Information for Radio Amateurs
The satelitte received its frequency through AMSAT and we are
therefore commmited to serve the radio-amateur community as part of
our mission. This page will provide more details for radio-amateurs
who are interested in our satelitte.
It should be noted that initially the satelitte does not implement any
functionality with the radio-amateur community in mind, because at
first we have to establish connection and evaluate the performance of
the subsystems. Following that phase we can begin to upload new
software to the satelitte that includes services for
radio-amateurs. Basically we want the satelitte to well up and running
before letting anybody else "fool around" with it. If you have ideas
for uses of the satelitte following the initial phase then let us
know.
The kepler elements for the satelitte, as of the 10th September 2003
are:
AAU CUBESAT
1 27846U 03031G 03250.46633699 .00000182 00000-0 10513-3 0 412
2 27846 98.7287 256.4998 0010407 87.6191 272.6177 14.20512143
9764
For the most recent elements goto: Data at celestrak.com and find "AAU-cubesat".You
will also be able to get azimuth and elevation data (as seen from
Aalborg) at our "whereis" page.
As the signal is very weak - wo don't know why - it is very difficult
to receive the signal so far the following stations have been able to
pick it up:
- Original groundstation at Aalborg university. First signal on the 1st of
July
- Radio amateur Ib Christoffersen (OZ1MY). Possible signal on the 2nd
of July
- The CanX-1 groundstation in Toronto. First signal on the 3rd of July
- Carsten Grøn's 8m amateur dish. First signal on the 26th of July
Frequencies, Modulation and Packet Format
The frequency is: 437.450MHz
The modulation scheme is GMSK at 9600baud
The packet format is dictated by the MX909 modem, please consult the
datasheet for details.
MX909. The bit-sync pattern used is: 0x3333, and the used
frame sync pattern is: 0xF0AA. Each MX909 packet encapsulates a single
AX25-frame.
If you want to build a modem your self then you will require a modem
PCB connected to a computer that runs the driver software. In our case
we have build a modem PCB that interfaces to a MCB167 evaluation board
that drives the modem and transmits AX25-frames to and from a standard
PC. The following files is a our modem desing and driver software for
the MCB167 board. You can use this as a starting point, if you have
questions then let us know:
- Modem driver code for MCB167 board ZIP-FILE
The Beacon Signal
When not in the radio-window of the groundstation in Aalborg (Denmark)
the satellite will transmit a beacon signal once every minute. This
signal is a AX25 UI frame encapsulated in a MX909 packet. If you
decode the information field of the UI frame you will find the
following information:
- A 15 byte duplicate of the AX25 frame header
- An 18 byte text string "www.cubesat.auc.dk" if satelitte is
running from PROM memory, and the same string in upper-case if it is
running from FLASH-memory
- The time from last reset in seconds. 4 bytes
- Number of software errors. 2 bytes
- OBC temperature. 4 bytes
- Battery Voltage. 2 Bytes
Byte ordering is little endian, signal length is 120ms
If you pick up the beacon signal (you don't have to be able to decode
it) then please mail to Lars
Alminde In the mail include: position of you ground station, the
time the signal was picked up and the orientation and type of your
antennas. Feel free to add as much additional information on the
signal as possible.
Below is an example of an advanced beacon received by the 8m dish on
the 20th of August:
The Safe Mode Beacon Signal
If for
some reason the on-board computer fails then the power supply (PSU)
will use the push to talk signal on the radio to transmit a simple
beacon signal every 20 or 40 seconds depending on the battery
voltage. The PSU will morse "AAV" (//*-/*-/***-//) (it should have
been "AAU" - but there is a bug) followed by a 12 bit value (battery
voltage) 1 is /-/ and 0 is /*/. Signal length is approximately
150ms. If you pick up this signal please report it to us
.
Below is an example of a basic beacon received by the 8m dish on
the 20th of August:
