Found here (italics added, bold in source):
Nanocrafts are gram-scale robotic spacecrafts comprising two main parts:
- StarChip: Moore’s law has allowed a dramatic decrease in the size of microelectronic components. This creates the possibility of a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and constituting a fully functional space probe.
- Lightsail: Advances in nanotechnology are producing increasingly thin and light-weight metamaterials, promising to enable the fabrication of meter-scale sails no more than a few hundred atoms thick and at gram-scale mass.
What are those photon thrusters? Why would it need thrusters, since its sail is pushed by an earth-based huge laser?
I think some man-made device able to reach 0.2c would already be an amazing achievement, even if it doesn't send back any picture from another stellar system, and even if it misses its destination. (Sputnik only said "bip" to tell everyone "I'm orbiting.")
What could be the mass of a probe saying "I'm going 0.145c"?
Probe's components would be:
- self aligning sail (with dihedral)
thin photovoltaic sheet powering an emitter with antenna
no photonic thruster or navigation system.
- no camera or any optical device
- no battery
- no reaction wheel or gyro