Utilization of Pan Chromatic and Multi Spectral Remote Sensing Imagery is wide spreading and becoming an established business for commercial suppliers of such imagery like ISI and others. Some emerging technologies are being used to generate Hyper-Spectral imagery (HSI) by aircraft as well as other platforms. The commercialization of such technology for Remote Sensing from space is still questionable and depends upon several parameters including maturity, cost, market reception and many others. HSI can be used in a variety of applications in agriculture, urban mapping, geology and others. One outstanding potential usage of HSI is for water quality monitoring, a subject studied in this paper. Water quality monitoring is becoming a major area of interest in HSI due to the increase in water demand around the globe. The ability to monitor water quality in real time having both spatial and temporal resolution is one of the advantages of Remote Sensing. This ability is not limited only for measurements of oceans and inland water, but can be applied for drinking and irrigation water reservoirs as well. HSI in the UV-VNIR has the ability to measure a wide range of constituents that define water quality. Among the constituents that can be measured are the pigment concentration of various algae, chlorophyll a and c, carotenoids and phycocyanin, thus enabling to define the algal phyla. Other parameters that can be measured are TSS (Total Suspended Solids), turbidity, BOD (Biological Oxygen Demand), hydrocarbons, oxygen demand. The study specifies the properties of such a space borne device that results from the spectral signatures and the absorption bands of the constituents in question. Other parameters considered are the repetition of measurements, the spatial aspects of the sensor and the SNR of the sensor in question.
Based on previous studies that showed significant correlation between crusted soil and their reflectance properties, we applied a systematic study over Loess soil from Israel using Hyperspectral (or Imaging Spectroscopy) technology. A simulation for rain events under laboratory conditions, using the selected soil and varying rain energy treatments was conducted and reflectance properties of the crusted soils were measured. A spectral parameter defined as a Normalized Spectral Area (NSA) was used to assess for the crust status (based on the area under a ratio spectrum relative to a known non-crusted soils' plot). The NSA laboratory parameter was applied to the AISA data using ground controlled soil plots (crusted and non crusted). A reasonable agreement was obtained between the two data sets (laboratory and air) suggesting that infiltration rates values can be estimated remotely. It is strongly suggested that future study, will use the full optical range (VIS-NIR-SWIR-TIR) in the IS technology to map the crust status in a better precise way.
The astronomical ultra-violet space telescope, TAUVEX, being developed in Israel by EL-OP Ltd., in conjunction with Tel Aviv University's Dept. of Astronomy and Astrophysics, has three co-aligned 20 cm diameter telescopes, each with an imaging photon-counting detector of the Wedge & Strip Anode type. The geometric and radiometric parameters of the system must be calibrated before launch in order that the image data acquired by the detector and signal processing sub-system can be converted into accurate maps of the UV sources in the sky. We describe the calibration philosophy and methodology involved in the TAUVEX system and sub-system calibration process. Also presented are the facilities and equipment specially designed and adapted for this purpose.
An athermalized objective has been designed for a compact, lightweight push-broom camera which is under development at El-Op Ltd. for use in small remote-sensing satellites. The high performance objective has a fixed focus setting, but maintains focus passively over the full range of temperatures encountered in small satellites. The lens is an F/5.0, 320 mm focal length Tessar type, operating over the range 0.5 - 0.9 micrometers . It has a 16 degree(s) field of view and accommodates various state-of-the-art silicon detector arrays. The design and performance of the objective is described in this paper.
The TAUVEX UV astronomical telescope, which is designed and manufactured by El-Op with the collaboration of the Tel-Aviv University Wise Observatory and sponsored by ISA (Israel Space Agency), consists of three identical telescopes operating in the 140 nm - 280 nm spectral range. This range is characterized by increased sensitivity to both molecular and particulate contaminants, which requires a strict contamination control approach. The present work describes the contamination control approach for TAUVEX that was jointly developed by Soreq NRC and El-Op. It covers all the project phases: design, manufacturing, integration, and testing. It contains various activities including contamination budget allocation, materials selection policy, theoretical analysis of molecular contamination due to outgassing and prediction of optical degradation in the space environment, experiments to measure transmission loss vs. contaminant concentration, special design features, assembly and testing environment, cleanliness control of thermal vacuum and vibration tests and selection and use of monitoring equipment.
A compact horizon sensor has been developed for use on TECHSAT-1 and other small satellites. The stringent requirements for low weight and power have been met by designing a static sensor with a new type of thermal detector array. The sensor uses four identical telescopes mounted at an optimal angle for the satellite altitude, and a microprocessor to convert the data from the detectors into an accurate measure of the angle to the nadir.
The space ultrahigh vacuum environment induces outgassing of spacecraft organic materials which may condense on optical surfaces and degrade the performance of optical systems. Lab simulation outgassing tests show transmission and/or reflection losses of optical components (i.e., optically polished plates and mirrors) measured at the wavelength range of 200 - 800 nm. The losses caused by deposition of outgassed products on the optical surfaces at the amount of 10<SUP>-6</SUP> - X10<SUP>-4</SUP> g/cm<SUP>2</SUP> were measured. The loss mechanism is most likely scattering of light. This experimental data was combined with a computerized ab-initio model which calculated the contamination developed in a simulated preliminary design of the TAUVEX astronomical UV research telescope. This enabled us to estimate the performance of TAUVEX's optical system as a function of mission time, and served as a guideline for selection of materials, cleanliness requirements, thermal conditions and bakeout processes.
An astronomical UV space telescope, TAUVEX (Tel Aviv University Ultra-violet Explorer), is being built by EL-OP in conjunction with the Tel Aviv University Wise Observatory. It will be launched in 1995 on the SRG satellite to act as the optical monitor for the Danish X-Ray Telescope, SODART, and to survey the sky simultaneously in three UV wavelength bands. This paper describes the imaging aspects of the system.
The TAUVEX UV Space Telescope currently under construction by El-Op Ltd. in Israel is designed both for recording images of the sky in the UV region and to serve as the optical monitor for the SODART X-Ray Telescope being built by the Danish Space Research Institute. The two systems, together with several other experiments, will be flown on the S-R-G satellite to be launched by the CIS in 1995. TAUVEX will image a field of about 1 deg simultaneously in three spectral bands. In addition, it will record a selected object in a high-speed time-resolved mode in these bands. The concept and design of TAUVEX is described in this paper.