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Calibration of Astronomical Spectrographs with Stabilized Fabry-Perot Etalons

Periodic Reporting for period 1 - STABLE_FABRY (Calibration of Astronomical Spectrographs with Stabilized Fabry-Perot Etalons)

Reporting period: 2016-04-15 to 2018-04-14

Over the past twenty years, planets orbiting other stars have become an important research topic, capturing the interest of scientists and the general public alike. Detecting such objects requires very precise astronomical measurments. One technique that has been very successful for this research is the so-called radial-velocity technique. It measures the motion of the star due to the gravitational pull of the planet, therefore we can learn about the existence of the planet, and even about its mass, without ever actually seeing it. An important prerequisite for such measurements is the availability of calibration sources, which provide very stable references with which the motion of the star can be compared. The objective of this project is the development of a new type of calibration source, which is more reliable and costs less than alternative technologies.
The measurement priniciple for detecting small motions of the star is based on the so-called Doppler effect. The stellar spectrum contains many sharp lines, and these move slightly in wavelength (i.e. they change slightly in color) when the star moves towards the telecope or away from it. Our calibration source also produces many sharp spectral lines. At the telescope, the light from both the star and the calibration source are fed with optical fibers into a spectrograph, where the line positions can be compared. We have demonstrated that we can use a laser to keep the calibrations lines fixed over a long time with extremely high precision, and we have built a robust package for our calibration source that can be used at an observatory, where very high reliability is needed. The production and maintenance costs of our system are much lower than those of much the more complex calibration systems that are currently used by some observatories.
Our calibrations system is based on a physical method that has been known and used in laboratories around the world for many years. The important progress beyond the state of the art was making the system compact and robust enough to put it in a sealed box that can be used easily at any observatory, without the need of employing laser specialists, or of having the system serviced by a company in regular intervals. Therefore a number of world-leading observatories are planning to use our system for their next-generation instruments. Our project will thus make an imporant contribution to further research on extrasolar planets; perhaps it will help to identify a planet that could harbor life.
Small is beautiful: This sealed box contains the laser at the heart of the calibration system.