Re: ALERT: Iridium 48 ambiguity

Eberst (
Tue, 13 Apr 1999 10:41:06 -0700 (PDT)

At 06:31 99/04/13 -0400, Walter Nissen wrote regarding Iridium 48:
>Observations are badly needed to help resolve the ambiguity.  "Last good 
>elset" didn't show up in "deep search" predictions for my location 
>tonight.  Perhaps in the Southern Hemisphere?  Or far North?  A careful 
>observation of a bright glint of a normal character from "Last good elset" 
>would go a long way toward confirming the "misidentification" hypothesis. 
>Equally, it would be wonderful to know how bright the "New, from OIG" 
>object is. 
>It is ironic that just as observations are most needed, the usual tools 
>and procedures experience difficulties.  Murphy's what?? 

Never fear, observations from your reliable spotter are available.
I checked the Iridium 48 standard orbit (revs= 14.34217) on April 7
under good conditions and nothing was seen within 2 minutes either
side of predicted time. Therefore it seemed likely that the 25107 orbits
showing a powered, continuous, but erratic descent by Iridium 48 did
indeed refer to the original satellite and not some small fragment that
had been ejected. On April 12, I had a good pass (max. elevation well over
80 degrees) and with very recent elements available from Alan Pickup, I
was able to observe the Iridium on time and track. Two positional fixes
were made, and the magnitude estimated at +5.6 steady.

2420 9904 0.211 1204
9708204 210824.61 102731+391249 5.6 5.6 0 S
9708204 210844.88 103807+531355 5.6 5.6 0 S

So the question arises, is the descent intended and planned (perhaps to
start a plane change) or is it due to a malfunction such as a jammed
valve that has used all the station-keeping fuel in one massive prolonged
burst?  It will be interesting to see if the descent stops when the
revs/day reaches around 15.16 (as with #25527and #25529, 98-66A and C)
or if it continues until Irid48 reaches the denser layers of the atmosphere.
best wishes 
Russell  Eberst  @   North: 55 degrees, 56 minutes, 55 seconds:
West:  3 degrees, 8 minutes, 18 seconds: 
43metres (150 feet) above sea-level