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(meteorobs) IMO-NEWS: Bright meteors flash detector?




From: Slaven Garaj <slaven@visnjan.hr> (via Lew Gramer <dedalus@latrade.com>)
To: imo-news@imodot net
Subject: Bright meteors flash detector?
Message-Id: <Pine.SOL.3.91.970712140443.4914A-100000@astro>
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Dear friends,

I need help in constructing flash detector for meteors brighter than, 
say -4m. 

As you already heard from Nikola Biliskov and Neven Grbac at IMC 
1996, our group observe Very Low Frequency radio meteor emission. It is 
suspected that only very bright fireballs produce such VLF radiation. 

Since the probability of occurence of such bright fireballs is very low, 
we decided to construct automatic station for monitoring in the VLF.
It is very frustating that from April 1995, till now, we recorded only 
100% VLF event, in Leonids 1995. 

The flash detector is needed:
- to give signal to the computer, which part of digitized VLF signal is 
  connected with the occurence of the meteor, and have to be stored.
- to determine very approximate magnitude of fireball
- to record relative light curve

Now, some questions:

- Is it possible to construct such flash detector without photomultiplier 
tube? I have HAMAMATSU 1P28 tube, but is not very sensitive in red and IR 
region. Further, the construction is not so simple because very stabile 
high voltage source is needed.

- I've heard that practically same sensitivity and excellent spectral 
sensitivity in red and IR, can be obtained using avalanche photodiodes-APD. 
Do you have some experience with this? Where can I find more informations 
in constructing circuits with APD?

- My friend told me that the output from photomultiplier tube should go 
to the differentiator circuit with time constant of 0.01s, and then through 
the A/D converter to PC. Any suggestions?

I would be very grateful for any sort of help. Thanks in advance,

			bye, till IMC 1997 in Petnica
			
					Goran Zgrablic
			      write at: slaven@astro.visnjan.hr						
			       subject: for Goran