Development and Launch of the First Ultra-short Femtosecond Pulse Laser as a Satellite Payload
A foundation in the field of optical science and high-speed high-accuracy(ultra-precision) measurement technology in outer space
"The ultra-short femto-second laser can be applied to the technology verification of the absolute distance measurement for the next-generation satellite formation flying missions as well as the field of multi-channel optical communication between ground-to-satellite and satellite-to-satellite channels . Furthermore, it will be applied to various future space missions, including the broadband spectroscopic LIDAR, the development of the optical watch(clocks), and the calibration of the high-accuracy .spectrometers. Currently, we are measuring and analyzing the oscillation performances of the femtosecond laser on the Naro-Science Satellite operating in outer space over an year. We expect that this results can be used as the fundamental results for future space technologies based on ultrafast photonics."
The ultra-short femto second laser that is operating in the space environment for the first time in the world
In January 2011, FSO, the world’s first femto-second laser resonating(oscillator) system, was selected as the body structure( stellite payload) of Naro Science Satellite for its missions in space. Since then, the research team led by Professor Seung Woo Kim at KIOST focused on the development of the FSO space body structure(payload) for a year and a half until August 2012, when the structure was tested for the last time and transfered to the launching center . Optical, electrical, and mechanical performance of the FSO was faithfully tested and successfully satisfied all the criteria such as high-level vibration, temperature variation, high vacuum condition, and space radiation.
The development process of the FSO space body structure(payload) can be largely divided into DM (Developing model), QM (Qualification model), and FM (Flight model) development steps. Since the process had to go through a strict procedure consisting of at least four steps of development and environmental verification, the research team spent a long time to repeat the system development, evaluation and verificationduring a limited period of one and half a year. Through such a procedure, many characteristics that is required in the space environment were considered and continuously reflected in the re-designing process in order to improve the completion of the technology.
The femto-second laser is a kind of ultra-short (pulse) laser that has a narrow pulse width of 0.000000000000001 seconds. It could sends the femtosecond light pulses with the exact time interval of 1/1,000,000 (100MHz). By using the femto-second laser, it is possible to make an optical clock that can be used to measure time with high accuracy of up to 1/1,000,000,000,000,000 seconds. Because femtosecond pulse laser provide a high precision in distance measurement, we can determine the location of an object that is hundreds of kilometers away with a small error less than a nanometer (1/1,000,000,000 m). This can be utilized for the precise determination of the geological information by more than hundreds of times than now. If the ultra-short femto-second laser is applied to the field of space science, it will be possible to use it in various application fields based on its superior characteristics of a short pulse duration, a large(broad) wavelength bandwidth , and a high stability in the time and frequency domain.
The research team led by Professor Seung Woo Kim has carried out R&D for next-generation metrological applications of ultrashort femto-second lasers.
First, the team has focused on the development of the precision absolute ranging technology in order to large-caliber ( constitute a large synthetic aperture) for high-resolution space telescopes based on satellite formation flying. Second, the team has studied the technology related to multi-channel remote security optical communications. Third, they have focused on the development of the next-generation high-accuracy optical clocks and the verification of the general theory of relativity in space by using an optical clock. Fourth, they have studied the earth monitoring spectroscopic LIDAR technology that can be used in the process of monitoring global warming, fine dust, and yellow sand in the air. Fifth, they have focused on the technology related to the high-accuracy correction of the space spectroscope(spectrometers). Sixth, they have compared various time and frequency standards in different locations even on different continents.
Synthetic aperture imaging in space) based on satellite formation flying of several satellites (femtosecond laser pulses can be used to measure and control the accurate distance between satellites) makes it possible to establish an imaginary large-sized telescope based on the formation flying of several small-sized satellites instead of using such large-scaled telescopes as the Hubble Space Telescope, which could provide a great burden not only for the time and cost required to develop the satellites and payloads but also for the launching system that is used to send the satellite out to space. Since the femto-second(femtosecond) laser provides an extreme level of accuracy for measurements under 10-15, it is the indispensible and core light source for this formation-flying satellitetechnology.
Multi-channel remote secure optical communication based on femtosecond laser makes it possible to drastically increase the transfer rate ofprevious space communication based on microwaves. Whenthe transmission of an image data would take about an hour from Mars to earth, with the optical communication, it could be transfered within a minute. Furthermore, if we implement high-density communication using a large number of optical modes of the femtosecond laser, the transmission can be complete within several seconds. In 2013, National Aeronautics and Space Administration (NASA) started the single-channel optical communication between the earth and the moon, successfully transmitting images for the first time. Since the femto-second(femtosecond) laser could provide hundreds of thousands of different types of optical wavelength at the same time, it could be utilized for the multi-channel optical communication and greatly improve the transmission speed. Also, compared to microwave, its wavelength is extremely short and has a low beam divergence, so it is advantageous for high secure communication in space.
Development of the next-generation high-accuracy optical clock and the verification of the general theory of relativity makes it possible to compare the optical clocks developed in different continents. Furthermore, it enables the experimental measurement and verification of the general theory of relativity and the observation of the gravitational red transition(red-shift) at different altitude (through which it is possible to see a planet passing the central star from the earth). The European Space Agency (ESA) is planning the STE-QUEST mission for creating an optical clock in space by 2025. As one of the core elements for the mission, the (frequency comb of a femtosecond laser) is planned to be installed.
As stated above, the ultra-short femto-second(ultrashort femtosecond) laser, which has been developed by the research team led by Professor Seung Woo Kim can be considered as the first femtosecond laser system in space. It will be the foundation for application researches regarding the verification and confirmation of various possibilities of the ultrafast optics and phootnics in space.
Prof. Kim, Seung Woo
2013 Annual Report