STS69

Ted Molczan (molczan@utcc.utoronto.ca)
Sun, 27 Aug 1995 16:47:43 -0400

The following should be of interest to observers and analysts alike.

I rarely find much time to devote to satellite-related work these days, but
this morning, while scrolling through the latest *.n2l file, my eye caught the
elements of Pageos fragment 63014DA (NORAD #5994). I noticed that its mean
motion was the highest I had ever seen it, and its ndot/2 was also very high.
Pageos fragments are large sheets of very thin aluminized mylar. Their very
high area to mass ratio makes them highly susceptible to solar radiation
pressure (SRP) perturbations. Most of the time, their perigee height is well
above the atmosphere, so SRP is the dominant perturbation. Periodically, SRP,
produces a large increase in eccentricity, usually raising apogee and decrease
perigee simultaneously. If the perigee height falls much below about 700 km,
atmospheric drag begins to destroy the orbit. As the orientation of the orbit
changes with repsect to the sun, the SRP forces change in magnitude and
direction. If this reversal happens soon enough, the perigee height will rise
up out of the lower atmosphere, and the orbit will avoid destruction. Sooner or
later, a subsequent dip into the atmosphere will prove deep enough and long
enough to permit drag to destroy the orbit. That has been the fate of all but a
few of the remaining Pageos fragments. So what about 63014DA?

The following table summarizes 63014DA's key elements since early 1995.
Epoch, Inclination, eccentricity (e) and mean motion (n0) are taken from NORAD
2-line elements. Semi-major axis (a0), Perigee height (hP) and apogee height
(hA) are in km. The rate of change of perigee height (hPDOT), is in km/d.

The object began the year with perigee well above most of the drag, so SRP
was dominant. hP fell rapidly, until it reached a plateau around day 95070,
whereupon it began to rise. By about day 95100 hP was again falling, and at a
rapidly accelerating rate.

While hP was falling, hA was rising, reaching a maximum of about 6950 km at
about day 95185. Sometime around day 95160, the effects of drag began to
counteract the SRP's expansion of hA, and by about day 95200, the net effect of
the two perturbations was to decrease hA.

Based on the situation of the past few days, it is clear that the object is in
danger of decaying during the present dip into the atmoshpere. hP is now down
to at most 330 km, and may still be decreasing. It should be noted that NORAD's
determination of eccentricity is not always reliable in these situations, often
producing a near steady hP for days at a time, then suddenly "jerking" down
another notch, so it is not clear whether or not, nor how fast, the hP has been
changing over the past week or so. Even if hp is in a new plateau, it is
experiencing considerable drag at 330 km.

At the mid-northern latitudes, the object is now in morning visibility, making
near-perigee passes, becoming as bright as magnitude zero. Due to the very high
rate of decay, I recommend obtaining daily updates of the elements. Also,
historically, NORAD tends to lose these objects well before (days even
weeks)they decay, so amateur observations may provide the only record of their
final days in orbit.

