Lucky-7 is a Czech Amateur 1U cubesat that was launched on July 5 together with the meteorological Russian satellite Meteor M2-2 and several other small satellites in a Soyuz-2-1b Fregat-M rocket from Vostochny. The payload it carriers is rather interesting: a low power GPS receiver, a gamma ray spectrometer and dosimeter, and a photo camera.
It transmits telemetry in the 70cm Amateur satellite band using 4k8 FSK with an Si4463 transceiver chip. Additional details about the signal can be found here.
After some work trying to figure out the scrambler used by the Si4463, I have added a decoder for Lucky-7 to gr-satellites. This post shows some of the technical aspects of the decoder.
Continue reading “Lucky-7 decoded”
Last Sunday, Julián Fernández EA4HCD, released a high altitude balloon carrying a LoRa payload as a preliminary test for the FossaSat-1 pocketqube that he is devolping with Fossa Systems. You can see a video of the release in this tweet. The balloon was launched near Madrid, and burst at an altitude of approximately 24km, having travelled some 180km southeast.
The payload had two transmitters: An SX1278 LoRa transceiver transmitting at 434.5MHz with 10mW alternating between LoRa and RTTY, and an 868MHz 25mW LoRa transceiver that was received on The Things Network. Simple groundplane 1/4-wave monopole antennas were used.
I went to the countryside just outside my city, Tres Cantos, and set up a station to record the transmissions on 434.5MHz. The station consisted of a 7 element yagi by Arrow Antennas, set in vertical polarization and placed on a camera tripod on the roof of my car, and a FUNcube Dongle Pro+. This is a brief analysis of the recording.
Continue reading “Receiving a LoRa high altitude balloon”
A couple months ago, I added a decoder for Astrocast 0.1 to gr-satellites. I spoke about the rather non-standard FX.25 protocol it used. Since then, Mike Rupprecht DK3WN and I have been in contact with the Astrocast team. They noticed the mistake about using NRZ instead of NRZ-I, and in February 13 they sent a software update to the satellite to use NRZ-I instead of NRZ. However, the satellite has some failsafe mechanisms, so sometimes it is seen transmitting in the older NRZ protocol.
Mike has also spotted Astrocast 0.1 transmitting sometimes in 9k6, instead of the usual 1k2. This is used to download telemetry, and it is only enabled for certain passes. The coding used for this telemetry download is different from the FX.25 beacon. The team has published the following information about it. The coding follows CCSDS, using five interleaved Reed-Solomon encoders. A CCSDS scrambler is also used.
Following this variety of protocols, I have added new decoders for Astrocast 0.1 to gr-satellites. The
astrocast.grc decoder does NRZ-I FX.25, and should be used for the beacon. The
astrocast_old.grc decoder implements NRZ FX.25, and should be used for the beacon when the satellite is in failsafe mode. The
astrocast_9k6.grc decoder serves to decode the 9k6 telemetry downloads. Sample recordings corresponding to these three decoders can be found in satellite-recordings.
Astrocast 0.1 is an Amateur satellite built by the Lucerne University of Applied Sciences and Arts (Hochschule Luzern). It is an in-orbit demonstrator for a future constellation of small satellites providing L-band data services for internet of things applications. The Amateur payload includes an on-board GPS receiver and a PRBS ranging signal transmitter for precise orbit determination .
This satellite was launched on December 3 on the SSO-A launch, but we only have payed attention to it recently. Its IARU coordinated frequency is 437.175MHz (actually it is a bit strange, because the IARU coordination data speaks about Astrocast 0.2, which hasn’t been launched yet). However, the satellite appears to be transmitting on 437.150MHz.
As it turns out, we had an unidentified object transmitting on 437.150MHz. This object was first thought to be RANGE-A, which was also on the SSO-A launch, as this frequency was assigned to RANGE-A. However, the RANGE-A team confirmed that this wasn’t their satellite, and I wasn’t able to identify the modem used by the mystery 437.150MHz signal.
Yesterday, Mike Rupprecht DK3WN noticed that this unidentified signal corresponded to Astrocast 0.1, and sent me some technical documentation about the protocols used by this satellite. Using that information, I confirmed that the mystery satellite at 437.150MHz was indeed Astrocast 0.1 and now I have added a decoder to gr-satellites.
Continue reading “Decoding Astrocast 0.1”
D-STAR One are a series of Amateur satellites with an on-board D-STAR digital voice repeater. The first satellite of the series, called D-STAR One, was launched on November 2017 but was lost due to a problem with the upper stage of the rocket. The second satellite, called D-STAR One v1.1 Phoenix, was launched in February 2018 but never worked. On 27 December 2018, a Soyuz rocket launched the next two satellites in the series: D-STAR One Sparrow and D-STAR One iSat. I hear that, unfortunately, these two newer satellites haven’t been coordinated by IARU.
Besides using the D-STAR protocol, these two satellites also transmit telemetry in the 70cm Amateur satellite band using the Mobitex protocol, as described in the CMX990 modem datasheet. They use GFSK at 4800 baud.
In the past, I have talked about the Mobitex protocol in the context of the BEESAT satellites by TU Berlin. I described some notes about the Mobitex-NX variant used in these satellites, and contributed to the beesat-sdr GNU Radio decoder for the Mobitex-NX protocol.
