(Entschuldige für der Englische Tekst)
subject: Hunting the lower orbit H2A rockets
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neues Bild:
http://www.cloudynights.com/ub…t_20080625_023347akt1.jpg
http://www.cloudynights.com/ub…H2Arocket_20080625cts.jpg
http://www.cloudynights.com/ub…H2Arocket_20080625bt1.jpg
http://www.cloudynights.com/ub…H2Arocket_20080625ats.jpg
From most for the observers visible rocket stages,I pointed out that
the Japanese H-2A rockets may be the most interesting,as their dimensions
are a good 13.5m x 2.5m.General problem with rocket bodies is that
the lower orbit bodies are often small and not very interesting with
dimensions of around 2.5m x 2.5m,making them appear as just disks,even
with highest possible resolution.There are some rocket stages with
around 8 meter in length(Titan upper stages)and some with 10 meter,but
these are in relatively high orbit(mostly round 800-900km)Most H-2A bodies
are in high orbit as well,but 2 interesting exceptions are the rockets
which carried the IGS-3A and IGS-4 spy-satellites.These move in orbits
considerably below 500km,making them more interesting to hunt.(the spinning
fairings E and F of the IGS-4 rocket can be seen often as flashing satellites).
Attached is the final observation,I managed on June 25,after several nights of
overcomming problems.An important problem for such lower orbit objects is
their relative fast dimming when they depart in the Earths shadow.
Most passes of either IGS-3R or-4R couldn't that way be tracked until culmination
when the distance is closest.Exactly what I expected though,the elongated
shape is clearly visible in all frames,even when we see the body probably
slant side-on.
For observers interested in the difficulty of imaging these objects,
I have created the following simulation.It shows different stages of
unsharpness,caused by effects of either bad seeing or limited resolution
of the optical system.The file on top shows a rocket body with dimensions
of a H-2A as seen from an optimal angle,showing full length.The lower file
presents a situation as we see it slant side-on,showing not the full
length in proportion to its width.the simulation at left shows the dimensions
of the body like we would see it in perfect resolution,without any optical
or atmospheric limits.Only a slight blurring caused by atmospheric or optical
effects is necessary to see the situation presented in the mid.This can be
compared to what a good telescope approximately shows in good seeing.
In the worst case,you will only see a narrow elliptical or even round image
as presented in the righter example.Note that most rocket bodies are even
shorter in proportion.
Simulation:
http://img237.imageshack.us/im…ketbodysimulation2eq5.jpg
Best regards,
Ralf Vandebergh
