A couple of months ago I looked up XPOP and LVLH, since they didn't mean a thing to me. Here are three links that I found, with some explanation: http://stationpayloads.jsc.nasa.gov/J-reference/documents/ssp50254F.pdf Geocentric Equatorial Inertial (known to NASA as J2000) Quasi-Inertial Vehicle-Centered Reference Frame (known to NASA as XPOP) Vehiclecentric Orbital Rotating (known to NASA as LVLH) http://www.lib.cas.cz/www/space.40/MRPO/2002/01/IS020107.HTM XPOP (x-axis perpendicular to orbit plane) to LVLH TEA (local vertical/local horizontal -- torque equilibrium attitude). With this reference frame, the station rotates once while circling Earth, i.e., with respect to an inertial (space-fixed) reference frame like XPOP. http://www.spaceref.com/news/viewsr.html?pid=9156 earth-oriented LVLH (local vertical/local horizontal) attitude to XPOP (x-axis perpendicular to orbit plane) Ed Cannon - ecannon@mail.utexas.edu - Austin, Texas, USA ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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