So what can you put into a TiS CubeSat frame? The answers are as varied as the sciences. Electronics comprise the bulk of most experiments, even life sciences. They perform monitoring and data collection duties. Here are few option and source links to get you started.
This is the workhorse of the maker-space movement and for good reason. Easy to to program and expand, this micro-controller is great for any sort of sensors you can think of. There are lots of source for code as well, starting with www.arduino.cc.
SparkFun and Adafruit are good sources for the hardware. Amazon has some decent deals on them as well.
For data storage both companies have excellent microSD breakout boards that will do the job.
A simple sensor setup would be to use the Aduino with a data logger to report basic weather elements. The DHT22 temperature and humidity sensor.
Another great experiment would be to incorporate a 9 degree of freedom sensor board. This would allow you to track and record the CubeSat’s position, orientation and magnetic position. This makes for a great second project.