2 Mission

Abstract: On December 3rd, 2014, the Japanese Space Agency (JAXA) launched successfully the Hayabusa2 (HY2) spacecraft to its journey to Near Earth asteroid (162173) Ryugu. Aboard this spacecraft is a compact landing package, MASCOT (Mobile Asteroid surface SCOuT), which was developed by the German Aerospace Centre (DLR) in collaboration with the Centre National d’Etudes Spatiales (CNES). Similar to the famous predecessor mission Hayabusa, Hayabusa2, will also study an asteroid and return samples to Earth. This time, however, the target is a C-type asteroid which is considered to be more primitive than (25143) Itokawa and provide insight into an even earlier stage of our Solar System. Upon arrival at asteroid Ryugu in 2018, MASCOT will be released from the HY2 spacecraft and gently descend by free fall from an altitude of about 100 m to the surface of the asteroid. After a few bounces, the lander will come to rest at the surface and perform its scientific investigations of the surface structure and mineralogical composition, the thermal behaviour and the magnetic properties by operating its four scientific instruments. Those include an IR imaging spectrometer (MicrOmega, IAS Paris), a camera (MASCAM, DLR Berlin), a radiometer (MARA, DLR Berlin) and a magnetometer (MASMAG, TU Braunschweig). In order to allow optimized payload operations the thermal design of MASCOT is required to cope with the contrasting requirements of the 4-year cruise in cold environment versus the hot conditions on the surface of the asteroid. Operations up to 2 asteroid days (∼16 hours) based on a primary battery are currently envisaged. A mobility mechanism allows locomotion on the surface. The mechanism is supported by an attitude and motion sensing system and an intelligent autonomy manager, which is implemented in the onboard software that enables MASCOT to operate fully independently when ground intervention is not available.

A feasibility study of a mobile communication network using a constellation of low Earth orbit satellites

Abstract: An effort was made to study whether the increased survivability, true global coverage, and reduced path loss of a LEO (low Earth orbit) network could be utilized to give a viable mobile communication system. The architecture of such a network is complex, but it is expected that the use of advanced technology can overcome most limitations. An optimum constellation is considered, and the first three layers of a digital network are examined. Under certain simplifying assumptions it is shown that the proposed configuration is viable and compares favorably with a similar geostationary network with regards to the overall space-segment cost. The cost benefit begins to favor the LEONET for simpler spacecraft. It is also noted that it may be possible to scale down the LEO constellation to a small size so as to provide continuous coverage above approximately=70 degrees latitude, where geostationary satellites are ineffective. This hybrid architecture is also likely to minimize interference with geostationary satellite systems in the congested mobile bands. >

Hayabusa2 Mission Overview

Abstract: The Hayabusa2 mission journeys to C-type near-Earth asteroid (162173) Ryugu (1999 JU3) to observe and explore the 900 m-sized object, as well as return samples collected from the surface layer. The Haybusa2 spacecraft developed by Japan Aerospace Exploration Agency (JAXA) was successfully launched on December 3, 2014 by an H-IIA launch vehicle and performed an Earth swing-by on December 3, 2015 to set it on a course toward its target Ryugu. Hayabusa2 aims at increasing our knowledge of the early history and transfer processes of the solar system through deciphering memories recorded on Ryugu, especially about the origin of water and organic materials transferred to the Earth’s region. Hayabusa2 carries four remote-sensing instruments, a telescopic optical camera with seven colors (ONC-T), a laser altimeter (LIDAR), a near-infrared spectrometer covering the 3-μm absorption band (NIRS3), and a thermal infrared imager (TIR). It also has three small rovers of MINERVA-II and a small lander MASCOT (Mobile Asteroid Surface Scout) developed by German Aerospace Center (DLR) in cooperation with French space agency CNES. MASCOT has a wide angle imager (MasCam), a 6-band thermal radiator (MARA), a 3-axis magnetometer (MasMag), and a hyperspectral infrared microscope (MicrOmega). Further, Hayabusa2 has a sampling device (SMP), and impact experiment devices which consist of a small carry-on impactor (SCI) and a deployable camera (DCAM3). The interdisciplinary research using the data from these onboard and lander’s instruments and the analyses of returned samples are the key to success of the mission.

MASCOT—The Mobile Asteroid Surface Scout Onboard the Hayabusa2 Mission

Abstract: On December 3rd, 2014, the Japanese Space Agency (JAXA) launched successfully the Hayabusa2 (HY2) spacecraft to its journey to Near Earth asteroid (162173) Ryugu. Aboard this spacecraft is a compact landing package, MASCOT (Mobile Asteroid surface SCOuT), which was developed by the German Aerospace Centre (DLR) in collaboration with the Centre National d’Etudes Spatiales (CNES). Similar to the famous predecessor mission Hayabusa, Hayabusa2, will also study an asteroid and return samples to Earth. This time, however, the target is a C-type asteroid which is considered to be more primitive than (25143) Itokawa and provide insight into an even earlier stage of our Solar System. Upon arrival at asteroid Ryugu in 2018, MASCOT will be released from the HY2 spacecraft and gently descend by free fall from an altitude of about 100 m to the surface of the asteroid. After a few bounces, the lander will come to rest at the surface and perform its scientific investigations of the surface structure and mineralogical composition, the thermal behaviour and the magnetic properties by operating its four scientific instruments. Those include an IR imaging spectrometer (MicrOmega, IAS Paris), a camera (MASCAM, DLR Berlin), a radiometer (MARA, DLR Berlin) and a magnetometer (MASMAG, TU Braunschweig). In order to allow optimized payload operations the thermal design of MASCOT is required to cope with the contrasting requirements of the 4-year cruise in cold environment versus the hot conditions on the surface of the asteroid. Operations up to 2 asteroid days (∼16 hours) based on a primary battery are currently envisaged. A mobility mechanism allows locomotion on the surface. The mechanism is supported by an attitude and motion sensing system and an intelligent autonomy manager, which is implemented in the onboard software that enables MASCOT to operate fully independently when ground intervention is not available.

Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu

Abstract: C-type asteroids are among the most pristine objects in the Solar System, but little is known about their interior structure and surface properties. Telescopic thermal infrared observations have so far been interpreted in terms of a regolith-covered surface with low thermal conductivity and particle sizes in the centimetre range. This includes observations of C-type asteroid (162173) Ryugu1–3. However, on arrival of the Hayabusa2 spacecraft at Ryugu, a regolith cover of sand- to pebble-sized particles was found to be absent4,5 (R.J. et al., manuscript in preparation). Rather, the surface is largely covered by cobbles and boulders, seemingly incompatible with the remote-sensing infrared observations. Here we report on in situ thermal infrared observations of a boulder on the C-type asteroid Ryugu. We found that the boulder’s thermal inertia was much lower than anticipated based on laboratory measurements of meteorites, and that a surface covered by such low-conductivity boulders would be consistent with remote-sensing observations. Our results furthermore indicate high boulder porosities as well as a low tensile strength in the few hundred kilopascal range. The predicted low tensile strength confirms the suspected observational bias6 in our meteorite collections, as such asteroidal material would be too frail to survive atmospheric entry7. The MASCOT lander observed a boulder on the surface of asteroid Ryugu up close. The boulder’s low thermal inertia is closer to fine regolith or comets rather than stony boulders, indicating high porosity and low tensile strength. Orbit measurements confirm that Ryugu’s surface is covered with similar boulders.