Firefly Alpha Launch - 2021-09-03 01:00 UTC

Satellites & Observations Launches
21

Hi Fredy,

I checked with the CubeSat developer Joe Latrell from Teachers in Space and he confirmed that it is 4k8 AFSK AX.25. So it is FM modulated. So not FSK.

73,
Alan

2 Likes
22

Thereā€™s a nice way to throw away ~7dB of your link budget :frowning:
(The ā€˜double modulationā€™ of AFSK uses more bandwidth than necessary, resulting in decreased performance - see https://www.rowetel.com/wordpress/?p=3799 )

Whatā€™s the tone spacing going to be?

2 Likes
23

Hi Patrick,

Here you go:

WU2M0 audio level = 49 [NONE] ||||
[0.1] WU2M0>WU2M0:H1 BA97 BB95 S6.12 LT+40.1573 LN-76.2106 DT 00:41:23 2020/11/24<0x0a>

U frame UI: p/f=0, No layer 3 protocol implemented., length = 80
dest WU2M0 0 c/r=1 res=3 last=0
source WU2M0 0 c/r=1 res=3 last=1
000: ae aa 64 9a 60 40 e0 ae aa 64 9a 60 40 e1 03 f0 ā€¦d.@...d.@ā€¦
010: 48 31 20 42 41 39 37 20 42 42 39 35 20 53 36 2e H1 BA97 BB95 S6.
020: 31 32 20 4c 54 2b 34 30 2e 31 35 37 33 20 4c 4e 12 LT+40.1573 LN
030: 2d 37 36 2e 32 31 30 36 20 44 54 20 30 30 3a 34 -76.2106 DT 00:4
040: 31 3a 32 33 20 32 30 32 30 2f 31 31 2f 32 34 0a 1:23 2020/11/24.

73,
Alan

2 Likes
24

Hi Mark,

I donā€™t know any more details. I donā€™t have an IQ file, just this audio WAV file:

73,
Alan

2 Likes
25

4k8 AFSK AX.25 is fairly non-standard. What are the space and mark frequencies? 1k2 uses 1200 and 2200 Hz. But this 1 kHz spacing would make the tones non-orthogonal at 4k8.

The only 4k8 AFSK modem I remember seeing in cubesats was the GOMspace U482C, which used 2400 and 4800 Hz tones (basically GMSK at audio frequency). But this didnā€™t use AX.25.

2 Likes
26

Hi Alan, that audio file doesnā€™t work for me. Could you give a direct link?

2 Likes
27

Hi Daniel,

I donā€™t know, but Direwolf decodes it just with the -B 4800 option, and Soundmodem decodes it with the DW 8PSK 4800bd setting with a frequency of 1700 Hz set.

Hereā€™s a link to the Raw Audio file: https://github.com/alanbjohnston/CubeSatSim/blob/FIAB-v3/groundstation/WAV/beacon_test_2.wav?raw=true

73,
Alan

2 Likes
28

I can confirm that itā€™s working now!

1 Like
29

Hi Alan,

Thanks for the info. That is not AFSK, however. It is 8PSK, based on the V.27 modem, as Direwolf indicates. Itā€™s the first time I encounter this mode, but I think that it was probably popular in the past, in the era of packet radio and BBSs, since both Direwolf and Soundmodem support this. It is probably the first satellite using 8PSK. Do you know if there is an FM layer over an audio-frequency 8PSK (thatā€™s what Iā€™m guessing) or does it transmit 8PSK directly?

30

Do you know if the TLEā€™s are on the DB? Doesnā€™t seem possible to program passes.

31

@ea4hcd1
We are re-checking the pre-launch TLE atm and thus it is not in db yet.

What absolute launch / deployment time did you assume when generating the TLE above (which was also published in this post via AMSAT-ML)?

There will be a post here when TLEs are in db.

32

The TLE I sent assumed a launch time of 18:00 PST and deployment time of +891s

2 Likes
33

Sorry for the delay there was a discussion about the TLE sets. In the next 30 minutes Iā€™m going to add them so we can schedule the satellites in Network.

3 Likes
34

All nine satellites have been scheduled for the first 12h. TLE sets used are calculated with 3:00 UTC launch time, if the actual launch time differes more than 3min then all future observations will be removed and will need to be re-scheduled.

2 Likes
35

I think thereā€™s a slight confusion with the TLEā€™s after having done some further propagation due to the estimated deployment time, in any case we will be ready to update TLEā€™s at launch as the deployment time will most likely change.

Of course this considers a correct orbital injection, which hopefully Firefly will update as soon as we reach orbit.

Best,

36

Hi Daniel,

Iā€™m told it has an FM carrier which to me said it was AFSK. But I guess it has amplitude and phase modulation? So what demodulation setting should we use? FM like AFSK or USB like FSK?

73,
Alan

37

Can you not obtain any further information about the radio? e.g. what radio chipset it is, what settings are in use? That would avoid any further guessing.

38

Sad news, the launch vehicle failed about two minutes after launch :frowning:

39

Congratulations to all the teams, hopefully a new launch soonā€¦

4 Likes
40

Oh noā€¦ And what about QUBIKs, they are probably lost? :frowning: @pierros - are you going to try again?