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How to receive from ³Cat-1

Would you like to collaborate with us and receive and decode ³Cat-1's telemetry? Here is how you should do it.

The ³Cat-1 was successfully launched on November 29th, 2018. It's beacon signal transmits telemetry data openly and can be decoded following the instructions in this public repository.

We recommend using the 2018-096AA TLE for receiveing 3Cat-1. If you find another TLE from the PSLV C-43 launch that suits best, please contact us!

About 3Cat-1 Communications System

³Cat-1's communication subsystem is based on TI's CC1101 and broadcasts housekeeping data approximately every 90 seconds. Beacon packets include spacecraft time, state of charge and readings of on-board sensors. Packets can be decoded with GNURadio and processed with the provided functions written in C. 

The system is tunned at 437.250 MHz, nevertheless a small frequency drift can appear due to the temperature changes in the communications subsystem. The system transmitts the data at 9k6 bps with a GMSK modulation. A Reed Solomon algorithm is used to enhance the SNR. The polarization used by 3Cat-1 is RHCP.

Recommended Equipment

To receive and properly decode beacon messages from 3Cat-1, a UHF antenna tuned at the 433-437 MHz band is needed. Despite an omnidirectional antenna is, in some cases, enough to receive the signal from the satellite, a Yagi (or similar) antenna with better gain is recommended to obtain the best SNR. After the antenna it is recommended to use a selective RF chain to properly filter and amplify the signal. The RF chain should be designed and tuned depending on the antenna temperature and interference in your area. However, in general, we recommend to have a selective (narrow-band) LNA followed by a filter. In case of using a wide-band LNA or having interference in your area, we recommend to add a very selective filter before the LNA. This worsens the noise figure of the receiver but avoids inter-modulation products created by the interferences inside the LNA. After the RF stage a receiver is needed to demodulate and decode the signal. We recommend to use the provided beacon decoder based on GNU Radio and a Software Defined Radio (SDR)-based receiver. There exists a large variety of SDRs in a wide price range and many of them might be good enough to receive from 3Cat-1. We normally use the USRP B200 or B210 from Ettus Research in our ground stations but something in a lower price range might be appropriate as well to properly receive and decode the beacon signal.

 

If you wish to contact ground operators, you may reach us at: