ISRO SSLV-D2 - EOS07/JANUS-1/AzaadiSAT-2 - 2023-02-10 3:48 UTC

Some info for this launch can be found also in:

There are two cubesats:


Both added in DB but their frequencies are still unknown. The second one probably will transmit in amateur frequency, however there isn’t any IARU coordination.

Hello Everyone!

Our next satellite AzaadiSAT-2 is getting launched in less than 2 days. We are kindly requesting you all in tracking and receiving our satellite from space.

RF Parameters and TLE file are available at GitHub - Space-Kidz-India/AzaadiSAT-2_RF_Parameters: RF Parameters of AzaadiSAT-2 Satellite

Decoding software and other details will be also provided soon. To begin with, 1200 sound modem would work fine.

This is a replacement satellite to the previously launched AzaadiSAT back in August 7, 2022 aboard SSLV-D1 where the mission was lost due to an issue in the launch vehicle.

This new satellite is similar to the old one but has a completely new bus. Mission Page will be up on our website soon with all the details and will keep you all updated in this thread.

Thank you, Everyone!


The IARU Coordination can be found at IARU Sat Coordinator

Since it is a replacement satellite for the AzaadiSAT-1, we have requested IARU for reusing the same coordination request and it has been approved. We got the coordination letter a week ago.


The coordination info is available here: IARU Sat Coordinator


For anyone who would like to use the SatNogs Temp ID# for AzaadiSAT-2 in their tracking app, here is the TLE w/ that unique object number:

1 99198U          23041.16871528  .00000000  00000-0  50000-4 0    06
2 99198  37.3137 114.2571 0004561 331.7707 224.7728 15.39388745    02

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Could you specify the endianess of the data transmitted?

Is that 425Hz shift for AFSK AX.25 really correct? I didn’t check with other setups, but it sounds strange to me.

Thanks for any information provided and good luck with your second attempt!

Btw: this is a nice spacecraft :grinning::+1:

I’m waiting on confirmation from the Team, along with (hopefully) a sample file to confirm the characteristics of that 1k2 FSK downlink. But if it’s the same that was in the original AzaadiSAT, then for reference please note in the image below the custom tones (3000:4250) required for Direwolf to decode the signal. (but again, this is from their FIRST satellite - waiting to confirm that we have the same radio for this mission)

Thanks Scott,

Again an orbit that can’t be used by me, a pity.

That’s a pity! This will exclude all native SatNOGS clients from reception :-/

Could you also please add the callsigns used in the AX.25 transmissions?

I’ve started some work, still some clarification is needed!

Please leave comments on the MR or here, whatever fits best for you :grinning:

Pleased to report on an update from the AzaadiSAT-2 Team regarding the FSK downlink!

With a sample I/Q file, and at their direction, I was able to confirm that the 1200 baud FSK downlink decodes perfectly fine in standard AFSK decoders such as Direwolf and UZ7HO SoundModem as long as the signal is demodulated as USB.

You can also see the DEST & SOURCE callsigns in the decodes below:



Good morning,

Can you share the IQ recording?
I want to try the FSKAX25 decoder from UZ7HO.

Absolutely Jan - so sorry! I had uploaded it but then forgot to include the URL. Thanks so much for catching that.

(you’ll see a quick FSK packet after the LoRa burst but before the CW)


That demodulated data clarifies some things! Source callsign is AZDSAT and destination calling is SKITRC - very good! The packet is of message_type == 1, a health beacon packet! Is there a chance we can get a S&F Message packet, too? I didn’t understand if this is only transmitted via LoRa or also via AX.25. I could have a guess on the float sizes, too - let me see!

Scott, could you somehow append the data in ASCII (so I don’t have to copy it from the screenshot :wink: ).

Got it typed down from the screenshot! The hexadecimal representation of that data is:


Convert it to binary:

echo "a69692a8a4866082b488a682a86100f0415a445354323a010012080f473a0000c0ff0000c0ff0000c0ff0000c0ff0000000039" | xxd -r -p - > health_beacon_01.bin

There are some questions leftover:

  • float indeed seems to be 4 bytes of size, but endianness is still a question
  • conversion formulas are missing (how to interpret the obc_temperature e.g.)
  • I have two bytes leftover that are unparsed at the end (in the screenshot, line 030: positions 2 and 3, values 00 39). Either there is something missing in the struct or there’s a size that doesn’t match
  • transmitted_on is the indicator on which transmitter the data has been transmitted?

Thanks Scott,

And indeed this can be decoded with the FSKAX25 soundmodem from UZ7HO, so no need to use the USB work around.

For gr_satellites use the following yml file:

norad: 99198
  &tlm Telemetry:
    telemetry: ax25
  1k2 FSK downlink:
    frequency: 437.275e+6
    modulation: FSK
    baudrate: 1200
    framing: AX.25
    - *tlm

Then this will be the output:

-> Packet from 1k2 FSK downlink
    header = Container: 
        addresses = ListContainer: 
                callsign = u'SKITRC' (total 6)
                ssid = Container: 
                    ch = False
                    ssid = 0
                    extension = False
                callsign = u'AZDSAT' (total 6)
                ssid = Container: 
                    ch = False
                    ssid = 0
                    extension = True
        control = 0x00
        pid = 0xF0
    info = b'AZDST2:\x01\x00\x12\x08\x0fG:\x00\x00\xc0\xff\x00\x00\xc0\xff\x00\x00\xc0\xff\x00\x00\xc0\xff\x00\x00\x00\x009' (total 35)
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Thank you so much, everyone! Not able to reply immediately due to launch-related activities. Soon we will post more details. Please keep an eye on our Twitter.

Here are some more details:
Azaadisat 2 – Space Kidz India

We are yet to setup our SatNOGS station yet so not able to schedule observations, can someone help with creating observations over potential passes of the ground station? TLE is already given in the previous message.

Thank you!


I would be ready in less than an hour creating a dashboard, but that needs some clarification as mentioned above!

Please have a look at the structure and the float formats being used.

All the best luck for your launch!


That’s great news, Jan. Thanks for much for testing out a SoundModem that works w/ FM demod!!