Re: N of MIR

Dave Cappellucci (dcappell@rmii.com)
Sat, 28 Oct 95 19:13 MDT

> 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 -
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