re: STS88 and ISS: Different Behavior

Walter Nissen (dk058@cleveland.Freenet.Edu)
Wed, 6 Jan 1999 20:32:20 -0500 (EST)

Thanks very much to Alan Pickup and Don Gardner for their very prompt 
responses to my elset request. 
A careful reading of a message from Jim Cook suggests there are now 2 
sources for elsets: 
As it turns out, based on a preliminary analysis of OIG elsets, as well as 
the reports here in SeeSat-L, the available info at that time shed no 
light on the spacing between Endeavour and ISS.  A guesstimate based on 
prior shuttle-Mir operations was the best available source. 
Personally, I was clouded out on the early morning of the 14th (I was able 
to time a yellowish-green Sun rise despite 95% overcast), but I expect 
that the alert I generated allowed a number of people further South of 
Lake Erie to see Endeavour and ISS.  Too bad, after thrashing about trying 
to obtain better data, and waiting for the weather to clear, I ran out of 
my limited energy before I could generate an alert for DC and vicinity. 
Later elsets from OIG and the STS-TLE mailing list confirm the 
observations posted here, so historians will have a clear understanding of 
the situation. 
Ron Lee, you and some others, including Mike McCants, Rainer Kracht, Ted 
Molczan, (I'm probably forgetting some important names here, I recall 
Alan Pickup and Bjorn Gimle having done so for decaying objects), have 
displayed a wonderful ability to generate elsets for anticipated, i.e., 
powered, flights.  Is it possible you could teach me to do that for 
shuttle operations?  Or possible that someone would be interested in doing 
it and posting the results here?  To communicate with the Cleveland and DC 
media, I need roughly 1-minute accuracy roughly 4 or 5 days in advance. 
I'm quite willing to cope with numerous updates occasioned by 
unanticipated changes in the operational schedule, but when they occur, I 
need either  a) to know how to munge the elsets back to life, or  b) new 
elsets.  (Those of you who are doing the same thing for your own local 
media may not need quite so much lead time).  I need the same lead time 
for reboosts and the like. 
The people of the nations who are paying for the ISS certainly should have 
every opportunity to see the operations in progress.  NASA Administrator 
Dan Goldin certainly seemed to reflect that idea when he said of ISS, with 
typical Goldin enthusiasm, "You'll be able to see it flying overhead with 
the naked eye!".  I'd like to help them. 
Jim Varney writes: 
> The striking difference in behavior showed that magnitude/phase angle 
> models based on theoretical spheres don't always hold up that well. 
Yes, indeed.  When newbies express disappointment at the challenges of 
satellite observing, I offer them the alternative to observe more 
predictable phenomena, such as comets, meteors, Sun spots, etc. 
Endeavour seemed to display a pretty normal light curve as seen from here, 
but ISS, when located at my roof edge, 91.06 seconds later at 981215 
110828.97 UTC, no personal equation applied, at mag -1?, displayed a curve 
consistent with the intended slow rotation reported here earlier.  It 
dimmed to something in the vicinity of mag 2? or 3?, then reached mag -3? 
at 111012.12 and dropped to mag 1?? at 111025.73.  With a slow rotation, 
predicted magnitudes will have to be taken with a very large grain of 
salt, and patience exercised in locating ISS, at least until the station 
grows large enough to be somewhat more consistent.  Fortunately, it is 
already easy naked-eye on favorable passes. 
> I 
> assume the shuttle was flying "white side down" and that helped the 
> brightness considerably in the east. 
I believe the general consensus is that the bright metal of the payload 
bay doors is typically responsible for the brightest of the glints 
displayed by shuttle orbiters.  The dark underbelly is apparently 
responsible for the occasional reports of the shuttle at mag 3 under 
favorable conditions.  For one pass, we had enough careful reports from 
the DC area to distinguish a trend from the favored, bright area to the 
darker one and to perceive that conditions evolved rapidly during the 
I apologize to the correspondents whose contributions I am ignoring in 
this over-simplified message. 
Walter Nissen         
-81.8637, 41.3735, 256m elevation


Astronomy is looking up.