Re: The sky really is going to fall on June 30

Ed Cannon (ecannon@mail.utexas.edu)
Wed, 10 Jun 1998 20:48:06 -0400 

Before I offer some thoughts on the OIG situation, here are some 
Tuesday evening (10 June UTC) observations:  Iridium 38 (pred. +5, 
obs. +3.5?), Iridium 41 (pred. -2, obs. -2), and USA 81 (21949, 
92-23A) sparkling at one-power (+2.5).  I saw flashing episodes 
from Iridium 11 at about 2:48:40, 2:48:55, and a really bright 
flash at about 2:50:05.  I'm pretty sure I saw a series of one- 
power flashes from Iridium 20 (a.k.a. Ir 18, #24871) at about 
2:55:40-45.  (The uncertainty was that it was quite low in the
sky, so they weren't very bright; also I didn't see the beginning 
of the episode.)

Now, regarding OIG, Richard Fredrick (rfredric@tfs.net), on Tue, 
09 Jun 1998, at 23:34:54 -0500, wrote:

> First, I want to make clear that I owe a huge debt of gratitude 
> to Mike McCants, Ted Molczan, T.S. Kelso, Alan Pickup and Allen 
> Thompson for their years of work in bringing to the "Net" the 
> TLE's on which our hobby depends. 

I've only been observing satellites for 2.25 years, but I want to 
vigorously second what Richard said above.  Many very appreciative
thank yous to the five named -- and all others! -- who've been 
providing elements sets to the rest of us!!

Now, belatedly, I'll add some thoughts on the potential Web-only
situation.  First, in general, if even one person can get a 
desired group of elsets from OIG and put it in an FTP and/or Web 
site and/or e-mail it to someone who does, then others would be 
able to get the data.  And perhaps an "elsets-only" mailing list 
could be set up for those without Web or FTP access.  Another 
method of distribution could be the Usenet newsgroup.  Now here 
are a couple of specific "plans":

   1.  My understanding of the messages I've read so far is that 
it appears that OIG will (may?) provide *ALL* their elsets in one 
file to at least a few users in some way.  If so, then the main 
problem is smaller, but still large, files.  Maybe OIG will make 
special arrangements for certain files containing several hundred 
or up to 1,500 objects, such as Mike McCants' leo.tle, eccen.tle, 
and geo.tle files.  The Molczan.tle file consists of leo.tle plus 
classified objects.  If OIG will make such special arrangements 
for a very few large files, then maybe things will work out with 
only a limited amount of transitional confusion.

   2.  If all else fails, I'll be glad to join the others who've 
said they would cooperate in a collaborative effort to collect 
needed elsets.  One consideration that I think someone else
mentioned is prioritizing elements.  One important priority is
the stability of the elements.  Objects within a few days of 
decay would be the highest priority, and their elements need to 
be acquired as frequently as they are updated.  (Perhaps OIG 
would consider setting up a mailing list for such objects.)  The 
next priority is maneuvering and high-drag objects; their 
elements would need to be acquired at least every day.  The 
lowest priority objects would be "dead" objects that encounter 
very little atmospheric drag.  It might be sufficient to get 
elements for those once per week or even less frequently.  

   The plan might be something like this.  In a week, I can get
get 700 special-query element sets from OIG's new Web site.  I 
would make seven text files, each containing a list of 100 
objects (with some high-priority objects in every file) for a 
given day of the week, and then cut-and-paste a day's list into 
the OIG special-query form.  Then I could e-mail the elsets to 
Mike or whomever -- or just put them on my Web site.  Using 
Mike's files again as an example, leo.tle contains 1294 elsets, 
eccen.tle has 631, and geo.tle has 634, for a total of 2,559.  
Subtracting the ones now available in OIG's groups (visible, 
iridium, thirty, geo, etc.) should leave fewer than 2,000 
objects.  Four people getting 100 special-query element sets per 
day could get 2,800 "special" elsets in a week.  So I think that 
working together we could surely come up with a way to get all 
the elsets we need, including getting the high-priority objects 
daily or more frequently.  Perhaps we could form teams -- the 
"leo" team, the "eccen" team, the "geo" team -- of people with 
specific interests.

In relation to all this, I'd be interested in a listing of what 
the main, most popular elset files are.  I've been using mainly 
Mike's files for a couple of years, plus Rainer Kracht's "top 50", 
Jay Respler's "visual.txt", OIG's "visible" file, and Alan 
Pickup's "select.tle" and "iridiums.tle" more recently.  I've 
been aware of others that I haven't been using, and this week I'm 
hearing about others of which I haven't even been aware.

Ed Cannon -- ecannon@mail.utexas.edu -- Austin, Texas, USA