RE: Foton 12 R/B

Ted Molczan (molczan@home.com)
Sat, 25 Sep 1999 12:43:36 -0400

I too would have expected the object to have been glowing at a lower altitude
than the approximately 138 km given by the predicted elements for the epoch of
Mike DiMuzio's observation. One question that arises is just how high can an
object be and still glow due to heating on contact with the upper atmosphere?

Desmond King-Hele commented in Observing Earth Satellites, that satellites
begin to glow at a height of about 90 km. I imagine that the exact height
depends on the object's orbital velocity and the local atmospheric density at
perigee.

The only other case of high-altitude glowing I recall, was an observation by
Steve Bolton of what he thought might have been the final decay of Raduga 33 r,
on 20 Aug 96 UTC:

http://www2.satellite.eu.org/seesat/Aug-1996/0151.html

In fact, at the time of his observation, the object's apogee was still over
1800 km, and it did not decay until 21 Aug. It turned out that Bolton had the
good fortune to see it near perigee, about 100 km. Apparently, it was glowing
brightly during each pass near perigee:

http://www2.satellite.eu.org/seesat/Aug-1996/0153.html

Note that in my above post, I mis-typed Steve Bolton's longitude:

"Below is an ephemeris for Saint John N.B. (45.28 N, 60.05 W):"

should have been:

"Below is an ephemeris for Saint John N.B. (45.28 N, 66.05 W):"

I have since found an official NORAD elset, that is reasonably close to the
epoch of Bolton's observation, which occurred at about 96233.03264 (if anyone
has any closer official elsets, please post them):

1 23797U 96010D   96233.24950077  .54585672  30314-4  12533-2 0  3101
2 23797  47.8008 201.2704 1459706  74.9309 300.8107 13.15295436  5404

This confirms that the object was slightly more than 100 km above the Earth
when observed by Bolton. Note that the altitude calculated by my ephemeris
generator is relative to the actual sub-satellite Earth radius.

20/ 8/96  00:00 - 04:00 UTC  J2000.0  EL >  1  Steve Bolton
Raduga 33 r    96010D   23797   Bull = 310
SGP4  Age =   -0.2 d  Unc =   87 s ( 50%)
Offset =   0.00 min

  TIME      %I   Mv     AZ  EL     R.A.       DEC     FE   VANG  RANGE   ALT
--------    --  ----   ---  --   --------  ---------  --   ----  -----  -----
00:44:30    12   7.7   263   0   12:35:55  -04:19:53   7   0.09   1104    106
00:45:54      UMBRA    274  10   12:33:41   11:12:45   8   0.43    449    100
00:46:12      UMBRA    283  16   12:27:17   21:33:21   8   0.82    320    100
00:46:21      UMBRA    291  21   12:20:16   30:12:39   8   1.22    262    101
00:46:27      UMBRA    299  25   12:12:08   38:12:12   8   1.61    228    101
00:46:32      UMBRA    308  28   12:00:53   46:39:15   8   2.00    205    101
00:46:36      UMBRA    317  31   11:45:55   54:40:44   8   2.33    189    101
00:46:39      UMBRA    325  33   11:27:36   61:19:09   9   2.55    181    101
00:46:42      UMBRA    334  34   10:56:37   68:11:30   9   2.71    176    102
00:46:45      UMBRA    344  35   09:57:20   74:37:54   9   2.78    174    102
00:46:48      UMBRA    354  34   07:57:04   78:58:23   9   2.74    175    102
00:46:51      UMBRA      3  33   05:15:25   78:32:47   9   2.61    179    102
00:46:54      UMBRA     12  32   03:34:09   74:15:36   9   2.41    187    102
00:46:57      UMBRA     19  30   02:44:38   68:55:04  10   2.17    197    103
00:47:00      UMBRA     25  28   02:17:53   63:40:31  10   1.92    210    103
00:47:04      UMBRA     32  25   01:57:34   57:23:01  10   1.62    229    103
00:47:09      UMBRA     39  22   01:43:15   50:47:50  10   1.29    257    104
00:47:15      UMBRA     45  19   01:33:22   44:32:17  10   0.99    295    105
00:47:23      UMBRA     51  16   01:25:49   38:16:53  10   0.71    349    106
00:47:34      UMBRA     56  12   01:20:13   32:14:34  10   0.48    428    107
00:47:50      UMBRA     61   9   01:16:18   26:29:32  10   0.30    548    109
00:48:15      UMBRA     65   5   01:14:11   21:02:19  10   0.18    741    114
00:48:57      UMBRA     69   1   01:14:28   15:50:56  11   0.10   1072    124

Of course, this does not answer the question of exactly what height produced
the glowing. It could have started glowing well above 100 km.

Ted Molczan