Introduction to Design and Optimization of HVAC System of Spacecraft
From Manned spacecraft and space shuttle to the scale of space station, the technology of manned spacecraft has been developing. The astronauts have to work and live in the cabin for much longer time. Therefore, the spacecraft environmental control and life support systems is not only asked to control the cabin environment parameters within a certain range, but also to ensure the cabin environment with high thermal comfort which can meet…
Introduction to Modularity and Reliability in Low Cost AOCSs
The use of off the shelf electronic components is now common in university and low cost satellites. The advantage against space qualified parts consists in a significant cost reduction, a wider range of components selection, better second sourcing capabilities and an effective reuse of existing technologies, devices, circuits and systems from other engineering domains. Commercial Off The Shelf Components (COTS) are sometimes subject to reliability requirements which are often tougher than those applied to space devices, as they have to be used in markets (e.g., automotive) where safety concerns and the huge number of systems manufactured set demanding constraints on the components. Yet, the drawbacks of COTS components and other low cost design methods, mostly in space missions, remain the higher sensitivity to radiation-induced effects and the reduced system level tolerance to faults. Compensation of these weak points is possible with the development of appropriate design techniques and their proper application throughout the lifecycle of the system, from system level design down to manufacturing. The use of COTS components has thus enormous capabilities and benefits in, but not limited to, small satellite missions. Low cost spacecraft design not only refers to COTS devices but to several other aspect of the design of a spacecraft.…
Introduction to Spacecraft Relative Orbital Motion
The relative orbital motion problem may now be considered classic, because of so many scientific papers written on this subject in the last few decades. This problem is also quite important, due to its numerous applications: spacecraft formation flying, rendezvous operations, distributed spacecraft missions. The model of the relative motion consists in two spacecraft flying in Keplerian orbits due to the influence of the same gravitational attraction center (see Fig. 1). The main problem is to determine the position and velocity vectors of the Deputy satellite with respect to a reference frame originated in the Leader satellite center of mass. This non-inertial reference…
Introduction to Physics-Based Control Methods
Spacecraft control suffers from inter-axis coupling regardless of control methodology due to the physics that dominate their motion. Feedback control is used to robustly reject disturbances, but is complicated by this coupling. Other sources of disturbances include zero-virtual references associated with cascaded control loop topology, back-emf associate with inner loop electronics, poorly modeled or un-modeled dynamics, and external disturbances (e.g. magnetic, aerodynamic, etc.). As pointing requirements have become more stringent to accomplish missions in space, decoupling dynamic disturbance torques is an attractive solution provided by the physics-based control design methodology. Promising approaches include elimination of …
Introduction to Middle Atmosphere: Discharge Phenomena
The layer between 10 and 100 km altitude in the Earth atmosphere is generally categorized as the middle atmosphere (Brasseur & Solomon, 1986). The boosting development of rocket and satellite technologies during the past 50 years has made it possible to directly probe the middle atmosphere (Brasseur & Solomon, 1986). Recently, transient luminous events (TLEs) open up another window; through observing the discharge phenomena in the …
Surface Reflectance Characteristics and Snow Surface Variations from GNSS Reflected Signals
Nasser Najibi1, 2, 3 and Shuanggen Jin1 Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai,…
