Methods of breaking the correlation of the inflow parameters of interstellar neutral gas, observed in direct-sampling experiments

Direct-sampling measurements of the interstellar neutral (ISN) gas have been performed for many years using several instruments. During recent years, the Ulysses and IBEX missions gave a quite accurate assessment of the ISN parameters. The results obtained from the IBEX-Lo detector onboard the Interstellar Boundary Explorer, however, show a correlation between the temperature, direction, and speed of the interstellar neutral gas inflow into the heliosphere while those obtained from GAS/Ulysses do not feature such a correlation. Here, we point out that the correlation found in the IBEX results is based on one hand on the geometry of the measurements (short orbital arc around the Sun for useful data collection), and on the other hand on the wide energy band of the instrument sensitivity. As a result, we don`t know exactly what energy had the atoms registered by the detector. Here we propose a method of breaking the parameter correlation using the new instrument on the IMAP mission, which will operate in the terrestrial L1 point. The IMAP-Lo detector has a much broader range of available solar angles in which it can collect the ISN atoms. We show that if we have available measurements collected from different arcs well separated during the year, the parameter correlation tube disappears. We also show that a good method to remove the correlation is combining ISN observations for the direct and indirect beams of ISN gas, which is a unique capability of the IMAP-Lo instrument.