Monitoring CPDLC

[rabrol]

I've been reading that a lot of aircraft are now receiving ATC instructions via SAT using their Controller Pilot Data Link Control (CPDLC). It seems this is running on Inmersat and Irridium.

Is it possible to receive these transmissions and decode them? Would it be like running an ACARS decoding software just on a different frequency?

Anyone here given this a shot?

 

[whitenoise]

Hello rabrol,

Yes, CPDLC and also regular ACARS are active on Inmarsat. Yes, it's possible to receive and decode them. Regular ACARS software can only be used to parse the ACARS data if in appropriate format. The main issue is 1) equipment to monitor Inmarsat 2) the software decoder to handle Inmarsat P channels.

There are 3 Inmarsat P channels on the Pacific Ocean Region satellite, which is the one I monitor.

Here is example ACARS message via Inmarsat P:
*******************
ACARS (71)
AES ID = 8960D1
GES ID = 82
LCN = 71
Sequence = 1E (240B)
Last SSU = 6
Data = FFFF70
ACARS TEXT:<SOH>2.A6-EBJ<NAK>H1O<STX>- #T1:M04171711/J0040/M80/Q04Syrian PM 'survives car bombing'/./Q21Syrian Prime Minister Wael al-Halqi has/.survived a car bomb attack in the/.capital, Damascus, which has caused/.casualties, reports sa<ETB>$K<DEL>

Here is example of CPDLC message via Inmarsat P:

DATA (71)
AES ID = 7C4922
GES ID = 85
LCN = 0F
Sequence = 20 (256B)
Last SSU = 4
Data = 30FE47
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

I will let you figure out if this is encrypted or in the clear Both types of messages occur.

 

[VE2FXL]

Hi whitenoise,

What is your software for receiving Acars over Inmarsat? Is there a way to receive clear voice comms from aircrafts to ATC or airline companies? If so, what is needed?

Thanks
Luc

 

[whitenoise]

Hi whitenoise,

What is your software for receiving Acars over Inmarsat? Is there a way to receive clear voice comms from aircrafts to ATC or airline companies? If so, what is needed?

Thanks
Luc

The software is my own. Yes, voice comms are generally in the clear, however, you only hear one side of the conversation unless you can monitor both L and C band. L is ground to aircraft and C is aircraft to ground.The calls are mostly medical related but you can also find maintenance, scheduling, business calls etc.

As far as I know there is no company offering such software (wavecom would be the closest but they only due ACARS not voice).

 

[brandon]

Very cool! Also saw your videos on your site. Quite impressive what your doing there with Inmarsat B and C

 

[whitenoise]

Very cool! Also saw your videos on your site. Quite impressive what your doing there with Inmarsat B and C

Thanks Brandon. Yeah, i have been busy. I need to write up the Aero stuff and post that too. The Aero voice is much more difficult than B because of proprietary AMBE codec from DVSI. I actually have to use DSP chip from DVSI for the voice decoding.