EARS PocketQube Picosatellite

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Introduction

EARS has an exciting heritage in the field of satellite technology. With our latest efforts in the high altitude balloon project it seems like a good time to start rekindling satellite building in the society. PocketQubes are a great way to enter the field, as they are a brand new type of picosatellite which is both affordable and easy to build, with great launch opportunities being promised over the coming years.

What is a PocketQube?

Camera PocketQube Shop Render

After the invention of the Cubesat in 1999, it's co-inventor Professor Bob Twiggs pushed ahead and miniaturized the personal spacecraft platform even further, creating what is now called a PocketQube[1]. These spacecraft measure just 50x50x50mm per unit (either 'P' or 'Q' depending on who you ask!) and have been launched up to 3P in size so far.

Wren PocketQube

The most technologically advanced PQ design was from startup Stadoko in Germany, to test it's micro pulsed-plasma thruster design[2]. This demonstrates just how useful PQs are as technology demonstrators.

The famous $50SAT

However, the most reliable design so far has been that of $50SAT[3] - an effort led by Bob Twiggs, Morehead State University and three radio amateurs (AB2S, KD8QBA and GW7HPW). This satellite is still broadcasting a year after launch, and was built for $250 - they missed the $50 mark due to the cost of the solar cells. Perhaps one of the best resources for designing our boards is their Dropbox folder[4].

As the phenomenon is developing, there are several start-ups/SMEs that have created shops for parts. Some are aiming rather high for what is to become a hobbyist-friendly platform[5], but the open-source hardware mindset is beginning to show - for example the OzQube store on Tindie.

EARS Project

The mission of the EARS project is to develop a stack of boards which, when combined, can produce a complete electronics system for a PocketQube. There are preliminary standards in development for both the mechanical and electrical specification. These are known as the PocketQube standard[6] and PQ60 standard[7]

Boards

The aim will be to produce the boards listed below. As people wish to start developing a board, they can add their names to the developers list for that section.

OBC (On-Board Computer)

The OBC board contains the main processor plus any support hardware required. This includes supervision and reset circuitry as is required for any inaccessible embedded system. The board may include temperature and other telemetry sensors. It should interface to the 14 GPIO pins as specified in the PQ60 document and follow all electrical standards therein.

  • Teensy 3.1 OBC
    • The Teensy is an ARM Cortex M4 based development board that runs an Arduino bootloader and is programmable via the Arduino IDE / AVR Studio.
    • Developer(s): Mark Barnes
    • Status: In Progress
  • ATMega328P OBC
    • The classic Arduino workhorse.
    • Status: Not Started - Start It!
  • TI MSP430 OBC
    • A popular low-cost microcontroller from Texas Instruments. It is used in the PocketQubeShop OBC.
    • Status: Not Started - Start It!
  • Freescale Kinetis L OBC
    • A more commercially used device, often used in medical and automotive environments.
    • Status: Not Started - Start It!
  • Intel Edison OBC(!)
    • An i386 processor in a tiny footprint. This is likely to draw too much current so it must be investigated first.
    • Status: Not Started - Start It!

Power Supply

The power supply board must provide solar charge regulation and maintain clean power on all the required busses as defined in the PQ60 standard. Optionally, it can include USB charging and battery bypass for development purposes and also include thermal sensing. It must provide several switched busses. The control of this can either be accommodated through the GPIO lines or the I2C interface.

  • Initial Design

Radio

The radio board allows telemetry data to be send back to Earth and telecommands to be received on the satellite. At first we should focus on ISM band frequencies (UHF) and then progress into other areas. $50SAT used RFM22b transceivers, however these are being retired. The OzQube-1 project has developed the QubeCast Max[8] as part of the Hackaday contest. It may be a good place to start!

  • Initial Design

Tracking Board

The tracking board is an additional board which is used on high altitude balloon (HAB) test flights. It will consist of a GPS module, microSD card, dedicated radio and microcontroller and will ensure that the spacecraft being tested is not lost.

Template Board

The Template Board serves as a reference board to be used for all other PQ60 designs. It features standard sized FX8C-60 connectors and follows the PQ60 mechanical dimensions.

smdProtoBoard

This board extends the Template board by adding a prototyping area with several common SMD footprints. The PQ60 bus is broken out into 20 pins that would commonly be used to interface to payloads, and the footprints are also connected to breakout holes. It is then possible for the user to patch the connections that they require. It can also be used as a handy marketing tool when unpopulated.

Breakout Board

This board allows the PQ60 bus to be accessed using standard pitch pin headers for use with either IDC connectors and ribbon cable to a breakout board, or female jumper cables like the ones used for the Raspberry Pi header. The board must be located at the top of the stack.

Flatsat Board

The flatsat/development board is designed to allow a PQ builder to lay all of their boards out separately while preserving bus connections between them. This is very useful when debugging issues such as bus communication and timing, and any analogue signals routed between boards. Due to the innovative "signal shifting" scheme used with the GPIO and switched power busses, this board may be a challenge to develop.

  • Initial Design

Mechanical Design

An impression of a typical PocketQube structure.

The mechanical design must conform to the PocketQube standard and should be extendible to "multi-P" configurations. Some projects have not used any outer casing, while other have a complete set of panels and frame components that fully enclose the payload and satellite systems.

References

  1. Twiggs, Bob. "Making it small". Retrieved 7 September 2013. 
  2. Krebs, Gunter. "Wren - Gunter's Space Page". Retrieved 22 December 2014. 
  3. "$50SAT Website". Retrieved 22 December 2014. 
  4. "$50SAT Dropbox". Retrieved 23 December 2014. 
  5. "PocketQubeShop". Retrieved 22 December 2014. 
  6. "PocketQube Standard". Retrieved 22 December 2014. 
  7. "PQ60 Standard". Retrieved 22 December 2014. 
  8. McAndrew, Stuart. "QubeCast Max". Retrieved 22 December 2014.