Open AccessDuring development of the spacecraft laser radar systems (LRS) it is a problem to make a choice of laser sources and photo-detectors both because of their using specifics in onboard equipment and because of the limited number of domestic and foreign manufacturers.
Previous publications did not consider in detail the accuracy versus laser pulse repetition frequency, the impact of photo-detector sensitivity and dynamic range on the LRS characteristics, and the power signal-protected photo-detector against overload.
The objective of this work is to analyze how the range, accuracy, and reliability of onboard LRS depend on different types of laser sources and photo-detectors, and on availability of electromechanical optical attenuator.
The paper describes design solutions that are used to compensate for a decreased sensitivity of photo-detector and an impact of these changes on the LRS characteristics.
It is shown that due to the high pulse repetition frequency a fiber laser is the preferred type of a laser source in onboard LRS, which can be used at ranges less than 500 m for two purposes: determining the orientation of the passive spacecraft with the accuracy of 0.3 and measuring the range rate during the rendezvous of spacecrafts with an accuracy of 0.003... 0.006 m/s.
The work identifies the attenuation level of the optical attenuator versus measured range. In close proximity to a diffusely reflecting passive spacecraft and a corner reflector this attenuator protects photo-detector. It is found that the optical attenuator is advisable to apply when using the photo-detector based on an avalanche photodiode. There is no need in optical attenuator (if a geometric factor is available in the case of sounding corner reflector) when a photo-detector based on pin-photodiode is used. Exclusion of electromechanical optical attenuator can increase the reliability function of LRS from Р (t) = 0.9991 to Р (t) = 0.9993.
The results obtained in this work can be used in development of different purpose onboard and ground-based LRS, laser range finders, and lidars.
In further studies it is advisable to consider the factors that affect the measuring accuracy of onboard LRS with a range of more than 500 m.