Changes to Operating Mode of the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) Aboard the Lunar Reconnaissance Orbiter (LRO)

As its name implies, the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which has been orbiting the Moon aboard NASA's Lunar Reconnaissance Orbiter (LRO) since 2009, is mainly designed to measure the radiation effects of the low, steady flux of galactic cosmic rays that pervades the solar system. However, it also measures the much more intense radiation that can occur during solar energetic particle events. To ensure that useful data is returned in telemetry even when particle event rates get very high, CRaTER switches from its normal "low rate" mode of operation to "elevated rate" or "extreme rate" modes. It is necessary when analyzing data from the sensor to know in which mode a given sample was acquired, so that homogeneous datasets can be extracted for intercomparison. To enable researchers to do such sorting, this dataset tabulates, at one-second resolution, the mode in which the sensor was operating through each of the days when it exited the low rate mode (only a few dozen out of the sixteen years of the mission as of this writing); it also lists parts of other days when particle-event data were invalid, usually during brief self-calibration periods. This dataset will be updated for as long as CRaTER remains operational.