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 Memo about the contents of this directory ($SSWDB/ydb/orbit_sol) 
                                         14-May-2010, Aki Takeda
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There are two series of files, orbit_???? and traj_????, in this 
directory. The orbit_ series were obtained weekly (or bi-weekly
in the later in the mission) from NASDA and contain the orbital 
elements for the day specified in the file. The traj_ series were 
processed from the orbit_ file and contain the prediction for 
every day in the week.

Archiving of the traj_ files started in 1993, from the file for
the week of 27-July. For the period earlier than this date, we
only have orbit_ files, starting from 30-Aug-1991. (There are
several missing entries exist in both series.) 

While the traj_ files are well-annotated, the orbit_ files are
simply numeric (see sample below). These figures should be
interpreted as follows.

<< sample file : orbit_0123 >>

930803080000.000 49202.333333333  5768.931614413 -1335.690031767 -3604.404888046
     1.813329030     7.407408962    -0.027790551   -31.486009601   275.047235788
   559.932733744  7012.689379088     0.017050811    31.329164479    76.587556723
   221.858922854    47.012389744  7009.761227698     0.016743430    31.345861170
    76.590939896   220.631846846    48.239962343-5.891898951D-03-6.258864541D-05
 5.876752574D-05-6.126456538D+00 9.671191295D+00    14.786807945 1.864308399D-05
    97.384101108-1.227810615D-04   748.990677951   514.255777444     7.415578135
     7.668131175

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Row-Column explanation of the orbit_???? files.
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* EPOCH
1-1: EPOCH (UTC)
1-2: EPOCH (MJD)
* Osculating orbital elements 
1-3: Cartesian : X (km)
1-4: Cartesian : Y (km) 
1-5: Cartesian : Z (km) 
2-1: Cartesian : VX (km/s)
2-2: Cartesian : VY (km/s)
2-3: Cartesian : VZ (km/s)
2-4: Sub Satellite Point : PIN (deg.n)
2-5: Sub Satellite Point : LAM (deg.n)
3-1: Sub Satellite Point : H (km)
3-2: Keplerian : A (km)
3-3: Keplerian : E 
3-4: Keplerian : I (deg)
3-5: Keplerian : AN (deg)
4-1: Keplerian : AP (deg)
4-2: Keplerian : MA (deg)
* Mean orbital elements 
4-3: Keplerian : A (km)
4-4: Keplerian : E 
4-5: Keplerian : I (deg)
5-1: Keplerian : AN (deg)
5-2: Keplerian : AP (deg)
5-3: Keplerian : MA (deg)
5-4: Dot elements : A.dot (km/day)
5-5: Dot elements : E.dot (  /day)
6-1: Dot elements : I.dot (deg/day) 
6-2: Dot elements : AN.dot (deg/day)
6-3: Dot elements : AP.dot (deg/day)
6-4: Number of revolution : N (rev/day)
6-5: Dot elements : N.dot (rev/day^2)
7-1: Period of revolution : P (min)
7-2: Dot elements : P.dot (min/day)
7-3: APSIS : HA (km)
7-4: APSIS : HP (km)
7-5: APSIS : VA (km/s)
8-1: APSIS : VP (km/s)
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