Tumbling debris object 07013, 73-086D

Craig Cholar (3432P@VM1.CC.NPS.NAVY.MIL)
Mon, 01 Dec 97 15:41:29 PST

Things have been pretty quiet here on Seesat-L lately.  I guess cloudy,
cold winter nights, the deepening earth's shadow in the northern
hemisphere causing dusk to occur during commute hours for many of us,
smoke & haze in Australia from brush fires, a major 4-day holiday period
in the U.S. where many people visit relatives, Christmas shopping, etc.
all add up to reduced observing time.  For those who can find the time,
and like to hunt down some of the dimmer objects, I have a challenge for
you...

Friday night 11/28 I saw object 7013 = 73086D = NOAA 3 Rk D, an
interesting debris piece I hadn't seen before, tumbling with about a 1
second period.  I found it rather nice to look at (disclaimer:  I'm easily
entertained!), as long as you use a scope or binoculars.  I looked in
the PPAS 7 logs and couldn't find an entry for it, nor was it in the
Molczan file or Quicksat magnitude file.  I guess it's not bright enough
to qualify for the Molczan file, but elsets for it can be obtained by
telneting to OIG, or from ALLDAT.ZIP at http://www.fc.net/~mikem/tle.html

I observed it at 18:35:08 local time, 1h45m after sunset, with a max
alt. of 63 degrees at azimuth 260.  It was somewhere around mag 7 to 8
during maxima as it wafted through the dense Milky Way clouds in Cygnus,
but I'll confess that my magnitude estimates aren't world-class; Suffice
to say it was easy to follow in a 114mm (4.5 in) newtonian.  I didn't
try it in my soon-to-be-retired, clunky old 7x50's.  I've heard good
things about Orion Ultraview 10x50's, which I'm hoping I'll get for
Christmas.  I've left the Orion catalog on the dining room table with
the page opened and the item circled, for a few days now.  :-)

BTW, there are currently 178 (!) explosion-related debris objects in
ALLDAT.TLE associated with the NOAA 3 launch in 1973, the vast majority
of which are very small; too small to be seen, really.  Some of the
largest pieces are within reach, though.  Those looking for a little
diversion and a challenge might enjoy hunting down the NOAA 3 debris
objects I've included elsets for.  These objects orbit at about 1500km
(930sm), so observations are possible without interference from
twilight.

PPAS-7 entries for NOAA 3 debris...

73- 86 B 75-06-07 22         CE                 3.83
73- 86 B 75-06-07 22         LA                 3.90
73- 86 E 82-04-14 21:05.8    BK                10
73- 86 E 82-04-14 21:07      BK                10
73- 86 R 96-09-15 21:49:19.5 RE                 0.1
73- 86DC 75-02-07 19         CE                 0.4
73- 86DC 75-02-16 18         CE                 0.728 dm
73- 86DC 75-02-16 18         HB                 0.75
73- 86DC 75-02-20 19         CE                 0.368 vm
73- 86DC 75-02-21 18         CE                 0.363 vm, every second min inv
73- 86DC 75-02-25 17:56      HK                 0.5
73- 86DC 75-02-25 17:56      HK                 0.5


Averaged RCS of selected NOAA 3 debris objects, courtesy of Mike McCants'
RCS.ZIP file...   ftp://ftp.fc.net/pub/users/mikem/rcs.zip

   Norad   Cospar   RCS
   07013  73- 86D   1.88  <- The tumbler I saw Friday 11/28
   07017  73- 86H   5.63  <- In Molczan.tle
   07018  73- 86J   1.54
   07019  73- 86K   1.13
   07025  73- 86R   0.30  <- Very small RCS, but I've seen it.
   07028  73- 86U   1.23
   07032  73- 86Y   4.33  <- In Molczan.tle
   07079  73- 86BX  1.02
   07138  73- 86DC  1.86

For newcomers, RCS is the Radar Cross Section, in square meters.  It
supposedly gives a rough idea how large an object is, but it can be
deceiving.  RCS values as generated by USSPACECOM for the same object
can vary widely, sometimes extremely so; see Ed Cannon's page about huge
variations in RCS values for the identical Iridium satellites at
http://wwwvms.utexas.edu/~ecannon/iridium_rcs.htm

A big thanks to Mike McCants, for creating his file with averaged RCS
values.  Using his numbers, I use the RCS to help filter out from my
TLE's those objects that are too small for my scope, but sometimes even
objects that supposedly have relatively large RCS values end up being
extremely difficult to see.  The converse can be true, as well.  Large
objects that are poor radar reflectors can generate low RCS values, but
still be visually observed.  Sometimes, you just can't win!

I finally saw NOAA 4 a few weeks ago, but it took many tries and to me
it appeared much dimmer than the RCS would indicate.  Granted, it could
just have been bad pass geometry conspiring against me during all those
attempts, but I have my doubts.

NOAA 3 Rk D                                      1513 x 1409 km
1 07013U 73086D   97335.09889713 -.00000031 +00000-0 +10000-3 0 00177
2 07013 102.0324 349.3690 0066047 337.9497 021.8734 12.50856403098561
NOAA 3 Rk H      2.7  0.0  0.0  6.2 d            1531 x 1509 km
1 07017U 73086H   97335.17922707 -.00000033 +00000-0 +10000-3 0 05493
2 07017 102.2793 013.3935 0014097 051.2219 309.0098 12.36821686086709
NOAA 3 Rk J                                      1524 x 1503 km
1 07018U 73086J   97335.17179450 -.00000033  00000-0  10000-3 0  9161
2 07018 102.2554  11.0629 0012849 330.9741  29.0604 12.38340860 87738
NOAA 3 Rk K                                      1554 x 1446 km
1 07019U 73086K   97335.05589449 -.00000033 +00000-0 +10000-3 0 08431
2 07019 102.2255 354.5455 0068297 287.4262 071.9343 12.41618617090520
NOAA 3 Rk R      2.0  0.0  0.0  6.8 d            2281 x 1504 km
1 07025U 73086R   97334.95050730 -.00000027 +00000-0 +10000-3 0 07018
2 07025 101.9234 116.1529 0468851 153.9765 208.5647 11.54229943014613
NOAA 3 Rk U                                      1640 x 1509 km
1 07028U 73086U   97335.11227077 -.00000035 +00000-0 +10000-3 0 07468
2 07028 102.5971 013.2487 0082112 295.9501 063.3112 12.24100645075490
NOAA 3 Rk Y      2.3  0.0  0.0  6.5 d            1554 x 1507 km
1 07032U 73086Y   97335.09374511 -.00000034 +00000-0 +10000-3 0 05171
2 07032 102.4293 347.1221 0029657 126.9959 233.3819 12.34451384084573
NOAA 3 Rk BX                                     1561 x 1507 km
1 07079U 73086BX  97334.89112872 -.00000033 +00000-0 +10000-3 0 09756
2 07079 102.2386 287.4911 0034654 155.3212 204.9516 12.33635260077428
NOAA 3 Rk DC                                     1585 x 1498 km
1 07138U 73086DC  97335.02265831 -.00000035 +00000-0 +10000-3 0 00441
2 07138 102.6325 333.2312 0054411 212.3109 147.4610 12.31802971082467

Craig Cholar