Delfi-C3 Telemetry Reception


On 8 July 2015, the Delfi-C3 telemetry server is migrated to a new environment. This also means that the RASCAL server settings need to be changed. The new settings are:

Port: 1099


RASCAL is the software package that is offered to radio-amateurs around the world to be able to collect and decode data of the Delfi-C3 satellite. This program does this by demodulating the incoming audio-signal on the system's soundcard that is originating from a transceiver tuned to the frequency of the VHF telemetry downlink. Next to decoding and making the telemetry information visible to the users, RASCAL also stores and forwards the telemetry to our data collection server(s).


Installing RASCAL
Download RASCAL and extract ALL contents from the zip file. This will create a directory called 'RASCAL', which should contain the RASCAL.jar file and a subdirectory called 'lib'. If you do not have this 'lib' subdirectory you will not be able to run RASCAL. After running RASCAL two more subdirectories will appear, named 'config' and 'repository'. Always run RASCAL from this directory. If you have to move it somewhere else after installation, make sure to include all the subdirectories.

>>> Download RASCAL v1.1.1 <<<

RASCAL requires JAVA runtime environment installed on the computer and can be used with many operating systems (MS Windows, Linux, Mac OS, etcetera).

Starting RASCAL
If Java has been installed on Windows you can start RASCAL by double-clicking the RASCAL.jar file. If for some reason this is not the case or doesn't work, you will have to start RASCAL from the command prompt. You will also have to use the command prompt on other operating systems other than Windows. This can be done as follows: <path to JRE directory>/bin/java -jar RASCAL.jar or java -jar RASCAL.jar if the java executable is available at all locations (e.g. through the PATH system variable).

RASCAL will sample the system's soundcard to try and decode the telemetry downlink signal. This means that in order to decode the telemetry you will have to connect your transceiver to the soundcard input (microphone or line-in). Please make sure that the appropriate input is selected on your soundcard's mixer panel. Please note that applications like Skype are known to modify these mixer-settings, so please double check!

Audio Level: The bar at the top of this area indicates the input level of the audio signal. RASCAL performs best if the bar stays green, while the optimal input level is about half of the bar. The dropdown box contains a list of soundcards detected on your system that are ready for use with RASCAL. You can select another soundcard at any time and RASCAL will immediately start sampling the selected soundcard.

Frequency (and tuning): RASCAL expects a BPSK signal with a center frequency of 1600Hz. Therefore, when using an Upper Side Band (USB) receiver, you must tune 1600Hz below the actual downlink frequency. RASCAL can compensate for tuning errors and Doppler shift up to + and - 200Hz using a software Costas loop PLL algorithm, but, since the Doppler shift on VHF can be as large as + and - 3500Hz, either manual or computer controlled tuning (by means of tracking software) is required in order to keep the signal within the lock range of the demodulator. Once lock is achieved, the green "sync" label will light up, and decoded packets should show up in the terminal screen.
Tuning can sometimes be difficult, in the presence of Doppler shift, fading due to polarization changes, frequency offset due to temperature of the spacecraft oscillators and there is the possibility that the Costas Loop indicates a false sync because of lock on one of the signal's sidebands. If possible, you can use a waterfall display in software like MixW running parallel to RASCAL which will give you an indication of the centerfrequency. During transmission of flags, the actual carrier frequency is the highest peak, with sidebands exactly 150Hz apart. Now, using the waterfall display, tune such that this peak corresponds to 1600Hz +/-100Hz, in order to achieve sync.

Terminal: This area shows the decoded AX.25 frames as they are decoded by the program. The source and destination address are shown, followed by the contents of the data field in the AX.25 frame.

Status messages: This area gives an overview of the status of RASCAL.

  • Packets received - number of valid packets received and decoded by RASCAL during this session
  • Last packet received - time at which the last valid packet has been received and decoded
  • Repository data
    • Primary / secondary repository - the names for our two data collection server(s)
    • Disk - the number of telemetry frames that are currently stored on your harddisk (waiting for submission)
    • Sent - the number of telemetry frames sent to the repository during this session
  • Status messages - shows a number of messages concerning connectivity and actions taken in the program

Telemetry fields: The remainder of the screen is dedicated to displaying the decoded values received in the telemetry downlink. Almost all of these values are housekeeping values and will be updated once every 5 seconds. Please note that you can also see the IV-curves produced by the TFSC payload in real-time by selecting 'Show IV curves' from the 'Options' menu.

RASCAL User Account
RASCAL uses the anonymous 'guest' account by default for submitting decoded telemetry. We would however like to encourage all participants to request a user account by sending an e-mail to This email address is being protected from spambots. You need JavaScript enabled to view it., specifying at least the following information:

  • name
  • callsign
  • location (maidenhead gridsquare) 

We will reply with user credentials that you can use in RASCAL (see section below). Please note that having a callsign is not a requirement to participate in the telemetry collection.

Modifying user credentials: In order to submit telemetry to the data server(s), users are required to provide login information. This way we can keep track of how many data has been submitted by who and we are planning to turn this into a competition of sorts. RASCAL takes care of the login procedure, if provided with the proper user credentials. By default, RASCAL is configured to use the anonymous user account 'guest' that uses the password 'guest'. In case you have applied for a user account and have received user credentials from us, we would like you to change the credentials used in RASCAL. Modifying these credentials is done by opening the Options menu and then selecting Settings. Note that the server settings are also at their default values but do not have to be changed.

Server settings: It's also possible to change the IP address and data reception port of the two data collection servers in RASCAL. Do not change these unless you are explicitly instructed by us to do so! Changing these settings will prevent RASCAL from sending the decoded telemetry to our data collection servers. If you have accidently changed these settings please contact us at This email address is being protected from spambots. You need JavaScript enabled to view it. .