SoylentNews

upstart writes in with an IRC submission for SoyCow0570:

CHEOPS space telescope ready for scientific operation:

A team of scientists, engineers and technicians put CHEOPS through a period of extensive testing and calibration from the beginning of January until the end of March. "We were thrilled when we realized that all the systems worked as expected or even better than expected," explains CHEOPS Instrument Scientist Andrea Fortier from the Univerisity of Bern, who led the commissioning team of the consortium.

The team began by focusing on the evaluation of the photometric performance of the space telescope. CHEOPS has been conceptualized as a device of exceptional precision capable of detecting exoplanets the size of planet Earth. "The most critical test was in the precise measurement of the brightness of a star to a variance of 0.002% (20 parts-per-million)," explains Willy Benz. This precision is required so as to clearly recognize the dimming caused by the passage of an Earth-sized planet in front of a Sun-like star (an event known as a "transit," which can last several hours). CHEOPS was also required to demonstrate its ability to maintain this degree of precision for up to two days.

To verify this, the team focused on a star known as HD 88111. The star is located in the Hydra constellation, some 175 light years away from Earth, and it is not known to host planets. CHEOPS took an image of the star every 30 seconds for 47 consecutive hours (see Figure 1). Every image was carefully analyzed, initially using a specialized automatic software package, and subsequently by the team members, to determine in each image the brightness of the star as accurately as possible. The team had expected the brightness of the star to change during the period of observation due to a variety of effects, such as other stars in the field of view, the tiny jitter motion of the satellite, or the impact of cosmic ray hits on the detector.

The results of the 5,640 photos taken by CHEOPS over 47 hours are shown in Figure 2 as a "light curve." The curve depicts the change over time in the brightness measurements from all the images, showing a root-mean-square scatter of 0.0015% (15 parts-per-million). "The light curve measured by CHEOPS was pleasingly flat. The space telescope easily surpasses the requirement for being able to measure brightness to a precision of 0.002% (20 parts-per-million)," explains Christopher Broeg, Mission Manager for the CHEOPS mission at the University of Bern.

[...] Benz explains that the measurements by CHEOPS are five times more accurate than those from Earth. "That gives us a foretaste for what we can achieve with CHEOPS over the months and years to come," continues Benz.

Original Submission