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851.
Vitally important to the success of any mission is the ground support system used for commanding the spacecraft, receiving the telemetry, and processing the results. We describe the ground system used for the STEREO mission, consisting of the Mission Operations Center, the individual Payload Operations Centers for each instrument, and the STEREO Science Center, together with mission support from the Flight Dynamics Facility, Deep Space Mission System, and the Space Environment Center. The mission planning process is described, as is the data flow from spacecraft telemetry to processed science data to long-term archive. We describe the online resources that researchers will be able to use to access STEREO planning resources, science data, and analysis software. The STEREO Joint Observations Program system is described, with instructions on how observers can participate. Finally, we describe the near-real-time processing of the “space weather beacon” telemetry, which is a low telemetry rate quicklook product available close to 24 hours a day, with the intended use of space weather forecasting. 相似文献
852.
Emge S. Bennett S. Dyott R. Brunner J. Allen D. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(4):18-21
Further cost reduction of the fiber optic gyroscope is necessary to meet the economic requirements of land navigation systems. Previous concentration was on the reduction of the number of splices and component improvements in the open-loop minimum configuration. Now non-essential components and splices are eliminated. The source-detector coupler is not part of the Sagnac interferometer, and serves solely to direct light from the interferometer into the output photodetector. Many commercial laser diodes incorporate a back-facet photodetector to monitor laser intensity. The signal returned from the Sagnac traverses the laser, and can be detected at this photodetector. The gyro signal can be distinguished from the laser signal by the bias modulation applied in the interferometer. Configuring a gyro in this manner eliminates a directional coupler and the separate photodetector, as well as up to two fiber splices in an all-fiber gyroscope. A production, open-loop fiber optic gyroscope has been modified to demonstrate this principle. The gyroscope exhibits performance comparable to the conventional minimum configuration 相似文献
853.
Y Kitaya J Tsuruyama T Shibuya M Yoshida M Kiyota 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(1):177-182
To obtain basic data on adequate air circulation to enhance plant growth in a closed plant culture system in a controlled ecological life support system (CELSS), an investigation was made of the effects of the air current speed ranging from 0.01 to 1.0 m s-1 on photosynthesis and transpiration in sweetpotato leaves and photosynthesis in tomato seedlings canopies. The gas exchange rates in leaves and canopies were determined by using a chamber method with an infrared gas analyzer. The net photosynthetic rate and the transpiration rate increased significantly as the air current speeds increased from 0.01 to 0.2 m s-1. The transpiration rate increased gradually at air current speeds ranging from 0.2 to 1.0 m s-1 while the net photosynthetic rate was almost constant at air current speeds ranging from 0.5 to 1.0 m s-1. The increase in the net photosynthetic and transpiration rates were strongly dependent on decreased boundary-layer resistances against gas diffusion. The net photosynthetic rate of the plant canopy was doubled by an increased air current speed from 0.1 to 1.0 m s-1 above the plant canopy. The results demonstrate the importance of air movement around plants for enhancing the gas exchange in the leaf, especially in plant canopies in the CELSS. 相似文献
854.
855.
T H Sweetser C A Halsell R J Cesarone 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(3):257-260
Planetary protection has been an important consideration during the process of designing the Mars Observer mission. It affected trajectory design of both the interplanetary transfer and the orbits at Mars; these in turn affected the observation strategies developed for the mission. The Project relied mainly on the strategy of collision avoidance to prevent contamination of Mars. Conservative estimates of spacecraft reliability and Martian atmosphere density were used to evaluate decisions concerning the interplanetary trajectory, the orbit insertion phase at Mars, and operations in orbit at Mars and afterwards. Changes in the trajectory design, especially in the orbit insertion phase, required a refinement of those estimates. 相似文献
856.
C. J. Gramling A. C. Long 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,16(12):77-80
The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is currently developing a Tracking and Data Relay Satellite (TDRS) System (TDRSS) Onboard Navigation System (TONS) to provide onboard knowledge of highly accurate navigation products autonomously to users of TDRSS. The TONS I operational system processes Doppler data derived from scheduled forward-link S-band services to provide onboard orbit and frequency determination and time maintenance. TONS I is implemented using a stable onboard frequency reference, a Doppler measurement capability in the user transponder, and onboard navigation/signal acquisition software. The success of the TONS experiment (1992/1993), which was implemented on the Explorer Platform/Extreme Ultraviolet Explorer (EP/EUVE) spacecraft, demonstrated the flight readiness of TONS I. TONS II-A provides the user with additional Doppler data derived from an S-band beacon signal, available approximately 80 percent of the time. This paper describes the TONS operational capabilities, configurations, and expected performance. 相似文献
857.
A discussion of the current and emerging core technologies and philosophies that will enable Air Force personnel to quickly, accurately and intuitively diagnose faults in increasingly complex systems 相似文献
858.
Earp S.L. Hughes E.S. Elkins T.J. Vickers R. 《Aerospace and Electronic Systems Magazine, IEEE》1996,11(9):30-39
The suitability of ultra-wideband ground-penetrating radar as a tool for the detection of buried metallic mines is explored in this paper. The analysis centers around a 200-800 MHz, dual-polarized ground penetrating radar (GPR) designed and built by SRI International. The analysis consisted of fusing the images from the dual polarizations into a single image to enhance the target objects and suppress clutter. Results are shown for several variations of a Mahalanobis-based fusion technique, and “soft decision” minefield detection results based upon Monte Carlo statistical techniques are also presented. Although relatively few scenes were analyzed, these results show that the dual-polarized GPR is potentially very effective at finding buried mines and minefields 相似文献
859.
Angle glint can be explained as distortions in the radar echo signal phase front, or alternatively, deviations of the direction of power flow from the radial direction. Here we show that these two theories yield identical results when the polarization of the scattered waves and the receiving antenna are considered. 相似文献
860.
Björn J. R. Davidsson 《Space Science Reviews》2008,138(1-4):207-223
This paper reviews some important results about Knudsen layers obtained in theoretical gas kinetics research in the last few decades, focusing on the weak and strong evaporation problems in two-surface, half-space, and spherical geometries. Furthermore, the application of such results in cometary science is reviewed. In order to illustrate some properties of the half-space evaporation problem for water ice surfaces at temperatures relevant for active comets, a number of numerical Direct Simulation Monte Carlo calculations are presented. 相似文献