In the realm of energy and space exploration, understanding the behavior of cosmic rays is crucial for the longevity and accuracy of space-based technologies. Researchers Bernard J. Rauscher and D. J. Fixsen, affiliated with NASA’s Goddard Space Flight Center, have recently published their findings on cosmic ray interactions with the James Webb Space Telescope’s Near Infrared Spectrograph (NIRSpec). Their work, published in the Journal of Astronomical Instrumentation, sheds light on the challenges posed by cosmic rays and offers insights that could benefit future space missions, including the Nancy Grace Roman Space Telescope.
The James Webb Space Telescope (JWST) operates in a halo orbit around the Sun-Earth-Moon L2 point, where it encounters energetic ions that can penetrate the radiation shielding of its NIRSpec instrument. The researchers characterized these cosmic ray interactions using “dark” exposures, which are images taken without any light entering the instrument. They found that the rate of cosmic ray hits decreased from approximately 4.3 to 2.3 ions per square centimeter per second during the first three years of JWST’s operation. This decrease is likely due to the solar cycle, as the Sun’s activity can influence the flux of galactic cosmic rays.
As we approach solar maximum, the researchers expect the galactic cosmic ray flux to increase, leading to a rise in the NIRSpec cosmic ray hit rate. They anticipate the rate to return to around 4.3 ions per square centimeter per second by early 2027 and potentially reach about 6 ions per square centimeter per second in the early 2030s. Each cosmic ray hit typically affects around 7.1 pixels and deposits about 6 keV of energy in the detector material, equivalent to approximately 5200 charges. The corresponding linear energy transfer is about 0.86 keV per micrometer.
The researchers also investigated rare, large “snowball” hits and even less frequent events with secondary showers. These events pose significant calibration challenges and could originate from heavy ions, secondary particles from shielding, or inelastic scattering in the detector material. Understanding these events is crucial for accurate data calibration and interpretation.
For the energy sector, this research highlights the importance of radiation shielding and mitigation strategies for space-based technologies. As we look to expand our presence in space, including the deployment of satellites for energy monitoring and management, understanding and mitigating the effects of cosmic rays will be essential. The findings from this study can inform the design and operation of future space missions, ensuring their longevity and accuracy in the harsh radiation environment of space.
In conclusion, the work of Rauscher and Fixsen provides valuable insights into the behavior of cosmic rays and their interactions with space-based instruments. As we continue to explore and utilize space for energy and other applications, this research will play a crucial role in guiding the development of robust and reliable technologies.
This article is based on research available at arXiv.