     Epoch       Inc       e         no       ao      hP     hA   hPDOT
95020.25378998 86.1399 0.2511649 8.43507858 10194.9 1263.3 6384.5	
95025.11411091 86.1371 0.2544686 8.43930108 10191.5 1227.1 6413.9  -7.5
95034.23827033 86.0463 0.2599293 8.44154511 10189.5 1170.0 6467.1  -6.3
95039.68845064 86.0168 0.2620694 8.44192632 10189.2 1147.9 6488.4  -4.1
95044.19056255 85.9453 0.2641175 8.44235268 10188.6 1126.6 6508.6  -4.7
95055.20800286 85.7873 0.2673364 8.44322030 10187.4 1093.0 6539.9  -3.1
95061.13091484 85.7085 0.2677121 8.44351894 10186.9 1088.8 6543.1  -0.7
95069.06719797 85.5843 0.2680141 8.44397580 10186.1 1085.1 6545.1  -0.5
95076.17400012 85.4748 0.2677890 8.44435417 10185.4 1086.9 6541.9   0.3
95082.56992017 85.4039 0.2673972 8.44456341 10185.0 1090.6 6537.4   0.6
95088.84732621 85.2714 0.2672251 8.44475468 10184.4 1091.9 6535.0   0.2
95095.47992859 85.1772 0.2673162 8.44494322 10184.0 1090.7 6535.4  -0.2
95103.05985580 85.0974 0.2683206 8.44527803 10183.6 1080.1 6545.1  -1.4
95108.50756668 85.0013 0.2690182 8.44603491 10182.8 1072.5 6551.2  -1.4
95124.84128691 84.8994 0.2760771 8.45541175 10175.2  995.1 6613.3  -4.7
95127.32473026 84.8956 0.2780528 8.45838695 10172.8  973.2 6630.4  -8.8
95136.66050447 84.8556 0.2839266 8.47007386 10163.4  906.7 6678.1  -7.1
95144.21389058 84.8540 0.2885196 8.48150180 10154.3  853.6 6713.0  -7.0
95150.57921696 84.8489 0.2950501 8.49048428 10147.1  782.2 6770.0 -11.2
95157.28932814 84.8388 0.3003574 8.50324753 10136.9  721.2 6810.6  -9.1
95163.28472748 84.8292 0.3061899 8.51335033 10128.9  656.5 6859.2 -10.8
95178.76358515 84.7966 0.3160486 8.54678309 10102.4  538.5 6924.2  -7.6
95182.85832845 84.7781 0.3185541 8.55501316 10095.9  508.8 6941.0  -7.3
95184.37879755 84.7651 0.3195620 8.55903733 10092.7  496.5 6947.0  -8.1
95206.75228756 84.4938 0.3261223 8.63843857 10031.1  388.8 6931.5  -4.8
95215.75144273 84.3206 0.3257695 8.71715447  9971.1  351.8 6848.4  -4.1
95221.56180175 84.1952 0.3175680 8.86405400  9861.1  358.5 6621.7   1.1
95229.56645019 84.0724 0.3058097 9.12963681  9669.3  341.4 6255.3  -2.1
95234.14225365 83.9825 0.3011143 9.23440615  9596.4  335.8 6115.0  -1.8
95235.11677055 83.9635 0.3006879 9.25009979  9585.6  332.4 6096.9  -3.5
95236.51724086 83.9467 0.2975043 9.32086600  9537.1  328.8 6003.5  -2.0
95237.37457132 83.9382 0.2956245 9.35488804  9514.0  330.4 5955.6   1.9
95237.58838658 83.9337 0.2950277 9.36586823  9506.6  330.9 5940.3   2.1


Elements since early 1995:

Note: most of these have had their ndot/2 averaged by the software that
produced the *.n2l files. Those with near-zero values are the original
NORAD values. NORAD's differential corrections software seems to "choke"
on SRP objects, which is one of the reasons I use ndot/2 averaging for
predictions.

