eROSITA known issues during eRASS1

eROSITA has proven to be an excellent and functional X-ray instrument. However, some issues have appeared since the Commissioning phase of the mission. These issues impact the telescope operations and the quality of the data. The main problems have been described in the Early Data Release site (EDR). Here you can find additional information about the known eROSITA issues during the first eROSITA all-sky survey (eRASS1).

Data artefacts due to light leak and solar activity

eROSITA's telescope modules (TM) 5 and 7 are contaminated by optical light: a small fraction of sunlight reaches the CCD, bypassing even the filter wheel. The intensity of the light leak is continuously changing with the orientation of the spacecraft and therefore with time. In addition the effect is different for TM 5 and 7.

During eRASS1 (December 2019 - June 2020), the Solar activity was at its minimum. Nevertheless, some Coronal Mass Ejections (CMEs) reached the orbit of SRG, impacting the quality of the eROSITA data.

On this page you will find information about the times when eRASS1 data is affected by either of the above mentioned issues.

Micrometeoroids impacts

Since the Commissioning phase of eROSITA and until the end of eRASS1, only one of the CCD cameras of eROSITA was hit by a micrometeoroid. This event occurred on 2019.12.05, a week before eRASS1 started. The affected CCD was TM4, and four pixels of this camera were damaged. These pixels were bright for a short period and had a minor impact on the total telemetry of the instrument. Moreover, these pixels faded after each computation of a new offset map, which is done regularly when the camera differs by more than 0.5-1.0 degrees Celsius compared to the temperature of the previous offset map computation.

You can find further information about eROSITA micrometeoroid impacts and their effects in Freyberg, M., et al., (2022) and Coutinho, D., et al., (2022).

Camera electronics susceptibility

Since the Commissioning phase of the eROSITA instrument, it is known that the seven camera electronics (CE) are radiation susceptible to single event upsets (SEUs). In this link, you can find further information on the CE disturbances or crashes during eRASS1.

Other camera electronic issues

In addition to true events caused by photons (plus the expected, constant rate of false events due to thermal fluctuations in the detectors), all seven eROSITA CCDs detectors generate sporadic bursts of false events. The cause of these bursts is still under investigation, although it is probably connected to collisions of energetic particles (cosmic rays, solar protons) with the detector. You can find further information about these artefacts here.