IRSUTE, a small satellite for water budget estimate with high resolution infrared imagery

The estimation of land surface fluxes has been recognized in the last ten years as a major scientific issue for the improvement of our knowledge on heat and water budgets and therefore of models in meteorology, hydrology, agriculture and environment. Remote sensing is an adequate mean for filling the gap which exists between small scale instruments or modeling (10m) and the regional or global scales where they have to be determined with a typical grid element of the order of 1 to 10 km. IRSUTE (for Infra Red miniSatellite Unit for Terrestrial Environment) is a scientific small satellite mission providing thermal imagery for the determination and analysis of soil/vegetation/atmosphere processes at the field scale and therefore for providing the necessary data for a scaling-up of these processes from local to regional scales. The main specifications, will allow this instrument to optimize the correction of the sensed radiance and to retrieve the fluxes with an accuracy of the order of 50w/m² (or 0.8mm/day). IRSUTE is designed to have high spatial resolution (50m), across and along track viewing capabilities, 5 channels : visible/NIR, 3.7 μ, and 3 TIR in the 8–11 μm band with a good radiometric sensitivity (NEΔT = 0.1 K). The instrument is to be implemented onboard a small satellite (typically a PROTEUS platform) placed on a sun-synchronous orbit allowing high repetitivity (1 to 3 days). It is based on the push-broom technique which uses IR-CCD linear array detectors positioned in the cryocooled focal plane of a large bandwidth collecting optics.     

High Dynamic GPS Receiver Using Maximum Likelihood Estimationand Frequency Tracking

A new high dynamic global positioning system (GPS) receiver ispresented and its performance characterized by analysis,simulation, and demonstration. The demonstration receiver is abreadboard model capable of tracking a single simulated satellitesignal in pseudorange and range rate. Pseudorange and range rateestimates are made once every 20 ms, using a maximum likelihoodestimator, and are tracked by means of a third-order fadingmemory filter in a feedback configuration. The receiver trackspseudorange with rms errors of under 1 m when subjected tosimulated 50 g, 40 g/s circular trajectories. The tracking thresholdis approximately 28 dB·Hz, which provides 12 dB margin relativethe the minimum specified signal strength, assuming 3.5 dB systemnoise figure and 0 dB antenna gain.     

A bioreactor system for the nitrogen loop in a Controlled Ecological Life Support System.

As space missions become longer in duration, the need to recycle waste into useful compounds rises dramatically. This problem can be addressed by the development of Controlled Ecological Life Support Systems (CELSS) (i.e., Engineered Closed/Controlled Eco-Systems (ECCES)), consisting of human and plant modules. One of the waste streams leaving the human module is urine. In addition to the reclamation of water from urine, recovery of the nitrogen is important because it is an essential nutrient for the plant module. A 3-step biological process for the recycling of nitrogenous waste (urea) is proposed. A packed-bed bioreactor system for this purpose was modeled, and the issues of reaction step segregation, reactor type and volume, support particle size, and pressure drop were addressed. Based on minimization of volume, a bioreactor system consisting of a plug flow immobilized urease reactor, a completely mixed flow immobilized cell reactor to convert ammonia to nitrite, and a plug flow immobilized cell reactor to produce nitrate from nitrite is recommended. It is apparent that this 3-step bioprocess meets the requirements for space applications.     

关于Nielsen数的注记

通过构造基本群的正规子群，得到有限复迭空间和自映射的提升。并定义了NL数，指出用NL数可以估算自映射的Nielsen数。     

Ten years of Arianespace

This article celebrates the tenth birthday of Europe's satellite launch corporation. It was born at a time when expendable launch vehicles were widely believed to be redundant, but has confounded its critics to become the leader in the world commercial satellite launch market. The author notes the milestones on Arianespace's path, and expresses confidence in its ability to the growing competitive challenge of the 1990s.     

A SAR processor based on two-dimensional FFT codes

A synthetic aperture radar (SAR) processor approach based on two-dimensional fast Fourier transform (FFT) codes coupled with an asymptotic evaluation of the unit response function is presented. For the latter, no approximation is made to the distance function, so that the full range of geometric aberrations is analytically considered, enabling an effective reference filter to be designed. The two-dimensional FFTs were designed as to run on computers of very limited memory: the required FFT is computed by means of FFTs of lower order. Two FFT codes were considered: one is faster and allows full or reduced (quick look or multilook) resolution performance to be obtained easily; the second is slower but allows the use of a space-varying filter and/or investigations on limited portions (zoom) of the image. Both codes are suited to parallel processing, e.g. by a transputer net. A full discussion on computer memory and time requirements is presented as well as first examples of image processing results     

Further study of the Pencil-MUSIC algorithm

For finding 2-D angles and polarizations of waves arriving at a rectangular array of crossed dipoles, the Pencil-MUSIC method can achieve the near optimum performance with much less computational burden than the MUSIC (multiple signal classification). Following an angle-only ESPRIT (estimation of signal parameters via rotational invariance techniques) method, an angle-only Pencil-MUSIC can be easily formulated which is far more accurate than the former especially in the coherent case. The angle-only Pencil-MUSIC is analyzed and compared with the original Pencil-MUSIC. The new version sacrifices the polarization estimation to achieve about 8 times more efficient computation The accuracy of the new version seems no more than 4 times worse in terms of estimation deviation     

Interstellar grains in the solar system: Requirements for an analysis

We discuss present knowledge about interstellar dust grains in the heliosphere in order to give goals for future investigations. As far as the identification of the interstellar flux from brightness observations is concerned we calculate the influence of interstellar dust entering the solar system on the Zodiacal light and Zodiacal emission brightness. In case of the Zodiacal light produced by the scattering of solar radiation, the brightness from interstellar dust within the solar system is not detectable within the limits of present observations. In the case of the thermal emission a distinction of the brightness from the interstellar dust component may be possible. This would be especially interesting for an analysis of the overall spatial distribution of the interstellar flux in the solar system. As far as the identification of the interstellar flux from impact experiments is concerned, parameters like the impact direction are essential. Since the interstellar dust flux is modified in the outer solar system already, it is helpful to probe its variation with increasing distance from the Sun in interstellar upstream direction.