1 05994U 63014 DA 95020.25378998  .00059951  00000-0  15477 1 0  5829
2 05994  86.1399 275.1162 2511649  38.1745 337.3259  8.43507858171385
1 05994U 63014DA  95025.11411091  .00000010  00000-0  10000-4 0  5958
2 05994  86.1371 274.3783 2544686  33.2385 340.5165  8.43930108171793
1 05994U 63014DA  95034.23827033  .00000009  00000-0  10000-4 0  6104
2 05994  86.0463 272.9505 2599293  24.5266 345.9729  8.44154511172563
1 05994U 63014 DA 95039.68845064  .00000009  00000-0  10000-4 0  6180
2 05994  86.0168 272.1135 2620694  18.8781 349.2904  8.44192632173024
1 05994U 63014 DA 95044.19056255  .00004735  00000-0  79979-1 0  6242
2 05994  85.9453 271.3562 2641175  14.8670 351.6706  8.44235268173406
1 05994U 63014 DA 95055.20800286  .00000007  00000-0  10000-4 0  6394
2 05994  85.7873 269.5368 2673364   3.8496 357.9169  8.44322030174331
1 05994U 63014 DA 95061.13091484  .00002521  00000-0  37542-1 0  6485
2 05994  85.7085 268.5349 2677121 357.8211   1.2721  8.44351894174834
1 05994U 63014 DA 95069.06719797  .00002878  00000-0  42367-1 0  6597
2 05994  85.5843 267.1729 2680141 349.6363   5.8338  8.44397580175505
1 05994U 63014 DA 95076.17400012  .00002662  00000-0  39461-1 0  6732
2 05994  85.4748 265.9434 2677890 342.0816  10.1123  8.44435417176104
1 05994U 63014 DA 95082.56992017  .00001636  00000-0  24570-1 0  6828
2 05994  85.4039 264.8182 2673972 335.1167  14.1038  8.44456341176641
1 05994U 63014 DA 95088.84732621  .00001523  00000-0  23012-1 0  6890
2 05994  85.2714 263.6985 2672251 328.0746  18.2700  8.44475468177171
1 05994U 63014 DA 95095.47992859  .00001421  00000-0  21391-1 0  6961
2 05994  85.1772 262.4950 2673162 320.4502  22.8531  8.44494322177736
1 05994U 63014 DA 95103.05985580  .00002209  00000-0  32065-1 0  7054
2 05994  85.0974 261.1212 2683206 311.5531  28.4035  8.44527803178372
1 05994U 63014 DA 95108.50756668  .00006947  00000-0  98232-1 0  7154
2 05994  85.0013 260.0982 2690182 305.0636  32.8367  8.44603491178839
1 05994U 63014 DA 95124.84128691 -.00000002  00000-0  10000-4 0  7379
2 05994  84.8994 257.0469 2760771 285.3675  46.1428  8.45541175180217
1 05994U 63014 DA 95127.32473026  .00059901  00000-0  58639 0 0  7411
2 05994  84.8956 256.5790 2780528 282.2813  48.3597  8.45838695180428
1 05994U 63014 DA 95136.66050447  .00062592  00000-0  46712 0 0  7448
2 05994  84.8556 254.7228 2839266 271.4240  56.7984  8.47007386181216
1 05994U 63014 DA 95144.21389058  .00075648  00000-0  44675 0 0  7498
2 05994  84.8540 253.1853 2885196 262.6618  64.1871  8.48150180181850
1 05994U 63014 DA 95150.57921696  .00070558  00000-0  29672 0 0  7578
2 05994  84.8489 251.8756 2950501 255.1533  70.8252  8.49048428182394
1 05994U 63014 DA 95157.28932814  .00095105  00000-0  29040 0 0  7605
2 05994  84.8388 250.4500 3003574 247.4682  78.6762  8.50324753182968
1 05994U 63014 DA 95163.28472748  .00084255  00000-0  17693 0 0  7668
2 05994  84.8292 249.1451 3061899 240.6888  85.4636  8.51335033183476
1 05994U 63014 DA 95178.76358515  .00000108  00000-0  10000-3 0  7857
2 05994  84.7966 245.6595 3160486 223.0359 107.5127  8.54678309184799
1 05994U 63014 DA 95182.85832845  .00100496  00000-0  74052-1 0  7884
2 05994  84.7781 244.7084 3185541 218.3673 114.1660  8.55501316185142
1 05994U 63014 DA 95184.37879755  .00000153  00000-0  10000-3 0  7899
2 05994  84.7651 244.3529 3195620 216.6956 118.8062  8.55903733185272
1 05994U 63014 DA 95206.75228756  .00386654  00000-0  86405-1 0  8259
2 05994  84.4938 238.9484 3261223 191.1744 159.4870  8.63843857187191
1 05994U 63014 DA 95215.75144273  .00599165  00000-0  83199-1 0  8362
2 05994  84.3206 236.6147 3257695 180.6894 179.0280  8.71715447187977
1 05994U 63014 DA 95221.56180175  .01264117  00000-0  18883 0 0  8474
2 05994  84.1952 235.0878 3175680 173.2851 192.0210  8.86405400188487
1 05994U 63014DA  95229.56645019  .01589128  00000-0  17098+0 0  8553
2 05994  84.0724 232.9056 3058097 163.2343 209.8031  9.12963681189203
1 05994U 63014DA  95234.14225365 +.01016568 +00000-0 +10007-0 0 08682
2 05994 083.9825 231.5560 3011143 156.9645 220.1194 09.23440615189624
1 05994U 63014DA  95235.11677055  .00894154  00000-0  83921-1 0  8621
2 05994  83.9635 231.2586 3006879 155.6456 222.2976  9.25009979189711
1 05994U 63014 DA 95236.51724086  .02380816  00000-0  20412 0 0  8635
2 05994  83.9467 230.8510 2975043 153.6347 225.2640  9.32086600189849
1 05994U 63014DA  95237.37457132  .02194110  00000-0  19195+0 0  8642
2 05994  83.9382 230.5815 2956245 152.4762 227.0398  9.35488804189925
1 05994U 63014DA  95237.58838658  .02342166  00000-0  20501+0 0  8651
2 05994  83.9337 230.5201 2950277 152.2242 227.6700  9.36586823189940