Do you want to build a cubesat or nano-satellite, and you need practical, useful advice on how to go about it, but cannot find any despite having done extensive research?
The sad truth is that among the millions of words that have been written about nano-, and pico-satellites, there are precious few that deal with practical issues such as the availability of components, construction methods, standards, and systems integration/integrity, which is where this article comes into the picture.
Aero-space engineers might not have much of a problem building a cubesat from scratch using components that are available off the shelf from more than forty suppliers, but for the novice satellite builder, things are not so easy. Fortunately though, there are cubesat kits available at reasonable prices, which include almost everything required to build a functional satellite and in most cases, all that is needed beyond the basic kit is a power supply and an antenna, which are also available from dozens of suppliers.
In practical terms, this means that if you have a round $10 000 ready at hand, you can build a small satellite with which to monitor weather conditions or changes in the Earth’s magnetic field, track ships at sea, or even to monitor the rate at which glaciers are retreating. The possible uses for cubesats are almost endless, and if you satisfy the requirements set by NASA, you might even be able to get a free launch opportunity for your satellite.
So to bridge the gap between general descriptions of cubesats, which incidentally, is a standard, and not a specification, and practical advice on design and construction issues, we have compiled a list of ten frequently asked questions (and their answers) to help you get your satellite mission off the workbench, and into Low Earth Orbit.
Why should I buy a cubesat kit?
Kits are designed to assist you in the successful completion of your mission in the shortest possible time, and at the lowest possible cost. When you purchase a kit, you typically receive the following items:
- Development board on which you can develop prototypes of mission-specific hard-, and software. This allows you to develop ideas, carry out performance measurements, set operational parameters, and test general functionalities of the entire package before you assemble the final product.
- Software Libraries to make it easier to develop mission-specific software using the Salvo RTOS.
- One fully assembled chassis on which to mount your instrument package and electronics. The chassis is in full compliance with all standards, regulations, and specifications required to obtain a launch opportunity.
- You can choose your processors/controllers from a large selection that is available off-the-shelf. This allows you almost total freedom to design a specific, goal oriented satellite that can do almost anything you can think of. Typical choices would be multi-functional processors such as for COMM and CD & H duties.
- Support for most popular, and widely available transceivers.
- One, or more of several available types of power supplies.
- Tools to further develop and expand functionality, such as USB interfaces and drivers.
Are antennas and solar cells included in the kit?
In general terms, cubesat kits are designed to supply the basic needs and wants of almost any design; however, since power sources and antennas are specific to each mission and its objectives, it is impossible to include these items to satisfy every imaginable requirement.
Nevertheless, all required equipment such as remove-before-launch-and flight switches, a functional connector scheme, and microprocessors/controllers are included in the kit, and are fully compatible with off-the shelf antennas and power sources.
Do I need additional printed circuit boards?
This would of course depend on the objectives of your mission, but in some cases, you will be required to design and develop your own additional circuitry that is mission specific. However, simple designs may require nothing more than the included motherboard’s integral MCU to act as a controller. Moreover, should you need more electronics such as sensors, additional power sources, serial EEPROM’s or almost anything else, it is a relatively simple matter to mount these items on a kit protoboard, from where they can be connected via Bus connectors.
How do I program the processor(s)?
Programming is accomplished via a PC, or laptop computer equipped with a USB port, and a CubeSat-kit compatible and certified C-compiler/IDE (Integrated Development Environment). The basic kit includes all required hardware connectors between the PC and the development board to enable you to develop your own mission-specific software.
Moreover, with the Kit you also receive a project licence to run the Salvo Pro RTOS on both the mother-, and development boards, in addition to a customized version of HCC’s embedded EFFS-THIN-FAT file system, which allows you to use SD memory cards in your satellite.
How are the Mother-, and Development boards different?
In terms of design, the mother board is only a component of the development board, which is bigger than the mother board to accommodate multiple power sources, +5V and +3.3V regulators, LED indicator lights, and an RS-232 port. These features allow you to isolate specific circuits during the design and test phases.
What if I can’t fit my payload into the standard chassis?
Fortunately, you are not limited to the standard 10cm×10cm×10cm dimensions, which in micro-satellite jargon is referred to as 1U. Other sizes, such as 10cm×10cm×15cm (1.5U), 10cm×10cm×20cm (2U), and 10cm×10cm×30cm (3U) are also available for bigger payloads.
What temperature ranges can cubesat kits cope with?
There are no parts in the basic kit that cannot cope with the accepted industrial temperature range of between -400C and +850C. The only possible exception to this are normal SD/ MMC storage devices that are commonly used in cell phones and cameras, but these are not included in the kit. However, more robust mass storage devices that can cope with industrial temperatures are available.
Can I run Linux in my micro-satellite?
Although most PPM processors are not able to run Linux, there are many Linux-compatible PC/104 modules available off the shelf that can run Linux with no problem at all. Moreover, a single-board Linux enabled computer such as those supplied by www.gumstix.com are perfect for installation in almost any micro-satellite. The only problem you have is choosing the correct one for your application.
What software is included in the basic kit?
PPM processors are programmed with what amounts to a “shell”, which is an application that provides a good starting point for subsequent programming. Based on the Salvo RTOS, this makes it a lot easier to manage the various tasks the processor will be required to perform. In addition, all the required source code is included; however, programming a satellite requires above-average skills in programming environments and paradigms that go beyond simple fore-, and background loops.
Why should I use RTOS-based software?
The primaryadvantage of using RTOS-based software involves the fact that it is a dominant paradigm for programming that is embedded and it has proven itself to be stable, and up to the task. Moreover, RTOS software enables optimum use of processor’s full functionality, since it is driven by events, which leads to significant reductions in power consumption.
One more thing- you may need a license!
It is one thing to design, test, and launch a cubesat. To licence it is something else entirely, and in some cases, it is required to obtain both NOAA (National Oceanic And Atmospheric Administration), and FAA authorization.
As a first step in planning any nano-satellite mission, it would be good idea to familiarize yourself with all licensing requirements and processes, especially if the mission will involve earth-imaging in any shape or form.