The exploration of Mars gets on a new wider scale nowadays. Knowledge of the space radiation environment in s/c transition to Mars, around Mars and on Mars surface becomes a significant factor in missions’ planning. The Trace Gas Orbiter (TGO) is the first spacecraft of the ExoMars mission - a joint ESA-Rosscosmos program for investigating Mars.
The dosimetric telescope Liulin-MO for measuring the radiation environment onboard the ExoMars Trace Gas Orbiter (TGO) is a module of the Fine Resolution Epithermal Neutron Detector (FREND). Liulin-MO provides data for the deposited energy spectra, dose rates, particle fluxes, linear energy transfer (LET) spectra, radiation quality factor (Q), and dose equivalent rates in 2 perpendicular directions.
Liulin-MO successfully operated during TGO transit to Mars and on the high elliptic Mars orbits. Since April 16, 2018 Liulin-MO operates in TGO circular orbit at 400 at altitude above Mars. Data handling and processing were objectives of the previous contract DOSIMETRY between ESA and our team (http://esa-pro.space.bas.bg/). The present projects aims to make Liulin-MO data more universally applicable for assessment of the radiation conditions in the interplanetary space and in Mars orbit, independent of instrument’s and s/c configuration and orbit parameters.
To reach this aim the effect of instrument’s surrounding matter, the planet’s shading of the cosmic rays and the contribution of the albedo radiation from Mars surface and atmosphere should be accounted for.
Objective: To assess the radiation conditions in Mars orbit and in the interplanetary space from Liulin-MO data
In Mars circular orbit the planet shades detectors’ field of view (FOV), thus cutting part of cosmic rays flux – galactic (GCR) and Solar. The cut part of FOV is an angle dependent on TGO orientation and its altitude. TGO orientation can vary by 1800 though not often; TGO altitude varies within 50 km in every orbital pass. To estimate the contribution of the albedo particles is a rather complicated problem as theoretically it can depend except on the incident primary cosmic rays flux also on the season, the relief, on soil composition, atmospheric composition, etc. The extrapolated data will be the derived data supplied to ESA Planetary Space Archive PSA.
Analyses of the data processed under project Dosimetry (http://esa-pro.space.bas.bg/) identified some shortcomings in the calibrated data, e.g. is some controversial in the time attached to each measurement, not corrected artificial data, etc. Data will be carefully examine for another inconsistencies and decisions will be taken for each of them.
The Standard Radiation Environment Monitor (SREM) measures high energy electrons and protons with a fair angular and spectral resolution using similar to Liulin- MO method. It was mounted on several ESA space missions situated in different orbits. In particular aboard Rosseta s/c it measured the radiation conditions in deep space during its journey towards and around comet Churyumov-Gerasimenko. Comparison of both Liulin-MO and SREM data sets will provide results about cosmic rays behavior at different locations in the Solar system and different phases of solar activity.
The charged particles registered by Liulin-MO prior hitting the instruments’ sensors interact with the surrounding materials and undergo changes in energy and eventually produce secondary particles, which in turn could hit the sensors and contaminate the measured LET spectra. To process Liulin-MO data to the state of the art level numerical simulations of the measurements is necessary. The simulations will be performed using GEANT 4 software.
Duration of the project: 01.02.2021 – 31.01.2023 extended till 01.06.2023