Re: OA-4/Atlas V launch orbit estimations (updated)

From: Skywayinc--- via Seesat-l <seesat-l_at_satobs.org>
Date: Fri, 4 Dec 2015 11:39:18 -0500
Should the launch be scrubbed tonight (and with a 70% probability of a  
weather violation this seems likely to be the case), the prospects of  sighting 
the OA-4 Atlas V launch along the Atlantic Seaboard now takes on a new  
circumstance in that over this weekend the vehicle will be illuminated by the  
Sun on its ascent to orbit.  
 
This would make it appear considerably brighter as opposed to relying  
simply on the light of the single Centaur rocket to make it visible. 
 
On September 12, 1991, STS-48 (Discovery) lifted off from the Kennedy Space 
 Center at 7:11 p.m. EDT.  Eight minutes later, during civil twilight  
conditions I was clearly able to see the sunlit orbiter and its external tank,  
climbing into orbit from Levittown, NY.  Unlike a nighttime launch where  
the Shuttle's three main engines gave the shuttle a brightness of magnitude  
-1 to -2, this twilight launch made it appear more like magnitude -4  to -5!  
In addition, unlike a night launch where I would lose sight  of the shuttle 
at MECO, on this one occasion, being in sunlight,  I was able to actually 
see MECO and its almost immediate separation from the  external tank 
appearing visually as a "puff" of vapor . . .  and I was able  to follow it almost 
all the way down to my northeast horizon.  
 
It was the only time in 135 shuttle flights that such lighting conditions  
existed during a shuttle launch.
 
Obviously the OA-4/Atlas launch is much smaller than that of a shuttle . .  
. but the odds of making a sighting on its ascent into orbit along the 
eastern  seaboard will markedly increase should it occur during this weekend 
with the  vehicle illuminated by sunlight.  On Saturday, the 30-minute launch 
window  opens at 5:10 p.m. EST and on Sunday the launch window will open at 
4:44 p.m.  EST.
 
Unfortunately, the latest forecast suggests unsettled weather may persist  
through the weekend in and around Cape Canaveral, possibly precluding any  
rescheduled launch attempt. 
 
-- joe rao
 

In a message dated 12/4/2015 10:59:53 A.M. Eastern Standard Time,  
seesat-l_at_satobs.org writes:
(See the original message at:  http://satobs.org/seesat/Nov-2015/0143.html)


Hello  all;

Yesterday the launch was scrubbed because of bad weather. New launch  time
is today 2015/12/04 at 22:33:00 UTC. The probabilities of weather  violation
criteria are of 70%. Here is the updated orbit assuming the launch  at
window open:

OA-4 estimation  #2                                        224 X 225 km
1 70002U 15502A   15338.95664222 0.00000000   00000-0  00000+0 0    00
2 70002  51.6203 307.2078  0000467  48.0984  63.0723 16.18189066    02

This  orbit is only valid if launch occurs at window open. The window is 30
minutes  long.
As allways, please replace the above elset once the JSPOC releases  their
own one.
​Also, european observers will have a nice radio pass,  specially UK's
observers.

Be good!


Jon.​
​​
--  
Jon, COSPAR 6242, 42.9453, -2.82839, 623m, Bitoriano, Basque  Country.
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Received on Fri Dec 04 2015 - 10:39:55 UTC

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