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Obtaining other values from NASA 2-Line Element
Hi, We are trying to use the NASA two line elements as the source for
satellite nodes in Network Simulator (an open source network simulation program) to generate simulation scenarios. Is there a straight forward algorithm we can use to convert the NASA 2-Line elements to get all of the values we need (altitude and semi-major axis are not separately called out, and it would also be useful to fix the start of the orbit at a specific point in time)? Below is the excerpt from the NS-2 manual as well as what I believe I can get from the 2-Line element. Thanks Ray Value Source altitude Can this be computed from 2-Line? semi-major axis Can this be computed from 2-Line? eccentricity 2-Line! right ascension of ascending node 2-Line! inclination 2-Line time of perigee passage Argument-of-Perigee (is this what I want?)? For now it seems we need altitude and the semi-major axis, but as these satellite orbits are continuously changing (at least for the polar orbits) it would seem we want to tie them to a simulation where we know what time we start and tie network events to them to see how the orbits affect them (e.g. if we use a LEO bird it may not be in view, but 5 minutes into the simulation come on line to affect the available bandwidth). From the ns-2 manual at http://www.isi.edu/nsnam/ns/doc/node200.html # Position/Sat/Geo A geostationary satellite is specified by its longitude above the equator. As simulation time evolves, the geostationary satellite moves through the coordinate system with the same orbital period as that of the Earth's rotation. The longitude ranges from degrees. As we describe further below, two flavors of geostationary nodes exist: ``geo'' (for processing satellites) and ``geo-repeater'' (for bent-pipe satellites). The node generator can be used to create a geostationary satellite with an attached position object as follows: $ns node-config -satNodeType geo (or ``geo-repeater'') \bs (other node config commands go here...) set n1 [$ns node] $n1 set-position $lon; # in decimal degrees # Position/Sat/Polar A polar orbiting satellite has a purely circular orbit along a fixed plane in the coordinate system; the Earth rotates underneath this orbital plane, so there is both an east-west and a north-south component to the track of a polar satellite's footprint on the Earth's surface. Strictly speaking, the polar position object can be used to model the movement of any circular orbit in a fixed plane; we use the term ``polar'' here because we later use such satellites to model polar-orbiting constellations. Satellite orbits are usually specified by six parameters: altitude, semi-major axis, eccentricity, right ascension of ascending node, inclination, and time of perigee passage. The polar orbiting satellites in have purely circular orbits, so we simplify the specification of the orbits to include only three parameters: altitude, inclination, and longitude, with a fourth parameter alpha specifying initial position of the satellite in the orbit, as described below. Altitude is specified in kilometers above the Earth's surface, and inclination can range from degrees, with corresponding to pure polar orbits and angles greater than degrees corresponding to ``retrograde'' orbits. The ascending node refers to the point where the footprint of the satellite orbital track crosses the equator moving from south to north. In this simulation model, the parameter longitude of ascending node specifies the earth-centric longitude at which the satellite's nadir point crosses the equator moving south to north.17.3 Longitude of ascending node can range from degrees. The fourth parameter, alpha, specifies the initial position of the satellite along this orbit, starting from the ascending node. For example, an alpha of degrees indicates that the satellite is initially above the equator moving from north to south. Alpha can range from degrees. Finally, a fifth parameter, plane, is specified when creating polar satellite nodes- all satellites in the same plane are given the same plane index. The node generator used to create a polar satellite with an attached position object as follows: $ns node-config -satNodeType polar \bs (other node config commands go here...) set n1 [$ns node] $n1 set-position $alt $inc $lon $alpha $plane |
#2
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Obtaining other values from NASA 2-Line Element
Hi, We are trying to use the NASA two line elements as the source for
satellite nodes in Network Simulator (an open source network simulation program) to generate simulation scenarios. Is there a straight forward algorithm we can use to convert the NASA 2-Line elements to get all of the values we need (altitude and semi-major axis are not separately called out, and it would also be useful to fix the start of the orbit at a specific point in time)? Below is the excerpt from the NS-2 manual as well as what I believe I can get from the 2-Line element. Thanks Ray Go here for an explination of the 2 line format. http://amsat.org/amsat/keps/formats.html |
#3
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Obtaining other values from NASA 2-Line Element
Hi, We are trying to use the NASA two line elements as the source for
satellite nodes in Network Simulator (an open source network simulation program) to generate simulation scenarios. Is there a straight forward algorithm we can use to convert the NASA 2-Line elements to get all of the values we need (altitude and semi-major axis are not separately called out, and it would also be useful to fix the start of the orbit at a specific point in time)? Below is the excerpt from the NS-2 manual as well as what I believe I can get from the 2-Line element. Thanks Ray Go here for an explination of the 2 line format. http://amsat.org/amsat/keps/formats.html |
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Obtaining other values from NASA 2-Line Element
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#5
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Obtaining other values from NASA 2-Line Element
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#6
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Obtaining other values from NASA 2-Line Element
(Ray Williams) wrote:
Hi, We are trying to use the NASA two line elements as the source for satellite nodes in Network Simulator (an open source network simulation program) to generate simulation scenarios. Is there a straight forward algorithm we can use to convert the NASA 2-Line elements to get all of the values we need (altitude and semi-major axis are not separately called out, and it would also be useful to fix the start of the orbit at a specific point in time)? format http://www.mindspring.com/~n2wwd/htm...le_format.html model http://celestrak.com/NORAD/documentation/spacetrk.pdf library http://www.brodo.de/english/pub/sgp/ The answer to your question is in one or more of those; only you know how much accuracy you require. |
#7
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Obtaining other values from NASA 2-Line Element
(Ray Williams) wrote:
Hi, We are trying to use the NASA two line elements as the source for satellite nodes in Network Simulator (an open source network simulation program) to generate simulation scenarios. Is there a straight forward algorithm we can use to convert the NASA 2-Line elements to get all of the values we need (altitude and semi-major axis are not separately called out, and it would also be useful to fix the start of the orbit at a specific point in time)? format http://www.mindspring.com/~n2wwd/htm...le_format.html model http://celestrak.com/NORAD/documentation/spacetrk.pdf library http://www.brodo.de/english/pub/sgp/ The answer to your question is in one or more of those; only you know how much accuracy you require. |
#8
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Obtaining other values from NASA 2-Line Element
"Ralph Mowery" wrote in message ...
Go here for an explination of the 2 line format. http://amsat.org/amsat/keps/formats.html Have already looked up the TLE, but after looking around some we found at http://iss-transit.sourceforge.net/c...ions.java.html the routine which converts out of the TLE to get us altitude and semi-major axis. And being java guys we are happy as all we have to do is a slight mod to that code and we are in business. Ray |
#9
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Obtaining other values from NASA 2-Line Element
"Ralph Mowery" wrote in message ...
Go here for an explination of the 2 line format. http://amsat.org/amsat/keps/formats.html Have already looked up the TLE, but after looking around some we found at http://iss-transit.sourceforge.net/c...ions.java.html the routine which converts out of the TLE to get us altitude and semi-major axis. And being java guys we are happy as all we have to do is a slight mod to that code and we are in business. Ray |
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