It has been considered that FEP is one of candidates for thermal control material applicable to VLEO due to its high durability in LEO environment. However, effect of hyperthermal N2 collision on FEP erosion needs to be clarified quantitatively to ensure the survivability of FEP in VLEO environment, because FEP erosion is known to be sensitive to collision energy of neutral atoms. In this presentation, we will report the experimental results of quantitative evaluation of erosion yield of FEP due to atomic oxygen (Ey(AO)) and to argon (Ey(Ar)) in simulated VLEO environments independently. A series of experiments were done by the laser detonation beam source with gas mixing system at Kobe University. O2 and Ar gases were used as source gases. Ar was used to simulate physical effect of N2 collision in VLEO. Two beam conditions (50%Ar+50%O2 and 90%Ar+10% O2) were used in the experiment. Because FEP erosion in simultaneous exposure condition of AO and Ar beam is known to be additive, Ey(AO) and Ey(Ar) were evaluated by solving the simultaneous equations regarding mass loss of FEP in two different conditions. The analytical results indicated that Ey(Ar) is more than 20 times greater than Ey(AO). This experimental data are implied that the erosion of FEP in VLEO is mainly due to N2 collision, and that by AO gives a minor effect. This surprising conclusion is supported by the fact that Ey(AO) obtained in this study is close to that measured in MISSE series in LEO where N2 effect is negligible. We are now attempting to certify this conclusion with SLATS/MDM flight data which is the world first and only FEP erosion data in VLEO by collaborating with the materials group of JAXA. A part of this study was supported by KAKENHI form JSPS under contract #22H01682, #22H01681 and #22K18859.