E-THEMIS Thermal Anomaly Simulation Observations

This dataset contains 5000 simulated observations of Europa with the E-THEMIS instrument. Each observation was generated by randomly selecting (1) one of 46 planned Europa flybys by the Europa Clipper and (2) the distance of the spacecraft to Europa (±5000 km from closest approach). We used a thermal model to simulate the Europa surface temperature as a function of latitude, longitude, and local solar time (Sun position). We simulated the appearance of Europa within the E-THEMIS field of view given the Europa radius of 1591 km. We used ray tracing to determine, given the surface temperature model and the relative positions of Europa and the spacecraft, the amount of thermal radiation from Europa that a given pixel would collect. We used Monte Carlo integration over 100 uniformly random sub-pixel locations within each pixel.

We injected artificial thermal anomalies into the simulated Europa observations by selecting a random radius between 1 m and 25 km and random temperature between 130 K and 275 K, then modifying the modeled surface temperature. We used an instrument model that converts temperature to digital numbers to generate the final E-THEMIS data product.

The ethemis_dn_to_temp.mat file contains the mapping from digital number to temperature in each of the three E-THEMIS bands. Each observation is also a MATLAB-formatted file containing the following entries:

event_time: the simulated time at which the observation was acquired

trial: the trial identifier (should match the file name)

samples: the number of samples used in the Monte Carlo integration

anomaly_radius_m: the (circular) anomaly radius in meters

temperature: the temperature of the anomaly

band1_dn: the digital number for each pixel in the observation (similar entries exist for the other bands)

band1_mask: a mask specifying the fraction of each pixel containing an anomaly (similar entries exist for the other bands)

The extracted dataset is roughly 24 Gb in size.