How to Find Superbird-A's Phase Shift

Ron Lee (
Sat, 21 Mar 1998 11:56:23 -0700

This is a short tutorial on finding the phase shift for Superbird-A
(#20040).  It is based upon my observation early on 21 Mar 98.  I used
7x50 binoculars, a 100 lap stopwatch and a microcassette recorder.

I started the stopwatch when my just synchronized watch  reached 8:05 PM
local (3:05 UT on 21 Mar).   Each flash was recorded timewise by the 
stopwatch and I made voice recording of the brightness, etc on the 
recorder.  When finsished observing, I record all the lap times on a notepad
then replay the recorder to annotate the brightness and other comments.

What follows below are the observed flashes numbered 1-29.  I am omitting
the lap times since they are not relevant to the process.  Obviously, when
I decide on the selected phase shift point, I add that lap time to the
time (3:05 UT in this case), to get the actual time.

The first column will be the flash number, followed by whether it was B
or F (faint).  These terms are relative to preceding flashes  and are not
absolute...except where the comment relates it to another.

Flash     Brightness        Comment

1		B		First recorded flash
2		B		23.2 sec since #1	
3		B		23.2 sec since #2
4		--           Uncertain  (11.8 sec since #3)
5		B		
6		F
7		B
8		F
9		B
10		F		getting brighter
11		B
(start of phase shift)
12		B		Less bright than #11
13		B		Uncertain
14		B		Same as #13
15		B		Really bright
16		B		Good one
17		B		Good one
18		B		Less bright than #17
19		B
(end phase shift)
20		B		fainter
21		F		definitely
22		B
23		F
24		B		dimmer
25		F
26		B
27		F		really dim
28		B
29		B		(23+ seconds since #28)


First, note the 23+ second interval between flashes 1/2 and 2/3.  
This is typical and you can expect that those flashes will be the starting
sequence Bright flashes.  Flashes 5-10 show a definite F-B pattern, that
gets murky around flash 12.  What I do is follow the F-B pattern until
a Faint flash becomes a Bright flash.  Here that is #12.  I consider that
the start of the phase shift interval.

At the tail end, flashes 21-28 show another F-B pattern. Working towards
the middle, I determine the end of the phase shift to be the Faint flash
that is actually this case #19.   So the phase shift is between
flashes 12 and 19.  This is the subjective part.  There are eight flashes
so I picked the fourth one from the start which is flash #15.  Coincidentally,
that was the brightest flash. So I added the lap time from the stopwatch for
flash #15 to the starting time to get the actual phase shift time.

If you go about this process, pick a bright from the beginning...then 
continue every other flash (11.6 sec intervals) through the phase shift
flashes...and discounting whether you call it B or F...then you will
see that on the other side of the phase shift that you eventually have
a Faint flash where you should have a Bright.  That is what we are now
calling the phase shift.

I would encourage folks to try this. First you get to see a geosynchronous
satellite with binoculars or naked eye.  Secondly, by reporting it here
with your location (longitude/latitude), you can help Rob Matson with data
for his technical analysis.

Ron Lee