Delfi-n3Xt Telemetry Reception
Delfi-n3Xt can be received by anyone interested is our satellite and having proper equipment. You can also help the project by gathering data which will be sent to our central telemetry server. We will use the term 'radio amateur' for everyone involved in receiving telemetry. It might however not be nescessary that you are an official licenced radio amateur. In many countries it is legal to use equipment for reception only without license and/or registration.
In the sections below it is explained how you can participate.
Hardware & Software Required
- Antenna with at least 2 dB of gain. You will have to point the antenna to the satellite, either by hand or with automated tracking. More gain will yield better results, but also better tracking capabilities.
- Receiver suitable for the 145 MHz band, with 5 kHz bandwidth and (virtual) audio output. A cost-effective and easy solution is the FunCube Dongle.
- A personal computer with sound card (or USB in case of a dongle).
- JAVA runtime environment.
- Tracking software like Orbitron or WXtrack. You should use orbital elements in two-line element (TLE) format. After a few days you can retrieve them automatically with these programs, but for the first days you should consult our website and insert them manually.
- DUDe telemetry client (see dedicated section).
- Internet connection (for automatically forwarding data to the Delfi-n3Xt server).
Two-Line Elements (TLE)
Delfi-n3Xt has been identified as object 13066N in the SpaceTrack database. It can be automatically downloaded from tracking programs and be fount in the list 'TLE-new'. It is expected that it will enter the 'amateur' and or 'CubeSat' list soon.
Registration & Download of Telemetry Client
To participate in the gathering of data you need a Delfi-n3Xt radio amateur account. Once you have an account you can log in to the server with DUDe to automatically submit demodulated frames and on the radio amateur website to view your submitted data or change your profile.
You can register and log in here: http://delfi-n3xt.lr.tudelft.nl/radioamateur/index.php
DUDe can be downloaded here: DUDe 5.1
We kindly ask you not to log in on the website on the launch date of 21 November 2014 to avoid high peak loads on our server. Of course, you can (automatically) log in to the server with the DUDe telemetry client to help in gathering data.
Please note that your Delfi-C³ account is not valid for Delfi-n3Xt.
DUDe Telemetry Client
After first start up of the DUDe client, your account details are asked. They are stored on your local PC for next time. You can use DUDe withoun a valid account, but in this case data will not be forwarded to our server. We therefore highly recommend you to create and use an account. You can change or fill your credentials later through Options > Settings.
The Graphic User Interface (GUI) is composed by different panels:
- Audio panel. The audio input can be selected. DUDe can be used with the soundcard of the computer.
- Frequency panel. This panel will show the frequency at which DUDe is receiving a signal. This is an audio subcarrier created by tuning the receiver about 1600 Hz below the the actual frequency (+/- Doppler). It can be used for setting the radio frequency and should best be tuned to 1600 Hz.
- Terminal. The history of received frames from last start up will be shown with hexadecimal digits. Only the raw frame content (without AX.25 headers) is shown.
- Status panel. In this panel, a counter of the received frames can be found. Another counter will update the number of frames that are successfully forwarded to the server. In addition, a history of the actions made by the user is included in this panel.
- Telemetry panels.The data generated by Delfi-n3Xt is split in two AX.25 frames before being sent to Earth. The rawframe shown in the Terminal can be either a part 1 or a part 2 of the generated data. A part 1 and its corresponding part 2 will show the same value in the field Framecounter contained in the sub-panel Frame ID. Delfi-n3Xt sends a part every second, so the data in the panels is updated in alternating fashion.
Delfi-n3Xt sends it data in BPSK modulation on the VHF band. For demodulation using a PC and sound card, you need to tune about 1600 Hz below the VHF downlink frequency of 145.870 MHz (upper sideband) and correct for the Doppler effect. The Doppler frequency can by identified by tracking software. For some combinations of tracking software and receivers, you can automate the Doppler corrections.
The VHF downlink of Delfi-n3Xt will in principle only be on in the sunlit part of the orbit. The satellite will be in eclipse every orbit for about 1/3 of the time. You can see in the orbit tracking software if the satellite is in eclipse or not during a pass.
The S-band downlink will send data all the time in beacon mode at short pulses of 50 kbit/s. The content of this pulse is the same frame as send over the VHF downlink. The S-band patch antenna onboard Delfi-n3Xt is very directional and may not always be pointed towards Earth. Once the satellite has established ground tracking capability, at passes over Delft attempts will be made to downlink large quantities of data. In both cases, radio amateurs are free to receive the data and try to demodulate it. The signal strength is however very weak, and at least 35 dB gain is needed to be able to demodulate the signal. At this moment in time we do not have a public telemetry client. It might however be a nice experiment (if you have the right equipment) to see if you can identify the 'pulses' of the beacon.
We will try to help and answer questions where and when we can. Please note however that we are limited in resources and the launch and early operations will require our full attention. For this phase we might not be able to answer all emails of individuals and will limit ourselves to problems and questions which are applicable to many radio amateurs. If you are inexperienced in the field we recommend try to find more general information on the internet, contact a local experienced radio amateur or wait untill the most critical phase of the mission is over.