TRACERS 1 Analyzer of Cusp Electrons (ACE) Differential Energy Flux and Counts, Level 2 (L2), Data

Subtraction of background can lead to negative differential energy fluxes, especially for low count rate data. Depending on the use case, these negative values can either be retained or replaced with zeroes. The calibration matrix incorporates instrument sensitivity and relative sensitivity factors for each anode, both estimated based upon a combination of pre-flight laboratory calibrations and inflight data.

Energy values for each energy step and anode are computed utilizing the known sweep voltage table and pre-flight laboratory calibrations. The ACE instrument was intended to be operated in a particular spacecraft orientation, with the TSCS +Z axis aligned with the magnetic field. In this orientation, incoming electron trajectories are not occluded by the spacecraft.

However, for a portion of the TRACERS mission, the spacecraft are oriented in the opposite sense, which leads to an occlusion of a portion of the instrument field of view by the spacecraft body for low-energy (<~200 eV) electrons. Low-energy ACE data should not be utilized for quantitative purposes when the spacecraft are in this orientation.