Now, I have adapted the Mobitex-NX decoder to work also with the D-STAR One satellites, and added a decoder to gr-satellites. The decoder requires my fork of beesat-sdr to be installed.
Continue reading “D-STAR One Mobitex protocol decoded”
ESEO is an educational satellite project for university students led by ESA. It is a microsatellite based on the S-50 platform by SITAEL and indeed serves as an in-orbit validation of that platform. It carries payloads developed by students in 10 European universities, and also a FUNcube payload from AMSAT-UK. It was launched last Monday in the SSO-A launch.
The satellite transmits 9k6 GFSK telemetry in the 70cm Amateur satellite band (do not confuse this telemetry with the telemetry sent by the FUNcube payload in the 2m Amateur satellite band). Last week I wrote an open letter to the directors of the ESEO program requesting the publication of the complete specifications for this telemetry. The existing documentation is published here as two documents called attachment 1, which describes the coding of the frames, and attachment 2, which describes the structure of the telemetry frames.
The main problem motivating my open letter was that the information in attachment 2 was insufficient to produce a telemetry decoder for ESEO. However, last Tuesday an updated version of this document was published. This new version seems to include all the information we need. Apparently, this new version has been published due to my open letter and the pressure made by some people at ESA surrounding the ESEO project.
I would like to thank all the people that have expressed their opinion about the importance of having well documented protocols in the Amateur radio service, as well as all the people in ESA that have pushed for the publication of the documentation, and understood that this is an important matter.
In this post we look at the coding used by ESEO, that is, everything described in attachment 1, and how the decoder in gr-satellites is implemented.
Continue reading “Decoding ESEO”
Yesterday I spoke about decoding the telemetry of PW-Sat2 with gr-satellites. Today I have added to gr-satellites a telemetry submitter block that sends the frames to the PW-Sat2 telemetry server. All users of the PW-Sat2 decoder from gr-satellites are recommended to set this up and submit telemetry to the PW-Sat2 telemetry server, as well as to the SatNOGS database. Here are the instructions to configure the submitter.
Continue reading “Uploading PW-Sat2 telemetry with gr-satellites”
PW-Sat2 is a students satellite made by the Students Space Association at Warsaw University of Technology, in Poland. The project started in 2013 and was finally launched last Monday in the SSO-A launch. The satellite carries a sail to aid in deorbiting. This will be deployed on the 39th mission day. The deorbit is expected to happen in one year.
The satellite team has made available a lot of open-source software, such as groundstation software for Radio Amateurs, a telemetry server and even the software that runs on the on-board computer. There is also a good amount of design documentation. This is something a bit unusual and admirable for a university satellite.
PW-Sat2 transmits standard G3RUH-scrambled BPSK AX.25 frames in the 70cm Amateur Satellite band. The baudrate can be selected between 1k2, 2k4, 4k8 and 9k6 by the satellite team. The interesting thing is that there are many types of packets besides telemetry. For instance, it can list and transfer on-board files, such as the images taken by the satellite camera. These packets can be decoded by using the FramePayloadDecoder software.
Since the FramePayloadDecoder software is quite complex and it is written in Python, I have decided to make a telemetry parser for gr-satellites that simply loads this software into GNU Radio and passes the frames to the decoder. Here are the instructions to set this up.
Continue reading “Decoding PW-Sat2 with gr-satellites”
A few days ago I spoke about my Reaktor Hello World decoder in gr-satellites. Another of the satellites that were launched with Reaktor Hello World in the November 29 PSLV launch is 3CAT-1, a 1U cubesat from the NanoSat Lab in Universidad Politècnica de Catalunya. It is designed as a technology demonstrator of COTS parts, and integrates four scientific payloads.
The communications system of 3CAT-1 uses a Texas Instrument CC1101 FSK transceiver chip, which is very similar to the CC1125 used in Reaktor Hello World. It transmits a 9k6 FSK telemetry beacon in the 70cm Amateur band. An interesting thing about this beacon is that it is powered by a temperature gradient that generates naturally within the satellite. A Peltier module is used to collect energy from the gradient and power the communications module. This is called “eternal self-powered beacon demonstrator” by the designers of the satellite, since it doesn’t depend on batteries or solar cells.
I have been in contact with Juan Fran Muñoz from NanoSat Lab, who has been kind enough to send me a telemetry recording for 3CAT-1. With this, and following my implementation of the Reaktor Hello World decoder, I have added a decoder for 3CAT-1 to gr-satellites.
Continue reading “Decoding 3CAT-1”
Reaktor Hello World is a 2U cubesat built by the Finnish company Reaktor Space Lab as a test of their cubesat platform and demonstration of the first miniature infrared hyperspectral imager. It was launched on November 29 by a PSLV from Satish Dhawan Space Centre, together with several other cubesats. It transmits 9k6 GFSK telemetry in the 70cm Amateur satellite band.
The satellite uses a Texas Instruments CC1125 FSK transceiver chip. This is very similar to the CC1101 that I used a few years ago in my 70cm Hamnet experiments, so I already knew the coding and features of this chip quite well. The satellite team has a Github repository with a GNU Radio decoder based on the gr-cc11xx decoder block for the CC11xx series of chips. Since gr-cc11xx doesn’t seem to be maintained anymore, I wanted to implement my own CC11xx decoder in gr-satellites and use it to decode Reaktor Hello World.
Continue reading “Decoding Reaktor Hello World”