Superbird A, CO, 2 Mar 97: Corrected

Ron Lee (ronlee@pcisys.net)
Sun, 2 Mar 1997 08:59:20 -0700 (MST)

The previous message was sent before completed. This is the complete
report

This was my third attempt with 7x50 binoculars and my first quality
obs.  Times/dates are UT unless otherwise stated.  The satellite 
first became visible at about 02:44:52 UT on 2 Mar 97.  I observed
three 23.4 second flashes before the fainter flash was detected.

Below are the stopwatch lap number (flash number), lap time from 
previous flash and UT of Flash along with comments recorded on a
tape.  Only enough flashes are included to show justification for
later analysis of mid point.
                                                                      
Flash    Lap time       UT             Comment
10        11.72     02:47:24.6      Faint
11        11.67     02:47:36.3      Bright; Brightest yet
12        11.75     02:47:48.0      Faint
13        11.66     02:47:59.7      Bright; less than #11
14        11.70     02:48:11.4      Faint (See #15)


15        11.69     02:48:23.1      Bright, almost like #14
16        11.70     02:48:34.8      Bright, same as #16
17        11.68     02:48:46.5      Bright, a little fainter
18        11.98     02:48:58.4***   Brightest yet; bad time
19        11.44     02:49:09.9      Bright
20        11.68     02:49:21.5      Bright; same as #19
21        11.72     02:49:33.3      Bright: a little fainter
22        11.68     02:49:45.0      Bright; like #21


23        11.70     02:49:56.7      Faint
24        11.77     02:50:08.4      Bright
25        11.66     02:50:20.1      Faint
26        11.62     02:50:31.7      Bright
27        11.8      02:50:43.5      Faint; hard to see  

***  Bad time. See below for correction

Note:  I use the Faint/Bright terms to differentiate relative
brightness changes between flashes.  It is not an absolute
term!  Also, the UT times are rounded to the nearest 0.1 sec.

Analysis:   If you follow the pattern of Faint/Bright flashes as
shown in Flashes #10-14, through flashes #15-22, you will see a
discontinuity once you reach #23.   This is the phase shift
previously reported.   Using those times to define a mid point
would yield a time about 02:48:58 UT if #14 is assumed the
same brightness as #15.

This basically puts the mid point near flash #18 which I recorded
as the brightest flash (likely brighter than #11).  noting that
#18's lap period is high and #19's is low, I would subtract about
0.26 second from the recorded #18 time of 02:48:58.42 UT to get
02:48:58.16 UT (2 Mar 97) as the actual midpoint.

Accuracy of the midpoint may be off by as much as one 23.4 second
period, but I have a high confidence level in this obs and derived
midpoint.

The satellite was not observed until no longer visible since a 
Flash satellite was due at 02:54 UT, but I estimate that in my
binoculars, it was only visible for about 7 minutes. 

For others who would like to observe this satellite, time of obs
is very critical if you use binoculars.  Rob Matson has determined
some characteristics that should get you in the ballpark.  West
coast observers will see the bright point about 7-8 minutes earlier
than me and east coast (USA) observers about 15 minutes later.  
There is a shift of about 1.4 minutes per day LATER when the bright
flashes occur.  For me, two days later the bright point will be
about 02:48.7 plus 2.8 minutes = 02:51.5 UT.

Obviously the more obs from geographically separated observers that
we get, the better the flashes can be predicted.  Hopefully Rob will
be able to use this obs to further refine his estimates for others, 
but the info included here should be a start. Allow perhaps 10 minutes
either side of your predicted time for uncertainties.

Predictions by Rob obviously supercede any I have made here.

sbird 041
1 20040U 89041A   97041.91454771 -.00000298  00000-0  10000-3 0  9081
2 20040   4.9888  60.7476 0004868  86.1366 274.0928  0.99749139 27553

Ron Lee
104.5614 W, 38.9478 N, 2073 m  , MST or UT-7