ESA reported about direct contact with space debris of their radar satellite operating under Copernicus program.
Incident took place on August 23, 2016, at 17:07 GMT. Very small piece of space debris hit into solar panel of Sentinel-1A satellite remaining on around 693 km circular orbit with inclination at 98.18°. Effects of the direct hit were rapid power loss which luckily appeared to be only periodically and small change of the orbit. Specialists from mission control center in Darmstadt noticed surprising problems with power and little orbit change and decided to perform inspection of the satellite. One of the phases of the test was turning on two cameras, which are focused on solar panels and remained turned off after successful deployment of arrays two years ago. Detailed analysis of the pictures, along with comparison of last images of the panels taken just after deployment, gave answer for all the questions. On one of the panels, specialists discovered that structure of the array is damaged on surface of around 40 cm. According to ESA and its space debris office, object, which hit Sentinel-1A was smaller than 5 cm (under this size pieces of debris are not trackable); scale of the destruction of the array gives reasons to assume, that this particular piece was not larger than 5 mm in diameter. Fortunately in spite of problems with power and slight change of the course, satellite is still operational in 100% and is continuing its mission of monitoring forests, water, climate change and disaster relief. ESA did not confirm if debris, which broke into solar panel of Sentinel-1A was piece of human made or it was micrometeoroid.
Sentinel-1A remains in space from April 3, 2014, when it was launched on atop of the Soyuz-2.1A rocket from Guiana Space Center. Satellite was launched with assumption of at least seven years of the operational life. Sentinel-1A was based on Prima bus, developed by Italian Space Agency (ASI) and Alenia Aerospazio. Satellite was built by Thales Alenia Space. Its main payload is C band synthetic aperture radar (SAR) for radar imaging with resolution fitting in the range from 5 to 25 meters operating on 5.405 GHz frequency. Radar is able to operate with swath of 80 km with 5 m x 5 m resolution up to swath of 400 km with 25 m x 100 m. Sentinel-1A weighs 2280 kg (with 130 kg of propellant for 14 thruster able to provide 1 N of thrust) with following diameters: 3.9 m x 2.6 m x 2.5 m with folded solar panels. Span of the solar batteries (Gallium-Arsenide) is 20 m (each with length of the 10 m); radar antenna is long for 12 m and is placed under fuselage. Solar arrays are able to provide up to 4800 W of power. Satellite is equipped with attitude control system based on four reaction wheels, three magnetic torquers, star tracker, fine sun sensors, magnetometers, fine gyroscope and two channel GPS receiver. Communication with four ground stations for transmitting SAR data is conducted on X band; satellite is communicating with Svalbard in Norway, Matera in Italy, Maspalomas in Spain and Inuvik in Canada ground stations. It is also (along with first Sentinel-2 satellite) using EDRS laser data relay system. Commands and tracking are provided by station based in Kiruna in Sweden.