...

See ReportBeaconsAndPassInfo for reporting info to us

Spacelink Format

AAUSAT3 transmits CSP packets encapsulated in a custom spacelink framing format. The radio subsystem works as a router, where subsystems communicate directly with the ground station server.

The spacelink frames start with a variable length training sequence (default 60 bytes 010101010....), followed by a 6 byte syncword ("OZ3CUB"). The packet format supports two different packet lengths, either 25 or 86 bytes. A one byte Frame Size Marker (FSM) is used to differentiate between long and short packets. The FSM is 0xA6 for short frames and 0x59 for long frames.


Next, 31 or 92 bytes (short or long packets) of FEC coded data follows. After applying the FEC, the FEC data length is:

Short Frame: ((2 + 4 + 23 + 2) bytes [data] + 32 bytes [RS] + 1 byte [Conv. tail]) * 2 [Conv.] = 128 bytes
Long Frame: ((2 + 4 + 84 + 2) bytes [data] + 32 bytes [RS] + 1 byte [Conv. tail] * 2 [Conv.] = 250 bytes

Technical Details

  • Frequency: 437.425 MHz (in LEOP we were at 437.450)
  • Frequency deviation: 9.6 kHz
  • Modulation Scheme: Gaussian 2FSK (BT=0.5)
  • Bitrate: 1200 to 19200 bps (default 2400 bps)
  • Callsign: OZ3CUB
  • Forward Error Correction:
    • Inner code: Rate 1/2, k=7 convolutional code
    • Outer code: (255,223) Reed-Solomon code.

Example Python code for decoding the FEC is available as part of the BlueBox project:

https://github.com/satlab/bbctl/tree/master/fec

https://github.com/satlab/bbctl/blob/master/fec.py


Beacon details

AAUSAT3 has a CW beacon (30 wpm PARIS) and CSP encoded beacons in the ratio 1:10, meaning - 9 CSP encoded beacons - 1 CW beacon

The beacon transmission will start approximately 90 minutes after launch, and then transmit either FSK or CW encoded beacon every 30 seconds.

CW Beacon

CW beacon is constructed as follows

OZ3CUB Bx.x(battery voltage) Txx(temp)

An example from 24. May 2013:


A CW beacon from 24. May 2013 Morse Alphabet is here



Handheld yagi

If you want to receive morse(cw) beacon a handheld antenna should be enough.


Yagi antenna

Company

:-) AAUSAT3 emit two types of messages

1) Messages for which you need special decoding SW (and HW)

2) Old fashion morse/CW beacons.

It is 2) you can receive if you have an radio that can recieve around 437.425 MHz.

So you can record the morse/CW beacon from the audio/headphone output on the radio.

We use audacity (program) for editing sound and the beacon you see on the hoempage is just a screen snapshot from audacity. So I think hand decoding is possible :-) You can download orbitron(windows) or gpredict(linux) and select AAUSAT3 in cubesats. It can predict/calculate when you will be able to see AAUSAT3 meaning direction(azimuth) and elevation. So having a watch, a compass and a handheld antenna you should be able to point at AAUSAT3 and receive beacon. Doppler:

Due to the 7.5km/Sec velocity there is doopler shift on the radio. AAUSAT3 is on 437.425 MHz but when comming over the horizon you should increase freq on radio with approx 12 kHz. 0KHz when above your head and subtract 12 kHz just before leaving behind the horizon. It is not so critical but many radios has a input filter with width approx 15 kHz so you see it is better to correct a little


TLE

see LEOP-LaunchAndEarlyOperation


Decoder


Our Antennas at the Roof

Our decoder are on way for all of us. Apology for being late but we are busy.

We are working hard on our Blue Box ground station. It is a small - with USB interface - radio for receiving communication from AAUSAT3. It is based on the same ADF radio chip as AAUSAT3.

It is our humble intention to give it away to people who will help us listening to AAUSAT3.

More info about BlueBox here.



Ground Station antenna

Our Ground setup



If you are going to listen for our satellite please drop us an e-mail:

aausat3 AT space.aau.dk with subject AAUSAT3 HAM-info and a short explanation of who you are.

At the launch date we will be more than delighted to receive fresh information from you :-) And will of course mention you on this launch web site if you don't mind - just use the email above.