[amsat-bb] Re: [Re: Prospero] Commanding Error

g.shirville at btinternet.com g.shirville at btinternet.com
Thu Oct 27 01:04:13 PDT 2011

Hi Tony,

The chuff chuff noises are from space...they are a sort of beacon carried on 
every Orbcomm satellite. They are 125msec long pulses of 57.6kb data and 
have a bandwidth of around 50kHz. They are quite distinctive when you only 
hear one at a time but sometimes one can hear two or more signals at the 
same time and that sort of changes the sound:)



-----Original Message----- 
From: Tony Abbey
Sent: Wednesday, October 26, 2011 8:56 PM
To: rjad at mssl.ucl.ac.uk
Cc: Phil Guttridge ; amsat-bb at amsat.org
Subject: [amsat-bb] Re: [Re: Prospero] Commanding Error

Hi Roger

Nothing other than the chuff- chuff on the 1600 pass. And as you said, its 
also there with Prospero over the horizon. I 'm not using a beam presently - 
using a 360deg parasitic Lindenblad for circular polarisation, but it is 
susceptible to all the high power pager stuff nearby. Its just strange that 
there are elements shifting in frequency in the chuff chuff like a signal 
from a real satellite.
Have just come back from a Rosat re-entry celebration!

Tony Abbey - Senior Research Fellow (retired)
Space Research Centre
Dept of Physics and Astronomy
University of Leicester
University Road SRC Web page: http://www.src.le.ac.uk
LEICESTER LE1 7RH, United Kingdom

On 26 Oct 2011, at 16:17, Roger Duthie wrote:

> Tony -
> We heard something intriguing after about 14:43:40 UT as the tracking said 
> the satellite was on it's way off to the north pole.
> The 'chuff-chuff' description reminds me of a sound we seem to hear quite 
> a lot.  Quite often it coincides with a pass, though I think we hear the 
> same (or very similar) during times when Prospero is over the horizon.
> We are going to try the next pass at ~16:00UT if you want to listen in 
> again.  Our new ploy is to wait for the last most opportune moment to 
> command, as the power _may_ be at it highest (longest charging of 
> batteries, potentially).  So, we'll do short commanding at above 30o el, 
> and listen.
> -Rr.
> Tony Abbey wrote:
>> Hi Roger
>> I could hear some "chuff-chuff" noises on the last pass and they show a 
>> related doppler shift (although I am not correcting sufficiently) as you 
>> can see in the attached plot. Maybe its some other noise but you never 
>> know.
>> On 26 Oct 2011, at 13:39, Roger Duthie wrote:
>>> Commanding went well, from as far as we could make out.  We're not sure 
>>> if we're getting anything back, however.
>>> We'll be doing this pass today, hopefully:
>>> 26 Oct 7.3 15:31:43 10 S 15:38:26 60 E 15:46:11 10 NNE [Times in BST = 
>>> UTC + 1]
>>> -Roger

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