4,807 research outputs found
Satellite-to-satellite attitude control of a long-distance spacecraft formation for the Next Generation Gravity Mission
The paperpresentsthedesignandsomesimulatedresultsoftheattitudecontrolofasatelliteformation
under studybytheEuropeanSpaceAgencyfortheNextGenerationGravityMission.Theformation
consists oftwospacecraftswhich fly morethan200kmapartatanaltitudefromtheEarth'sgroundof
between 300and400km.Theattitudecontrolmustkeeptheopticalaxesofthetwospacecraftaligned
with amicroradianaccuracy(pointingcontrol).Thisismadepossiblebyspecific opticalsensors
accompanyingtheinter-satellitelaserinterferometer,whichisthemainpayloadofthemission.These
sensors alloweachspacecrafttoactuateautonomousalignmentafterasuitableacquisitionprocedure.
Pointing controlisconstrainedbytheangulardrag-freecontrol,whichisimposedbymissionscience
(Earth gravimetryatalowEarthorbit),andmustzerotheangularaccelerationvectorbelow0.01 ÎŒrad/s2
in thesciencefrequencyband.Thisismadepossiblebyultrafine accelerometersfromtheGOCE-class,
whose measurementsmustbecoordinatedwithattitudesensorstoachievedrag-freeandpointing
requirements.EmbeddedModelControlshowshowcoordinationcanbeimplementedaroundthe
embedded modelsofthespacecraftattitudeandoftheformationframequaternion.Evidenceand
discussion aboutsomecriticalrequirementsarealsoincludedtogetherwithextensivesimulatedresults
of twodifferentformationtypes
DECIGO and DECIGO pathfinder
A space gravitational-wave antenna, DECIGO (DECI-hertz interferometer Gravitational wave Observatory), will provide fruitful insights into the universe, particularly on the formation mechanism of supermassive black holes, dark energy and the inflation of the universe. In the current pre-conceptual design, DECIGO will be comprising four interferometer units; each interferometer unit will be formed by three drag-free spacecraft with 1000 km separation. Since DECIGO will be an extremely challenging mission with high-precision formation flight with long baseline, it is important to increase the technical feasibility before its planned launch in 2027. Thus, we are planning to launch two milestone missions. DECIGO pathfinder (DPF) is the first milestone mission, and key components for DPF are being tested on ground and in orbit. In this paper, we review the conceptual design and current status of DECIGO and DPF
The control challenges for the Next Generation Gravity Mission
Several activities are on going in preparation of a "Next Generation Gravity Mission" (NGGM) aimed at measuring the temporal variations of the Earth gravity field over a long time span with high spatial resolution and high temporal resolution. The most appropriate measurement technique identified for such mission is the "Low-Low Satellite-Satellite Tracking" in which two satellites flying in loose formation in a low Earth orbit act as proof masses immersed in the Earth gravity field. The distance variation between the satellites and the non-gravitational accelerations of the satellites, measured respectively by a laser interferometer and by ultra-sensitive accelerometers, are the fundamental observables from which the Earth gravitational field is obtained. The control system for the NGGM must fulfil the challenging combination of requirements for the orbit and formation maintenance, attitude stabilisation, drag compensation and microradian laser beam pointing. This paper presents the assessment and the preliminary design of the NGGM control system, performed by Thales Alenia Space Italia and Politecnico di Torino for the European Space Agency
Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View
Small satellite systems enable whole new class of missions for navigation,
communications, remote sensing and scientific research for both civilian and
military purposes. As individual spacecraft are limited by the size, mass and
power constraints, mass-produced small satellites in large constellations or
clusters could be useful in many science missions such as gravity mapping,
tracking of forest fires, finding water resources, etc. Constellation of
satellites provide improved spatial and temporal resolution of the target.
Small satellite constellations contribute innovative applications by replacing
a single asset with several very capable spacecraft which opens the door to new
applications. With increasing levels of autonomy, there will be a need for
remote communication networks to enable communication between spacecraft. These
space based networks will need to configure and maintain dynamic routes, manage
intermediate nodes, and reconfigure themselves to achieve mission objectives.
Hence, inter-satellite communication is a key aspect when satellites fly in
formation. In this paper, we present the various researches being conducted in
the small satellite community for implementing inter-satellite communications
based on the Open System Interconnection (OSI) model. This paper also reviews
the various design parameters applicable to the first three layers of the OSI
model, i.e., physical, data link and network layer. Based on the survey, we
also present a comprehensive list of design parameters useful for achieving
inter-satellite communications for multiple small satellite missions. Specific
topics include proposed solutions for some of the challenges faced by small
satellite systems, enabling operations using a network of small satellites, and
some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications
Surveys and Tutorial
On Small Satellites for Oceanography: A Survey
The recent explosive growth of small satellite operations driven primarily
from an academic or pedagogical need, has demonstrated the viability of
commercial-off-the-shelf technologies in space. They have also leveraged and
shown the need for development of compatible sensors primarily aimed for Earth
observation tasks including monitoring terrestrial domains, communications and
engineering tests. However, one domain that these platforms have not yet made
substantial inroads into, is in the ocean sciences. Remote sensing has long
been within the repertoire of tools for oceanographers to study dynamic large
scale physical phenomena, such as gyres and fronts, bio-geochemical process
transport, primary productivity and process studies in the coastal ocean. We
argue that the time has come for micro and nano satellites (with mass smaller
than 100 kg and 2 to 3 year development times) designed, built, tested and
flown by academic departments, for coordinated observations with robotic assets
in situ. We do so primarily by surveying SmallSat missions oriented towards
ocean observations in the recent past, and in doing so, we update the current
knowledge about what is feasible in the rapidly evolving field of platforms and
sensors for this domain. We conclude by proposing a set of candidate ocean
observing missions with an emphasis on radar-based observations, with a focus
on Synthetic Aperture Radar.Comment: 63 pages, 4 figures, 8 table
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