Archive for October, 2010


This paper, written in 2008, provides a summary of the communication subsystems utilized in various CubeSat missions, and compares their performance.

Some CubeSats utilize one radio for the data downlink and another one, with much lower power consumption, for the beacon. A different radio is utilized in almost every one of the missions discussed in the paper. Most of the downlink frequencies are around 437MHz, which is in the amateur radio band range, and most of them utilized a 1200 baud rate.

Out of the 23 CubeSats analyzed, two of them stand out for the amount of data downlinked. These are the QuakeSat-1 and CanX-2, both being 3U CubeSats.

QuakeSat-1 utilized two ground stations that were linked via the internet, so it could download more data. The transceiver on this satellite downlinked at 436.675 MHz with a 9600 baud rate.

CanX-2 utilized a custom S-Band radio, operating at 2.2Ghz up to 256 kbps. It took 4 years for the team to obtain a frequency in the licensed Space Research spectrum.

Some subsystem recommendations are included in the paper:

  • Utilize a long beacon.
  • Include a way to easily reset the satellite if it becomes non-responsive.
  • Make sure the ground station is operating properly before launching the satellite.

From this paper we can gather that utilizing the amateur radio frequencies could be the best option for us, since obtaining a restricted frequency can take up to several years.

Reference: http://www.klofas.com/papers/CommSurvey-Bryan_Klofas.pdf

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The objective of the ground station is to make possible the communication by receiving data of the satellite and sending commands to it. The minimum necessary hardware in a ground station is:

  • Antenna – for receiving and transmitting electromagnetic waves.
  • Radio – to receive and transmit data.
  • Computer – for data handling and for decision making.

Hardware Specifications

Antenna:

  • Able to operate within the chosen frequency band of the radios.
  • Able to withstand the weather conditions at the location of the ground station.
  • Able to operate with signals in the radio amateur band (433-438).
  • An estimate 15dB antenna gain.

Radio:

  • The operating frequency band have to be around 437 MHz
  • A minimum 50 W transmitting capability.
  • Must be controllable from the ground station main computer.
  • Frequency scanning, automatic frequency control and adjustable squelch level.

These specifications can be used as a guide for our ground station model for the CubeSat.

Reference: http://www.cubesat.aau.dk/documents/gshw.pdf

Here at University of Puerto Rico in Mayaguez (UPRM), under the guidance of Dr. Lizdabel Morales-Tirado, we are part of the CubeSat Transmission Module Research. Our group is composed of enthusiastic Electrical and Computer Engineering students. A CubeSat is a pico-satellite, which can be built less expensively and faster than a traditional satellite. It provides a low budget solution for researchers to study more complex problems.