For distances within our solar system, or other solar systems, the common unit is the Astronomical Unit (A.U.) 1 A.U. = the average distance between the Earth and the Sun
For most everything else, stars,galaxies,etc..., the distance unit is the parsec (pc). This is a convenient unit when measuring distances to stars by triangulation (what astronomers call parallax).
1 pc = 3.26 light years = about the distance to the nearest star
1 pc = 60 x 60 x 180/pi A.U. = 206265 A.U. ( by definition).
for distances within our galaxy or other galaxies it is kiloparsecs (kpc):
1 kpc = 1,000 pc
for distances between galaxies, and cosmology it is Megaparsecs (Mpc):
1 Mpc = 1,000,000 pc
The convenient astronomical mass unit is the mass of the Sun. One Solar mass is 2x10exp30kg
It is also convenient to mesure the luminosities of celestial objects in terms of the bolometric luminosity of the Sun ( 3.90x10exp26W).
The flux density is the energy incident per second per unit area pr unit frequency band at the Earth. The S.I.units of flux density are watts per square meter per hertz. The typical flux densities of the astronomical objects are wery small and so the radioastronomers introduced the unit 10exp(-26)W/squar meter xHz witch is known as 1Jansky (1 Jy)
In optical astronomy the traditional systems of optical magnitudes is still commonly used:
m=constant-2.5 log S were S is the flux density of the object. The magnitude system is normalized so that a standard star, chosen to be Vega in the constellation of Lyra has zero magnitude.
marți, 17 noiembrie 2009
luni, 16 noiembrie 2009
Advanced Maui Optical and Space Surveillance Technologies Conference
Ultra-Wide Field of View Stereoscope for Low Earth Orbits Surveillance Autors:Octavian Cristea, Paul Dolea BITNET CCSS
(Abstract)
Optical detection of LEO objects with unknown orbital parameters is problematic. In a wide area search mission, an optical sensor collects frames of data on consecutive directions in order to find objects in its range of detection. Taking into account that a LEO object is fast moving on the sky and the visibility window is very small (the sky is clear, the sensor is in the Earth’s shadow and the object is above the horizon and illuminated), and taking into account a typical surveillance sensor FOV of less than one degree, the probability to detect unknown objects is very small. Another limitation is that accurate determination of the target’s position requires correlation of data from more than one passive sensor (a single passive sensor suffers from an inability to get unambiguous range data, even against fairly deterministic tracks such as satellites). This paper examines the setup of a ground-based stereoscopic imager which can detect LEO objects and provide data regarding their orbits. In its minimal configuration, the stereoscope consists of a pair of (COTS) large aperture ultra-wide FOV lenses, backed with a high-quality CCD. While an ultra-wide FOV camera raises problems related to the detection magnitude and orbit estimation accuracy, such a camera significantly increases the probability of unknown objects detection. The stereoscopes base-line is of the order of tens of Km, a compromise between simultaneous detection of low altitude objects from two locations and triangulation accuracy. Each camera continuously images the night sky and sends captured images to a local computer for off-line data processing. Each computer has a GPS card for pair cameras synchronization and it is connected to internet through a Ku band VSAT. Geometric calibration of the image is made automatically, by matching captured stars in the image with an astronomical catalogue of stars. Making interpolation between these reference points, the computer attaches astronomical coordinates to each pixel of the sky image. This way, many errors due to light propagation through the atmosphere or f-Theta distortion can be corrected. The recovery of orbital depth is made by correlating matching feature points from pairs of simultaneous images. Since any pair of captured images practically contains the same star field, another application of the stereoscope is to produce 3D images of the night sky with LEO objects floating in front of the star field. This project is in the concept development phase and it is based on a research cooperation agreement between BITNET CCSS, the Technical University of Cluj and the Astronomical Observatory of Cluj.
(Abstract)
Optical detection of LEO objects with unknown orbital parameters is problematic. In a wide area search mission, an optical sensor collects frames of data on consecutive directions in order to find objects in its range of detection. Taking into account that a LEO object is fast moving on the sky and the visibility window is very small (the sky is clear, the sensor is in the Earth’s shadow and the object is above the horizon and illuminated), and taking into account a typical surveillance sensor FOV of less than one degree, the probability to detect unknown objects is very small. Another limitation is that accurate determination of the target’s position requires correlation of data from more than one passive sensor (a single passive sensor suffers from an inability to get unambiguous range data, even against fairly deterministic tracks such as satellites). This paper examines the setup of a ground-based stereoscopic imager which can detect LEO objects and provide data regarding their orbits. In its minimal configuration, the stereoscope consists of a pair of (COTS) large aperture ultra-wide FOV lenses, backed with a high-quality CCD. While an ultra-wide FOV camera raises problems related to the detection magnitude and orbit estimation accuracy, such a camera significantly increases the probability of unknown objects detection. The stereoscopes base-line is of the order of tens of Km, a compromise between simultaneous detection of low altitude objects from two locations and triangulation accuracy. Each camera continuously images the night sky and sends captured images to a local computer for off-line data processing. Each computer has a GPS card for pair cameras synchronization and it is connected to internet through a Ku band VSAT. Geometric calibration of the image is made automatically, by matching captured stars in the image with an astronomical catalogue of stars. Making interpolation between these reference points, the computer attaches astronomical coordinates to each pixel of the sky image. This way, many errors due to light propagation through the atmosphere or f-Theta distortion can be corrected. The recovery of orbital depth is made by correlating matching feature points from pairs of simultaneous images. Since any pair of captured images practically contains the same star field, another application of the stereoscope is to produce 3D images of the night sky with LEO objects floating in front of the star field. This project is in the concept development phase and it is based on a research cooperation agreement between BITNET CCSS, the Technical University of Cluj and the Astronomical Observatory of Cluj.
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About BITNET
BITNET CCSS is a small private company registered in Cluj, Romania, which is active since 1993 in the field of technological research & consulting. BITNET‘ s activities are carried out at our facilities in Cluj county, or on a teleworkingbasis. The team is currently composed of 10 professionals, plus personnel employed on a project-by-project basis. It is our solution for keeping project costs low and still high level expertise and flexibility. Actually, BITNET CCSS is participating to several national and international research networks and programs, operating in the following business areas: satellite communications, surveillance of space, information technology and innovation. The financial support for our projects is obtained from governmental research grants and contracts concluded with public and private organizations on a commercial basis.
BITNET CCSS is involved in the development of the Romanian space program and has completed more than 40 R&D projects until today. Many of our research projects have been co-funded with up to several hundreds of K Euros through national research programs.
Space Objects Surveillance Projects Expertise: from orbital dynamics to optical and radio tracking technologies, system integration and deployment. Available test beds: astronomical observatory at 750 m altitude and orbital radio & optical sources tracking facility at 1.200 m altitude.
Earth-based Surveillance of Space Projects (selection)
LEOSCOPE (2008-2011): The "Experimental Low Earth Orbit Surveillance Stereoscope" will detect and provide information concerning the orbital parameters of LEO satellites and other bright space objects (meteors, comets, boosters, etc). In the case of big objects in its FOV, the LEOSCOPE will provide photometric and shape parameters. Other applications are related to stereoscopic astronomy. Partner organizations: BITNET (co-ordinator), the Technical University of Cluj and the Astronomical Observatory of the Romanian Academy - Cluj branch. Supported through the Space & Security priority within the "Partnerships in priority S&T domains" Program.
COSMOS (2007-2009): S-band mobile space communication platform for LEO nano-satellites. Partner organization: the Technical University of Cluj. Supported by the national Innovation Program.
URSA(2007-2010): A joint project targeting the development of an experimental ground-based electro-optic and radio deep space surveillance facility in Romania. Partner Organizations: BITNET, the Technical University of Cluj, the Romanian Space Agency and the Astronomical Observatory of the Romanian Academy -Cluj branch. Supported through the Space & Security priority within the "Partnerships in priority S&T domains" Program.
PLURIBUS (2007-2010): BITNET is participating to a joint project led by the Romanian Space Agency, regarding co-orbital clusters of nano-satellites operating in a networked environment. Supported through the Space & Security priority within the "Partnerships in priority S&T domains" Program.
DOG (2005-2006):A preparatory project supporting the development of the first Romanian satellite survey facility. Contracted in the framework of the national Security Research Program. Partner organization: the Astronomical Observatory of the Romanian Academy -Cluj branch.
ScanSat (2004-2006):A small multi-band radio telescope for GEO satellites observation and broadcasts analysis. Contracted in the framework of the Romanian Aerospace Program. Partner organization: the Astronomical Observatory of the Romanian Academy -Cluj branch.
GOLIAT (2005-2008): BITNET signed a contract with the Romanian Space Agency for participation to the GOLIAT project. GOLIAT is the first microsatellite that will be built and operated by Romania. Supported by the CEEX program.
Other projects
MARCH - Multilink Architecture for Multiplay Services (2008-2011): An EUREKA CELTIC project which is targeting the development of innovative business models and technical solutions that will enable the evolution from today's still segmented service architectures to scalable integrated telecommunication architecture for mutiplay services. The project aims at convergence of broadband, mobile, and broadcast approaches and its application to urban and rural deployment. BITNET is a partner within an international project consortium led by TELENOR (Norway).
FORMUAV (2007-2010): BITNET is participating to a joint project led by the Romanian Space Agency, regarding Unmanned Aerial Vehicles flying in a networked environment. Supported through the Space & Security priority within the "Partnerships in priority S&T domains" Program.
BITNET CCSS research infrastructure
Office with 9 rooms in Cluj-Napoca, close to downtown
A test bed for space communication and surveillance of space experiments –in development, 1200 m altitude, 55 Km far from Cluj-Napoca, electromagnetic quiet zone. The test bed hosts BITNET’s astronomical observatory and several antennas.
Satellite communication equipment
Surveillance of space equipment, in development
IT&C equipment.
BITNET CCSS team expertise covers:GEO and LEO satellite terminals deployment, space applications development and demonstration, radio and optical satellite tracking technologies, custom software development (Operating Systems and Platforms:Windows (Desktop, console and web applications), Unix based and POSX compliant systems (Console and web applications), Other platforms (Development of applications with respect the availability of support for development languages and environments). Programming Languages:C/C++, Pascal/Object Pascal, PHP, PERL, Java, SQL, Cold Fusion Script, JavaScript/JScript/VBScript, JavaScript/JScript/VBScript, XML, UML, HTML/XHTML, SOAP, CSS. Database Engines:Oracle, Sybase, MSSQL, PostgreSQL, Interbase, MySQL. Modeling Tools:Rational Rose, Visio, ERwin. Development Environments:Microsoft Visual Studio, Borland C++ Builder, Borland Delphi, Borland J Builder, Macromedia Dreamweaver, Zend Development Environment. Graphic Design:Adobe Photoshop, CorelDRAW Graphics Suite, Macromedia Flash).
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