The National Physical Laboratory (NPL) has helped to establish that femtosecond comb lasers can provide accurate measurement of absolute distance in formation flying space missions.
NPL, along with collaborators, produced technical reports for the European Space Agency (ESA). The conclusions demonstrated that the lasers were a suitable method for measurement in such missions.
Formation flying missions involve multiple spacecraft flying between tens and hundreds of metres apart, which autonomously control their position relative to each other. The benefit of such missions is they can gather data in a completely different way to a standard spacecraft – the formation can effectively act as one large sensor.
Measuring absolute distance between the formation spacecraft is critical to mission success. Femtosecond comb lasers are an accurate way of making such measurements. The lasers emit light with very short pulses – each lasting just a few femtoseconds (a femtosecond is one billionth of one millionth of a second). The short pulses allow time of flight measurements to be used to determine distance to a few microns.