> I have some TL of MIR for the year 1995 > I'm surprised to see how the "N" of MIR > always increases. Specialy from day 291 to 300 > It's more visible on a curve I made of it. > Is it a coincidence that N never decreases > for the TL I have? > How could I get more TL of MIR in just one file > if possible? > > Day N N./2 > >138 15.56561 0.00007202 >195 15.57069 0.00001252 >205 15.57125 0.00002002 >228 15.57236 0.00001565 >230 15.57245 0.00001589 >237 15.57281 0.00001322 >242 15.57325 0.00006883 >248 15.57363 0.00003035 >258 15.57424 0.00003351 >268 15.57499 0.00003780 >275 15.5755 0.00002780 >276 15.57557 0.00002366 >279 15.57592 0.00003320 >289 15.57662 0.00002048 >290 15.57675 0.00002939 >291 15.5769 0.00004119 >300 15.57882 0.00009490 > >Alphonse POUPLIER 100723.2613@compuserve.com > What you are seeing is normal decay behavior. Mir is a very large object and is subject to significant atmospheric drag. If allowed to continue unchecked, Mir would eventually re-enter the earth's atmosphere and burn up. What keeps this from happening are periodic station-keeping maneuvers performed to either increase the period (decrease the mean motion), circularize the orbit or both. You can see this by plotting the orbital period over a long period of time. What you will see are fairly regular discontinuities that appear whenever a maneuver is performed. It is also interesting to plot eccentricity vs time and apogee/perigee vs. time. These plots show when circularizing maneuvers are performed. I believe you can find some fairly large files in the Celestial Archives (archive.afit.af.mil) containing historical elsets for Mir and other satellites. Some of these files go back several years. ------------------------------------------------------------------------- - Dave Cappellucci http://www.usa.net/~dcappell - - Acappella Publishing http://www.usa.net/acappella - -------------------------------------------------------------------------