What would you do with your own private satellite? If you haven’t decided, you should. PhoneSat — a project overseen by NASA’s Ames Research Center in Silicon Valley — wants to lower the cost of building space satellites to the point where anyone with space ambitions could launch one.

Yes, it’s a satellite made from a phone. The not-so-secret ingredient is Google’s Android mobile operating system.

As NASA points out in announcing PhoneSat, smartphones already have many of the features that a satellite needs, including fast processors, built-in cameras, and a variety of sensors. So why build a custom system for scratch when a common Android phone will do?

The project is part of a larger effort to build dirt-cheap satellites for the masses. As NASA builds its PhoneSat, a startup called Nano Satisfi is building a satellite designed to be programmed by the world at large, and an outfit called Southern Stars hopes to launched a satellite called SkyCube, which will let you instantly grab space photos from your mobile phone down here on Earth.

The first version of NASA’s satellite — PhoneSat 1.0 — costs about $3,500 to build. It’s a coffee-cup-sized cube designed to withstand cosmic radiation, containing an HTC Nexus One phone running the Android operating system, an external radio beacon, external bateries, and a circuit that will reboot the phone if it stops transmitting data — all off-the-shelf commercial parts.

It has been tested under various adverse conditions, such as “thermal-vacuum chambers, vibration and shock tables, sub-orbital rocket flights and high-altitude balloons.” The plan is to launch this month with the modest goal of staying alive long enough to send a few photos back to Earth.

The next version, PhoneSats 2.0, will use newer Samsung Nexus S phones and include a two-way radio system that will enable researchers to control the satellite from Earth. Other enhancements include solar panels and magnetorquer coils.

Last April, NASA sponsored a development contest giving programmers the chance to write Android apps that will run on the PhoneSat. Examples of potential applications include star tracking and radiation-monitoring apps.

Meanwhile, Nano Satisfi has raised over $100,000 on Kickstarter to fund the development of a satellite based on the open source circuit board the Arduino. The goal is to make it the first satellite programmable by the general public.

Because the Arduino is an open standard, anyone can write software for it from home. Backers will be able to write programs for controlling satellites in space and collecting data. The organization will test the software and run it on a real satellite for an allotted amount of time. The data collected will be sent to the customer who wrote the software.

SkyCube is the brainchild of Southern Stars, makers of astronomy apps for iOS and Android. The plan is to launch a cube satellite from a SpaceX Falcon 9 rocket in 2013. Backers of the project will be able to broadcast their own messages from the satellite, as well as request photos from the satellite using mobile apps. The project has raised nearly $70,000 of its $82,500 goal as of this writing.