The first radio was invented late in the nineteenth century. From its invention until now, radios have undergone some mighty technological advances. Conventional or legacy radios are not programmable. They are designed for one fixed configuration. They are built to produce a single waveform at a specified frequency. Conventional radios often also have limited tuning options and fixed data rates. While some conventional radios carry multiple types of data, they are incapable of adapting to new waveforms. To make changes on these legacy radios, the radio would physically need to be changed. Once a radio is out in space, that task becomes near impossible to accomplish. These limitations created a number or needs for improved communication in space.
NASA engineers needed radios to be more flexible, adaptable, and evolvable. In the late twentieth century, a new type of radio was developed that would be able to meet those very needs. Software defined radios (SDR) are a type of reconfigurable radio in which some or all of the physical layers of functionality are implemented in software and/or firmware.
In the future, more and more missions will be utilizing SDR technology. The SCAN Testbed project tests various software defined radio technologies on the International Space Station.
The Mars Science Laboratory (MSL) currently employs second generation Software Defined Radios (SDRs),while the SCAN Testbed has third generation SDRs. The SCAN Testbed is currently undergoing validation onboard the International Space Station and testing ways to further NASA's space communication capabilities.